TAG HIV Basic Science, Vaccines, and Cure Project Blog

TB Vaccine Including a Latency-Associated Protein Shows Pre- and Post-Exposure Efficacy in Mouse Model

In a new paper published yesterday by Nature Medicine, researchers from the Statens Serum Institut (SSI) in Denmark describe encouraging results obtained with a new TB vaccine candidate. The design of the vaccine was informed by data showing that a particular TB protein, Rv2660c, remains strongly expressed during latent infection. This knowledge prompted the development of a “multistage” vaccine including Rv2660c along with two other TB antigens, Ag85B and ESAT-6. The resulting fusion protein vaccine is named H56. The goal is to create a vaccine capable of preventing active TB regardless of whether it is given before or after exposure.

In a mouse model of TB infection, the H56 vaccine was shown to be significantly superior in reducing bacterial load when compared to both the standard BCG vaccine and another candidate, H1, which contains only Ag85B and ESAT-6 antigens. The differences in efficacy took some time to become evident: 12 weeks after challenge in comparison to H1, and 24 weeks in comparison to BCG. Immune responses to the Rv2660c protein were weak early on but grew in magnitude over the period of follow up. In an experiment designed to evaluate the potential for post-exposure protection, H56 was found to provide a significant degree of protection against TB reactivation.

Based on these results, SSI is now initiating clinical development of H56. The current status of new TB vaccine candidates in clinical trials, including SSI’s, is summarized in a recent report from the 2010 Global TB Vaccines Forum on TAG’s website.

Nature Medicine (2011) doi:10.1038/nm.2285

Received 12 October 2010 Accepted 07 December 2010 Published online 23 January 2011

A multistage tuberculosis vaccine that confers efficient protection before and after exposure

Claus Aagaard, Truc Hoang, Jes Dietrich, Pere-Joan Cardona, Angelo Izzo, Gregory Dolganov, Gary K Schoolnik, Joseph P Cassidy, Rolf Billeskov & Peter Andersen

All tuberculosis vaccines currently in clinical trials are designed as prophylactic vaccines based on early expressed antigens. We have developed a multistage vaccination strategy in which the early antigens Ag85B and 6-kDa early secretory antigenic target (ESAT-6) are combined with the latency-associated protein Rv2660c (H56 vaccine). In CB6F1 mice we show that Rv2660c is stably expressed in late stages of infection despite an overall reduced transcription. The H56 vaccine promotes a T cell response against all protein components that is characterized by a high proportion of polyfunctional CD4+ T cells. In three different pre‐exposure mouse models, H56 confers protective immunity characterized by a more efficient containment of late-stage infection than the Ag85B-ESAT6 vaccine (H1) and BCG. In two mouse models of latent tuberculosis, we show that H56 vaccination after exposure is able to control reactivation and significantly lower the bacterial load compared to adjuvant control mice.

Dubious Analysis of a Therapeutic Tat Vaccine Trial

Toward the end of last year, a group of Italian researchers led by Barbara Ensoli published some limited data from an ongoing trial of a therapeutic HIV vaccine, and issued a press release to draw attention to the paper. The resulting press coverage was generally favorable. Somewhat lost in the discussion of the results was the fact that they were obtained in an “ad hoc exploratory interim analysis,” which is generally considered to be a dubious and unreliable way to analyze trial data. The vaccine candidate contains the Tat protein from HIV-1, and Ensoli’s group has been developing it for many years now. The question of whether the approach has any potential has been controversial; a macaque study suggesting protection against SHIV was not confirmed and there have also been reports of disputes about the vaccine’s development among the Italian research community. In light of this background, trumpeting the results of an ad hoc exploratory interim analysis via press release seems an imprudent strategy for the researchers to pursue.

The trial described in the paper is not placebo controlled, which adds to the challenge of trying to interpret the results. Because there is no control arm, comparisons in the paper are made between vaccine recipients and HIV positive individuals enrolled in “a parallel prospective observational study at the same sites.” Most of the immunological analyses reported in the paper involve small subsets of the 87 participants, but it is not clear how these subsets were selected. The primary aim of the trial is to compare the immunogenicity (ability to induce anti-Tat immune responses) of two different doses and two different dosing schedules of the vaccine. The secondary aim is to monitor safety. The trial protocol, which is included in the supporting information for the paper, does not make reference to the conduct of ad hoc exploratory interim analyses or their publication.

Amidst this sea of caveats, the researchers report that the higher vaccine dose was more immunogenic but no significant differences were apparent between the 3-dose and 5-dose immunization schedules. The vaccine was also found to be generally safe and well tolerated. From these top-line results, the paper descends into murky sub-analyses suggesting that the vaccine may have decreased CD8 T cell activation, both increased and decreased in CD4 T cell activation (depending on the marker), increased regulatory CD4 T cells, increased CD4 T cells and B cells, decreased CD8 T cells and natural killer cells, and altered representation of different memory T cell subsets. None of the reported analyses are statistically corrected for the multiple comparisons being performed.

Although the suggestion that therapeutic vaccination might reduce immune activation in HIV is not unprecedented, there is a discomforting gap between the murkiness of the methodology and the breezily conclusive title of the paper: “Therapeutic Immunization with HIV-1 Tat Reduces Immune Activation and Loss of Regulatory T-Cells and Improves Immune Function in Subjects on HAART.” The only way to show whether the vaccine can achieve these outcomes is with a randomized placebo-controlled study.

PLoS ONE 5(11): e13540. doi:10.1371/journal.pone.00135

Therapeutic Immunization with HIV-1 Tat Reduces Immune Activation and Loss of Regulatory T-Cells and Improves Immune Function in Subjects on HAART

Barbara Ensoli1*, Stefania Bellino1, Antonella Tripiciano1,2, Olimpia Longo1, Vittorio Francavilla1,2, Simone Marcotullio1, Aurelio Cafaro1, Orietta Picconi1, Giovanni Paniccia1,2, Arianna Scoglio1,2, Angela Arancio2, Cristina Ariola2, Maria J. Ruiz Alvarez1,2, Massimo Campagna2, Donato Scaramuzzi2, Cristina Iori2, Roberto Esposito3, Cristina Mussini3, Florio Ghinelli4, Laura Sighinolfi4, Guido Palamara5, Alessandra Latini5, Gioacchino Angarano6, Nicoletta Ladisa6, Fabrizio Soscia7, Vito S. Mercurio7, Adriano Lazzarin8, Giuseppe Tambussi8, Raffaele Visintini8, Francesco Mazzotta9, Massimo Di Pietro9, Massimo Galli10, Stefano Rusconi10, Giampiero Carosi11, Carlo Torti11, Giovanni Di Perri12, Stefano Bonora12, Fabrizio Ensoli2, Enrico Garaci13

1 National AIDS Center, Istituto Superiore di Sanità, Rome, Italy, 2 Core Laboratory of Virology and Immunology, San Gallicano Hospital, “Istituti Fisioterapici Ospetalieri”, Rome, Italy, 3 Division of Infectious Diseases, University Policlinic of Modena, Modena, Italy, 4 Unit of Infectious Diseases, University Hospital of Ferrara, Ferrara, Italy, 5 Department of Infectious Dermatology, San Gallicano Hospital, Rome, Italy, 6 Division of Infectious Diseases, University of Bari, Policlinic Hospital, Bari, Italy, 7 Department of Infectious Diseases, S. Maria Goretti Hospital, Latina, Italy, 8 Division of Infectious Diseases, S. Raffaele Hospital, Milan, Italy, 9 Unit of Infectious Diseases, S.M. Annunziata Hospital, Florence, Italy, 10 Institute of Tropical and Infectious Diseases, University of Milan L. Sacco Hospital, Milan, Italy, 11 Division of Tropical and Infectious Diseases, Spedali Civili, Brescia, Italy, 12 Clinic of Infectious Diseases, Amedeo di Savoia Hospital, Turin, Italy, 13 Istituto Superiore di Sanità, Rome, Italy

Abstract 

Although HAART suppresses HIV replication, it is often unable to restore immune homeostasis. Consequently, non-AIDS-defining diseases are increasingly seen in treated individuals. This is attributed to persistent virus expression in reservoirs and to cell activation. Of note, in CD4+ T cells and monocyte-macrophages of virologically-suppressed individuals, there is continued expression of multi-spliced transcripts encoding HIV regulatory proteins. Among them, Tat is essential for virus gene expression and replication, either in primary infection or for virus reactivation during HAART, when Tat is expressed, released extracellularly and exerts, on both the virus and the immune system, effects that contribute to disease maintenance. Here we report results of an ad hoc exploratory interim analysis (up to 48 weeks) on 87 virologically-suppressed HAART-treated individuals enrolled in a phase II randomized open-label multicentric clinical trial of therapeutic immunization with Tat (ISS T-002). Eighty-eight virologically-suppressed HAART-treated individuals, enrolled in a parallel prospective observational study at the same sites (ISS OBS T-002), served for intergroup comparison. Immunization with Tat was safe, induced durable immune responses, and modified the pattern of CD4+ and CD8+ cellular activation (CD38 and HLA-DR) together with reduction of biochemical activation markers and persistent increases of regulatory T cells. This was accompanied by a progressive increment of CD4+ T cells and B cells with reduction of CD8+ T cells and NK cells, which were independent from the type of antiretroviral regimen. Increase in central and effector memory and reduction in terminally-differentiated effector memory CD4+ and CD8+ T cells were accompanied by increases of CD4+ and CD8+ T cell responses against Env and recall antigens. Of note, more immune-compromised individuals experienced greater therapeutic effects. In contrast, these changes were opposite, absent or partial in the OBS population. These findings support the use of Tat immunization to intensify HAART efficacy and to restore immune homeostasis.

T Cell Activation & Senescence Associate with Carotid Artery Disease in HIV-Positive Women

In the early 1990s, UCLA researcher Janis Giorgi published evidence that the activation of the immune system by HIV (as measured by expression of a marker called CD38 on CD8 T cells) was a strong predictor of the pace of progression to AIDS. At the time the idea was controversial, but a voluminous amount of evidence has since accumulated confirming Giorgi’s finding and demonstrating that immune activation is central to the pathogenesis of HIV infection. Furthermore, it is now clear that while antiretroviral therapy (ART) greatly reduces immune activation, it can often persist at levels significantly higher than those seen in comparable HIV-negative individuals. The magnitude of this residual immune activation is linked to the CD4 count at the time of ART initiation: the lower the CD4 count, the higher the degree of residual activation.

Because the nadir (lowest ever) CD4 count is also the strongest predictor of the risk of illness in people on ART, there has been reason to suspect that residual immune activation contributes to ill health. Studies documenting associations between elevated levels of inflammatory biomarkers and mortality have bolstered this suspicion. However, data linking immune activation to specific clinical conditions is sparse. Similarly, one of the consequences of persistent immune activation is a type of T cell dysfunction called senescence. Senescent T cells are essentially old and worn out, and they have a bad habit of producing large amounts of inflammatory cytokines and appear to get in the way of T cells that do work properly. While the proportion of senescent T cells has been associated with the pace of disease progression in HIV, their role in specific diseases is unclear.

A new open access paper in the Journal of Infectious Diseases goes some way to addressing these information gaps. Led by Robert Kaplan of the Women’s Interagency HIV Study (WIHS), the research reveals that both CD8 T cell activation and CD8 T cell senescence predict carotid artery disease in HIV-positive women. Disease was assessed based on the extent of carotid lesions, which were defined as focal thickening (>1.5 mm) of the intima-media layer. The authors note that while these measures of subclinical vascular disease predict incident cardiovascular disease events in the general population, this has yet to be formally confirmed in the HIV-positive population. They conclude by stating: “our data provide further evidence that persistent activation of the immune system is associated with vascular abnormalities among HIV-infected individuals. This relationship was suggested by a small prior study that, unlike the present investigation, did not feature multivariate analyses, did not control for potential confounding effects of HIV-related and CVD-related variables, and lacked an HIV-uninfected control group. These results have important implications for assessment of vascular risk among adults with HIV infection.”

An accompanying commentary by Virginia Triant and Steven Grinspoon (link below) further discusses the implications of the findings, and posits that “studies investigating the mechanisms of these immunologic alterations in relation to cardiovascular events and exploring therapies to modify T cell activation and senescence will advance our understanding of this complex field and help to optimize the long-term care of HIV-infected individuals.”

J Infect Dis. (2011)doi: 10.1093/infdis/jiq071

First published online: January 10, 2011

T Cell Activation and Senescence Predict Subclinical Carotid Artery Disease in HIV-Infected Women

Robert C. Kaplan1, Elizabeth Sinclair2, Alan L. Landay4, Nell Lurain4, A. Richey Sharrett5, Stephen J. Gange5, Xiaonan Xue1, Peter Hunt2, Roksana Karim3, David M. Kern1, Howard N. Hodis3 and Steven G. Deeks2

Author Affiliations

1 Department of Epidemiology and Population Health, Albert Einstein College of Medicine of Yeshiva University, Bronx, New York

2 Division of Experimental Medicine, University of California, San Francisco

3 Atherosclerosis Research Unit, Departments of Medicine and Preventive Medicine, University of Southern California, Los Angeles, California

4 Rush University Medical Center, Chicago, Illinois

5 Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland

Abstract

Background. Individuals infected with human immunodeficiency virus (HIV) have increased risk of cardiovascular events. It is unknown whether T cell activation and senescence, 2 immunologic sequelae of HIV infection, are associated with vascular disease among HIV-infected adults.

Methods. T cell phenotyping and carotid ultrasound were assessed among 115 HIV-infected women and 43 age- and race/ethnicity-matched HIV-uninfected controls participating in the Women's Interagency HIV Study. Multivariate analyses were used to assess the association of T cell activation (CD38+HLA-DR+) and senescence (CD28−CD57+) with subclinical carotid artery disease.

Results. Compared with HIV-uninfected women, frequencies of CD4+CD38+HLA-DR+, CD8+CD38+HLA-DR+, and CD8+CD28−CD57+ T cells were higher among HIV-infected women, including those who achieved viral suppression while receiving antiretroviral treatment. Among HIV-infected women, adjusted for age, antiretroviral medications, and viral load, higher frequencies of activated CD4+ and CD8+ T cells and immunosenescent CD8+ T cells were associated with increased prevalence of carotid artery lesions (prevalence ratio_lesions associated with activated CD4+ T cells, 1.6 per SD [95% confidence interval {CI}, 1.1–2.2]; P = .02; prevalence ratio_lesions associated with activated CD8+ T cells, 2.0 per SD [95% CI, 1.2–3.3]; P < .01; prevalence ratio_lesions associated with senescent CD8+ T cells, 1.9 per SD [95% CI, 1.1–3.1]; P = .01).

Conclusions. HIV-associated T cell changes are associated with subclinical carotid artery abnormalities, which may be observed even among those patients achieving viral suppression with effective antiretroviral therapy.

J Infect Dis. (2011) doi: 10.1093/infdis/jiq084

First published online: January 10, 2011

Immune Dysregulation and Vascular Risk in HIV-Infected Patients: Implications for Clinical Care

Virginia A. Triant1 and Steven K. Grinspoon2

Author Affiliations

1 Division of Infectious Diseases

2 Program in Nutritional Metabolism, Massachusetts General Hospital, Boston, Massachusetts

Anchors Away: New HIV Entry Inhibitor Study Creates a Splash

Just before the holidays, the journal Science Translational Medicine published results from a phase I trial of a new type of anti-HIV drug named VIR-576. The drug inhibits the entry of HIV into target cells by blocking the mechanism the virus uses to anchor itself to the cell. This mechanism involves a harpoon-like extension called the gp41 fusion peptide, which shoots into the cell membrane. VIR-576 gloms onto the end of the gp41 fusion peptide, preventing its penetration (a bit like covering the spear end of a harpoon so it just bounces off the target). Although VIR-576 is not the first entry inhibitor HIV drug, it is the first to target the gp41 fusion peptide. The researchers have dubbed it an "anchoring inhibitor."

The phase I study administered three different doses of VIR-576 to three groups of six untreated HIV-positive people with viral loads over 10,000 copies and CD4 T cell counts above 350. Because VIR-576 is a peptide, administration was via continuous intravenous infusion. The total duration of treatment was 10 days. At the highest dose of 5 grams per day, VIR-576 caused an average viral load reduction of 1.2 logs (over 90%). The drug was well tolerated but two participants (one in each of the two lower dose groups) showed signs of an allergic reaction that resolved once treatment was stopped. No evidence of resistance to VIR-576 was documented.

The findings are potentially encouraging for several reasons:

• They show that HIV’s gp41 fusion peptide is a viable drug target, which was previously uncertain.
• The gp41 fusion peptide does not appear able to tolerate mutations as easily as other drug targets, suggesting resistance will be slower to develop.
• The activity of VIR-576 is not affected by resistance to available anti-HIV drugs.
• Fusion peptides are essential to the replication of most enveloped viruses, suggesting the general approach could be applied to other viral pathogens.

However, there are also caveats that were not clearly articulated in some of the media stories that appeared when the study was published. Most obvious is that the current formulation of VIR-576 cannot practically be used a treatment due to the requirement for continuous intravenous infusion. The high dose and potential cost are additional impediments; the dose of the approved HIV entry inhibitor Fuzeon (T-20) is 0.18 grams/day (with a cost of around $25,000 per year) whereas the most effective dose of VIR-576 was a daunting 5 grams/day. The researchers highlight these concerns in the discussion section of the paper and state: “to overcome these drawbacks in costs and administration, we are currently working on the development of small-molecule inhibitors with an analogous mode of action.” In interviews, investigator Frank Kirchoff has estimated that it will likely be at least a year before any oral analogs of VIR-576 are ready for testing.

Sci Transl Med 22 December 2010: Vol. 2, Issue 63, p. 63re3

DOI: 10.1126/scitranslmed.3001697

REPORTS

Short-Term Monotherapy in HIV-Infected Patients with a Virus Entry Inhibitor Against the gp41 Fusion Peptide

Wolf-Georg Forssmann1,2,3, Yu-Han The1, Matthias Stoll1, Knut Adermann1,2,3, Uwe Albrecht4, Kleomenis Barlos5,6, Annette Busmann1,2, Angeles Canales-Mayordomo7, Guillermo Giménez-Gallego7, Jochen Hirsch1,2,3, Jesus Jiménez-Barbero7, Dirk Meyer-Olson1, Jan Münch8, Javier Pérez-Castells9, Ludger Ständker1, Frank Kirchhoff8,* and Reinhold E. Schmidt1

1 Department of Immunology and Rheumatology, Hannover Medical University, Carl-Neuberg-Strasse 1, D-30625 Hannover, Germany.

2 VIRO Pharmaceuticals GmbH & Co. KG, Feodor-Lynen-Strasse 31, D-30625 Hannover, Germany.

3 Pharis Biotec GmbH, 30625 Hannover, Germany.

4 Mediconomics GmbH, Misburger-Strasse 81b, D-30625 Hannover, Germany.

5 Department of Chemistry, University of Patras, GR-26500 Rion-Patras, Greece.

6 CBL-Patras, 26333 Patras, Greece.

7 Departamento de Biología Físico-Química, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, E-28040 Madrid, Spain.

8 Institute of Molecular Virology, University Hospital of Ulm, Meyerhofstrasse 1, D-89081 Ulm, Germany.

9 Departamento de Química, Facultad de Farmacia, Universidad San Pablo CEU, E-28664 Madrid, Spain.

Abstract

To infect host cells, most enveloped viruses must insert a hydrophobic fusion peptide into the host cell membrane. Thus, fusion peptides may be valuable targets for developing drugs that block virus entry. We have shown previously that a natural 20-residue fragment of α1-antitrypsin, designated VIRus-Inhibitory Peptide (VIRIP), that binds to the gp41 fusion peptide of HIV-1 prevents the virus from entering target cells in vitro. Here, we examine the efficacy of 10-day monotherapy with the optimized VIR-576 derivative of VIRIP in treatment-naïve, HIV-1–infected individuals with viral RNA loads of ≥10,000 copies per ml. We report that at the highest dose (5.0 grams per day), intravenous infusion of VIR-576 reduced the mean plasma viral load by 1.23 log10 copies per ml without causing severe adverse effects. Our results are proof of concept that fusion peptide inhibitors suppress viral replication in human patients, and offer prospects for the development of a new class of drugs that prevent virus particles from anchoring to and infecting host cells.