TAG HIV Basic Science, Vaccines, and Cure Project Blog

New HIV Remission Case Report at AIDS 2020

Today, a presentation by Ricardo Diaz at the ongoing virtual International AIDS Conference (AIDS 2020) caused a major splash in the media by reporting that one out of 30 participants in a clinical trial conducted in Brazil has experienced a lack of viral load rebound for a little over a year (64.7 weeks) after interrupting antiretroviral therapy (ART).

The trial was launched in 2015 and involved a complex design in which 30 participants with HIV were divided into six groups of five people each. One group continued on a standard ART regimen and served as controls, while the other five groups received the following additional interventions:

• Group 2: Dolutegravir and the CCR5 inhibitor maraviroc (which has been reported to also exert HIV latency-reversing effects)
• Group 3: Dolutegravir, maraviroc and nicotinamide (a water-soluble form of vitamin B3 that may have HIV latency-reversing activity)
• Group 4: Dolutegravir, maraviroc and auranofin (an antiproliferative drug)
• Group 5: Dolutegravir and a dendritic cell therapeutic vaccine
• Group 6: Dolutegravir, a dendritic cell therapeutic vaccine, auranofin and nicotinamide

Results from the trial have been presented on a number of previous occasions, including at AIDS 2018, CROI 2019, and the 2019 HIV Persistence Workshop (see abstract OP 8.6 in the abstract book and the report from NATAP toward the base of this page). Results from participants who received auranofin were also the subject of a published paper last year. Overall, declines in HIV DNA levels (a surrogate measure of the HIV reservoir) were found to be greatest among recipients of the multiple interventions in group six.

The original study design did not include an analytical treatment interruption (ATI), but the protocol was later revised and 25 of the participants underwent an ATI approximately 2.5 years after the end of the 48-week study period (during which the interventions were administered).

The presentation at last year's HIV Persistence Workshop reported that two participants in group six and one in group three displayed undetectable HIV viral loads after the ATI. However, after around 16 weeks the two people from group six showed evidence of viral load rebound and restarted ART.

The remaining participant from group three was the subject of today's AIDS 2020 presentation. The individual was diagnosed with HIV infection in October 2012 and started ART two months later. According to an article by Jon Cohen in Science, they estimate the date of HIV acquisition to be around June 2012 (the last previous HIV negative test result was in 2010). Viral load at ART initiation was relatively low: 20,221 copies/mL.

At the time of entry into the trial in September 2015, viral load was undetectable and the CD4 count 720. Two very low level transient viral load blips occurred while receiving the study interventions but otherwise undetectable levels have been maintained while on ART.

HIV DNA was detectable in rectal tissue and blood samples at the end of the 48-week intervention period. Measurements of blood HIV DNA levels subsequently showed a decline during treatment with regular ART regimens, eventually becoming undetectable immediately prior to the ATI which was initiated in March 2019.

After the ATI, viral load did not rebound and has remained undetectable ever since (the last available measurement at the time of the presentation was from June 22, 2020). Slides showing CD4 count and CD4:CD8 ratio over time indicated a notable decline shortly after the ATI, which is surprising given the apparent lack of viral load rebound in the blood, but no further longitudinal data on these measures was reported.

HIV antibody levels evaluated by the Abbott ARCHITECT antigen/antibody combination assay have declined throughout follow up, with the exception of one possible slight increase immediately after the ATI. Results of a rapid HIV antibody test are now negative (in some media reports this has been mistakenly represented as indicating that no HIV antibodies are detectable, which is not accurate). 

The case appears encouraging for HIV cure research, with the caveat that late rebounds in viral load have occurred in some previous examples of HIV remission. Importantly, it's unclear as yet whether the interventions received during the trial contributed to the outcome; the person may have started ART fairly soon after HIV acquisition and there have been other case reports of early-treated individuals containing viral load for variable periods after ART interruptions.

Notably, of the other 29 study participants, nine received nicotinamide and 14 received dolutegravir and maraviroc. Although it's unclear whether all of these other participants were among those that underwent ATI, no additional examples of similarly prolonged absence of viral load rebound were observed. This appears to argue against a strong effect of these interventions. Additionally, HIV DNA levels continued to decline long after the cessation of the interventions in the participant who has not rebounded.

Emphasizing the uncertainty about the role of the study drugs is important given that nicotinamide is available over-the-counter as a supplement. At the current time, there is no evidence to suggest that adding dolutegravir, maraviroc and nicotinamide to ART regimens would lead to similar outcomes in other people with HIV.

Further analyses will hopefully shed light on how viral load rebound has so far been prevented, and whether the interventions contributed in some way. Information on HIV-specific T cell responses and the individual's HLA type could be particularly helpful. The Associated Press article on the research includes the welcome news that Diaz will receive support to conduct a larger 60-person trial, so more robust results should be forthcoming.

A Step Forward for AAV-Mediated Delivery of bNAbs

Many years ago, Phil Johnson from the Children’s Hospital of Philadelphia began pursuing a novel workaround to overcome the challenge of inducing broadly neutralizing antibodies (bNAbs) against HIV. The idea borrows from gene therapy, using adeno-associated virus (AAV) as a vector to deliver the genetic code for a bNAb into the body. The aim is for the AAV to persist inside cells and act as a factory for churning out the bNAb into systemic circulation. As previously covered on the blog, promising results were obtained in macaques over a decade ago, but the first human trial (conducted in HIV-negative volunteers) did not achieve detectable levels of the bNAb PG9—likely due to the induction of anti-PG9 antibodies. At CROI 2020, Joseph P. Casazza from the Vaccine Research Center (VRC) at the National Institutes of Health presented evidence that the approach may yet have promise.

Casazza described preliminary results from an ongoing trial of the bNAb VRC07 delivered via an AAV serotype 8 (AAV8) vector. The vector was designed by David Baltimore and Alejandro Balazs, and is different to the AAV serotype 1 vector used in the previous human trial. The study is recruiting people with HIV on ART with undetectable viral loads, and Casazza presented data from eight participants (six men and two women, with five African American and three Caucasian).

Three escalating doses are being evaluated, and Casazza’s presentation included data from three recipients of the lowest dose, two recipients of the intermediate dose and three recipients of the highest dose. Follow up ranged from five months to a little over two years.

In contrast to the prior trial with AAV1, the bNAb VRC07 became persistently detectable in a majority of participants (six out of eight). In most cases, a pattern was observed in which an initial peak in levels occurred 2-4 weeks after injection, followed by a decline and then a rebound toward steady state levels after around 14-16 weeks.

Three participants developed anti-VRC07 antibodies, which has been the Achilles heel of the AAV-based delivery approach. In two of these individuals VRC07 levels became undetectable after the initial peak, and in the third the secondary peak was blunted. Casazza noted that anti-VRC07 antibodies did not appear to be the only factor influencing VRC07 levels, because one participant in the high dose group experienced a significant decline between weeks 22 and 40 which has yet to be explained.

Adverse events were minimal, with mild pain and tenderness at the injection sites reported in the high dose group and one case of muscle pain in the intermediate dose group—all resolved within seven days.

Casazza did not discuss the potential reasons for the greater success compared to the results achieved with AAV1-based delivery but, in addition to differences in the technical aspects of vector design, AAV8 is liver tropic and it’s been suggested that this is more likely to lead to immunological tolerance of the delivered bNAb.

Notably, the maximum VRC07 concentration achieved was a little over one microgram/mL in the high dose group, which is low compared to the levels that are obtained by intravenous infusion of bNAbs. For example, levels of well over 50 micrograms/mL have been reported in studies involving i.v. administration of the bNAb VRC01. In a recent trial that administered a combination of the bNAbs 3BNC117 and 10-1074 and then interrupted antiretroviral therapy (ART), an undetectable viral load was maintained for as long as the concentration of both antibodies was above 10 micrograms/mL.

Casazza’s results offer some hope that the use of AAV vectors to deliver bNAbs (or other therapeutic proteins) will turn out to be feasible. However, work remains to improve both the consistency and magnitude of bNAb production. In a preclinical macaque study in which an AAV8 vector was used to deliver VRC07, the addition of transient immune suppression with cyclosporine was able to increase average peak bNAb levels to ~40 micrograms/mL (compared to ~5 micrograms/mL without), however it’s unclear if this approach could be practically adapted for human use.

Casazza and his colleagues at the VRC are not the only research group still pursuing the idea. Michael Farzan from the Scripps Institute gave a talk at CROI describing the latest results obtained with AAV-based delivery of eCD4-Ig, a protein that inhibits HIV replication by binding the virus envelope at sites that attach to CD4 and CCR5 receptors on CD4 T cells.

In a therapeutic experiment involving six macaques infected with the SIV/HIV hybrid virus SHIV-AD08, eCD4-Ig delivered by AAV (two injections, the first using an AAV8 vector and the second using an AAV1 vector) was able to maintain viral load control to varying degrees after an ART interruption. At the most recent timepoint after 80-90 weeks off ART, five animals have viral loads ≤15 copies/mL and the sixth has a viral load of 25 copies/mL. Concentrations of eCD4-Ig ranged from 4.7 to 10.3 micrograms/mL, and Farzan explained that they hope to further refine delivery to achieve higher levels.

The laboratory of Ron Desrosiers is also working on AAV delivery, focusing on payloads of combination bNAbs. Farzan cited the best known example of this work: the “Miami monkey,” a recipient of AAV-delivered 3BNC117 and 10-1074 that has exhibited prolonged containment of a SHIV AD8 challenge at such vanishingly low levels that the virus has been extremely challenging to even detect (at one point it was thought virus eradication may have occurred).

On March 17th, Desrosiers and colleagues provided an update on another individual macaque that was originally part of a prevention study published in 2015. This animal has now maintained high levels (240-350 micrograms/mL) of the anti-SIV antibody 5L7 for over six years. The researchers are now working to create this type of response more reliably and they conclude:

“If satisfactory delivery methods are found, it becomes possible to envision long-term control of viral replication in the absence of antiretroviral treatment by delivering a combination of antibodies in people, and long-lasting protection when this approach is used in a prophylactic setting.”

It may still be a big “if,” but the data clearly justify efforts to solve the technological challenge.

Halting Start for Kick & Kill, CROI Previews New Approaches on the Horizon

One of the most widely discussed and publicized ideas for targeting the HIV reservoir is “kick and kill” or “shock and kill.” The aim is to kick dormant, latent HIV into revealing itself so the cells that contain the virus are visible to the immune system; the kill aspect involves trying to enhance the immune response so it’s able to recognize and destroy these HIV-infected cells. The ultimate goal is to deplete the latent HIV reservoir that persists in people on antiretroviral therapy (ART).

The RIVER trial, launched in the UK in December 2015, represents the first large, randomized controlled evaluation of the approach. Preliminary results were first reported at the AIDS 2018 conference in Amsterdam, and have now been described in detail in a paper in Lancet HIV. While the interventions were unable to reduce the HIV reservoir, the negative outcome still holds important lessons for the cure research field. New candidates for both the kick and the kill are in the research pipeline.

RIVER recruited a total of 60 participants with primary HIV infection—all men—and randomized them to receive either a standard ART regimen plus the integrase inhibitor raltegravir or standard ART, raltegravir, a prime-boost therapeutic HIV vaccine combination and a short course of the HDAC inhibitor vorinostat (a latency-reversing agent reported to have some activity in prior trials). The vaccines consisted of chimpanzee adenovirus and modified Vaccinia Ankara strain virus vectors carrying HIV antigens designed to induce T cell immune responses focused on parts of the virus that mutate the least (conserved regions).

The results showed that after 16-18 weeks there were no differences between the two groups in any measures of HIV persistence, including HIV DNA and the quantitative virus outgrowth assay (QVOA). A laboratory test assessing the ability of CD8 T cells to kill HIV-infected cells indicated that therapeutic vaccination helped maintain this capacity: killing activity declined from baseline in the ART only arm of the study but was maintained in the intervention arm. Vorinostat increased histone acetylation after dosing (the mechanism by which it can trigger the activity of latent HIV), however sensitive tests for low-level HIV RNA did not reveal any concomitant increases suggestive of HIV latency reversal.

In discussing their findings, the authors posit a number of possible reasons why this particularly kick and kill combination did not prove effective. Fewer doses of vorinostat were used than in some prior trials, and the evidence of latency reversal that has been described (increases in HIV RNA associated with dosing) was obtained in people with chronic rather than primary HIV infection. Another possibility is that even if vorinostat did cause some latently infected cells to reveal themselves to the immune system by expressing HIV antigens, the HIV-specific CD8 T cells induced and/or maintained by therapeutic vaccination may not have been capable of recognizing these antigens. Presentation of the antigens to CD8 T cells could also be inhibited by the HIV Nef protein, which is known to have the capacity to interfere in this process.

The researchers also acknowledge the argument that analytical treatment interruptions (ATIs) may be a better test of the effects of interventions than laboratory measures of the HIV reservoir, but at the time RIVER was designed ATIs were not in favor due to safety concerns, and they still believe that an ATI wouldn’t be justified in this case. They conclude that:

“RIVER helps to set the standard for how future trials might be done because of the new insights gained with regard to trial design, the inclusion of community representation, the need for better interventions, the necessity for clarity regarding the most relevant measures of the reservoir, and probably the use of an analytical treatment interruption approach.”

An example of a next generation kick and kill study was presented last week at CROI by Ole Schmeltz Søgaard. Known as ROADMAP, the trial compared romidepsin (an HDAC inhibitor that appears to have greater latency-reversing activity than vorinostat) to romidepsin plus the broadly neutralizing antibody (bNAb) 3BNC117 in people with chronic HIV infection on long-term ART. The bNAb was included in hopes of both promoting killing of HIV-infected cells via antibody-dependent cellular cytotoxicity (ADCC) and enhancing HIV-specific T cell immunity (as recently reported in a study of 3BNC117 combined with another bNAb, 10-1074).

A total of 20 participants were enrolled (17 men and three women); 11 were randomized to receive 3BNC117 and romidepsin, nine to romidepsin. There were two cycles of romidepsin administration: at weeks 0, 1, 2 and weeks 8, 9, and 10. The 3BNC117 group received a single infusion of the bNAb two days prior to these cycles. After 24 weeks, participants underwent an ATI in order to evaluate time to viral load rebound (defined as two consecutive measures equal to or greater than 200 copies/mL). Two participants opted out of the ATI, while a third was excluded after stopping ART while receiving romidepsin.

Søgaard reported that, disappointingly, there was no significant difference in time to viral load rebound between the two arms of the study: it took an average of 28 days in the romidepsin group compared to 17.5 days in the 3BNC117 plus romidepsin group. The slight difference in favor of the romidepsin group wasn’t statistically significant and Søgaard noted it was driven by one outlying participant who didn’t experience rebound until 12 weeks into the ATI.

HIV DNA levels measured at the midpoint between the romidepsin cycles and immediately prior to the ATI showed no significant changes. HIV-specific CD8 T cell responses remained stable over the same period and weren’t enhanced by 3BNC117 administration or negatively affected by romidepsin.

As was the case in the RIVER trial, Søgaard concluded that this particular combination was ineffective and that superior strategies are needed.

At CROI, Sharon Lewin—a leading scientist in HIV cure research—delivered an impressive, comprehensive update on the field, providing reasons to hope that better results will be obtainable in the future.

One key development is that the scientific understanding of HIV latency has improved significantly in recent years. The picture is now far more nuanced compared to when the HIV reservoir was first identified in the late 1990s.

The first relatively new concept highlighted by Lewin is that not all latent HIV remains stably latent (inactive) in people on effective ART. The HIV DNA that’s integrated into the genomes of infected cells can be transcribed into HIV RNA (which in turn can make HIV proteins), either intermittently or possibly also continuously in some cases.

A number of factors can affect the transcription of HIV DNA into HIV RNA, including the location of the infected cell. Lymph nodes, the gastrointestinal tract and the female genital tract are sites where HIV RNA is most frequently detected. Time of day also has an influence because proteins involved in the circadian cycle can activate HIV transcription, leading to fluctuations in HIV RNA levels.

Lewin described this phenomenon as “reservoir activity” and it’s important to stress that it does not represent ongoing HIV replication—any new infectious HIV viruses that are produced would be blocked from infecting new cells by the presence of ART. Gaining an understanding of the processes involved in reservoir activity should help researchers develop better latency-reversing agents.

Another aspect of HIV latency that is now coming into view is the importance of where exactly the virus lands when it integrates into the genome of a cell. As a loose analogy, if you think of the genome as a factory for producing all the proteins a cell needs to go about its business, HIV DNA tends to land in machinery that gets switched on regularly, which gives the virus opportunities to hijack that machinery to make more HIV RNA (and potentially more copies of infectious HIV).

But HIV DNA can also land in the genomic equivalent of a darkened factory storage room nobody goes into—in that case, the virus may be trapped and unable to reactivate. Between these two extremes there are likely a range of possibilities, from HIV DNA being integrated in a spot where the transcription of HIV RNA is likely, to HIV DNA being integrated into a genomic dead end from which it can never emerge. Again, these new findings have implications for latency-reversing agents because they demonstrate that there’s a spectrum of reversibility that will need to be addressed.

The potential importance of where latent HIV resides in a cell’s genome has been emphasized by recent studies of elite controllers (as presented at CROI by Chenyang Jiang), which suggest that their immune responses can clear the more active HIV reservoir, leaving behind only those cells containing HIV integrated in places from which it cannot reactivate—essentially, the intact HIV that remains in their bodies may be trapped, and unable to replicate or cause harm.

A further wrinkle in the latency story is the ability of CD4 T cells containing integrated HIV to proliferate, duplicating the viral genes they contain along with the cell. As Lewin noted, it’s now recognized that a large proportion—typically around half—of the HIV reservoir in people on ART has been created by what is referred to as clonal proliferation of CD4 T cells. The proportion of the HIV reservoir generated by clonal proliferation can be identified because the viruses are genetically identical and integrated into exactly the same spot in the genome of CD4 T cells that contain them.

The mechanisms driving the proliferation of latently infected CD4 T cells are still being elucidated but Lewin listed several possibilities:

• Homeostatic proliferation: this is a normal part of the life of CD4 T cells that facilitates the survival of the cell and maintenance of overall CD4 T cell numbers. Evidence that it plays a role in maintaining the HIV reservoir was first published back in 2009.
• Antigen-specific proliferation: the process by which CD4 T cells proliferate after recognizing a specific antigen (e.g. an antigen derived from HIV or other infectious agents such as CMV) and becoming activated to respond. Lewin cited several studies reporting new data on the importance of antigen-specific proliferation in HIV persistence (including two at CROI: Simonetti et al and Mendoza et al)
• HIV integration site driven proliferation: in this scenario, it’s been proposed that HIV can influence the proliferation of CD4 T cells by integrating into certain places in a cell’s genome. At CROI, John Coffin described findings that may support this possibility, but only for a limited number of integration sites.

There are published studies showing that latently infected CD4 T cell clones contribute to viral load rebound after ART interruption, and also that HIV reservoir activity in these cells can in some cases generate sufficient HIV RNA to be measurable by standard viral load tests (making it necessary for clinicians to be alert to the possibility of mistakenly attributing detectable HIV RNA in people on ART to treatment failure).

The last but critical point made by Lewin about the HIV reservoir is the distinction between intact and defective HIV. It’s been known for some time that the vast majority of HIV DNA present in people on ART represents defective viruses that are incapable of replicating (although in some cases capable of generating viral proteins), but researchers have lacked the tools to easily distinguish replication-competent HIV.

The recently developed intact provirus detection assay (IPDA) is an example of progress on this front. Lewin cited an encouraging new analysis by Gregory Laird and colleagues indicating that levels of intact HIV decline on ART, while the amount of defective HIV DNA remains relatively stable. Based on the case of the elite controller Loreen Willenberg, in whom no intact HIV can be detected, Lewin also suggested that perhaps a cure should be defined as the elimination of all intact virus (rather than the absence of any detectable HIV genetic material).

Moving on to the future of kick and kill, Lewin selected some examples of advances that offer reasons for optimism. Earlier this year, results of an evaluation of the candidate latency-reversing agent AZD5582 were published in the journal Nature. The compound belongs to a class of drugs called SMAC mimetics, which appear to have considerably less potential to cause toxicity compared to the drugs studied to date. In studies in both HIV-infected humanized mice and SIV-infected macaques, potent induction of viral RNA expression was observed in blood and multiple tissues after dosing.

Immunomodulatory compounds such as immune checkpoint inhibitors (e.g. anti-PD1 antibodies that are approved for cancer) and toll-like receptor (TLR) agonists may have the ability to both reverse HIV latency and enhance killing of infected cells. Concerns about serious immune-mediated side effects are currently limiting the use of the former, but might eventually be addressed by different formulations and dosing strategies. Two studies are testing TLR agonists in combination with dual bNAbs (one with the addition of therapeutic vaccination): TITAN and JAWS. Both trials involve ATIs. JAWS is taking place at the University of California San Francisco (UCSF) but was only due to start enrolling very recently (and is not yet registered in clinicaltrials.gov), so may well be delayed by the current COVID-19 emergency.

The field of gene therapy is contributing another kill strategy: Chimeric Antigen Receptor (CAR) T cells, which are genetically modified to efficiently target virus-infected cells for destruction. Blake Rust presented results of a small CAR T cell experiment in SHIV-infected macaques at CROI, which showed some potential to control viral replication—one animal experienced an 89 day delay in viral load rebound after ATI, and two out of the four total animals displayed post-ATI suppression of viral load. Other research groups are also pursuing the idea.

At the Pre-CROI Community HIV Cure Research Workshop—an event co-sponsored by TAG that was held via webinar this year—James Riley described the status of efforts to translate the CAR T cell approach for use in people with HIV. A pilot trial combining CAR T cells with CD4 T cells gene-modified to lack the CCR5 co-receptor is now underway the University of Pennsylvania.

The lack of success observed to date with kick and kill may seem disheartening, but it does not necessarily spell doom—the ever-improving understanding of the biology of HIV latency combined with the expanding array of therapeutic candidates suggests the stubborn persistence of the HIV reservoir can yet be overcome.

CROI 2020: Updates on the London and Düsseldorf Patients, New Case of Infant Remission

Important news has unfolded this week regarding possible additional cases of HIV cures and remission. Yesterday, the London Patient (LP) courageously publicly identified himself as Adam Castillejo in an excellent, thoughtful and empathetic article in the New York Times by Apoorva Mandivilli. While his name is now known, I’ll follow his preference to go by the acronym LP here. Following this story, a scientific update was published in Lancet HIV today (open access), timed to coincide with a poster presentation at the Conference on Retroviruses and Opportunistic Infections (CROI)—a conference that was due to occur in Boston this week, but is now ongoing in a virtual format due to concerns over coronavirus. The same poster session also featured new information on the similar case of the Düsseldorf patient, along with a report on an infant treated early with ART in whom treatment was subsequently interrupted without HIV rebound (which has echoes of the HIV remission described in the Mississippi baby in 2013).

The Lancet HIV paper describes the latest results from extensive studies of LP. The embargo on the publication was lifted at 8:30am ET today, so there are a number of excellent online articles reporting in detail on the findings, including those by Simon Collins for HIV i-Base and Ben Ryan for POZ Magazine. Simon Collins was the first to ever report on LP, after noticing a reference made to the case by Ian Gabriel at a British HIV Association conference in October 2018. LP also released a statement which is quoted extensively in an article by Eagle Radio.

LP has now been off antiretroviral therapy (ART) for 2.5 years and the major take home message from the science is that no evidence of intact, replication-competent HIV could be found in multiple samples of blood, cerebrospinal fluid, semen, gut and lymph nodes. Rare examples of extremely low-level positive signals for HIV DNA fragments were detected in memory CD4 T cells and samples from an axillary lymph node, but this represented a minority of samples from multiple replicates. It was not possible to sequence any HIV genes from these positive samples. The researchers suggest the results could be explained by detection of fragmentary, defective HIV DNA or false positives. Similarly rare low-level positive readings for HIV DNA and RNA were reported in some samples from Timothy Brown back in 2012. Antibody responses to HIV are waning, as was also observed in Brown.  

The researchers collaborated with mathematical modeler Alison Hill to explore the probability that LP is cured of HIV. The modeling takes into account donor chimerism, which refers to the proportion of cells in LP that are from the stem cell donor (who was homozygous for the CCR5Δ32 mutation). The model's output indicated that if greater than 90% of the cells in LP are from the donor, then a lifelong HIV cure is almost certain. Measures of the peripheral blood showed that donor chimerism was approximately 99%, so even accounting for the possibility of lower levels in tissues, the paper concludes that a cure has probably been achieved. Nevertheless, viral load testing will continue twice a year for up to 60 months after ART was interrupted, then be switched to yearly for a further 60 months.

As articulated in an accompanying commentary by Jennifer Zerbato and Sharon Lewin, certainty remains elusive when it comes to defining HIV cures. The most important factor is time. Much as confidence in Timothy Brown’s HIV cure has grown the longer he has gone without HIV rebound, the same will be true for LP. But as Zerbato and Lewin note: “We will need more than a handful of patients cured of HIV to really understand the duration of follow-up needed and the likelihood of an unexpected late rebound in virus replication.”

In the poster session scheduled for 2:30-4:00pm ET at CROI today (for which the embargo has just lifted), Björn-Erik 0. Jensen provided the latest information on the Düsseldorf patient, who might represent a third individual cured of HIV after receipt of a stem cell transplant from a donor homozygous for the CCR5Δ32 mutation. Follow up is considerably shorter in this case, at just 15 months after ART interruption. Mirroring the findings in both LP and Timothy Brown, the researchers have detected traces of HIV DNA in some samples from lymph nodes and the gastrointestinal tract, but not found any evidence of replication-competent HIV. Antibody responses to HIV are declining.

The same poster session also featured a report by Gloria Heresi from the University of Texas Health Science Center, describing a child experiencing apparent ongoing HIV remission for more three years after an ART interruption. The case closely parallels that of the Mississippi baby, who appeared to have possibly been cured by very early initiation of ART after birth but eventually rebounded after an interruption in treatment that lasted a little over 27 months.

For reasons that are not explained, the mother was untreated at the time of the birth and had a viral load of 14,400 copies the day after delivery. ART regimens were initiated in the infant after 33 hours, but subsequently stopped by the mother at 13 months of age. Viral load has remained <20 copies/mL since that time and the HIV antibody test has been negative from 15 months of age onward (the child is now 4 years of age).

While the mechanisms at work are unknown and further analyses and follow up will be needed, the case may indicate that early restriction of the HIV reservoir by ART can lead to longer periods of HIV remission than was seen in the Mississippi baby. This could be encouraging news for the IMPAACT P1115 trial, which is testing whether early initiation of treatment in HIV-exposed newborns can subsequently facilitate HIV remission, at least for some participants.  

Conference Catch Up: HIV Cure Research

A number of conferences and workshops related to HIV cure research have taken place over the past several months, many of which can be viewed or learned about online. Links and some brief reports from four events are provided below.

Promising Approaches to HIV Remission and Cure

HIV cure research was the chosen topic for the Harvard University Center for AIDS Research (CFAR) annual symposium, held on October 23rd. The organizers have created a YouTube playlist featuring all presentations and panel discussions from the event.  

5th Conference on Cell & Gene Therapy for HIV Cure

The only conference that specifically focuses on cell and gene therapy in HIV cure research was launched in 2014 under the auspices of the defeatHIV Collaboratory at the Fred Hutchinson Cancer Research Center in Seattle. The meeting has quickly become established as the key annual get together for this area of the cure research field. The 5th conference took place from August 22-23 in Seattle; the agenda is available on the event website and videos of presentations are now being added to the defeatHIV YouTube channel (a playlist is available for day 1).

Fred Hutch News published two stories about the conference, the first highlighting the work of keynote speaker Dr. Robert Siliciano and the second covering presentations and a workshop focused on strategies to make gene therapies more affordable and globally accessible.

The latter workshop was co-organized by the well-known HIV researcher Mike McCune, who is now leading the HIV Frontiers program at Global Health Innovative Technology Solutions, Bill & Melinda Gates Foundation. McCune recently co-authored a commentary in the journal EBioMedicine outlining how an accessible gene therapy might theoretically contribute to achieving an HIV cure.

A significant step toward making the hope of accessible gene therapies a reality was announced by the Bill & Melinda Gates Foundation and the National Institutes of Health (NIH) on October 23rd. The two research behemoths have joined forces to launch an initiative that will invest at least $100 million over the next four years to develop affordable, gene-based cures for sickle cell disease (SCD) and HIV.

In tandem with the Cell & Gene Therapy conference, defeatHIV’s indefatigable Community Engagement Project Manager Michael Louella organized a public event at the Seattle Library co-hosted by DeAunte' Damper, the LGBTQ Chair of the Seattle King County NAACP. Discussants included the researcher Carl June, gene therapy trial participants Matt Sharp and Matt Chappell, and defeatHIV Community Advisory Board members Tranisha Arzah and Manuel Venegas. Video is available on the Seattle Channel and the defeatHIV YouTube channel.

Finding and Characterizing HIV Reservoirs

A second example of collaboration between the Bill & Melinda Gates Foundation and the NIH in the area of cure research was a workshop on finding and characterizing HIV reservoirs, held July 30-31 on the NIH campus. Thanks to the wonders of the NIH videocast system, the entire meeting can be viewed online (see day 1 and day 2).

Particularly recommended is a tour de force presentation by Robert Siliciano, one of the first researchers to identify the HIV reservoir. Siliciano highlighted the recent shift in understanding of how the HIV reservoir persists despite antiretroviral therapy (ART). Initially, there were suspicions that continuing low-level viral replication in tissues (sometimes referred to as “sanctuary sites”) was playing a role, but it has now become apparent that—in his words— “the vast majority of cells in the reservoir are not generated by direct infection but by proliferation of previously infected cells.”

Siliciano also discussed a new assay developed in his laboratory that attempts to simplify the detection of the replication-competent HIV reservoir. In a study published in Nature earlier this year (now available free in PMC), Siliciano’s group described their approach to assessing the intactness of HIV DNA proviruses, which they’ve named the intact proviral DNA assay (IPDA).

In the workshop presentation, Siliciano showed unpublished data from Gregory Laird indicating that the decay of the HIV reservoir in people on ART is the same (~44 months) when measured with the IPDA or the far more cumbersome and expensive quantitative virus outgrowth assay (QVOA). He noted, however, that the IPDA also revealed outliers around the average value – some study participants had precipitous declines in their HIV reservoir, while others showed increases (likely the result of proliferation of latently infected CD4 T cells).

IAS HIV and HBV Cure Forum/IAS 2019

In recent years, the International AIDS Society (IAS) has scheduled symposiums on HIV cure research immediately preceding their main annual conference (which alternates between the International AIDS Conference and the IAS Conference on HIV Science). The theme differs at each event, and in 2019 the focus was on parallels between the efforts to cure HIV and hepatitis B (HBV).

A detailed report from the meeting was published on October 22nd in the open access Journal of Virus Eradication. Oral and poster abstracts are also available from the same journal. Slide presentations are posted on the IAS website for the event.

Among the presentations:

Maria Pino described research in the SIV/macaque model suggesting that the approved multiple sclerosis treatment fingolimod (trade name Gilenya) can cause retention of cytotoxic T cells in lymphoid tissue and reduce the reservoir of virus DNA in T follicular helper cells (some of the work was published in PLoS Pathogens on October 18th). A subset of macaques administered fingolimod at the time of ART initiation showed evidence of a delayed and lower magnitude viral load rebound after an analytical treatment interruption.

There is considerable interest in the prospects for Gilead Sciences toll-like receptor 7 (TLR-7) agonist vesatolimod in HIV, due to encouraging results in macaques. Preliminary data from a phase I trial in people on ART were presented by Sharon Riddler from the University of Pittsburgh School of Medicine. The compound appeared safe and there was evidence of immune-stimulating activity at doses over 6mg. The ultimate aim is to study vesatolimod in combination with other interventions such as broadly neutralizing antibodies.

One question that the trial didn’t address is whether responses to vesatolimod might be different in women compared to men. A decade ago the research group of Marcus Altfeld reported evidence of sex differences in responsiveness to TLR7 agonists, and female sex was associated with greater induction of interferon-stimulated gene expression in a previous trial of vesatolimod as a treatment for hepatitis B.

Out of 48 participants in the dose-escalating HIV trial, only five were women, and three of the six dose groups included only men. It will be important for future studies to investigate whether sex influences the response to vesatolimod in people with HIV. An ongoing trial is evaluating vesatolimod in HIV controllers who have started ART, but demographic information on participants is not yet available.

Sharon Lewin from the Doherty Institute in Australia described a new effort that is underway to develop a “target product profile” (TPP) for an HIV cure with particular focus on global accessibility, and the formation of a related “HIV Cure Acceleration for Africa” (HCAAP) working group. These plans grew out of a summit hosted by the IAS in partnership with the Annenberg Trust at Sunnylands.

A presentation at the main IAS 2019 conference that drew attention was delivered by Xu Yu from Massachusetts General Hospital. Yu highlighted cases of extreme elite control of HIV that may represent clearance of all replication-competent viruses, focusing in particular on a long-term elite controller referred to as the “San Francisco patient.” Recently, an article in Leapsmag by Bob Roehr revealed the individual to be Loreen Willenberg, who is renowned among activists for her key role in promoting elite controller research via the Zephyr Foundation. Official IAS 2019 video of Yu’s presentation is not available, but a partial recording is posted to the defeatHIV Facebook page.

Links to cure-related IAS 2019 sessions are appended below.

Stem cell and genome editing for HIV cure (plenary session, presentation starts at 0:31:40)
Paula Cannon, University of Southern California, United States

New and old players in HIV replication

HIV transcription: The sound of silence

What is the cure, why do we need it and how do we get there?

Keep control: Elite and post-treatment controllers

Hide and seek: Reservoirs and strategies to target them

Research by and for whom? Community engagement in research

HIV remission and control trials

50 shades of reservoirs

Kill the enemy: CTL and NK cells

Paediatric HIV infection: It's never too early

Pathogenesis: And the band plays on

Mission remission: Challenge accepted

Selected Highlights from CROI 2019

The 2019 Conference on Retroviruses and Opportunistic Infections (CROI) took place in Seattle from March 3rd-7th. The major news on the cure research front was the possibility of two additional cases similar to Timothy Ray Brown, who for the past 12 years has been the only individual considered cured of HIV infection (TAG issued a statement offering our perspective). Other notable reports included the first results from a study using CRISPR/Cas9 to target latent SIV in macaques and a novel insight into the source of residual viral load in people on ART. Immediately preceding the conference, TAG joined with multiple other organizations to co-sponsor the annual pre-CROI community HIV cure research workshop; slides and video from the event are available online.

Stem Cell Transplant Recipients as Possible Cure Cases

Eleven years ago at CROI, a little-noticed poster by Gero Hütter and colleagues provided the first description of the case of Timothy Ray Brown (among the few people to draw attention to it at the time was activist Martin Delaney of Project Inform). As part of a series of heavy-duty treatments for acute myelogeous leukemia (AML), Brown received two stem cell transplants from a donor Hütter identified who was homozygous for the CCR5Δ32 mutation, meaning they lacked the functional CCR5 co-receptor used by most strains of HIV to infect target cells. At the time of the 2008 CROI poster presentation, Brown’s AML was in remission and he’d been off antiretroviral therapy (ART) for 285 days with no sign of HIV rebound.

Over the ensuing years, Brown has remained free of detectable HIV and there is broad consensus that he has been cured. However, multiple attempts to repeat the outcome by finding donors homozygous for the CCR5Δ32 mutation for additional people with HIV needing stem cell transplants for cancers have met with disappointing failure; the individuals have all died due to graft-versus-host disease (GVHD) or the underlying cancer, and in one case death was preceded by a rebound of HIV capable of using an alternate co-receptor, CXCR4. At least one researcher expressed concern that the CCR5Δ32 mutation might be negatively affecting the success of stem cell transplantation in some way.

Despite the setbacks, efforts to study people with HIV and cancers who receive stem cell transplants from donors homozygous for the CCR5Δ32 mutation have continued, and two headline-making presentations at CROI 2019 showed that the work has been worthwhile.

Garnering the most attention was Ravindra Gupta’s oral abstract describing a person with HIV in London who received a stem cell transplant from a CCR5Δ32 homozygote donor to treat Hodgkin’s Lymphoma that had not responded to standard therapies. Details on the case were provided in a Nature paper that was published online immediately after Gupta’s talk.

The individual was diagnosed with HIV in 2003, and ART was initiated due to a relatively low CD4 T cell count of 290 cells and viral load of 180,000 copies/ml. The diagnosis of stage 4B Hodgkin’s Lymphoma occurred in December 2012, with the cancer proving refractory to first-line chemotherapies and several salvage regimens (among them was the anti-CD30 monoclonal antibody Brentuximab, which has been reported to have potential activity against HIV-infected cells, but it seems unlikely that this played a part in the eventual outcome).

Ultimately the decision was made to undertake a stem cell transplant, and an international registry was searched to identify an appropriate donor. Fortuitously, the most closely matched stem cell donor was homozygous for the CCR5Δ32 mutation.

The transplantation process involved administration of an anti-CD52 antibody (alemtuzumab) to deplete T cells, a conditioning regimen—Lomustine, Cyclophosphamide, Ara-C and Etoposide (LACE)—and then infusion of donor stem cells. Treatments to prevent GVHD were a short course of methotrexate and cyclosporine until 180 days post-transplant. ART was maintained throughout.

There were some complications: both Epstein-Barr virus and cytomegalovirus reactivated around three months after the transplant, necessitating treatment with Rituximab and ganciclovir respectively. Mild (grade 1) GVHD transiently manifested in the gut, but resolved without any intervention.

Tests showed that donor cells homozygous for the CCR5Δ32 mutation had fully taken over by day 30 post-transplant, replacing the individual’s original cells (which had wild type CCR5 genes and expressed the normal functional co-receptor). Complete remission of the Hodgkin’s Lymphoma was confirmed at days 120 and 365.

The researchers discussed the possibility of HIV remission with the individual prior to the procedures, after testing had indicated that he harbored CCR5-tropic virus. Ethical approval was obtained from the UK National Health Service for a potential eventual interruption of ART, with criteria established ahead of time:

“if viral load was consistently <50 copies/ml on treatment with ‘target not detected’ for at least six months on the two most recent consecutive visits ART would be withdrawn and thereafter viral load would be monitored weekly for the first three months, monthly for a further nine months if undetectable at all time points and three monthly between years one and four.”

ART was interrupted in September 2017, and the individual has been off HIV treatment for 18 months with no evidence of viral load rebound. Multiple blood tests for the presence of HIV have been persistently negative, with the exception of a single detection of a low-level signal in a digital droplet PCR assay for HIV DNA (among eight replicates, the remaining seven of which were negative). The researchers have not yet studied any tissues. Antibody responses to HIV are waning, echoing results in Timothy Ray Brown.

Gupta was cautious, using the term HIV remission rather than cure due to the relatively short time since ART interruption. He suggested that perhaps when follow up is beyond two years, the terminology will be revised. The individual is included in the larger amfAR-funded IciStem research consortium, which focuses on evaluating people with HIV who receive stem cell transplants for cancers.

A second participant in the IciStem consortium was the subject of a late-breaker poster presentation by Björn-Erik O. Jensen from the research group of Guido Kobbe in Dusseldorf. Kobbe and colleagues first described the case at CROI 2016, at which time he was on ART and being followed after receiving a stem cell transplant from a CCR5Δ32 homozygote donor to treat relapsing AML. HIV was undetectable by multiple measures. At CROI 2019 it was revealed that, after ethical approval, ART was interrupted in November 2018. So far there has been no HIV rebound.

IciStem are following two additional individuals with HIV who’ve received stem cell transplants from CCR5Δ32 homozygote donors to treat cancers, but they remain on ART at this time (Monique Nijhuis described the current status of IciStem in a presentation at the pre-CROI community HIV cure research workshop).

Inevitably, the possibility that Timothy Ray Brown may finally have some company inspired a deluge of media coverage. The London case had been mentioned very briefly by Ian Gabriel at a BHIVA meeting last fall, prompting a short article by Simon Collins at HIV i-Base, so there was some awareness that further news would be forthcoming at CROI. The Nature paper was also circulated to media under embargo prior to the conference. Regrettably, The Hindu broke the embargo the day before Gupta’s presentation (whether accidentally or deliberately is unclear), leading Nature to also lift it for other media, so the coverage—including a detailed New York Times article by Apoorva Mandivilli—began appearing on the evening of Monday, March 4th.

There has been debate regarding the implications of the new cases. Most clear is that there is robust justification for continued efforts to identify CCR5Δ32 homozygote donors for people with HIV who need stem cell transplants to treat cancers. Whether lessons can be learned to apply to the search for more broadly applicable curative strategies is less certain; there are differences between the treatments given to the three individuals that may be help untangle contributing factors (see the excellent summary table in the HIV i-Base article by Simon Collins).

The common thread of receiving cells lacking a functional CCR5 receptor is viewed as supporting gene therapy research aiming to ablate CCR5 expression. A research group in China is currently studying whether the CRISPR/Cas9 gene editing tool can be used to disable the CCR5 gene in stem cells being transplanted into people with HIV and cancers—if successful, this might represent a strategy that would circumvent the need to find matched CCR5Δ32 homozygote donors.

SB-728-T

Outside of the setting of stem cell transplants for cancers, the leading approach to knocking out CCR5 from CD4 T cells has been Sangamo Therapeutics SB-728-T. In clinical trials, CD4 T cells are extracted from individuals with HIV, edited at the CCR5 gene using zinc finger nuclease technology, and then expanded and reinfused. The company was hoping to achieve control of HIV viral load after ART interruption, but so far it hasn’t proven possible to modify sufficient numbers of CD4 T cells. Further commercial development for HIV has been abandoned, but some investigator-initiated studies continue.

Pablo Tebas presented new results from a trial of SB-728-T that broadly conformed to previous research. A total of 14 individuals on ART received a single infusion of modified CD4 T cells, either with or without a preceding dose of cyclophosphamide (intended to deplete existing CD4 T cells and make more room for modified cells). In a slight wrinkle, the delivery of the zinc finger nucleases to the cells was achieved using messenger RNA instead of the adenovirus vector employed in prior studies; the proportion of CD4 T cells successfully edited at the CCR5 gene by the two approaches was similar. The protocol included an ART interruption, and Tebas noted that there was a slight delay in viral load rebound compared to historical controls, but no cases of prolonged containment of HIV.

As observed in prior trials, participants heterozygous for the CCR5Δ32 mutation appeared to respond best. Because these individuals already have one disabled CCR5 gene, the zinc finger nucleases only have to edit one of the two alleles present in each CD4 T cell in order to prevent expression of a functional CCR5 co-receptor. Tebas concluded that more efficient CCR5 modification could potentially lead to more stringent control of HIV off ART, but it appears unlikely that such an outcome can be achieved with SB-728-T.

One variation on the theme of trying to genetically protect CD4 T cells from HIV infection involves focusing on modifying cells capable of recognizing and responding to the virus (HIV-specific CD4 T cells). A seminal study by Danny Douek many years ago showed that the virus preferentially infects HIV-specific CD4 T cells, which become dysfunctional and unable to perform their task of coordinating an effective immune response to the virus. The company American Gene Technologies is pursuing a strategy involving the genetic modification of HIV-specific CD4 T cells, with trials planned soon, and results should shed light on whether this is a better approach than attempting to modify CD4 T cells in bulk.

Taking a Bite Out of the Latent Reservoir with CRISPR/Cas9

One of the more intuitively appealing ideas in cure research involves attempting to cut the integrated HIV genome out of the DNA of latently infected cells. In this scenario, gene-editing strategies are targeted against the virus itself rather than a host gene like CCR5. The goal is to perform a sort of genetic surgery, excising HIV genes from infected cells without damaging the cell’s genome.

The gene-editing tool CRISPR/Cas9 has emerged as the leading candidate in this research, and some very preliminary results in mouse models have suggested it may have potential. The laboratory of Kamel Khalili at Temple University has pioneered these studies, in tandem with Excision Biotherapeutics, a company Khalili founded to move the approach into the clinic.

At CROI 2019, Tricia Burdo from Temple University debuted the results of a study exploring whether CRISPR/Cas9 could excise latent SIV in the SIV/macaque model of HIV infection. The cutting machinery of CRISPR/Cas9 is aimed at a target by the inclusion of molecules called guide RNAs (gRNAs), and in this case the researchers created gRNAs capable of recognizing three relatively conserved sites in the SIV genome (two in the long terminal repeats present at either end of the genome, and one in the gag gene). Burdo noted that the targeting of multiple sites is necessary for both attempting to excise large chunks of the viral genome and avoiding the potential development of resistance (somewhat similar to the rationale for combination ART). The technique produces “very little to no off-target effects,” according to Burdo.

The SIV-targeted CRISPR/Cas9 was delivered using an adeno-associated virus serotype nine (AAV9) vector. AAVs are a popular gene therapy delivery vehicle that can carry their payload into a broad range of both dividing and non-dividing cells without apparent safety issues (two AAV-delivered gene therapies have been approved by regulatory agencies).

The study included three macaques, all infected with SIVmac239 and placed on a suppressive ART regimen. In initial experiments, peripheral blood mononuclear cells (PBMC) sampled from the animals were transduced with the AAV9-CRISPR construct, producing evidence of excision of SIV genes between targeted sites.

AAV9-CRISPR was then infused into two of the macaques at a dose of 10¹³(ten trillion) copies per kilogram, a lengthy process involving the delivery of 100ml at a rate of 1ml per minute. Three weeks after the infusion, animals were euthanized and necropsy studies conducted. The third animal served as a control and was also euthanized to facilitate comparisons with the AAV9-CRISPR recipients.

Burdo reported that prior to euthanasia, fragments of the SIV genome that had been cut at targeted sites—referred to as excision products—could be detected in PBMC from the treated animals, as was observed when PMBC were exposed to AAV9-CRISPR in a laboratory dish. Cas9 DNA could also be detected in cells, indicating uptake of the gene-editing tool.

Necropsy studies included a preliminary evaluation of SIV outgrowth from PBMC samples. The PBMC were combined with SIV-susceptible CEM cells and then SIV p27 Gag protein levels were measured over time. SIV replication could be detected in samples from the control but not those from the macaques that received AAV9-CRISPR. However, Burdo emphasized that this assessment did not involve activating the PBMC to induce virus production (as is the case with the standard virus outgrowth assays used in human studies)—those experiments are pending.

Analyses of Cas9 DNA demonstrated widespread distribution in the tissues of the two treated macaques, ranging from around 1-10 thousand copies per million cells in the brain to over 10 million copies per million cells in the spleen and liver (presumably reflecting the presence of multiple copies in some cells). Burdo also showed evidence of SIV excision products in spleen, lung and several lymph nodes (including inguinal, submandibular, bronchial and colonic) from the animals.

The data appear very encouraging, but do not provide information on the magnitude of effect on the latent SIV reservoir (i.e. exactly how much latent SIV was successfully excised or disabled). In response to a question, Burdo reported that future plans include conducting analytical treatment interruptions in macaques treated with AAV9-CRISPR to assess whether viral load rebound is limited or prevented by the intervention.

An issue not covered in the presentation is the potential for the induction of immune responses against Cas9, which has been observed in mouse studies. Because Cas9 is derived from bacteria, it is treated as foreign by the immune system, and AAV vectors can have an adjuvant effect that seems to promote immune responses against AAV-delivered proteins (this has occurred in studies using AAV to deliver anti-HIV broadly neutralizing antibodies). Pre-existing anti-Cas9 immune responses have also been detected in humans due to infection with Staphylococcus aureus and Streptococcus pyogenes.

In a graph displaying longitudinal viral load measurements in the macaques (on slide #4 in the webcast), it looks as if administration of AAV9-CRISPR may have been temporally associated with a transient increase in SIV viral load—which could be suggestive of immune activation—although there were also viral load fluctuations in other animals. Gaining an understanding of whether AAV9-CRISPR delivery can activate the immune system and lead to the generation (or activation) of anti-Cas9 immune responses will be important prior to initiating human trials.

A theoretical concern that researchers have raised about strategies aiming to excise latent HIV relates to what might occur in cells that have more than one integrated copy of the HIV genome (this phenomenon is thought to be uncommon, but has been reported). In this situation, it’s possible that rather than just removing HIV genes, an excision approach might make cuts in each of the separate integrated virus genomes and thereby remove all of the cell’s DNA located between the different HIV integration sites. Damaging the genome of a cell in this way could potentially have untoward effects.

Overall, Burdo’s results offer significant encouragement for efforts to translate the approach into human clinical trials. Kamel Khalili and colleagues are now working toward that goal in collaboration with Jeffrey Jacobson, a highly experienced clinical HIV researcher who joined Temple University in 2016.

Attack of the Repliclones

The past few years have seen an increasing focus on the role of CD4 T cell proliferation in sustaining the latent HIV reservoir. Evidence has accumulated demonstrating that HIV proviruses can be faithfully copied into the daughter cells of latently infected CD4 T cells when they proliferate—the phenomenon can be discerned by the detection of genetically matching copies of the HIV provirus integrated into the exact same place in the genome of multiple CD4 T cells (the progeny of proliferating CD4 T cells are known as clones). Mathematical modeling suggests CD4 T cell proliferation may be the primary mechanism that allows the latent HIV reservoir to persist, and decline only very slowly over time.

Elias Halvas from the University of Pittsburgh showed at CROI 2019 that CD4 T cell clones containing integrated, intact HIV DNA are a source of low-level HIV viral load that can be detected in some individuals on ART. Essentially, some of these cells can spit out sufficient amounts of HIV RNA to be detectable, even though the virus is not actually replicating (i.e. going on to infect other cells—this is prevented by ART).

Halvas’s study involved 10 people who had been referred due to persistent low-level viral load despite ART (HIV RNA >20 copies/ml occurring for at least 6 months). The average time on treatment was 10 years, and viral load ranged from 40 to 356 copies/ml, with a median of 97.5 copies/ml.

One individual displayed evidence of ongoing HIV evolution and the development of drug resistance mutations and was considered a case of ART regimen failure, excluding them from further analysis.

Samples from the remaining nine showed the presence of genetically identical HIV RNA at multiple timepoints, and there was no sign of viral evolution or resistance mutations against current ART. The source of the HIV RNA was identified as CD4 T cell clones containing integrated, replication-competent HIV DNA (Halvas has christened them “repliclones”). In four cases the genetic sequence of the HIV RNA could be matched to viruses detected in the quantitative virus outgrowth assay (qVOA).

Halvas concluded that the possibility of production of HIV RNA by infected CD4 T cell clones needs to be borne in mind by clinicians caring for people with HIV, who might otherwise suspect that persistently detectable low-level viral load indicated non-adherence or treatment failure.

As to the implications for HIV cure research, Halvas suggested that repliclones may contribute to rapid viral load rebound after ART interruption (when the HIV RNA they produce is able to start infecting other cells), and he stressed that they will need to be targeted for elimination or suppression. The mechanisms prompting HIV RNA production by the cells are unclear, and need to be elucidated.

Notably, the data indicate that HIV latency can be more dynamic than was initially appreciated. It’s now clear that in some CD4 T cell clones containing integrated HIV DNA, the virus is not permanently latent, because there are times when production of HIV RNA is detectable.  

In an article by Jon Cohen for Science that covers the study, John Mellors points out that the data raise questions about the “kick & kill” strategy in HIV cure research. The rationale for providing a latency-reversing “kick” is that most latently infected cells do not produce HIV RNA and therefore remain invisible to the immune system. Halvas’s results demonstrate that at least some latently infected cells do intermittently generate HIV RNA, and don’t die off as a result.

One salutary possibility is that researchers developing “kill” strategies may be able to study their efficacy in individuals like those described by Havlas, who already have low-level viral load on ART without the need for administration of any latency-reversing candidate. In theory, an effective “kill” approach should be able to reduce the amount of HIV RNA detected in such cases.

Targeting the Latent HIV Reservoir with Anti-Proliferative Therapy

The recognition that the HIV reservoir is at least partly sustained by the proliferation of CD4 T cells is rekindling interest in testing the effects of anti-proliferative therapies in the context of cure research.

At the pre-CROI community HIV cure research workshop, Joshua Schiffer from the Fred Hutchinson Cancer Research Center described a small (four person) pilot trial of the anti-proliferativedrug mycophenolate mofetil (MMF) being conducted by his research group with funding from amfAR. The rationale is based on the results of mathematical modeling work suggesting that inhibiting CD4 T cell proliferation in people on ART should significantly accelerate the decay of the HIV reservoir. Results are anticipated to be available for CROI 2020. Links to the video of Joshua Schiffer’s talk are on the workshop web page, along with the slides.

Timothy Heinrich from UCSF presented results of an AIDS Clinical Trials Group (ACTG) trial of sirolimus (a drug with potent anti-proliferative activity, also known as rapamycin) in people on suppressive ART. In the 16 participants who completed 20 weeks of dosing, there was a slight but statistically significant 0.16 logs reduction in HIV DNA levels. CD4 T cell expression of the proliferation marker Ki67 was also significantly reduced.

Heinrich noted that rates of sirolimus discontinuation were high, and there were also transient increases in the inflammatory biomarkers IL-6 and sCD14 and the coagulation biomarker D-Dimer. The results appear consistent with the notion that inhibiting CD4 T cell proliferation can affect HIV reservoir size, but additional research is needed to confirm that this was the primary mechanism for the HIV DNA reduction. 

One of the pioneers in this area of HIV cure research is Andrea Savarino, who reported many years ago that the gold-based anti-proliferative drug auranofin reduced the SIV reservoir in ART-treated macaques.

Since that time, Savarino and colleagues have collaborated with investigators in Brazil to conduct a small pilot trial involving auranofin (which is a licensed treatment for rheumatoid arthritis). The latest results were presented in a poster at CROI 2019. The study design is complicated, involving multiple interventions administered to six groups, each with just five participants. The researchers report that auranofin combined with several other agents led to a reduction in HIV DNA, but the contribution of the anti-proliferative effect is unclear. Administration of the drug was not associated with any serious side effects. Given the renewed interest in targeting CD4 T cell proliferation and the uncertain safety profile of some anti-proliferative drugs, additional studies of auranofin may be justified. 

Additional Webcasts and Links

The CROI website offers comprehensive webcasting including every presentation. The pre-conference workshops on March 4th are a source of several excellent overview talks, such as Paula Cannon’s on gene editing techniques in HIV research. Also recommended is Irini Sereti’s insightful plenary on HIV and inflammation.

Multiple outlets provided high quality coverage from CROI 2019, including:

AIDSMap
HIV i-Base
NATAP
POZ
The Body

2018 NIAID Strategies for an HIV Cure Meeting

The biannual National Institute of Allergy and Infectious Diseases (NIAID) Strategies for an HIV Cure Meeting kicks off tomorrow, October 10, at 8:30am US Eastern Time and continues until Friday at 12:30pm. The agenda is available online. For those unable to attend in person the entire event is being made available for viewing via the National Institutes of Health videocast website (see the upcoming events link).

Post-AIDS 2018 Updates on HIV Cure Research

In the aftermath of the 22nd International AIDS Conference (AIDS 2018), which took place in Amsterdam in July, there has been some reflecting on the challenges facing the HIV cure research field. The presentations that garnered the most news coverage described disappointing study results, but there were also nuggets of novelty and encouragement to be found amidst the sea of data on offer (see previous post for links to relevant conference sessions, many of which now have video and/or slides available).

The RIVER Trial

The most widely reported findings came from a clinical trial in the UK known as RIVER (Research In Viral Eradication of HIV Reservoirs). Participants with primary HIV infection were randomized to receive a standard antiretroviral therapy (ART) combination plus the integrase inhibitor raltegravir or ART plus raltegravir along with a therapeutic HIV vaccine regimen and a short course of the HDAC inhibitor vorinostat (a candidate HIV latency-reversing agent). The primary purpose was to evaluate whether the vorinostat and vaccine combination—a version of the proposed “kick & kill” approach to depleting the HIV reservoir—had a significant effect on HIV reservoir measures compared to ART.

As described in detail in multiple online reports (e.g. see i-Base, AIDSMap, and the Imperial College website), the size of the HIV reservoir—as assessed by both total HIV DNA and the viral outgrowth assay—remained equivalent between the two arms. Presenter Sarah Fidler pointed out some possible caveats, such as the relatively short follow up time, but the data appear to rule out any significant effect by this particular kick & kill combination.

The researchers cited several potential explanations: the latency-reversing activity of vorinostat may be suboptimal, and there is uncertainty as to whether the HIV-specific T cell responses that were successfully induced by the vaccines were targeting parts of the virus most likely to be displayed by infected cells after latency reversal. As is emphasized in much of the coverage, the study itself should not be considered a failure because it provided a clear answer to the question it was designed to address. The interventions were also found to be safe and no participants withdrew.

The results echo a theme that has been sounding recently in HIV cure research: randomized controlled trials are required to rigorously evaluate the potential of candidate interventions, and positive results from single-arm exploratory trials (which tend to compare results to baseline values or historical controls) need to be interpreted with caution.

Studies published over the past year that have reached a similar conclusion include randomized controlled evaluations of a therapeutic vaccine combination and single doses of the candidate latency-reversing agent romidepsin.

Vedolizumab

The second piece of unwelcome news related to vedolizumab, an antibody that targets the α₄β₇ integrin, a protein involved in CD4 T cell trafficking to the gut that may also facilitate HIV entry into target cells. In 2016, an experiment in SIV-infected macaques generated excitement when administration of a version of vedolizumab adapted for macaques (see comment by Robert Reinhard below) was associated with control of viral load after ART interruption. Human trials were initiated relatively quickly because vedolizumab is already FDA approved as treatment for ulcerative colitis and Crohn's disease.

During a talk at the conference on HIV remission, Anthony Fauci from the National Institute of Allergy and Infectious Diseases (NIAID) provided a glimpse at the data from the first of these trials, and sadly the results did not mirror the published macaque study. While it appeared that one or two participants displayed some evidence of viral load containment after an analytical treatment interruption (ATI), the majority did not.

Fauci suggested the variations in viral load levels were similar to those his group has observed in placebo recipients in prior trials, and were not indicative of any effect from vedolizumab. At least two other clinical trials involving the antibody are ongoing, so additional results will be forthcoming.

In a separate presentation, Michele DiMascio put another dent in the optimism that had surrounded vedolizumab by reporting that an attempt to repeat the original results obtained in SIV-infected macaques had failed. This time, there was no evidence of antibody-induced SIV control. The reasons for the divergent outcomes are unclear, but may relate to the type of SIV used in the experiments, which has a mutation in the nef gene (update 3/21/19: the journal Science has now published an "editorial expression of concern" about the original study).

Reservoir Targeting

A number of presentations described novel approaches for targeting the HIV reservoir, highlighting the amount of work that is underway to try and improve upon the interventions tested to date.  

Isa Munoz-Arias and colleagues from UCSF and Merck reported that a number of FDA-approved chemotherapeutic drugs have HIV latency-reversing activity in laboratory studies. In some cases the magnitude of the effect was demonstrated to be greater than the combination of bryostatin and romidepsin, which has previously been shown to be among the most potent latency-reversing strategies in vitro. The effects were not associated with significant T cell activation or CD4 T cell death (although it’s important to note that this does not mean the drugs are without side effects - those are described on their labels).

A total of 12 FDA-approved chemotherapies were found to reverse HIV latency via a variety of novel pathways, suggesting new avenues for exploration beyond the current candidates, which primarily comprise HDAC inhibitors. The details of the presentation can be found on Jules Levin’s NATAP website (which often does more to make information public than conferences themselves), and it was also covered by Simon Collins for i-Base.

The research group of Wen Kang debuted data from a small, uncontrolled pilot study of the HDAC inhibitor chidamide, which is approved in China as a cancer therapy. Kang described evidence that the drug had stimulated production of HIV RNA in seven individuals on ART, and may have slightly reduced HIV DNA levels. However in the Q&A after the talk Sharon Lewin noted that the various possible markers of activity that were analyzed did not appear to necessarily correlate with each other. A larger randomized controlled trial that should provide more definitive results is now ongoing.

Tim Henrich from UCSF followed up on work published earlier this year in PLoS Pathogens identifying CD30—a cell surface molecule known for its association with lymphoma—as preferentially expressed on HIV-infected CD4 T cells.

In the paper, the researchers describe an individual with HIV who exhibited undetectable viral RNA and DNA levels after receiving therapy for lymphoma including brentuximab vedotin, an anti-CD30 antibody-drug conjugate. Unfortunately the individual died after cancer recurrence so no further investigation was possible.

Henrich's conference abstract reports the identification of a second person with HIV who received brentuximab vedotin as part of treatment for lymphoma (now in remission). Three weeks after administration of the first dose, HIV RNA was reduced to undetectable from a previous level of 7,359 copies per million CD4 T cells (a greater than 3 log reduction). HIV DNA levels fell by 42%. The individual is now being followed longitudinally.

This research opens up the possibility of targeting CD30 as a means to deplete the HIV reservoir, and in addition to brentuximab vedotin there are also CD30-specific chimeric antigen receptor (CAR) T cells in development that are already being studied in clinical trials for cancer.

An interesting presentation by Sarah Joseph from the University of North Carolina at Chapel Hill outlined an effort to establish when viruses enter the latent reservoir. Using complex phylogenetic analyses (see the abstract for an example), Joseph uncovered evidence that in most individuals studied, the majority (~72%) of the replication-competent latent HIV reservoir was most closely related to viruses circulating in the year prior to ART initiation. In contrast, only 5% was derived from virus replicating during the first year of infection.

A paper published in the journal eLife in 2016, involving ten participants, reported similar results, although Joseph also pointed out that a much smaller study presented at the conference by Zabrina Brumme (subsequently published in PNAS) reached different conclusions, finding more diverse dates of establishment of the reservoir.

Joseph’s data suggests that latently infected cells tend to be shorter-lived during untreated infection, with ART initiation triggering the formation of the bulk of the long-lived HIV reservoir. The implication for therapeutic strategies targeting the reservoir is that there might be a window of opportunity to intervene at the time ART is started (currently, almost all clinical trials involve testing candidate therapies in individuals after ART has suppressed viral load). This idea could potentially be explored in the SIV/macaque model.

HIV Control Off ART

Participants in the VISCONTI cohort represent the best known and most widely cited examples of post-treatment control of HIV replication. In 2013, when Asier Sáez-Cirión and colleagues published a detailed report in PLoS Pathogens, the cohort comprised 14 individuals. Updates have been fragmented since that time, occurring at various conferences, and as yet there have been no follow up publications as thorough as the original paper (at least that I’m aware of - for the sake of disclosure I should note that I chided the investigators about this situation in a public comment to the PLoS Pathogens article in 2017).

At AIDS 2018, Laurent Hocqueloux and colleagues presented a poster on factors associated with loss of post-treatment controller status that included an update on the VISCONTI cohort. The study also offered results from analyses of inflammatory biomarkers, which I’ve not seen described previously.

A total of 24 post-treatment controllers have now been added to the VISCONTI cohort; all started ART during primary infection and then interrupted after a median of 3.5 years of treatment. During subsequent follow up (current median of 12 years), five (21%) have restarted ART, four due to increasing viral load and one as a result of a head and neck cancer diagnosis.

These five participants were among seven who experienced one or more viral load measurements above 400 copies/ml during monitoring; none of the 17 who remained below this viral load level restarted ART (a highly statistically significant difference). The fact that the individual who developed cancer was in the former group, despite not reinitiating ART based on viral load criteria, may raise concern that prior exposure to detectable HIV viremia was a risk factor for cancer development. Whether remaining on ART would have been associated with lower risk is an unanswerable question. This conundrum illustrates that firm conclusions about the clinical benefits of post-treatment control compared to continuous ART cannot be drawn until post-treatment control can be induced in sufficient numbers of people to allow a randomized comparison.

Overall, CD4 counts and CD4:CD8 ratios have remained stable in the cohort with medians not significantly different between the time of ART interruption and last follow up. Individual plots are not shown in the poster, however, so it’s unclear if declines occurred in participants who experienced viral load increases.

Encouragingly, the majority of VISCONTI cohort members have maintained viral loads below 50 copies/ml, and levels of three inflammatory biomarkers—IP-10, sCD163 and sCD14—were not significantly different between these post-treatment controllers and healthy HIV-negative individuals (see figure 6 in the poster).

In a separate oral presentation, Asier Sáez-Cirión showed evidence that certain immune response genes are associated with post-treatment control in the VISCONTI cohort, and may be mediating their effects—at least partly—through superior natural killer (NK) cell activity against HIV (unfortunately neither slides or video of this presentation are available on the conference website).

Lisa Chakrabarti described an investigation of potential mechanisms of HIV control in a different population: elite controllers participating in the ANRS CODEX cohort. The researchers focused on HIV Gag-specific CD4 T cell responses, and found that CCR5 expression was lower among elite controllers compared to a control group of people with HIV on ART. 

The lower CCR5 expression by Gag-specific CD4 T cells was associated with reduced susceptibility to HIV infection, suggesting this may contribute to elite controller status. The results may offer support to efforts to protect virus-specific CD4 T cells from HIV infection using gene therapies that ablate CCR5 expression (or otherwise attempt to protect the cells from HIV entry), an approach being pursued by researchers at the defeatHIV collaboratory.

Analytical Treatment Interruptions (ATIs)

A controversial component of research working toward achieving post-treatment control of HIV is the use of ATIs. A systematic review of past studies involving ART interruptions could help shed light on the safest approaches to conducting ATIs in clinical trials, and Jillian Lau and colleagues from Alfred Hospital and Monash University in Melbourne, Australia delivered just such a review as a poster presentation at the conference. Their work is now in press at a journal and will hopefully be published soon.

Online Post-Conference Coverage

As is always the case, an array of excellent reporting has become available online since the conference. See below for a selection; please leave a comment if you know of coverage I’ve missed that should be included.

AIDS 2018 HIV Cure Research Highlights - Karine Dubé and Jeff Berry, Positively Aware

The Road Ahead for HIV Cure Research - Benjamin Ryan, POZ Magazine, September 6, 2018

Cure Updates from AIDS 2018 - hivcure.com.au/Doherty Institute

AIDSMap

i-Base

NATAP

HIV Cure-Related Research at AIDS 2018

Workshops, sessions and presentations related to HIV cure research at the upcoming AIDS 2018 conference in Amsterdam. 

HIV Cure Research with the Community Workshop 
Pre-Conference Meeting
Room E105–108, RAI, Amsterdam, Netherlands
Saturday July 21, 2018, 9:00-18:00

Strategies for diagnosing and managing acute HIV infection in the context of PrEP and immediate ART
Code: MOSA52
Session Type: Non-Commercial Satellite
Venue: Hall 11B
Monday July 23, 17:00 - 19:00

17:20 MOSA5203 
Acute HIV infection and HIV cure
Thumbi Ndung’u, Africa Health Research Institute, University of KwaZulu-Natal, South Africa 

Biomedical research innovations in the prevention, remission and cure of HIV/AIDS
Code: MOSA48
Session Type: Major Industry Sponsor Satellite
Venue: Elicium 2
Monday July 23, 17:00 - 19:00

17:05 MOSA4802
30 years of progress in the field of HIV/AIDS
Anthony Fauci, National Institutes of Health (NIH), United States 

18:05 MOSA4802
Passive immunization/bNAbs monoclonals both for prevention and treatment
Penny Moore, University of the Witwatersrand / National Institute for Communicable Diseases, South Africa 

18:25 MOSA4802
Remission and cure efforts
Javier Martinez-Picado, AIDS Research Institute irsiCaixa, Spain 

Besieging the reservoir and kicking it where it hurts
Code: TUPDA01
Session Type: Oral Poster Discussion Session Track A – Basic and translational research
Venue: G104-105
Tuesday July 24, 13:00 - 14:00

13:00 TUPDA0101 
Association between immunogenetic factors and post-treatment control of HIV-1 infection. ANRS VISCONTI and PRIMO studies
Asier Saéz-Cirion, Insitut Pasteur, France

13:05 TUPDA0102 
HCV treatment with direct-acting antivirals (DAAs) in HIV/HCV coinfected subjects affects the dynamics of the HIV-1 reservoir 
Natalia Laufer, INBIRS Institute (UBA-CONICET), Argentina 

13:10 TUPDA0103
IL-10 contributes to, and is a biomarker for, viral persistence in ART-treated, SIV-infected rhesus macaques 
Mirko Paiardini, Emory University, United States

13:15 TUPDA0104
Follicular CD8+ T-cells in gut-associated lymphoid tissue are associated with lower HIV-1 reservoir in the terminal ileum after ART initiated during primary HIV infection 
John Patrick Thornhill, Imperial College London, United Kingdom

13:20 TUPDA0105
HIV-1 reservoir diversity and genetic compartmentalization in blood and testis
Rosalie Ponte, The Research Institute of the McGill University Health Centre, Canada

13:25 TUPDA0106LB
Ixazomib reduces HIV-1 reservoir size in a Casp8p41-dependent manner
Nathan Cummins, Mayo Clinic, United States
 
Strategies for cure: Pitfalls, possibilities and promise
Code: TUAA02
Session Type: Oral Abstract Session Track A – Basic and translational research
Venue: E102
Tuesday July 24, 16:30 - 18:00

16:30 TUAA0201
Therapeutic Vaccines for Cure 
Steven Deeks, University of California, United States

16:45 TUAA0202LB
A randomised controlled trial comparing the impact of antiretroviral therapy (ART) with a 'Kick-and-Kill' approach to ART alone on HIV reservoirs in individuals with primary HIV infection (PHI); RIVER trial
Sarah Fidler, Imperial College London, United Kingdom

17:00 TUAA0203
Dominant HIV DNA populations present in different T-cell subsets before stem cell transplantation persist in tissues early after transplantation with CCR5Δ32 stem cells 
Annemarie Wensing, University Medical Center Utrecht, Netherlands

17:15 TUAA0204
Rapid rebound of a highly replication competent preexisting CXCR4-tropic HIV variant after allogeneic stem cell transplantation with CCR5Δ32 stem cells 
Monique Nijhuis, University Medical Center Utrecht, Netherlands

17:30 TUAA0205
Modular gene therapy vectors for gene therapy cure in resting immune cells 
Andrew Wong, The University Of New South Wales Sydney, Australia

17:45 TUAA0206LB
Evaluation of an antibody to Alpha4Beta7 in the control of SIV infection
Michele Di Mascio, National Institute of Allergy and Infectious Diseases, United States

Building bridges from scientific innovation to implementation 
Code: WEPL01 
Plenary Session 
Venue: Hall 12 
Wednesday July 25, 08:45 - 10:30 

08:55 WEPL0105
The newest science in the search for a cure and vaccine 
Brad Jones, Weill Cornell Medicine and The George Washington University, United States

Poking, prodding and purging the final reservoir frontier
Code: WEAA01
Session Type: Oral Abstract Session Track A – Basic and translational research
Venue: G104-105
Wednesday July 25, 11:00 - 12:30

11:00 WEAA0101
Chidamide reactivates and diminishes latent HIV-1 DNA in patients on suppressive antiretroviral therapy 
Wen Kang, Tangdu Hospital affiliated to The Fourth Military Medical University, China

11:15 WEAA0102
The antiretroviral CCR5-inhibitor maraviroc effectively reverses HIV latency by phosphorylation of Nf-κB 
Jori Symons, The Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Australia

11:30 WEAA0103
Activation of latent HIV and SIV RNA transcription in vitro and in vivo in ART suppressed SIV-infected rhesus macaques by the Ingenol-based protein kinase C agonist, GSK445A 
Afam Okoye, Oregon Health and Science University, United States

11:45 WEAA0104
The RNA-binding proteins, SRP14 and HMGB3 play a crucial role in controlling HIV replication and latency 
Georges Khoury, Peter Doherty Institute, Australia

12:00 WEAA0105
Using the PPARg antagonism to block/lock HIV reactivation in Th17 cells 
Petronela Ancuta, Universite de Montreal and CHUM Research Centre, Canada

12:15 WEAA0108LB
The majority of the replication-competent virus in the latent reservoir originates from viruses circulating near the time of ART initiation
Sarah B. Joseph, University of North Carolina at Chapel Hill, United States

Durable control of HIV infections in the absence of antiretroviral therapy: Opportunities and obstacles and Jonathan Mann Memorial Lecture: Data to drive equity
Code: WESS01
Session Type: Special Session
Venue: Hall 12
Wednesday 25 July, 13:00 - 14:00

13:05 WESS0102
Durable control of HIV infection in the absence of antiretroviral therapy: Opportunities and obstacles
Anthony Fauci, National Institutes of Health (NIH), United States

Acute infection and viral reservoir
Code: WEPDB01
Session Type: Oral Poster Discussion Session Track B – Clinical research
Venue: E102
Wednesday July 25, 13:00 - 14:00

13:00 WEPDB0101
Validation of Alere TM q HIV-1/2 detect for detection of acute HIV infection at Anonymous Clinic, The Thai Red Cross AIDS Research Centre 
Irin Srila-Or, The Thai Red Cross AIDS Research Centre, Thailand

13:05 WEPDB0102
Favorable clinical phenotype reached in less than half of people treated in acute HIV infection 
Jintanat Ananworanich, The Henry M. Jackson Foundation for the Advancement of Military Medicine, United States

13:10 WEPDB0103
Increasing contribution of integrated forms to total HIV1-DNA in blood, in primary infection during natural history - ANRS PRIMO and SEROCO cohorts 
Véronique Avettand-Fenoel, Université Paris Descartes, France

13:15 WEPDB0104
Intermittent viremia after treatment interruption increased risk of ART resumption in post-treatment HIV-1 controllers. ANRS VISCONTI study 
Laurent Hocqueloux, CHR d'Orléans - La Source, France

13:20 WEPDB0105
Auranofin plus nicotinamide impact HIV reservoir among ART suppressed HIV individuals 
Ricardo Sobhie Diaz, Federal University of Sao Paulo, Brazil

All fired up: Tackling inflammation
Code: WEPDA01 
Session Type: Oral Poster Discussion Session Track A – Basic and translational research 
Venue: Hall 11B 
Wednesday July 25, 13:00 - 14:00 

13:10 WEPDA0103
Persistence of myeloid cell-associated inflammation in HIV-infected children after 8 years on early initiated therapy - the key role players in HIV persistence? 
Shalena Naidoo, Stellenbosch University, South Africa 

Killers or helpers: The double life of T cells
Code: WEAA02
Session Type: Oral Abstract Session Track A – Basic and translational research
Venue: Hall 11B
Wednesday July 25, 14:30 - 16:00

14:30 WEAA0201
Increase in restriction factor expression in response to viral rebound after analytical treatment interruption in HIV-infected patients
Marie-Angélique De Scheerder, UZ Gent, Belgium 

14:45 WEAA0202
RhCMV-induced, SIV-specific MHC-E-restricted T cells recognize SIV through the T cell receptor 
Shaheed Abdulhaqq, Oregon Health and Science University, United States

15:00 WEAA0203
Genetic factors leading to loss of viral control in HIV elite controller patients 
José M. Benito, Instituto de Investigación Sanitaria Fundación Jiménez Díaz, Universidad Autónoma de Madrid (IIS-FJD, UAM), Spain 

15:15 WEAA0204
Frequent generation of HIV broadly neutralizing antibodies in infected children is associated with both increased help and regulation within germinal centers 
Julia Roider, University of Oxford, South Africa

15:30 WEAA0205
Initiation of antiretroviral therapy during hyperacute HIV infection preserves germinal center T follicular (GCTfh) helper cell function
Zaza Ndhlovu, University of KwaZulu Natal, South Africa

Eliminating HIV latency: Shock and kill or block and lock?
Code: WESY09
Session Type: Symposia Session
Venue: Hall 11B
Wednesday July 25, 16:30 - 18:00

16:44 WESY0902 
Introductory comments 
Maureen Goodenow, U.S. DHHS National Institutes of Health, Office of AIDS Research, United States

16:49 WESY0903
Understanding HIV persistence – do defective viruses matter? 
Ya-Chi Ho, Yale University School of Medicine, United States

17:06 WESY0904
Low level transcription on ART – implications for latency elimination 
Steve Yukl, University of California, United States

17:23 WESY0905 
TLR agonists and latency reversal: can they both shock and kill? 
Martin Tolstrup, Aarhus University, Denmark

17:40 WESY0906
Block and lock using gene silencing 
Anthony Kelleher, The University of New South Wales (UNSW), Australia

17:57 WESY0907 
Understanding community participation in cure studies: what scientists need to know 
Cipriano Martinez, National Association for People Living with HIV in Australia, Australia
 
Broadly neutralizing antibodies (bNabs): Towards a cure and vaccine
Code: THSY04
Session Type: Symposia Session
Venue: G104-105
Thursday July 26, 11:00 - 12:30

11:05 THSY0402
Factors determining bNab elicitation in HIV-infected individuals during natural infection: Challenges a vaccine has to overcome
Alexandra Trkola, Leiterin Group Trkola, Switzerland

11:25 THSY0403
Maturation of bNabs in HIV-1 infected patients (specifics of B-cell maturation), what is different from other infections?
Michel Nussenzweig, The Rockefeller University, United States

11:45 THSY0404
Induction of bNabs by vaccines: where do we stand, what is being needed for success
Rogier Sanders, AMC, Netherlands

12:05 THSY0405
bNabs for clinical use: antiviral activity and effector functions other than neutralization
Lynn Morris, University of the Witwatersrand, South Africa

How Far are We from HIV Remission? 
Code: THSA14 
Session Type: Non-Commercial Satellite 
Venue: Hall 11A 
Thursday July 26, 18:30 - 20:30

18:35 THSA1402 
An Update on Post-Treatment Controllers in France and Worldwide 
Laurent Hocqueloux, CHR d'Orléans - La Source, France

18:50 THSA1403 
Insights on Mechanisms of Post-Treatment Control 
Asier Saéz-Cirion, Insitut Pasteur, France

19:10 THSA1405
Lessons from Research Interventions aiming at HIV Remission

19:30 THSA1406
Very early ART Initiation during "Hyperacute" HIV Infection 
Timothy Henrich, University of California at San Francisco ( UCSF), United States

19:45 THSA1407
Stem Cell Transplantations: ICISTEM 
Monique Nijhuis, University Medical Center Utrecht, Netherlands

20:00 THSA1408
Interventions with broadly neutralizing antibodies (bNAb)
Michel Nussenszweig, Howard Hughes Institute, The Rockefeller University, United States

20:15 THSA1409
HIV Remission Research: Expectations and Questioning
Alain Volny-Anne, France

20:45 THSA1411
Concluding Remarks
Françoise Barré-Sinoussi, Institut Pasteur, France

New Data on Identifying and Targeting the Latent HIV Reservoir

Several recently presented and published studies offer potentially important new data relevant to efforts to identify cells containing latent HIV and target them for elimination.

At the 8th International Workshop on HIV Persistence held in Miami last December, multiple research groups reported on their attempts to confirm a newly published—and widely publicized—claim that the cell surface molecule CD32a is preferentially expressed on latently infected cells. The results indicate that the picture is considerably more complicated: the original findings could not be verified and instead it appears that expression of CD32a may be driven by other factors, including cell activation and active HIV transcription. Summaries of these studies can be found in the published abstracts from the workshop (see abstract numbers OP 1.5, OP 2.4, OP 2.6 and OP 4.2).

While disappointing, this work does not end hopes that markers of latently infected cells can be identified – other candidates that are being examined are CCR5, when expressed by resting memory CD4 T cells (see the study from the laboratory of Robert Siliciano published late last year), and CD30, a cell surface molecule better known for its association with lymphoma that is being investigated by Tim Henrich and colleagues.

One of the reasons why markers of latently infected cells would be a boon to the cure research field is that they might facilitate elimination strategies akin to those now being used successfully against cancers. A number of effective cancer immunotherapies involve equipping T cells with receptors that target cell surface molecules on malignant cells, such as CD19, CD22, and CD30. It is conceivable that this “chimeric antigen receptor” (CAR) T cell approach could be adapted to target latently infected cells if appropriate markers could be identified.

CAR T cells are also being developed that target HIV antigens, with a recent paper in PLoS Pathogens from Scott Kitchen colleagues reporting some encouraging results obtained with stem cell-derived CAR T cells in macaques. However, in order for the approach to work against latently infected cells, it would be necessary to activate the latent HIV first to trigger production of viral antigens. An article in STAT News by Sharon Begley provides an accurate and nuanced perspective on Kitchen’s paper, offering the appropriately cautious headline: “Preliminary study hints that genetically modified T cells might fight HIV.” In contrast, coverage in The Daily Beast unfortunately opts for misleading hype, with their piece titled: “This Doctor's Revolutionary Stem Cell Treatments Could Eradicate HIV.”

The research group of Jonathan Angel in Canada is pursuing a novel method for targeting latently infected cells: an oncolytic rhabdovirus named MG1, which is primarily being developed for its ability to preferentially infect and destroy cancer cells. Angel and colleagues have published a study in the Journal of Infectious Diseases demonstrating that MG1 also appears capable of targeting cells latently infected with HIV, while sparing uninfected cells (the paper is open access).

In an analysis of the effects of MG1 on memory CD4 T cells isolated from 14 HIV-positive individuals on ART, both total and integrated HIV DNA levels declined in 12 out of the 14 samples. The mechanism for MG1’s preferential targeting is unclear, but may relate to changes in latently infected cells that affect their response to the cytokine interferon. The authors note that clinical trials are already underway in cancer, which should help discern if the approach can be safely studied in HIV infection. In an interview with MD Magazine, Angel notes MG1 that can cause fever and malaise, and adverse events may be dose-dependent.

Another paper in PLoS Pathogens that has drawn attention comes from Christina Gavegnano and colleagues, who show that a class of drugs called Jak inhibitors can inhibit the maintenance of latently infected cells, and prevent them spreading infection when latent HIV is reactivated. Jak inhibitors target a pathway involved in the survival and proliferation of memory CD4 T cells, and have been found safe in the treatment of certain inflammatory diseases and myelofibrosis. The authors note that an ongoing clinical trial is evaluating the effects of the Jak inhibitor ruxolitinib in HIV-positive people on ART.