TAG HIV Basic Science, Vaccines, and Cure Project Blog

TAG’s HIV Cure-Related Clinical Research Listing: Background on the January 2024 Update

A total of eight changes were made to TAG’s listing for the first monthly update of 2024.

New Additions

One new study has been added from the Pan African Clinical Trials Registry: Scientists affiliated with the Centre for the AIDS Programme of Research in South Africa (CAPRISA) are launching a phase I cure-related trial investigating a combination of two long-acting broadly neutralizing antibodies (bNAbs) in people with HIV.

One of the two bNAbs, CAP256V2LS, was discovered by CAPRISA researchers in samples from a person living with locally prevalent clade C variants of HIV. The other, VRC07-523LS, is an enhanced version of the bNAb VRC01, which was isolated in 2008 from an untreated slow progressor living with clade B HIV infection by scientists at the National Institutes of Health in the United States. Both bNAbs are already being investigated as potential preventive options in HIV-negative women South Africa and have been found to be safe.

The new study, designated CAPRISA 095 or NeutArt, isn’t yet open for enrollment but plans to recruit 30 participants and assess whether the bNAb combination can enhance the immune system’s ability to control HIV viral load after an analytical treatment interruption (ATI). A number of similar studies are ongoing around the world with other dual bNAb combinations (see bNAb section of table 1 in the listing).

Updates to Enrollment Status

A clinical trial sponsored by the HIV Vaccine Trials Network (HVTN) that was added to the listing in September 2023 is now open for enrollment. The protocol is unusual because the primary focus is on generating information that may help with the design of preventive HIV vaccines that aim to induce bNAb responses. However, the results may also have the potential to inform the design of curative strategies, particularly therapeutic vaccines, and hence we’ve included it in our listing with an explanatory notation. Participants will receive a vaccine and then be asked to undergo an optional ATI to assess how rebounding viral load influences and modifies vaccine-induced immune responses.

Completed Studies

Three studies in the listing were completed over the past month:

A therapeutic vaccine study in Spain, BCN03, which assessed the effects of a combination of three vaccine constructs on control of viral load after an ATI. Two of the vaccines aim to induce T cell responses against HIV, while the third is designed to induce antibodies against the virus’s outer envelope. To our knowledge, results haven't been publicly presented yet. The work is building on two prior therapeutic vaccine studies conducted by the same team, BCN01 and BCN02.

An ACTG study of the anti-CMV drug letermovir (Prevymis) is now listed as completed after enrolling 44 participants. The study protocol included an option to recruit more participants based on an interim analysis, so it seems possible that certain targets involving measures of anti-inflammatory activity weren’t met. However, even if that’s the case, the results may still be relevant and of interest. More information is likely to be presented soon.

Another ACTG clinical trial investigating the trispecific bNAb SAR441236 (developed by Sanofi) has been stopped early. Trispecific means that the bNAb is engineered to target three different parts of the HIV envelope, essentially combining three distinct bNAbs into a single antibody molecule. Based on the updates to the clinicaltrials.gov entry, it appears that it was difficult for the researchers to recruit participants for Arm B of the study protocol, which planned to enroll people with HIV who hadn’t yet started antiretroviral therapy (ART) despite detectable viral loads. The problems encountered may highlight both ethical and practical concerns related to asking people to delay ART initiation in the era of immediate treatment and undetectable=untransmittable (U=U). As a consequence of the delays, the available SAR441236 study product passed its expiration date and hence the trial was ended.

Preliminary results are posted on clinicaltrials.gov, but the formatting used by the website makes them difficult to interpret. It appears that a total of 52 participants were enrolled, with 42 completing the study as planned. No serious adverse events considered related to SAR441236 were documented, but one participant was diagnosed with melanoma during the trial. Seven participants who weren’t on ART with baseline viral loads greater or equal to 5,000 copies/ml received doses of either 1 mg/kg or 30 mg/kg of SAR441236, but the resultant viral load declines measured a week later were minor (0.10 or 0.38 logs, respectively) and not sustained. Results will almost certainly be presented or published in the near future, possibly at the upcoming Conference on Retroviruses and Opportunistic Infections (CROI) in early March.

New Links to Study Results

Links to results were added for three entries in the listing:

The biotechnology company American Gene Technologies (AGT) is working on a candidate cure strategy that genetically modifies CD4 T cells capable of targeting HIV (HIV-specific CD4 T cells) to make them resistant to infection. The rationale for the approach is that HIV-specific CD4 T cells should be responsible for coordinating an effective immune response against the virus, but instead become preferential targets for infection and dysregulation.

AGT’s therapeutic candidate is named AGT103-T and involves sampling HIV-specific CD4 T cells from study participants, introducing genetic modifications to block HIV infection, expanding their number in the laboratory, and then reinfusing them. After an initial published report that indicated the infusions appeared safe with evidence of persistence of the modified cells, participants were given the option of undergoing an ATI to assess the immune system’s ability to control viral load in the absence of ART.

Preliminary results from this ATI portion of the research were published on the preprint server medRxiv in October of last year, but were only recently brought to our attention courtesy of Jeff Galvin from AGT. A preprint means that the paper has not yet been subjected to peer review.

The results offer some evidence of diminished viral load rebound, particularly after a second ATI, although the limited number of participants and open label study design make it difficult to evaluate the contribution of the gene-modified HIV-specific CD4 T cells. The authors also emphasize the expansion of CD8 T cells that occurred after ATI, which is atypical and may suggest that the modified HIV-specific CD4 T cells were able to better support proliferation of HIV-specific CD8 T cells in response to viral load rebound.

One potentially troubling issue mentioned in the paper is that some participants undertook ATIs on their own, which might suggest unrealistic expectations about the efficacy of AGT103-T. American Gene Technologies has made some misguidedly bullish statements about the prospects for their candidate in the past, and this may offer a regrettable cautionary tale about how such claims can affect adherence to a study protocol and the wellbeing of study participants.

American Gene Technologies has now spun off a company called Addimmune to pursue continued development of AGT103-T. According to a recent news report, the next step is a larger trial that will evaluate stopping ART at different timepoints after infusion of the gene-modified CD4 T cells.

A newly published paper by Tim Schacker and colleagues from the University of Minnesota has reported results from two clinical trials that investigated infusion of natural killer (NK) cells as an adoptive immunotherapy strategy. The researchers took inspiration from cancer research and used natural killer cells sampled from donors (typically family members) that were only partially genetically matched to the recipients, referred to as haploidentical NK cells.

The initial protocol combined the NK cell infusions with the cytokine IL-2 in an attempt to promote persistence and expansion of the cells, but was subsequently modified to administer N-803, which enhances production of the cytokine IL-15 (and avoids a potential issue involving IL- 2 stimulating regulatory or immunosuppressive responses). Two participants received NK cells plus IL-2, and four received NK cells plus N-803.

The interventions were generally safe with no serious adverse clinical events. Two serious (grade 3) toxicities were documented by laboratory measures: a low estimated glomerular filtration rate (eGFR) in one participant receiving IL-2 and a transient low absolute lymphocyte count in a recipient of N-803 that returned to normal around nine days after administration.

The researchers found evidence of persistence of infused NK cells in blood for around 6-8 days, and in tissues for as long as 28 days. In terms of efficacy against HIV, the proportion of cells producing HIV RNA declined in lymph node and gastrointestinal tissues, but because of the small number of participants the researchers weren’t able to formally confirm this with statistical analyses.

In discussing their findings, the authors write:

“These data suggest that providing functional NK cells could be a potential part of a successful strategy to cure HIV. Although it is not practical to consider infusions of haploidentical NK cells on a scale that would benefit the millions of PLHIV worldwide, this approach does provide the proof of principle for the potential role of these cells in controlling HIV. Several companies are currently studying the effect of NK cells with specific anti-tumor properties in both hematologic and solid organ malignancies. These cells are commercially manufactured and provided in simple dose packs that are kept frozen until infusion with no special equipment or processing needed, which allows this approach to be scalable.”

Investigators at the University of Minnesota are planning to soon launch a clinical trial of an off-the-shelf NK cell product called FT538 in people with HIV.

TAG’s HIV Cure-Related Clinical Research Listing: Background on the December 2023 Update

No new HIV cure-related trials or studies were added to the clinicaltrials.gov registry over the past month. A total of seven updates were made to TAG’s listing:

A clinical trial in Barcelona, Spain investigating the effects of the drug dasatinib on HIV persistence and inflammation is now open for enrollment. Dasatinib is a tyrosine kinase inhibitor approved for the treatment of certain forms of chronic myelogenous leukemia and acute lymphoblastic leukemia. Studies in people with HIV receiving the drug to treat cancer have reported an association with a smaller HIV reservoir size and reduced capacity to reactivate viable HIV from latently infected cells. Proposed mechanisms include enhancing the activity of an innate antiviral enzyme, SAMHD1 (by preventing phosphorylation of the enzyme), immunomodulatory effects on natural killer cells and T cells, and possibly also a reduction in the proliferation of HIV-infected CD4 T cells. Two poster presentations at the XIV Congreso Nacional GeSIDA last month reported additional evidence that the use of tyrosine kinase inhibitors in people with HIV and cancers is associated with reductions in the size of the viral reservoir and potential enhancement of the cell-killing potential of natural killer cells and CD8 T cells (see abstracts PT-07 and PT-08).

An ongoing clinical trial sponsored by Gilead Sciences in the FRESH cohort of young women in South Africa is now closed to enrollment. The study is investigating whether a combination of two broadly neutralizing antibodies (bNAbs) and vesatolimod, a toll-like receptor 7 agonist, can enhance viral load control during an analytical treatment interruption (ATI) in participants who started antiretroviral therapy (ART) very early after HIV acquisition.

A phase IIa study of the long-acting broadly neutralizing antibody GSK3810109A (formerly named N6-LS) is now completed. The focus of the research was more on potential use as a treatment rather than cure. The most recent presentation of results was at the European AIDS Clinical Society (EACS) conference, where researchers reported a good safety profile and favorable pharmacokinetics. A phase IIb trial is planned.

Two observational studies sponsored by Radboud University in the Netherlands have also been completed. The 2000HIV and 2000HIVTrained studies used new multi-omics approaches to investigate biological pathways and biomarkers potentially linked to a variety of variables including non-AIDS comorbidities, elite control, and the latent viral reservoir in a large cohort of people with HIV. Two abstracts reporting results were presented at CROI earlier this year (see abstracts 313 and 314).

Links to newly published results were added for two trials in the listing:

The IMPAACT P1115 study assessing the potential for HIV remission in infants treated very soon after birth described results in a paper in the Lancet HIV (access free with registration), following a presentation by principal investigator Deborah Persaud at CROI 2022. A subset of ten out of 54 infants studied became HIV antibody negative and had non-detectable HIV-1 DNA after two years, which represent the criteria for considering an ATI. The researchers note that overall HIV suppression rates were not optimal and improved pediatric ART regimens are still needed. The second iteration of IMPAACT P1115 is now testing regimens including an integrase inhibitor (raltegravir) and a broadly neutralizing antibody (VRC-01).

Scientists affiliated with the ACTG published a paper in the journal AIDS presenting results from a phase I/IIa study of an HIV-1 Gag conserved element DNA vaccine in people on ART. The aim is to induce or boost T cell responses targeting parts of the HIV Gag protein that appear constrained in their ability mutate, and are thus typically conserved among HIV variants. The vaccine, combined with vaccine containing the full Gag protein, induced new T cell responses to conserved elements in a little less than half of the 18 recipients (44.4%). Whether these T cell responses can effectively kill HIV-infected cells is not yet known. A paper published in Science yesterday reported that the ability of HIV vaccine-induced T cells to kill HIV-infected cells may be impaired by poor avidity - a measure of the ability of T cells to efficiently recognize and engage with low amounts of viral fragments displayed (like alarm signals) by cells infected with HIV.

Lastly we made an adjustment to the current clinical trials table this month, creating a separate category specifically for broadly neutralizing antibodies rather than using a general category of just “antibodies.” Other antibodies are now categorized based on mechanism of action e.g.  anti-α₄β₇ integrin antibodies, CD4 attachment inhibitors.

TAG’s HIV Cure-Related Clinical Research Listing: Background on the October 2023 Update

No new HIV cure-related trials or studies have been added to the clinicaltrials.gov registry over the past month. Two trials in the listing have changed status:

A study sponsored by the ANRS in France investigating the link between specific immune system genetics (MHC B35/53Bw4TTC2) and post-treatment control of HIV is now open for enrollment. Participants are being recruited from the large ongoing ANRS CO6 PRIMO cohort of people in France who were identified within three months of HIV acquisition. The rationale for the study derives from evidence that people with this particular genetic profile may be more likely to control viral load after an antiretroviral therapy (ART) interruption (see the session recording of Asier Sáez-Cirión’s presentation at IAS 2021, which starts at around 29 minutes). The mechanism is thought to involve the enhancement of natural killer cell immune responses against HIV.

A clinical trial of the drug baricitinib in people with HIV on ART has been temporarily suspended. The study is sponsored by Emory University and the registry record notes that the suspension is because the U.S. Food and Drug Administration (FDA) is requesting a new investigational new drug (IND) application to be filed. The drug is FDA-approved for the treatment of several conditions including severe rheumatoid arthritis but has not previously been specifically studied in people with HIV. Laboratory experiments in humanized mice have found that baricitinib can cross the blood-brain barrier and reduce the persistence of HIV in the central nervous system. The clinical trial aims to investigate if similar effects can be obtained in people with HIV, using blood samples, neurocognitive testing, magnetic resonance imaging (MRIs), and lumbar punctures.

The remaining updates this month are the additions of links to presented or published results from ten studies in the listing.

In seven cases, the results were presented as poster abstracts at the NIAID Strategies for an HIV Cure meeting which took place last week October 12-13. A recording of the event will soon be available on the NIH Videocast website and the poster abstracts are contained in the program book. Unfortunately we can’t link directly to the individual abstracts, so they need to be looked up by number. It’s unclear if the meeting book will remain online permanently, but if it’s taken down we’ll host a copy on the TAG website and redirect the links. A very brief summary of the presented results is below.

• Among participants in a small analytical treatment interruption (ATI) study in San Francisco, robust lymph node proliferation of CD8 T cells targeting the virus appeared to be linked to better control of HIV viral load off ART.
• An imaging study at the National Cancer Institute reported very preliminary information from the first participant to undergo ATI, indicating that lymph node metabolic activity associated with immune activation didn’t significantly increase prior to the detection of low level viral load in blood.
• Analyses of the HIV reservoir in neonates in the ongoing IMPAACT P1115 study found a high proportion of intact viruses mixed with defective and hypermutated viruses, indicating that HIV replication had occurred and established persistent infection in utero, prior to birth.
• The experiences of participants in a combination therapy trial with an extended ATI were assessed by John Sauceda and colleagues. During the ATI “depression and anxiety ratings increased to reach the mild severity category, and then reduced after re-starting ART.”
• Two poster abstracts presented information from the Last Gift study, which offers people with HIV reaching the end of life an opportunity to donate postmortem tissues to cure research. Karine Dubé and colleagues measured quality of life among participants and found it to be stable with some indication of a benefit to study participation. A second abstract described evidence of persistent HIV reservoirs in long-lived brain myeloid cells in tissues donated by four study participants.
• Researchers who conducted a completed ATI study Belgium used new techniques to investigate whether the detectable presence of intact HIV in the reservoir was associated with viral load rebound. Intact HIV couldn’t be detected in five participants but they still experienced a return of viral load after stopping ART, suggesting that this measure alone is insufficient to predict the outcome of an ATI.
• Lastly, in a study sponsored by Gilead Sciences investigating the toll-like receptor agonist vesatolimod in individuals with low viral load prior to starting ART (“viremic controllers”), a subset of CD8 T cells targeting the HIV Gag protein with broad functionality and cell-killing (cytotoxic) properties were associated with HIV reservoir reductions and a delayed time to viral load rebound after ATI.

Three other studies have had links added to published results:

• A small trial of high dose vitamin D₃ supplementation in Australia, previously presented at CROI 2022, has now been described in a paper in the Journal of Virus Eradication which reports evidence of immune modulation and an apparent decline in HIV DNA levels after supplementation was stopped.
• The Research in Viral Eradication of HIV Reservoirs (RIVER) trial in the UK tested therapeutic vaccination in people starting antiretroviral therapy (ART) early after HIV acquisition and published primary results in 2020. In a new paper in the journal Scientific Reports, study investigators report that the therapeutic vaccines (ChAdV63.HIVconsv and MVA.HIVconsv) increased the frequency and functionality of CD4 and CD8 T cells targeting HIV. These immunological effects weren’t associated with reductions in the HIV reservoir and the study didn’t include an analytical treatment interruption (ATI), so it’s not clear if the vaccine-induced T cell responses could mediate enhanced control of viral load in the absence of ART. The same vaccines have previously been studied by researchers in Spain with some evidence of reductions in viral load after an ATI, but there were no cases of sustained post-treatment control to undetectable levels.
• The Journal of Medical Virology has published results from an Italian study assessing three different ART regimens to treat acute HIV infection. HIV DNA levels were significantly reduced over 48 weeks and there was no difference between the regimens.

TAG’s HIV Cure-Related Clinical Research Listing: Background on the April 2023 Update

The April 2023 update to TAG’s HIV cure-related clinical research listing adds five new studies, two involving interventions and three observational.

Researchers at the University of Sao Paulo General Hospital in Brazil are opening a study of a therapeutic HIV vaccine based on dendritic cells (DCs). DCs are immune system cells tasked with initiating the immune response against pathogens like HIV, and the researchers aim to exploit this aspect of their function to bolster anti-HIV immunity and potentially enhance control of viral load after an antiretroviral therapy (ART) interruption. DCs are sampled from participants, cultured in a laboratory to promote their immune-stimulating function, exposed to HIV protein fragments sampled from the intended recipients, and then infused in large numbers.

The goal is to induce highly functional CD4 and CD8 T cell responses targeting HIV. The approach was tested as part of a combination regimen in a prior trial, with the researchers reporting encouraging preliminary results. The new trial will divide 30 participants into three arms: one will receive placebo (dummy infusion), one will receive dendritic cells (called alpha-type-1 polarizing dendritic cells or aDC1 for short), and the third will receive aDC1 and then undergo an analytical treatment interruption (ATI). Primary outcome measures will be safety and viral load and CD4 counts after ATI.

A trial of dasatinib, a tyrosine kinase inhibitor drug approved for the treatment of certain forms of chronic myelogenous leukemia and acute lymphoblastic leukemia, is being initiated at Hospital Universitari Germans Trias i Pujol in Barcelona, Spain. The rationale is based on previously published evidence that dasatinib therapy for cancer in people with HIV is associated with a smaller HIV reservoir and a reduced ability to reactivate viable HIV from latently infected cells. Proposed mechanisms include enhancement of the activity of an innate antiviral enzyme, SAMHD1 (by preventing phosphorylation of the enzyme), immunomodulatory effects on natural killer cells and T cells, and possibly also a reduction in the proliferation of HIV-infected CD4 T cells.

The main aim of the trial is to investigate safety and effects on SAMHD1 in people with HIV on ART, with secondary outcome measures assessing any impacts on the HIV reservoir. Another clinical study of dasatinib in people with HIV was registered in September 2022 and is also taking place in Spain. The design is slightly different, involving recruitment of people with recent HIV infection who’ve not yet started ART. Participants will receive dasatinib or placebo for a total of 16 weeks, with the first four-week period occurring prior to initiating an ART regimen.

Newly added observational studies are:

• The EARTH study (part of the larger EPIICAL project), which has enrolled children treated with ART within 90 days of birth. The goal is to assess virus and immune system parameters to identify potential participants for cure-related interventional trials. The study is sponsored by the PENTA Foundation and is taking place in South Africa, Mali, and Mozambique. The listed start date is May 2018 and participants are no longer being recruited, suggesting that the registry record has been created somewhat belatedly.
• MERCI (measuring the HIV-1 reservoir during cure interventions studies) is an observational study planned at Ghent University Hospital that will conduct detailed evaluations of the HIV reservoir using blood and tissue sampling (lymph node and colon biopsies) from 30 participants, before and after receipt of cure-related interventions in other (unspecified) trials.
• Similarly, a study at Icahn School of Medicine at Mount Sinai Hospital in New York City is investigating the HIV reservoir and immune system parameters in the gastrointestinal-associated lymphoid tissue (GALT) of eight participants in cure-related interventional trials (again, the specific interventional trials from which the participants are being recruited are not named).

Completed Studies

Multiple entries in the listing were shifted into the “completed studies” table this month. These include a first-in-human trial of a gene therapy approach developed by American Gene Technologies that aims to protect HIV-specific CD4 T cells (the cells responsible for coordinating the immune response against HIV) from infection and disruption by the virus. Preliminary results were published in Frontiers in Medicine in November 2022. Study participants were offered the opportunity to move into a follow up protocol involving an ATI, which remains ongoing.

IMPAACT P1107 was a study that sought to identify donor cells with the CCR5Δ32 mutation for people with HIV requiring stem cell transplants for life-threatening cancer diagnoses. The research project led to the widely publicized fourth case of a likely cure of HIV infection by this method, in a woman of mixed race in New York City. The case was described in detail in a paper published in the journal Cell last month. The paper notes that there was one other participant in P1107, a middle-aged man with HIV who died after a relapse of Hodgkin’s lymphoma within a year of receiving the stem cell transplant.

One observational study — ANRS CO24 OncoVIHAC — was moved to the completed table in error because the registry record hasn’t been updated since January 2018. After reaching out by email to investigators, Dr. Olivier Lambotte kindly replied to let us know that the research is still ongoing. The error will be corrected when the listing is updated again next month.

Two additional studies were moved to the completed table due to out-of-date registry records:

• Albuvirtide + 3BNC117 (registry identifier NCT04819347)
• Euphorbia kansui (registry identifier NCT04503928)

Neither was ever listed as open for enrollment and study contacts haven’t responded to email inquiries, so it’s not known if the trials went ahead as planned. We’ll continue to attempt to find out more information and update the table entries if successful.

Results

Results have been published from a completed study of valproic acid and pyrimethamine as candidate latency-reversing agents. Pyrimethamine is an old, FDA-approved antiparasitic drug used for the treatment of toxoplasmosis that has been shown to inhibit a cellular mechanism involved in maintaining HIV latency (the BAF complex). In an article published in the open access journal Science Advances, the investigators report evidence of “a rapid, modest, and significant increase in [cell-associated unspliced] HIV-1 RNA in response to pyrimethamine exposure.” The finding suggests that the drug could have a role in reactivating latent HIV, although the authors note that there was no evidence of a reduction in the size of the HIV reservoir. Valproic acid did not show any significant effects.

TAG’s HIV Cure-Related Clinical Research Listing: Background on the February 2023 Update

The February 15, 2023 update to TAG’s HIV cure-related clinical research listing includes three newly registered studies:

The AIDS Clinical Trials Group (ACTG) is initiating a study of two long-acting broadly neutralizing antibodies (bNAbs) named VRC07-523LS and PGT121.414.LS combined with antiretroviral therapy (ART) in people with acute (recently acquired) HIV infection. The trial has yet to begin recruiting but will take place at multiple sites in the United States, Brazil and Peru. The primary goals of the research are to evaluate the safety of the bNAbs, assess whether they can delay the rebound of HIV viral load after an analytical treatment interruption (ATI), and measure any effects on the HIV reservoir and/or HIV-specific immune responses. The registry entry lacks information on how long participants will be treated prior to the ATI. The hope is to build on preliminary evidence that bNAbs may be able to slightly reduce the size of the intact HIV reservoir, enhance HIV-specific immunity, and promote enhanced control of HIV viral load after ART interruption in some recipients.

Researchers at the Masonic Cancer Center, University of Minnesota are conducting a trial that will administer a natural killer (NK) cell product, FT538, either alone or in combination with vorinostat, an HDAC inhibitor and candidate HIV latency-reversing agent. NK cells are a subset of immune system cells that can potentially kill virus-infected targets such as CD4 T cells harboring HIV. A prior study in people with HIV has investigated adoptive transfer of NK cells — which involves extracting them from the blood of matched donors, expanding them in the laboratory and then infusing them into study participants — but results have not yet been presented to our knowledge. FT538 takes a different off-the-shelf approach that generates the NK cells in the lab from specially engineered “mother” cells called induced pluripotent stem cells (iPSC). The company developing FT538 is Fate Therapeutics and there are several other ongoing trials in people with cancers. The HIV study will investigate the safety of intravenous dosing of FT538 and look for evidence of a reduction in the low amounts of HIV RNA that can be generated by the HIV reservoir in people on ART. If FT538 proves safe, vorinostat will be administered to attempt to reactivate latent HIV and make additional HIV-containing cells vulnerable to destruction by the NK cells. Recruitment for the trial has not yet begun.

A new trial sponsored by the Hospital Universitari Vall d'Hebron Research Institute in Barcelona, Spain will test the effects of lauric acid, a dietary fatty acid, on the HIV reservoir. At the XII Congreso Nacional GeSIDA in 2021, the researchers conducting the study presented laboratory evidence that lauric acid can promote activation of latent HIV without negatively effecting CD8 T cell responses (a problem that has been reported with other candidate latency-reversing agents). The conference abstract is appended below. The clinical trial is open for enrollment.

The other updates to the listing this month are the addition of links to newly published results from the Early Infant Treatment (EIT) trial in Botswana and the ACTG HIV reservoirs cohort study (A5321). The latter publication describes a careful evaluation of the levels of intact HIV in people on ART during long-term follow up.

Lastly, there’s bad news about the EHVA T02 trial that intended to evaluate a combination of a therapeutic vaccine (MVA HIV-B) and the anti-α4β7 integrin antibody vedolizumab in people with HIV. The clinicaltrials.gov entry has not yet been updated, but the research had to be stopped due to slow enrollment and an imminent expiration date for the MVA HIV-B vaccine, which made it logistically impossible to complete the study as planned.

XII Congreso Nacional GeSIDA y XIV Reunión Docente de la Red de Investigación de Sida (RIS) November 2021

CO-16. LAURIC ACID, A NATURAL SATURATED FATTY ACID, INDUCES THE METABOLIC REPROGRAMING OF T CELLS AND REACTIVATES LATENT HIV, WHEREAS PRESERVES CD8 T CELL RESPONSES

Grau Expósito1, A. Rull2, J.N. Howard3, J. Burgos4, J. Navarro4, A. Curran4, B. Planas1, V. Falcó4, M. Genescà1, A. Bosque3, F. Vidal2 and M.J. Buzon1

1 Vall d’Hebron Institut de Recerca, Barcelona.

2 Institut d’Investigació Sanitària Pere Virgili, Tarragona.

3 George Washington University School of Medicine and Health Sciences, Washington D.C.

4 Hospital Universitari Vall d’Hebron, Barcelona.

Introduction:

Elimination of the latent HIV reservoir that persists in antiretroviral treated (ART) HIV-infected individuals is recognized as the main barrier to cure HIV. Current latency reversal agents (LRA) do not impact the reservoir in vivo and are relatively toxic compounds, precluding their prolonged clinical use. Here, we study the effect of Lauric Acid (LA), a natural non-toxic compound, on the HIV reservoir and cytotoxic CD8+ T cell responses.

Methods:

HIV reactivation assays were performed in latency models (cellular and tissue models) and in primary CD4+ T cells obtained from ART-suppressed HIV-infected individuals. Using different techniques, as qPCR and flow cytometry, we assessed the capacity of LA to promote HIV viral transcription and p24 protein production in vitro. Functional assays were also performed to determine the effect of LA on CD8+ T cell cytotoxic activity. Moreover, metabolomic, proteomic and lipidomic analyses were performed to elucidate the impact of LA on CD4+ and CD8+T cells.

Results:

Lauric acid was able to promote a significant increase in the viral transcription and protein production in both latency models and in primary cells from HIV-infected individuals, with reduced cell-associated toxicity (p<0.001 and FC=2.6). Functional assays demonstrated that LA did not induce a global activation of CD8+ T cells, nor precluded their cytotoxic function. Moreover, lipidomic assays of CD4+ T cells suggested that LA modifies the composition of the lipid content upregulating diacylglycerols and producing de novo phosphatidylcholines, which are necessary for viral protein production during HIV transcription. Furthermore, LA impacted the metabolism of CD8+ T cells with a significant upregulation of the β-oxidation pathway and the proteasome activity, reprogramming cells to obtain energy not only from glycolysis but also from fatty acids.

Conclusions:

Using different models of HIV latency, including human lymphoid tissues and cells from ART-treated individuals, we prove the ability of LA to reprogram cell metabolism and serve as a potent natural LRA. Thus, the capacity of LA to reactivate the latent virus and preserve immune responses, together with the low toxicity found in human studies and its low cost, shapes LA as an excellent candidate for a cost-effective therapeutic strategy directed to impact the HIV reservoir.

AIDS 2022: Another Possible HIV Cure Case After Stem Cell Transplantation for Cancer; Example of Extended Post-Treatment Control in Spain

The 24th International AIDS Conference (AIDS 2022) officially opens on Friday in Montreal, but a Zoom press conference today shared news of results from several studies, including two case reports relevant to HIV cure research.

Jana Dickter from the City of Hope hospital in Los Angeles described another instance of “prolonged HIV-1 remission” after receipt of a stem cell transplant required to treat a life-threatening cancer, this time in a 66-year-old man. The stem cell donor was homozygous for the CCR5Δ32 mutation, which causes immune cells to be resistant to most HIV variants. Dickter emphasized the unique aspects compared to previously reported cases:

• The person was older (63 at the time of the transplant procedure, 66 now)
• Has been living with HIV longer (over 31 years)
• Received a less immunosuppressive regimen during transplantation and a chemotherapy regimen that is better tolerated by older people

As explained in a press release from the City of Hope, the stem cell transplant was administered in early 2019 after a diagnosis of acute myelogenous leukemia (AML). Antiretroviral therapy (ART) was stopped in March 2021 and the man has now been followed for over 17 months with no HIV viral load rebound or HIV DNA detected. Antibody responses against HIV have waned and virus-specific T-cell responses are no longer detectable. The AML is in remission. Regrettably, the details of these results won’t become available until Dickter presents at the conference on Monday August 1 (the abstract text is unavailable until tomorrow).

Dickter noted that the particular protocol employed at City of Hope is likely better suited to older people with HIV who require stem cell transplants to treat cancers, and may offer additional opportunities to attempt cures if appropriate CCR5Δ32 homozygote donors can be identified.

As with the New York City woman reported at CROI earlier this year, the researchers are being cautious and using the term “remission” to describe the case rather than cure, due to limited follow-up. It would be helpful for the HIV cure research field to come to consensus on how best to define “cure” in such cases, because news coverage tends not to adhere to these distinctions in terminology.

There’s also an urgent need for consensus on how many cases of HIV cure/remission have been achieved by stem cell transplants from CCR5Δ32 homozygote donors: both the International AIDS Society and City of Hope press releases erroneously state that this represents the “fourth” such case but in fact, as reported for NBC News by Benjamin Ryan, there are five in total:

• Timothy Ray Brown (aka The Berlin Patient)
• Adam Castillejo (aka The London Patient)
• The Düsseldorf Patient
• The New York Patient
• The City of Hope Patient

Details on each of the prior cases is included in TAG’s latest Research Toward a Cure and Immune-Based Therapies Pipeline Report.

Dr. Núria Climent delivered the second report, about a case of “exceptional post-treatment control” in a woman with HIV who’d participated in a clinical trial in Barcelona. The Hospital Clínic-IDIBAPS have issued a press release about the findings. If I’m understanding correctly, it also involves an older individual: the woman was 59 at the time of study enrollment and so is in her 70s now.

The study was complicated, beginning by randomizing people with recent HIV infection to receive either ART or ART plus the immunosuppressant drug cyclosporine. There were a total of 20 participants, 19 cisgender men and the one cisgender woman (who was assigned to receive ART plus cyclosporine). Results from this initial part of the study were published in 2016.

The woman was then rolled over into another protocol that involved an analytical treatment interruption (ATI). A short course of GM-CSF and pegylated alpha interferon was given during the ATI, followed by another period of ART plus subcutaneous low-dose IL-2 before  treatment was interrupted completely. 

The crux of today’s report is that the participant has now maintained an undetectable HIV viral load for more than 15 years off ART and has displayed a progressive decline in measures of the HIV reservoir during that time. HIV that’s capable of replicating can still be detected at low levels, however, suggesting that control is being actively maintained by the immune system. In laboratory tests, the researchers identified “memory-like” natural killer cells and gamma-delta CD8 T cells as contributors to suppressing HIV replication (these represent relatively small subsets of immune system cells whose potential role in suppressing HIV hasn’t received much attention historically).

The woman does not have any genetic factors that have been associated with immunological control of HIV infection, and Climent explained that she experienced quite severe symptoms during primary infection (which was diagnosed at Feibig stage 5).

In response to questions, Climent noted that the woman was the only study participant who experienced post-treatment control, so the role (if any) of the immune-based interventions that were given is unclear. The researchers have also not tested for the presence of antiretrovirals in blood samples, which is necessary to confirm that the viral load control has occurred post-treatment. The formal presentation at the conference will occur on Sunday July 31.

There’s been at least one other report of extended post-treatment control in a person who received ART plus cyclosporine during early HIV infection; in that case it was a man described as “the Lausanne Patient” by researcher Guiseppe Pantaleo, who’d been off ART for over eight years at the time of the report back in 2009. HIV cure research might potentially benefit from compiling all the historical reports of post-treatment control and assessing their current status (if the information is available); so far the phenomenon appears rare but it has the potential to offer clues to help develop curative interventions.

AIDS 2022 will feature several sessions including HIV cure research in the coming days, listed below.

Thursday July 28

Pre-conference symposium: Pathways to an HIV cure: Research and advocacy priorities

Friday July 29

Satellite: Africa HIV cure research: Strengthening industry-community engagement in clinical research

Saturday July 30

The view from the bench: Advances in HIV basic and translational research

Late Breaker Track A

Global Village: On the road to HIV cure gene therapy: Who can learn from whom?

Novel insights into the nature of the HIV reservoir and mechanisms of persistence

Sunday July 31

Approaches for HIV cure and vaccine research

Combining immunotherapeutic agents to achieve ARV-free remission of HIV

Responding to the virus: Advances in HIV immunology

Monday August 1

Late Breaker Track B

Finding the needle in the haystack: Progress in understanding the HIV reservoir

Tuesday August 2

Shake and bake: Promising strategies for HIV cure

Significant Effects of a TLR7 Agonist Plus Broadly Neutralizing Antibody in the SHIV/Macaque Model

Among the most newsworthy presentations at CROI 2018 earlier this year was Dan Barouch’s description of a study involving a toll-like receptor 7 (TLR7) agonist combined with a broadly neutralizing antibody (bNAb) in SHIV-infected macaques (see contemporary coverage by AIDSMap, i-Base and POZ Magazine). The results have now been published in the journal Nature.

The specific experimental candidates that were tested are vesatolimod (formerly known as GS-9620), a TLR7 agonist, and PGT121, a bNAb initially discovered by researchers supported by the International AIDS Vaccine Initiative but now licensed to Gilead Sciences for therapeutic development. Previous laboratory experiments using CD4 T cells isolated from people on ART found that the combination promoted the reversal of HIV latency and killing of virus-infected cells.

A key goal of Barouch’s study was to establish whether bNAbs are capable of mediating depletion of the viral reservoir in vivo, in addition to displaying the direct antiviral activities that have been documented in other experiments (such as the trials described in the previous blog post).

A total of 44 macaques were infected with SHIV-SF162P3, a hybrid virus that combines elements of SIV and HIV. ART was initiated seven days later—extremely early after infection—leading to rapid suppression of SHIV replication that was maintained for 96 weeks without any viral load blips.

For the subsequent intervention phase, animals were divided into four groups of 11 and received, respectively: sham administrations (control group), vesatolimod alone, PGT121 alone, or the combination of vesatolimod and PGT121. Vesatolimod was given orally every other week between weeks 96 and 114 of the study, while PGT121 was administered five times via infusion from weeks 106-114. ART was then interrupted in all macaques at week 130.

The most dramatic finding was a significantly reduced incidence of SHIV viral load rebound in the group that received the dual vesatolimod/PGT121 combination. Out of the 11 macaques, six (55%) rebounded, compared to all 11 of the sham controls, 10 out of 11 (91%) assigned to vesatolimod alone and nine of 11 (82%) given PGT121.

Among the animals in the combination group that did rebound, viral loads were 2.6 logs lower at the peak and 1.5 logs lower at the set point compared to the controls. Additional analyses showed that levels of SHIV DNA in lymph nodes were significantly lower in the combination group prior to the ART interruption.

The interventions appeared to be well tolerated. Vesatolimod caused transient activation of CD4 T cells and natural killer cells, as well as transient increases in proinflammatory cytokines, which were evident the day after administration.

In an effort to assess whether a reservoir of replication-competent SHIV was still present in the animals that failed to rebound, experiments were conducted in which large numbers of cells were transferred into uninfected macaques. SHIV infection was not transmitted in any case. In contrast, cells from animals that experienced viral load rebounds uniformly transmitted SHIV infection.

CD8 T cells were also depleted from some macaques, as a test of whether SHIV was being actively contained by the immune system in the group that did not experience viral load rebounds. The depletion did not lead to the reappearance of SHIV viral load in these animals.

A computer modeling study indicated that the activation of natural killer (NK) cells by vesatolimod was the strongest correlate of delayed viral load rebound. The researchers suggest that this is consistent with a mechanism of action in which stimulation of innate immunity and CD4 T cells by vesatolimod causes virus-infected cells to express viral antigens, which are then recognized and bound to by PGT121, triggering killing of the infected cells by NK cells and/or other effector cells such as monocytes. This antibody-mediated recruitment of immune cells capable of delivering the coup de grâce to virus-infected cells is known as antibody-mediated cellular cytotoxicity (ADCC) or antibody-mediated cellular phagocytosis (ADCP).

In the discussion section of the paper, the researchers emphasize that the study represented an idealized circumstance due to the very early ART initiation, and that the effects of the interventions were most evident in animals with the lowest pre-ART viral loads. The implications for the more typical circumstance of chronic infection are therefore unclear.

They also note that the failure to transmit SHIV infection is not definitive evidence that all replication-competent virus has been cleared. This has recently been demonstrated by Ron Desrosiers in a study in which replication-competent SHIV was eventually detected in a macaque that had failed to transmit the virus in several cell transfer experiments.

Additionally, there is limited experience with the SHIV-SF162P3 challenge virus in the context of cure research and prior studies have not documented an ability of this virus to develop resistance to PGT121. More information on HIV resistance to PGT121 should emerge from ongoing clinical trials.

Despite these caveats, the evidence that the dual combination promoted clearance—or at least significant depletion—of the viral reservoir in some cases is encouraging.

Gilead Sciences ultimately aims to study vesatolimod combined with a derivative of PGT121 dubbed GS-9722 in people with HIV. GS-9722 is a version of PGT121 that has been modified in an effort to further enhance ADCC/ADCP activity, and it is currently being tested in a phase I trial (the trial is listed on the subscription-only website Adis Insight so details are scarce; there is no clinicaltrials.gov entry yet).

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

Elite Controllers: Sex Differences and Factors Associated with Loss of Immune Control

Over the past few months, several interesting papers addressing elite control of HIV infection have seen publication. The ability of elite controllers to maintain undetectable viral loads and relatively preserved CD4 T cell counts in the absence of ART has led them to be proposed as a model for a functional cure of HIV infection. But there is also evidence that many elite controllers exhibit elevated levels of inflammation compared to HIV-negative counterparts, and eventually experience disease progression, leading some researchers to call this proposition into question. The uncertain relevance of elite control to HIV cure research is prompting studies that attempt to parse the factors distinguishing individuals who preserve elite controller status from those who ultimately progress.

In the journal eBioMedcine, Wang Zhang and colleagues explore the expression of a variety of genes and proteins in a cohort of 19 elite controllers, compared to 32 individuals with progressive HIV infection and 23 healthy HIV-negative controls. Of particular note, nearly half the elite controllers (9) were women, allowing the researchers to compare results based on sex. The authors point out that several previous studies have reported that women tend to be overrepresented among elite controllers (e.g. see Crowell et al and de Azevedo et al).

A potentially important finding is that the gene expression profiles of female elite controllers were similar to HIV-negative females, but there were significant differences between male elite controllers and HIV-negative male controls. A potential implication is that women will be more likely to maintain elite controller status over time compared to men—this possibility will need to be investigated further. 

Among the differences observed in elite controllers compared to individuals with progressive HIV infection were downregulation of the genes for CXCR6 and SIGLEC1. The authors explain that these differences could be associated with decreased susceptibility of CD4 T cells for HIV entry and reduced cell-to-cell virus transmission mediated by myeloid cells.

Levels of the chemokine CCL4 (MIP-1β) were found to be higher among elite controllers versus progressors, consistent with a previous study. Conversely, levels of the inhibitory immune cell receptor PD-1 (and its ligand PD1-L2) were significantly lower, echoing another recent paper reporting lower levels of multiple inhibitory receptors in elite controllers.

BMC Medicine has published an analysis by José Benito and colleagues that looks at possible contributors to loss of elite control. The researchers evaluated 36 elite controllers followed for approximately a decade on average, comparing multiple immunological parameters between those with stable CD4 T cell counts (n=22) and those exhibiting significant CD4 T cell decline during the follow up period (n=14). Interestingly, women made up 67% of the former group but only 31% of the latter, a statistically significant difference (p=0.04). The authors don’t offer any comment on this apparent overrepresentation of women in the group of elite controllers with stable CD4 T counts.

Many immunological variables were found to differ between elite controllers and HIV-negative healthy controls, as well as between stable elite controllers and those experiencing CD4 T cell declines. Distinctions between elite controllers and HIV-negative healthy controls included lower levels of several T cell subsets: naïve, recent thymic emigrant, stem cell memory, and regulatory. Expression of the T cell costimulatory receptor CD28 was lower, whereas CD95—involved in apoptotic cell death—was increased.

Comparisons between the stable elite controllers and progressors revealed that the latter group had lower levels of naïve and recent thymic emigrant CD8 T cells, as well as higher levels of CD8 T cells with effector memory and senescent phenotypes. The finding suggests that CD8 T cells may have been differentiating at a higher rate in this group—in other words, naïve CD8 T cells were more frequently becoming activated and transitioning into memory cells (perhaps reflective of a more strenuous battle to keep HIV contained). The progressor group also showed increased expression levels of PD-1 in both total CD4 T cells and the central memory CD4 T cell subset.

In a separate study published in the Journal of Virology earlier this month, María Pernas and colleagues conducted a retrospective, longitudinal analysis of factors contributing to loss of viral load suppression in a cohort of elite controllers. A total of 31 elite controllers were included, defined based on having viral load below detectable levels (50 copies/ml) on three consecutive measures over a year of follow up.

Fourteen of these individuals subsequently experienced increases in viral load (two consecutive measures above the detection limit within a year), and were classified as transient controllers. The remaining 17 maintained undetectable viral loads and were classified as persistent controllers. Sex differences were not apparent in this study, with women making up 43% of the former group and 41% of the latter. The only significant differences were for time since diagnosis (averaging 8 years and 18 years, respectively) and sexual transmission as mode of HIV acquisition (71% vs. 35%).

The availability of samples prior to the viral load increases in the transient controller group allowed several factors associated with the loss of HIV suppression to be identified. CD8 T cells targeting the HIV Gag protein were found to be significantly less polyfunctional (assessed based on production of the cytokines IFN-γ, TNF-α and IL-2) and displayed a more activated phenotype a year prior to viral load becoming detectable. HIV genetic diversity within the env gene was also significantly higher, with a similar trend observed for the gag gene. In contrast, persistent controllers showed little or no evidence of ongoing viral evolution.

Inflammatory biomarkers were elevated in the transient controllers. and an analysis of 70 different cytokines and chemokines in plasma samples revealed that increased levels of RANTES and Platelet Derived Growth Factor (PDGF) AA were the best predictors of subsequent loss of elite controller status. RANTES in particular showed a strong association, being an average of four-fold higher in transient controllers.

In discussing their results, the authors emphasize the importance of focusing on examples of strict, persistent control of HIV if the goal is to identify “the right model of functional remission.” They also suggest that factors strongly predictive of future viral load rebound—such as RANTES levels—might have the potential to help discriminate elite controllers likely to benefit from ART from those who may not require it.

Similar points are made in a commentary in EBioMedicine by Laura Tarancon-Diez and colleagues. The commentary accompanies a paper describing an elite controller who has maintained extremely low levels of HIV RNA and HIV DNA for a decade, without fully seroconverting on the Western Blot antibody assay. Evidence of polyfunctional HIV-specific CD8 T cell responses and strong antibody-mediated cellular cytotoxicity (ADCC) by natural killer cells is reported. The individual acquired HIV from a partner who was not able to control the same CRF02_AG virus variant. Neither partner possesses known favorable HLA alleles although both are heterozygous for the CCR5Δ32 mutation.

The commentary also cites work published last year from the French CODEX cohort, which described a subset of HIV controllers in whom viral load had never been detectable using routine assays during an average of 18 years of follow up. In a comparison with controllers who had experienced viral load blips, T cell counts were reported to be stable (as opposed to progressively declining), and this was accompanied by lower T cell activation and HIV DNA measurements. This study also showed a trend toward an overrepresentation of women in the persistently undetectable group (34 out of 52, 65%) versus the viral load blips group (90 out of 178, 51%, p=0.06).

Tarancon-Diez and colleagues advocate concentrating on “this very scarce proportion of individuals that are able to persistently control the virus” in order to inform the design of cure strategies aiming to induce long-term remission in the absence of ongoing ART.

Whether there might be particular features of the immune response (or other factors) in women that increase the likelihood of persistent elite control needs to be elucidated. Ongoing work is investigating possible differences related to HIV persistence in women receiving ART, with Eileen Scully presenting the latest findings from her research as a poster at the CROI 2018 conference. Scully has uncovered a number of significant sex-based associations, including higher expression of several antiviral genes.

As Zhang and colleagues argue in the closing section of their EBioMedicine paper: "Despite extensive data on the male and female difference on disease outcome, research does not sufficiently take gender into account. Altogether, our study showed that it would be important to carefully consider gender in cohort design for future transcriptomic and intervention studies on HIV-1 patients."

Recruiting Natural Killer Cells to Target HIV Persistence

An important goal in HIV cure research is the identification of immune responses that might be induced or enhanced to promote clearance of virus-infected cells. The main focus of this work has been on adaptive immunity—components of the immune system that can specifically recognize HIV, which include CD4 T cells, CD8 T cells, B cells and antibodies. But there is growing interest in cells considered part of the innate immune system, particularly natural killer (NK) cells. NK cells have the potential to destroy virus-infected cells by several mechanisms, including the identification of generic signs of cellular distress or infection, or via antibody-mediated recruitment to a target cell (known as antibody-dependent cellular cytotoxicity/ADCC).

Over the past few months a number of studies have been published that support the idea that NK cells can play an important role in controlling virus replication. In the journal Nature Medicine, Nicolas Huot and colleagues describe evidence that NK cells contribute to suppression of SIV replication in the lymph nodes of African Green Monkeys (AGMs), a host species that does not experience pathogenic consequences from the infection.

In experiments comparing nonpathogenic SIV infection of AGMs to pathogenic infection in macaques, NK cells were found to localize within and around lymph node B cell follicles—the major site of virus replication and persistence—in AGMs, but were scattered randomly in macaques, with no accumulation in follicles. NK cell numbers in lymph nodes also progressively declined in macaques, while being maintained at pre-infection levels in AGMs.

Additional analyses found that these differences were associated with an increased frequency of NK cells expressing CXCR5 (a receptor governing homing into follicles) and localized production of the cytokine IL-15 in the follicles of AGMs. The role of IL-15 was further confirmed by administration of an anti-IL-15 antibody, which depleted NK cells from the lymph nodes of the AGMs and led to a significant increase in SIV replication.

The authors write in their conclusion: “On the basis of our results, we anticipate that better comprehension of NK cell biology in lymphoid tissues, as provided here, will endorse the search for new NK cell–based immunotherapies for HIV infection.”

A review published in the journal AIDS in November covers some of the potential NK cell–based immunotherapies that are under investigation. A panoply of clinical trials are testing broadly neutralizing antibodies (bNAbs), which may have the ability to promote NK cell-mediated ADCC. In some cases bNAbs are being evaluated in tandem with latency-reversing agents, with the aim of depleting the HIV reservoir.

Also cited is the toll-like receptor 9 (TLR9) agonist MGN1703, which researchers at the University of Aarhus have shown can promote NK cell activation in HIV-positive people on ART. The same research group has also reported that NK cell responses may have been linked to an HIV DNA decline in some participants in a trial of the latency-reversing agent panobinostat.

Other NK cell–based immunotherapies in clinical trials include ALT-803, a modified version of the cytokine IL-15. The research group of Timothy Schacker at the University of Minnesota is conducting a small study involving ALT-803 administration to HIV-positive individuals on ART. A paper published in the Journal of Virology late last year describes a transient anti-SIV effect of the compound in macaques that were not receiving ART. Schacker and colleagues have also recently launched a trial in which individuals will receive infusions of NK cells from matched donors in combination with the cytokine IL-2.

The effects of the cytokine alpha interferon on HIV persistence are a major topic of interest at the newly-funded BEAT-HIV Collaboratory led by Luis Montaner at the Wistar Institute in Philadelphia. Last month in Clinical Infectious Diseases, Stéphane Hua and colleagues presented evidence that NK cell activation associates with a decline in HIV DNA levels in HIV-positive individuals receiving alpha interferon for the treatment of hepatitis C.

In sum, after a long period in the shadow of the better-known components of the adaptive immune system, NK cells are now emerging as potentially important players in HIV cure research. Results from the ongoing trials should soon shed additional light on how they might be able to contribute.