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Antibody-dependent cell-mediated cytotoxicity in simian immunodeficiency virus-infected rhesus monkeys. J Virol 2011; 85:6906-12. [PMID: 21593181 DOI: 10.1128/jvi.00326-11] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
With the recent demonstration in the RV144 Thai trial that a vaccine regimen that does not elicit neutralizing antibodies or cytotoxic T lymphocytes may confer protection against human immunodeficiency virus type 1 (HIV-1) infection, attention has turned to nonneutralizing antibodies as a possible mechanism of vaccine protection. In the current study, we evaluated the kinetics of the antibody-dependent cell-mediated cytotoxicity (ADCC) response during acute and chronic SIVmac251 infection of rhesus monkeys. We first adapted a flow cytometry-based ADCC assay, evaluating the use of different target cells as well as different strategies for quantitation of activated natural killer (NK) cells. We found that the use of SIVmac251 Env gp130-coated target cells facilitates analyses of ADCC activity with a higher degree of sensitivity than the use of simian immunodeficiency virus (SIV)-infected target cells; however, the kinetics of the measured responses were the same using these different target cells. By comparing NK cell expression of CD107a with NK cell expression of other cytokines or chemokine molecules, we found that measuring CD107a expression is sufficient for evaluating the anti-SIV function of NK cells. We also showed that ADCC responses can be detected as early as 3 weeks after SIVmac251 infection and that the magnitude of this antibody response is inversely associated with plasma viral RNA levels in animals with moderate to high levels of viral replication. However, we also demonstrated an association between NK cell-mediated ADCC responses and the amount of SIVmac251 gp140 binding antibody that developed after viral infection. This final observation raises the possibility that the antibodies that mediate ADCC are a subset of the antibodies detected in a binding assay and arise within weeks of infection.
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Antibody-dependent cell-mediated viral inhibition emerges after simian immunodeficiency virus SIVmac251 infection of rhesus monkeys coincident with gp140-binding antibodies and is effective against neutralization-resistant viruses. J Virol 2011; 85:5465-75. [PMID: 21450829 DOI: 10.1128/jvi.00313-11] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Antibody-dependent cell-mediated viral inhibition (ADCVI) is an attractive target for vaccination because it takes advantage of both the anamnestic properties of an adaptive immune response and the rapid early response characteristics of an innate immune response. Effective utilization of ADCVI in vaccine strategies will depend on an understanding of the natural history of ADCVI during acute and chronic human immunodeficiency virus type 1 (HIV-1) infection. We used the simian immunodeficiency virus (SIV)-infected rhesus monkey as a model to study the kinetics of ADCVI in early infection, the durability of ADCVI through the course of infection, and the effectiveness of ADCVI against viruses with envelope mutations that are known to confer escape from antibody neutralization. We demonstrate the development of ADCVI, capable of inhibiting viral replication 100-fold, within 3 weeks of infection, preceding the development of a comparable-titer neutralizing antibody response by weeks to months. The emergence of ADCVI was temporally associated with the emergence of gp140-binding antibodies, and in most animals, ADCVI persisted through the course of infection. Highly evolved viral envelopes from viruses isolated at late time points following infection that were resistant to plasma neutralization remained susceptible to ADCVI, suggesting that the epitope determinants of neutralization escape are not shared by antibodies that mediate ADCVI. These findings suggest that despite the ability of SIV to mutate and adapt to multiple immunologic pressures during the course of infection, SIV envelope may not escape the binding of autologous antibodies that mediate ADCVI.
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Patterson LJ, Daltabuit-Test M, Xiao P, Zhao J, Hu W, Wille-Reece U, Brocca-Cofano E, Kalyanaraman V, Kalisz I, Whitney S, Lee EM, Pal R, Montefiori DC, Dandekar S, Seder R, Roederer M, Wiseman RW, Hirsch V, Robert-Guroff M. Rapid SIV Env-specific mucosal and serum antibody induction augments cellular immunity in protecting immunized, elite-controller macaques against high dose heterologous SIV challenge. Virology 2011; 411:87-102. [PMID: 21237474 PMCID: PMC3039060 DOI: 10.1016/j.virol.2010.12.033] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2010] [Revised: 10/31/2010] [Accepted: 12/19/2010] [Indexed: 12/15/2022]
Abstract
Three Indian rhesus macaques, Ad-SIV primed/protein boosted and exposed twice to high-dose mucosal SIV(mac251) challenges, exhibited elite control of viremia over 6.5 years. They were negative for host factors associated with control of SIV infection. After a third intrarectal challenge with SIV(smE660), all controlled viremia, with one (macaque #5) maintaining undetectable viremia in blood. Acquisition was not blocked, but virus was contained in the jejunum and draining lymph nodes. Polyfunctional memory T cell responses and high-titered neutralizing and non-neutralizing serum and mucosal antibodies were present before and maintained post-challenge. The level of protection seen for animal #5 was predicted from analyses of gene transcription in jejunum 2 weeks post-challenge. Macaques #7 and #9, exhibiting lower pre-challenge cellular and humoral immunity, partially controlled the SIV(smE660) challenge. Initial vaccine-induced control by macaque #5 extended to the SIV(smE660) challenge due to multiple immune mechanisms that were boosted and augmented by cryptic SIV exposure.
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Affiliation(s)
- L. Jean Patterson
- Vaccine Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Mara Daltabuit-Test
- Vaccine Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Peng Xiao
- Vaccine Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Jun Zhao
- Vaccine Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - William Hu
- Department of Medical Microbiology and Immunology, University of California School of Medicine, Davis, CA 95616
| | - Ulrike Wille-Reece
- Vaccine Research Center, National Institutes of Health, Bethesda, MD 20892
| | - Egidio Brocca-Cofano
- Vaccine Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | | | - Irene Kalisz
- Advanced BioScience Laboratories, Inc., Kensington, MD 20895
| | - Stephen Whitney
- Advanced BioScience Laboratories, Inc., Kensington, MD 20895
| | - Eun Mi Lee
- Advanced BioScience Laboratories, Inc., Kensington, MD 20895
| | - Ranajit Pal
- Advanced BioScience Laboratories, Inc., Kensington, MD 20895
| | | | - Satya Dandekar
- Department of Medical Microbiology and Immunology, University of California School of Medicine, Davis, CA 95616
| | - Robert Seder
- Vaccine Research Center, National Institutes of Health, Bethesda, MD 20892
| | - Mario Roederer
- Vaccine Research Center, National Institutes of Health, Bethesda, MD 20892
| | - Roger W. Wiseman
- Wisconsin National Primate Research Center, University of Wisconsin-Madison, Madison, WI 53711
| | - Vanessa Hirsch
- Laboratory of Molecular Microbiology, National Institutes of Allergy and Infectious Disease, Bethesda, MD 20892
| | - Marjorie Robert-Guroff
- Vaccine Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
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Excler JL, Parks CL, Ackland J, Rees H, Gust ID, Koff WC. Replicating viral vectors as HIV vaccines: summary report from the IAVI-sponsored satellite symposium at the AIDS vaccine 2009 conference. Biologicals 2011; 38:511-21. [PMID: 20537552 DOI: 10.1016/j.biologicals.2010.03.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2010] [Accepted: 03/29/2010] [Indexed: 01/30/2023] Open
Abstract
In October 2009, The International AIDS Vaccine Initiative (IAVI) convened a satellite symposium entitled 'Replicating Viral Vectors for use in AIDS Vaccines' at the AIDS Vaccine 2009 Conference in Paris. The purpose of the symposium was to gather together researchers, representatives from regulatory agencies, and vaccine developers to discuss issues related to advancement of replication-competent viral vector- based HIV vaccines into clinical trials. The meeting introduced the rationale for accelerating the development of replicating viral vectors for use as AIDS vaccines. It noted that the EMEA recently published draft guidelines that are an important first step in providing guidance for advancing live viral vectors into clinical development. Presentations included case studies and development challenges for viral vector-based vaccine candidates. These product development challenges included cell substrates used for vaccine manufacturing, the testing needed to assess vaccine safety, conducting clinical trials with live vectors, and assessment of vaccination risk versus benefit. More in depth discussion of risk and benefit highlighted the fact that AIDS vaccine efficacy trials must be conducted in the developing world where HIV incidence is greatest and how inequities in global health dramatically influence the political and social environment in developing countries.
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Affiliation(s)
- J L Excler
- International AIDS Vaccine Initiative, 110 William Street, 27th Floor, New York, NY 10038-3901, USA
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55
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Isitman G, Chung AW, Navis M, Kent SJ, Stratov I. Pol as a target for antibody dependent cellular cytotoxicity responses in HIV-1 infection. Virology 2011; 412:110-6. [PMID: 21269655 DOI: 10.1016/j.virol.2010.12.044] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2010] [Revised: 11/28/2010] [Accepted: 12/22/2010] [Indexed: 11/29/2022]
Abstract
Antibody-dependent cellular cytotoxicity (ADCC) may assist in preventing HIV or delaying disease progression. Most prior studies have analysed Env-specific ADCC responses. We hypothesized that effective ADCC-based immunity may target conserved internal viral proteins such as Pol. We analysed the ability overlapping Pol peptides to induce activation of NK cells via ADCC. We prospectively studied ADCC responses in 83 HIV+ subjects followed for 3 years. Pol peptides were commonly targeted by ADCC responses in these chronically infected subjects (in 32 of the 83 subjects). However, Pol-specific ADCC responses declined over time and did not correlate with delayed HIV progression, measured by either baseline CD4 T cells, CD4 T cell loss over time, baseline viral load or the need to start antiretroviral therapy. Although Pol is frequently targeted by ADCC in HIV+ subjects, the strength or specificity of Pol-specific ADCC responses needs to be modulated to be effective in delaying HIV progression.
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Affiliation(s)
- Gamze Isitman
- Department of Microbiology and Immunology, University of Melbourne, Victoria 3010, Australia
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56
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Abstract
PURPOSE OF REVIEW This review discusses select recent data that suggest that indeed it is possible to make a clinically useful preventive vaccine for HIV-1 and outlines some of the remaining obstacles that stand in the way of success. RECENT FINDINGS Passive protection studies, with broad neutralizing antibodies for mucosal simian-HIV challenges, in nonhuman primates have suggested that lower doses of neutralizing antibodies than previously thought may be effective in preventing HIV-1 infection. The use of recombinant antibody technology coupled with the ability to culture single memory B cells has yielded new broad neutralizing antibodies and new targets for vaccine design. The success of the RV144 Thai HIV-1 efficacy trials with a replication-defective recombinant canarypox vector (ALVAC)/gp120 prime, clade B/E recombinant gp120 protein boost showing 31% efficacy has given hope that indeed a protective HIV-1 vaccine can be made. SUMMARY Recent data in the last year have provided new hope that a clinically useful preventive HIV-1 vaccine can potentially be made. The path forward will require development of improved immunogens, understanding the correlates of protection to HIV-1, and development of immunogens to induce antibodies that can prevent the initial stages of HIV-1 infection at mucosal sites, in order to improve on the RV144 trial results.
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57
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Passive neutralizing antibody controls SHIV viremia and enhances B cell responses in infant macaques. Nat Med 2010; 16:1117-9. [PMID: 20890292 PMCID: PMC2952052 DOI: 10.1038/nm.2233] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2007] [Accepted: 09/07/2010] [Indexed: 11/09/2022]
Abstract
Maternal HIV-1-specific antibodies are efficiently transferred to newborns, but their role in disease control is unknown. We administered neutralizing IgG, including the human neutralizing monoclonal IgG1b12, at levels insufficient to block infection, to six newborn macaques before oral challenge with simian-HIV strain SF162P3 (SHIV(SF162P3)). All of the macaques rapidly developed neutralizing antibodies and had significantly reduced plasma viremia for six months. These studies support the use of neutralizing antibodies in enhancing B cell responses and viral control in perinatal settings.
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58
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Alpert MD, Rahmberg AR, Neidermyer W, Ng SK, Carville A, Camp JV, Wilson RL, Piatak M, Mansfield KG, Li W, Miller CJ, Lifson JD, Kozlowski PA, Evans DT. Envelope-modified single-cycle simian immunodeficiency virus selectively enhances antibody responses and partially protects against repeated, low-dose vaginal challenge. J Virol 2010; 84:10748-64. [PMID: 20702641 PMCID: PMC2950576 DOI: 10.1128/jvi.00945-10] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Accepted: 07/29/2010] [Indexed: 11/20/2022] Open
Abstract
Immunization of rhesus macaques with strains of simian immunodeficiency virus (SIV) that are limited to a single cycle of infection elicits T-cell responses to multiple viral gene products and antibodies capable of neutralizing lab-adapted SIV, but not neutralization-resistant primary isolates of SIV. In an effort to improve upon the antibody responses, we immunized rhesus macaques with three strains of single-cycle SIV (scSIV) that express envelope glycoproteins modified to lack structural features thought to interfere with the development of neutralizing antibodies. These envelope-modified strains of scSIV lacked either five potential N-linked glycosylation sites in gp120, three potential N-linked glycosylation sites in gp41, or 100 amino acids in the V1V2 region of gp120. Three doses consisting of a mixture of the three envelope-modified strains of scSIV were administered on weeks 0, 6, and 12, followed by two booster inoculations with vesicular stomatitis virus (VSV) G trans-complemented scSIV on weeks 18 and 24. Although this immunization regimen did not elicit antibodies capable of detectably neutralizing SIV(mac)239 or SIV(mac)251(UCD), neutralizing antibody titers to the envelope-modified strains were selectively enhanced. Virus-specific antibodies and T cells were observed in the vaginal mucosa. After 20 weeks of repeated, low-dose vaginal challenge with SIV(mac)251(UCD), six of eight immunized animals versus six of six naïve controls became infected. Although immunization did not significantly reduce the likelihood of acquiring immunodeficiency virus infection, statistically significant reductions in peak and set point viral loads were observed in the immunized animals relative to the naïve control animals.
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Affiliation(s)
- Michael D. Alpert
- Department of Microbiology and Molecular Genetics, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Department of Pathology, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Gene Therapy Program and Department of Microbiology, Immunology, and Parasitology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, SAIC—Frederick, National Cancer Institute at Frederick, Frederick, Maryland 21702, University of Massachusetts, Worcester, Massachusetts 01655, California National Primate Research Center, University of California, Davis, California 95616
| | - Andrew R. Rahmberg
- Department of Microbiology and Molecular Genetics, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Department of Pathology, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Gene Therapy Program and Department of Microbiology, Immunology, and Parasitology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, SAIC—Frederick, National Cancer Institute at Frederick, Frederick, Maryland 21702, University of Massachusetts, Worcester, Massachusetts 01655, California National Primate Research Center, University of California, Davis, California 95616
| | - William Neidermyer
- Department of Microbiology and Molecular Genetics, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Department of Pathology, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Gene Therapy Program and Department of Microbiology, Immunology, and Parasitology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, SAIC—Frederick, National Cancer Institute at Frederick, Frederick, Maryland 21702, University of Massachusetts, Worcester, Massachusetts 01655, California National Primate Research Center, University of California, Davis, California 95616
| | - Sharon K. Ng
- Department of Microbiology and Molecular Genetics, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Department of Pathology, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Gene Therapy Program and Department of Microbiology, Immunology, and Parasitology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, SAIC—Frederick, National Cancer Institute at Frederick, Frederick, Maryland 21702, University of Massachusetts, Worcester, Massachusetts 01655, California National Primate Research Center, University of California, Davis, California 95616
| | - Angela Carville
- Department of Microbiology and Molecular Genetics, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Department of Pathology, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Gene Therapy Program and Department of Microbiology, Immunology, and Parasitology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, SAIC—Frederick, National Cancer Institute at Frederick, Frederick, Maryland 21702, University of Massachusetts, Worcester, Massachusetts 01655, California National Primate Research Center, University of California, Davis, California 95616
| | - Jeremy V. Camp
- Department of Microbiology and Molecular Genetics, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Department of Pathology, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Gene Therapy Program and Department of Microbiology, Immunology, and Parasitology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, SAIC—Frederick, National Cancer Institute at Frederick, Frederick, Maryland 21702, University of Massachusetts, Worcester, Massachusetts 01655, California National Primate Research Center, University of California, Davis, California 95616
| | - Robert L. Wilson
- Department of Microbiology and Molecular Genetics, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Department of Pathology, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Gene Therapy Program and Department of Microbiology, Immunology, and Parasitology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, SAIC—Frederick, National Cancer Institute at Frederick, Frederick, Maryland 21702, University of Massachusetts, Worcester, Massachusetts 01655, California National Primate Research Center, University of California, Davis, California 95616
| | - Michael Piatak
- Department of Microbiology and Molecular Genetics, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Department of Pathology, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Gene Therapy Program and Department of Microbiology, Immunology, and Parasitology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, SAIC—Frederick, National Cancer Institute at Frederick, Frederick, Maryland 21702, University of Massachusetts, Worcester, Massachusetts 01655, California National Primate Research Center, University of California, Davis, California 95616
| | - Keith G. Mansfield
- Department of Microbiology and Molecular Genetics, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Department of Pathology, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Gene Therapy Program and Department of Microbiology, Immunology, and Parasitology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, SAIC—Frederick, National Cancer Institute at Frederick, Frederick, Maryland 21702, University of Massachusetts, Worcester, Massachusetts 01655, California National Primate Research Center, University of California, Davis, California 95616
| | - Wenjun Li
- Department of Microbiology and Molecular Genetics, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Department of Pathology, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Gene Therapy Program and Department of Microbiology, Immunology, and Parasitology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, SAIC—Frederick, National Cancer Institute at Frederick, Frederick, Maryland 21702, University of Massachusetts, Worcester, Massachusetts 01655, California National Primate Research Center, University of California, Davis, California 95616
| | - Christopher J. Miller
- Department of Microbiology and Molecular Genetics, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Department of Pathology, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Gene Therapy Program and Department of Microbiology, Immunology, and Parasitology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, SAIC—Frederick, National Cancer Institute at Frederick, Frederick, Maryland 21702, University of Massachusetts, Worcester, Massachusetts 01655, California National Primate Research Center, University of California, Davis, California 95616
| | - Jeffrey D. Lifson
- Department of Microbiology and Molecular Genetics, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Department of Pathology, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Gene Therapy Program and Department of Microbiology, Immunology, and Parasitology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, SAIC—Frederick, National Cancer Institute at Frederick, Frederick, Maryland 21702, University of Massachusetts, Worcester, Massachusetts 01655, California National Primate Research Center, University of California, Davis, California 95616
| | - Pamela A. Kozlowski
- Department of Microbiology and Molecular Genetics, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Department of Pathology, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Gene Therapy Program and Department of Microbiology, Immunology, and Parasitology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, SAIC—Frederick, National Cancer Institute at Frederick, Frederick, Maryland 21702, University of Massachusetts, Worcester, Massachusetts 01655, California National Primate Research Center, University of California, Davis, California 95616
| | - David T. Evans
- Department of Microbiology and Molecular Genetics, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Department of Pathology, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts 01772-9102, Gene Therapy Program and Department of Microbiology, Immunology, and Parasitology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, SAIC—Frederick, National Cancer Institute at Frederick, Frederick, Maryland 21702, University of Massachusetts, Worcester, Massachusetts 01655, California National Primate Research Center, University of California, Davis, California 95616
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Abstract
Individuals infected with HIV-1 and nearly everyone vaccinated with HIV-1 vaccines will, in time, generate antibodies against viral proteins. These antibodies do not resolve natural infection, and vaccine candidates that successfully stimulate the production of high titers of neutralizing antibodies have failed to protect against infection. In spite of this, antibodies continue to be a focus of vaccine research. One reason for the continued interest in antibodies is the failure of a vaccine engineered to generate cell-mediated immunity against HIV. Successful protective immunity against most intracellular pathogens involves several arms of the immune response. A successful vaccine should also stimulate both protective cell-mediated immunity and specific antibody. Efforts should be directed toward making a vaccine that will stimulate the production of 1) more antibody, 2) more broadly cross-reactive neutralizing antibody (broadly neutralizing antibodies), and 3) antibody with a particular functional activity (antibody-dependent cell-mediated cytotoxicity; catalytic antibodies).
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60
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Barnett SW, Burke B, Sun Y, Kan E, Legg H, Lian Y, Bost K, Zhou F, Goodsell A, Zur Megede J, Polo J, Donnelly J, Ulmer J, Otten GR, Miller CJ, Vajdy M, Srivastava IK. Antibody-mediated protection against mucosal simian-human immunodeficiency virus challenge of macaques immunized with alphavirus replicon particles and boosted with trimeric envelope glycoprotein in MF59 adjuvant. J Virol 2010; 84:5975-85. [PMID: 20392857 PMCID: PMC2876657 DOI: 10.1128/jvi.02533-09] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2009] [Accepted: 03/18/2010] [Indexed: 12/19/2022] Open
Abstract
We have previously shown that rhesus macaques were partially protected against high-dose intravenous challenge with simian-human immunodeficiency virus SHIV(SF162P4) following sequential immunization with alphavirus replicon particles (VRP) of a chimeric recombinant VEE/SIN alphavirus (derived from Venezuelan equine encephalitis virus [VEE] and the Sindbis virus [SIN]) encoding human immunodeficiency virus type 1 HIV-1(SF162) gp140DeltaV2 envelope (Env) and trimeric Env protein in MF59 adjuvant (R. Xu, I. K. Srivastava, C. E. Greer, I. Zarkikh, Z. Kraft, L. Kuller, J. M. Polo, S. W. Barnett, and L. Stamatatos, AIDS Res. Hum. Retroviruses 22:1022-1030, 2006). The protection did not require T-cell immune responses directed toward simian immunodeficiency virus (SIV) Gag. We extend those findings here to demonstrate antibody-mediated protection against mucosal challenge in macaques using prime-boost regimens incorporating both intramuscular and mucosal routes of delivery. The macaques in the vaccination groups were primed with VRP and then boosted with Env protein in MF59 adjuvant, or they were given VRP intramuscular immunizations alone and then challenged with SHIV(SF162P4) (intrarectal challenge). The results demonstrated that these vaccines were able to effectively protect the macaques to different degrees against subsequent mucosal SHIV challenge, but most noteworthy, all macaques that received the intramuscular VRP prime plus Env protein boost were completely protected. A statistically significant association was observed between the titer of virus neutralizing and binding antibodies as well as the avidity of anti-Env antibodies measured prechallenge and protection from infection. These results highlight the merit of the alphavirus replicon vector prime plus Env protein boost vaccine approach for the induction of protective antibody responses and are of particular relevance to advancing our understanding of the potential correlates of immune protection against HIV infection at a relevant mucosal portal of entry.
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Affiliation(s)
- Susan W Barnett
- Novartis Vaccines and Diagnostics, 350 Massachusetts Avenue, Cambridge, MA 02139, USA.
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61
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Abstract
Developing an HIV-1 vaccine that can elicit antibodies to prevent infection has been a formidable challenge. Although no single immunogen has generated antibodies that can neutralize diverse isolates, progress has been made in understanding (a) the structure of the HIV-1 envelope glycoprotein, which is targeted by neutralizing antibodies, (b) how HIV-1 evades antibodies made by an infected host, and (c) how rare monoclonal antibodies can exhibit broadly neutralizing activity. Advances in structural and molecular biology coupled with new approaches to isolate neutralizing antibodies from HIV-1-infected individuals are enhancing our understanding of what humoral immune responses will be required for a vaccine. This review summarizes progress in understanding the host antibody response to HIV-1 and current strategies for applying this information to develop an effective vaccine.
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Affiliation(s)
- James A Hoxie
- Division of Hematology/Oncology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
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62
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Multiple vaccine-elicited nonneutralizing antienvelope antibody activities contribute to protective efficacy by reducing both acute and chronic viremia following simian/human immunodeficiency virus SHIV89.6P challenge in rhesus macaques. J Virol 2010; 84:7161-73. [PMID: 20444898 DOI: 10.1128/jvi.00410-10] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have shown that following priming with replicating adenovirus type 5 host range mutant (Ad5hr)-human immunodeficiency virus (HIV)/simian immunodeficiency virus (SIV) recombinants, boosting with gp140 envelope protein enhances acute-phase protection against intravenous simian/human immunodeficiency virus (SHIV)(89.6P) challenge compared to results with priming and no boosting or boosting with an HIV polypeptide representing the CD4 binding site of gp120. We retrospectively analyzed antibodies in sera and rectal secretions from these same macaques, investigating the hypothesis that vaccine-elicited nonneutralizing antibodies contributed to the better protection. Compared to other immunized groups or controls, the gp140-boosted group exhibited significantly greater antibody activities mediating antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cell-mediated viral inhibition (ADCVI) in sera and transcytosis inhibition in rectal secretions. ADCC and ADCVI activities were directly correlated with antibody avidity, suggesting the importance of antibody maturation for functionality. Both ADCVI and percent ADCC killing prechallenge were significantly correlated with reduced acute viremia. The latter, as well as postchallenge ADCVI and ADCC, was also significantly correlated with reduced chronic viremia. We have previously demonstrated induction by the prime/boost regimen of mucosal antibodies that inhibit transcytosis of SIV across an intact epithelial cell layer. Here, antibody in rectal secretions was significantly correlated with transcytosis inhibition. Importantly, the transcytosis specific activity (percent inhibition/total secretory IgA and IgG) was strongly correlated with reduced chronic viremia, suggesting that mucosal antibody may help control cell-to-cell viral spread during the course of infection. Overall, the replicating Ad5hr-HIV/SIV priming/gp140 protein boosting approach elicited strong systemic and mucosal antibodies with multiple functional activities associated with control of both acute and chronic viremia.
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63
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Hidajat R, Kuate S, Venzon D, Kalyanaraman V, Kalisz I, Treece J, Lian Y, Barnett SW, Robert-Guroff M. Construction and immunogenicity of replication-competent adenovirus 5 host range mutant recombinants expressing HIV-1 gp160 of SF162 and TV1 strains. Vaccine 2010; 28:3963-71. [PMID: 20382241 DOI: 10.1016/j.vaccine.2010.03.046] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2009] [Revised: 03/19/2010] [Accepted: 03/25/2010] [Indexed: 01/17/2023]
Abstract
An HIV Env immunogen capable of eliciting broad immunity is critical for a successful vaccine. We constructed and characterized adenovirus 5 host range mutant (Ad5hr) recombinants encoding HIV(SF162) gp160 (subtype B) and HIV(TV1) gp160 (subtype C). Immunization of mice with one or both induced cellular immunity to subtype B and C peptides by ELISpot, and antibody responses with high binding titers to HIV Env of subtypes A, B, C, and E. Notably, Ad5hr-HIV(TV1) gp160 induced better cellular immunity than Ad5hr-HIV(SF162) gp160, either alone or following co-administration. Thus, the TV1 Env recombinant alone may be sufficient for eliciting immune responses against both subtype B and C envelopes. Further studies of Ad5hr-HIV(TV1) gp160 in rhesus macaques will evaluate the suitability of this insert for a future phase I clinical trial using a replication-competent Ad4 vector.
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Affiliation(s)
- Rachmat Hidajat
- Section on Immune Biology of Retroviral Infection, Vaccine Branch, National Cancer Institute, Bethesda, MD 20892, USA
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Abstract
PURPOSE OF REVIEW We summarize current information on Fc receptor-mediated antiviral activities of antibodies. These activities include Fcgamma receptor-mediated inhibition and neutralization of HIV on antigen-presenting cells, antibody-dependent cellular cytotoxicity, and antibody-dependent cell-mediated virus inhibition (ADCVI). RECENT FINDINGS An Fcgamma receptor-mediated mechanism that results in augmented neutralization and may render nonneutralizing antibodies inhibitory has been demonstrated in antigen-presenting cell. Antibody-dependent cellular cytotoxicity antibody activity correlates inversely with HIV disease progression in humans, and higher vaccine-induced antibody-dependent cellular cytotoxicity antibody responses are associated with lower acute simian immunodeficiency virus viremia levels in macaques. Following vaccination with rgp120, ADCVI antibody levels are higher among those with a lower rate of sexually acquired HIV infection. Nonneutralizing simian immunodeficiency virus immune serum that prevents infection of newborn macaques after oral challenge has potent ADCVI antibody activity. Abrogating the ability of the Fc segment of the broadly neutralizing mAb b12 to bind to Fcgamma receptors and to mediate ADCVI substantially reduces b12's protective effect in a simian/human immunodeficiency virus vaginal challenge model. SUMMARY Fc-FcgammaR interactions play a critical role in the biological function of antibody and are likely to be instrumental in preventing or modulating lentiviral infection. Exploiting antibody responses that depend on Fc-FcgammaR interactions may help widen the breadth and increase the potency of vaccine-induced antibody. Although the importance of generating optimal Fab-antigen interactions cannot be overestimated, improving Fc-FcgammaR interactions through adjuvants or other strategies provides another option for improving HIV vaccines and immunotherapies.
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65
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Geonnotti AR, Bilska M, Yuan X, Ochsenbauer C, Edmonds TG, Kappes JC, Liao HX, Haynes BF, Montefiori DC. Differential inhibition of human immunodeficiency virus type 1 in peripheral blood mononuclear cells and TZM-bl cells by endotoxin-mediated chemokine and gamma interferon production. AIDS Res Hum Retroviruses 2010; 26:279-91. [PMID: 20218881 PMCID: PMC2864054 DOI: 10.1089/aid.2009.0186] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Bacterial lipopolysaccharide (endotoxin) is a frequent contaminant of biological specimens and is also known to be a potent inducer of beta-chemokines and other soluble factors that inhibit HIV-1 infection in vitro. Though lipopolysaccharide (LPS) has been shown to stimulate the production of soluble HIV-1 inhibitors in cultures of monocyte-derived macrophages, the ability of LPS to induce similar inhibitors in other cell types is poorly characterized. Here we show that LPS exhibits potent anti-HIV activity in phytohemagglutinin-stimulated peripheral blood mononuclear cells (PBMCs) but has no detectable anti-HIV-1 activity in TZM-bl cells. The anti-HIV-1 activity of LPS in PBMCs was strongly associated with the production of beta-chemokines from CD14-positive monocytes. Culture supernatants from LPS-stimulated PBMCs exhibited potent anti-HIV-1 activity when added to TZM-bl cells but, in this case, the antiviral activity appeared to be related to IFN-gamma rather than to beta-chemokines. These observations indicate that LPS stimulates PBMCs to produce a complex array of soluble HIV-1 inhibitors, including beta-chemokines and IFN-gamma, that differentially inhibit HIV-1 depending on the target cell type. The results also highlight the need to use endotoxin-free specimens to avoid artifacts when assessing HIV-1-specific neutralizing antibodies in PBMC-based assays.
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Affiliation(s)
- Anthony R Geonnotti
- Department of Surgery, Duke University Medical Center, Durham, North Carolina 27710, USA
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66
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Brown SA, Surman SL, Sealy R, Jones BG, Slobod KS, Branum K, Lockey TD, Howlett N, Freiden P, Flynn P, Hurwitz JL. Heterologous Prime-Boost HIV-1 Vaccination Regimens in Pre-Clinical and Clinical Trials. Viruses 2010; 2:435-467. [PMID: 20407589 PMCID: PMC2855973 DOI: 10.3390/v2020435] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Revised: 01/12/2010] [Accepted: 01/22/2010] [Indexed: 12/21/2022] Open
Abstract
Currently, there are more than 30 million people infected with HIV-1 and thousands more are infected each day. Vaccination is the single most effective mechanism for prevention of viral disease, and after more than 25 years of research, one vaccine has shown somewhat encouraging results in an advanced clinical efficacy trial. A modified intent-to-treat analysis of trial results showed that infection was approximately 30% lower in the vaccine group compared to the placebo group. The vaccine was administered using a heterologous prime-boost regimen in which both target antigens and delivery vehicles were changed during the course of inoculations. Here we examine the complexity of heterologous prime-boost immunizations. We show that the use of different delivery vehicles in prime and boost inoculations can help to avert the inhibitory effects caused by vector-specific immune responses. We also show that the introduction of new antigens into boost inoculations can be advantageous, demonstrating that the effect of `original antigenic sin' is not absolute. Pre-clinical and clinical studies are reviewed, including our own work with a three-vector vaccination regimen using recombinant DNA, virus (Sendai virus or vaccinia virus) and protein. Promising preliminary results suggest that the heterologous prime-boost strategy may possibly provide a foundation for the future prevention of HIV-1 infections in humans.
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Affiliation(s)
- Scott A. Brown
- Department of Immunology, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN, USA; E-Mail: (S.A.B.)
- Department of Infectious Diseases, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN, USA; E-Mails: (S.L.S.); (R.S.); (B.G.J.); (K.B.); (N.H.); (P.F.); (P.F.)
| | - Sherri L. Surman
- Department of Infectious Diseases, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN, USA; E-Mails: (S.L.S.); (R.S.); (B.G.J.); (K.B.); (N.H.); (P.F.); (P.F.)
| | - Robert Sealy
- Department of Infectious Diseases, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN, USA; E-Mails: (S.L.S.); (R.S.); (B.G.J.); (K.B.); (N.H.); (P.F.); (P.F.)
| | - Bart G. Jones
- Department of Infectious Diseases, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN, USA; E-Mails: (S.L.S.); (R.S.); (B.G.J.); (K.B.); (N.H.); (P.F.); (P.F.)
| | - Karen S. Slobod
- Early Development, Novartis Vaccines and Diagnostics, 350 Mass Ave. Cambridge, MA 02139, USA; E-Mail: (K.S.S.)
| | - Kristen Branum
- Department of Infectious Diseases, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN, USA; E-Mails: (S.L.S.); (R.S.); (B.G.J.); (K.B.); (N.H.); (P.F.); (P.F.)
| | - Timothy D. Lockey
- Department of Therapeutics, Production and Quality, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN, USA; E-Mail: (T.D.L.)
| | - Nanna Howlett
- Department of Infectious Diseases, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN, USA; E-Mails: (S.L.S.); (R.S.); (B.G.J.); (K.B.); (N.H.); (P.F.); (P.F.)
| | - Pamela Freiden
- Department of Infectious Diseases, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN, USA; E-Mails: (S.L.S.); (R.S.); (B.G.J.); (K.B.); (N.H.); (P.F.); (P.F.)
| | - Patricia Flynn
- Department of Infectious Diseases, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN, USA; E-Mails: (S.L.S.); (R.S.); (B.G.J.); (K.B.); (N.H.); (P.F.); (P.F.)
- Department of Pediatrics, University of Tennessee, Memphis, TN 38163, USA
| | - Julia L. Hurwitz
- Department of Immunology, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN, USA; E-Mail: (S.A.B.)
- Department of Infectious Diseases, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN, USA; E-Mails: (S.L.S.); (R.S.); (B.G.J.); (K.B.); (N.H.); (P.F.); (P.F.)
- Department of Pathology, University of Tennessee, Memphis, TN 38163, USA
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Antibody-Mediated Fcγ Receptor-Based Mechanisms of HIV Inhibition: Recent Findings and New Vaccination Strategies. Viruses 2009; 1:1265-94. [PMID: 21994593 PMCID: PMC3185537 DOI: 10.3390/v1031265] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Revised: 12/01/2009] [Accepted: 12/08/2009] [Indexed: 01/11/2023] Open
Abstract
The HIV/AIDS pandemic is one of the most devastating pandemics worldwide. Today, the major route of infection by HIV is sexual transmission. One of the most promising strategies for vaccination against HIV sexual infection is the development of a mucosal vaccine, which should be able to induce strong local and systemic protective immunity. It is believed that both humoral and cellular immune responses are needed for inducing a sterilizing protection against HIV. Recently, passive administration of monoclonal neutralizing antibodies in macaques infected by vaginal challenge demonstrated a crucial role of FcγRs in the protection afforded by these antibodies. This questioned about the role of innate and adaptive immune functions, including ADCC, ADCVI, phagocytosis of opsonized HIV particles and the production of inflammatory cytokines and chemokines, in the mechanism of HIV inhibition in vivo. Other monoclonal antibodies - non-neutralizing inhibitory antibodies - which recognize immunogenic epitopes, have been shown to display potent FcγRs-dependent inhibition of HIV replication in vitro. The potential role of these antibodies in protection against sexual transmission of HIV and their biological relevance for the development of an HIV vaccine therefore need to be determined. This review highlights the potential role of FcγRs-mediated innate and adaptive immune functions in the mechanism of HIV protection.
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68
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Immunogenicity of viral vector, prime-boost SIV vaccine regimens in infant rhesus macaques: attenuated vesicular stomatitis virus (VSV) and modified vaccinia Ankara (MVA) recombinant SIV vaccines compared to live-attenuated SIV. Vaccine 2009; 28:1481-92. [PMID: 19995539 DOI: 10.1016/j.vaccine.2009.11.061] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Revised: 11/09/2009] [Accepted: 11/22/2009] [Indexed: 11/21/2022]
Abstract
In a previously developed infant macaque model mimicking HIV infection by breast-feeding, we demonstrated that intramuscular immunization with recombinant poxvirus vaccines expressing simian immunodeficiency virus (SIV) structural proteins provided partial protection against infection following oral inoculation with virulent SIV. In an attempt to further increase systemic but also local antiviral immune responses at the site of viral entry, we tested the immunogenicity of different orally administered, replicating vaccines. One group of newborn macaques received an oral prime immunization with a recombinant vesicular stomatitis virus expressing SIVmac239 gag, pol and env (VSV-SIVgpe), followed 2 weeks later by an intramuscular boost immunization with MVA-SIV. Another group received two immunizations with live-attenuated SIVmac1A11, administered each time both orally and intravenously. Control animals received mock immunizations or non-SIV VSV and MVA control vectors. Analysis of SIV-specific immune responses in blood and lymphoid tissues at 4 weeks of age demonstrated that both vaccine regimens induced systemic antibody responses and both systemic and local cell-mediated immune responses. The safety and immunogenicity of the VSV-SIVgpe+MVA-SIV immunization regimen described in this report provide the scientific incentive to explore the efficacy of this vaccine regimen against virulent SIV exposure in the infant macaque model.
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69
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Broadly neutralizing monoclonal antibodies 2F5 and 4E10 directed against the human immunodeficiency virus type 1 gp41 membrane-proximal external region protect against mucosal challenge by simian-human immunodeficiency virus SHIVBa-L. J Virol 2009; 84:1302-13. [PMID: 19906907 DOI: 10.1128/jvi.01272-09] [Citation(s) in RCA: 273] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The membrane-proximal external region (MPER) of HIV-1, located at the C terminus of the gp41 ectodomain, is conserved and crucial for viral fusion. Three broadly neutralizing monoclonal antibodies (bnMAbs), 2F5, 4E10, and Z13e1, are directed against linear epitopes mapped to the MPER, making this conserved region an important potential vaccine target. However, no MPER antibodies have been definitively shown to provide protection against HIV challenge. Here, we show that both MAbs 2F5 and 4E10 can provide complete protection against mucosal simian-human immunodeficiency virus (SHIV) challenge in macaques. MAb 2F5 or 4E10 was administered intravenously at 50 mg/kg to groups of six male Indian rhesus macaques 1 day prior to and again 1 day following intrarectal challenge with SHIV(Ba-L). In both groups, five out of six animals showed complete protection and sterilizing immunity, while for one animal in each group a low level of viral replication following challenge could not be ruled out. The study confirms the protective potential of 2F5 and 4E10 and supports emphasis on HIV immunogen design based on the MPER region of gp41.
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70
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Surman SL, Sealy R, Jones BG, Hurwitz JL. HIV-1 vaccine design: harnessing diverse lymphocytes to conquer a diverse pathogen. HUMAN VACCINES 2009; 5:268-71. [PMID: 19684481 DOI: 10.4161/hv.5.4.7706] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In the fall of 2007, the HIV-1 research field received news that their front-runner vaccine was not protective. In response to this disappointment, scientists are now reviewing the intricacies of the immune response toward HIV-1 to develop new and better strategies for vaccine development. Decades ago, researchers recognized the impressive amino acid and carbohydrate diversity of HIV-1, and the associated obstacles to vaccine development. At first glance, the diversity and other unique features of HIV-1 may seem insurmountable, but attention to vaccine successes in other fields serves to renew optimism. The newly-licensed rotavirus and papillomavirus cocktail vaccines remind scientists that diverse pathogens can be conquered and that the chronic nature of a virus infection need not thwart successful vaccine design. Here we describe current efforts to gain insights from other vaccine fields and to adopt a cocktail vaccine approach for the prevention of HIV-1 infections in humans.
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Affiliation(s)
- Sherri L Surman
- Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
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71
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DNA vaccination in rhesus macaques induces potent immune responses and decreases acute and chronic viremia after SIVmac251 challenge. Proc Natl Acad Sci U S A 2009; 106:15831-6. [PMID: 19717425 DOI: 10.1073/pnas.0902628106] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Optimized plasmid DNAs encoding the majority of SIVmac239 proteins and delivered by electroporation (EP) elicited strong immune responses in rhesus macaques. Vaccination decreased viremia in both the acute and chronic phases of infection after challenge with pathogenic SIVmac251. Two groups of macaques were vaccinated with DNA plasmids producing different antigen forms, "native" and "modified," inducing distinct immune responses. Both groups showed significantly lower viremia during the acute phase of infection, whereas the group immunized with the native antigens showed better protection during the chronic phase (1.7 log decrease in virus load, P = 0.009). Both groups developed strong cellular and humoral responses against the DNA vaccine antigens, which included Gag, Pol, Env, Nef, and Tat. Vaccination induced both central memory and effector memory T cells that were maintained at the day of challenge, suggesting the potential for rapid mobilization upon virus challenge. The group receiving the native antigens developed higher and more durable anti-Env antibodies, including neutralizing antibodies at the day of challenge. These results demonstrate that DNA vaccination in the absence of any heterologous boost can provide protection from high viremia comparable to any other vaccine modalities tested in this macaque model.
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72
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Zhao J, Lai L, Amara RR, Montefiori DC, Villinger F, Chennareddi L, Wyatt LS, Moss B, Robinson HL. Preclinical studies of human immunodeficiency virus/AIDS vaccines: inverse correlation between avidity of anti-Env antibodies and peak postchallenge viremia. J Virol 2009; 83:4102-11. [PMID: 19224993 PMCID: PMC2668498 DOI: 10.1128/jvi.02173-08] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2008] [Accepted: 02/07/2009] [Indexed: 11/20/2022] Open
Abstract
A major challenge for human immunodeficiency virus (HIV)/AIDS vaccines is the elicitation of anti-Env antibodies (Ab) capable of neutralizing the diversity of isolates in the pandemic. Here, we show that high-avidity, but nonneutralizing, Abs can have an inverse correlation with peak postchallenge viremia for a heterologous challenge. Vaccine studies were conducted in rhesus macaques using DNA priming followed by modified vaccinia Ankara boosting with HIV type 1 (HIV-1) immunogens that express virus-like particles displaying CCR5-tropic clade B (strain ADA) or clade C (IN98012) Envs. Rhesus granulocyte-macrophage colony-stimulating factor was used as an adjuvant for enhancing the avidity of anti-Env Ab responses. Challenge was with simian/human immunodeficiency virus (SHIV)-162P3, a CCR5-tropic clade B chimera of SIV and HIV-1. Within the groups receiving the clade B vaccine, a strong inverse correlation was found between the avidity of anti-Env Abs and peak postchallenge viremia. This correlation required the use of native but not gp120 or gp140 forms of Env for avidity assays. The high-avidity Ab elicited by the ADA Env had excellent breadth for the Envs of incident clade B but not clade C isolates, whereas the high-avidity Ab elicited by the IN98012 Env had excellent breadth for incident clade C but not clade B isolates. High-avidity Ab elicited by a SHIV vaccine with a dual-tropic clade B Env (89.6) had limited breadth for incident isolates. Our results suggest that certain Envs can elicit nonneutralizing but high-avidity Ab with broad potential for blunting incident infections of the same clade.
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Affiliation(s)
- Jun Zhao
- Emory Vaccine Center, Atlanta, Georgia 30329, USA
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73
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Chung AW, Rollman E, Center RJ, Kent SJ, Stratov I. Rapid degranulation of NK cells following activation by HIV-specific antibodies. THE JOURNAL OF IMMUNOLOGY 2009; 182:1202-10. [PMID: 19124764 DOI: 10.4049/jimmunol.182.2.1202] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Ab-dependent cellular cytotoxicity (ADCC) Abs stimulate NK cell effector functions and play a role in protecting from and controlling viral infections. We characterized ADCC Abs in a cross-sectional cohort of 80 HIV-infected subjects not on antiretroviral therapy. We analyzed ADCC response by killing fluorescently labeled target cells, as well as expression of IFN-gamma and the degranulation marker CD107a from activated NK cells as measured by a novel intracellular cytokine assay. HIV-specific ADCC directed toward Envelope proteins were present in the majority of 80 untreated HIV-infected individuals measured by killing function. Similarly, most subjects had HIV-specific Abs that mediated degranulation or cytokine expression by NK cells. Interestingly, there was a poor correlation between ADCC-mediated killing of fluorescently labeled whole Envelope protein-pulsed cell lines and Ab-mediated expression of IFN-gamma by NK cells. However, in contrast to healthy donor NK cells, autologous patient NK cells more effectively degranulated granzyme B in response to ADCC activation. Activation of NK cells in response to stimulation by HIV-specific Abs occurs at least as rapidly as activation of Gag-specific CTLs. Our studies highlight the complexity of ab-mediated NK cell activation in HIV infection, and suggest new avenues toward studying the utility of ADCC in controlling HIV infection.
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Affiliation(s)
- Amy W Chung
- Department of Microbiology and Immunology, University of Melbourne, Melbourne, Australia
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74
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Correlation of vaccine-elicited systemic and mucosal nonneutralizing antibody activities with reduced acute viremia following intrarectal simian immunodeficiency virus SIVmac251 challenge of rhesus macaques. J Virol 2008; 83:791-801. [PMID: 18971271 DOI: 10.1128/jvi.01672-08] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cell-mediated immunity and neutralizing antibodies contribute to control of human immunodeficiency virus/simian immunodeficiency virus (HIV/SIV) infection, but the role of nonneutralizing antibodies is not defined. Previously, we reported that sequential oral/oral or intranasal/oral (I/O) priming with replication-competent adenovirus type 5 host range mutant (Ad5hr)-SIV recombinants, followed by intramuscular envelope protein boosting, elicited systemic and mucosal cellular immunity and exhibited equivalent, significant reductions of chronic viremia after rectal SIV(mac251) challenge. However, I/O priming gave significantly better control of acute viremia. Here, systemic and mucosal humoral immunity were investigated for potential correlates with the acute challenge outcome. Strong serum binding but nonneutralizing antibody responses against SIV(mac251) were induced in both groups. Antibody responses appeared earlier and overall were higher in the I/O group. Reduced acute viremia was significantly correlated with higher serum binding titer, stronger antibody-dependent cellular cytotoxicity activity, and peak prechallenge and 2-week-postchallenge antibody-dependent cell-mediated viral inhibition (ADCVI). The I/O group consistently displayed greater anti-envelope immunoglobulin A (IgA) antibody responses in bronchoalveolar lavage and a stronger rectal anti-envelope IgA anamnestic response 2 weeks postchallenge. Pre- and postchallenge rectal secretions inhibited SIV transcytosis across epithelial cells. The inhibition was significantly higher in the I/O group, although a significant correlation with reduced acute viremia was not reached. Overall, the replicating Ad5hr-SIV priming/envelope boosting approach elicited strong systemic and mucosal antibodies with multiple functional activities. The pattern of elevated immune responses in the I/O group is consistent with its better control of acute viremia mediated, at least in part, by ADCVI activity and transcytosis inhibition.
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75
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Eastman D, Piantadosi A, Wu X, Forthal DN, Landucci G, Kimata JT, Overbaugh J. Heavily glycosylated, highly fit SIVMne variants continue to diversify and undergo selection after transmission to a new host and they elicit early antibody dependent cellular responses but delayed neutralizing antibody responses. Virol J 2008; 5:90. [PMID: 18680596 PMCID: PMC2518139 DOI: 10.1186/1743-422x-5-90] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2008] [Accepted: 08/04/2008] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Lentiviruses such as human and simian immunodeficiency viruses (HIV and SIV) undergo continual evolution in the host. Previous studies showed that the late-stage variants of SIV that evolve in one host replicate to significantly higher levels when transmitted to a new host. However, it is unknown whether HIVs or SIVs that have higher replication fitness are more genetically stable upon transmission to a new host. To begin to address this, we analyzed the envelope sequence variation of viruses that evolved in animals infected with variants of SIVMne that had been cloned from an index animal at different stages of infection. RESULTS We found that there was more evolution of envelope sequences from animals infected with the late-stage, highly replicating variants than in animals infected with the early-stage, lower replicating variant, despite the fact that the late virus had already diversified considerably from the early virus in the first host, prior to transmission. Many of the changes led to the addition or shift in potential-glycosylation sites-, and surprisingly, these changes emerged in some cases prior to the detection of neutralizing antibody responses, suggesting that other selection mechanisms may be important in driving virus evolution. Interestingly, these changes occurred after the development of antibody whose anti-viral function is dependent on Fc-Fcgamma receptor interactions. CONCLUSION SIV variants that had achieved high replication fitness and escape from neutralizing antibodies in one host continued to evolve upon transmission to a new host. Selection for viral variants with glycosylation and other envelope changes may have been driven by both neutralizing and Fcgamma receptor-mediated antibody activities.
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Affiliation(s)
- Dawnnica Eastman
- Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
- Program in Molecular and Cellular Biology University of Washington, Seattle, WA, USA
| | - Anne Piantadosi
- Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
- Department of Pathobiology, University of Washington, Seattle, WA, USA
| | - Xueling Wu
- Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
- Vaccine Research Center, NIAID, NIH, Bethesda, MD, USA
| | - Donald N Forthal
- Division of Infectious Diseases, University of California, Irvine, CA, USA
| | - Gary Landucci
- Division of Infectious Diseases, University of California, Irvine, CA, USA
| | - Jason T Kimata
- Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA
| | - Julie Overbaugh
- Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
- Department of Pathobiology, University of Washington, Seattle, WA, USA
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Forthal DN, Landucci G, Bream J, Jacobson LP, Phan TB, Montoya B. FcgammaRIIa genotype predicts progression of HIV infection. THE JOURNAL OF IMMUNOLOGY 2008; 179:7916-23. [PMID: 18025239 DOI: 10.4049/jimmunol.179.11.7916] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Polymorphisms in FcgammaR genes are associated with susceptibility to or severity of a number of autoimmune and infectious diseases. We found that HIV-infected men in the Multicenter AIDS Cohort Study with the FcgammaRIIa RR genotype progressed to a CD4(+) cell count of <200/mm(3) at a faster rate than individuals with the RH or HH genotypes (relative hazard = 1.6; p = 0.0001). However, progression to AIDS (using the broad definition of either a CD4(+) cell count <200/mm(3) or development of an AIDS-defining illness) was less impacted by FcgammaRIIa genotype, largely because HH homozygotes had an increased risk of Pneumocystis jiroveci pneumonia as an AIDS-defining illness. We also showed that chronically infected subjects develop a substantial anti-gp120-specific IgG2 response. Moreover, HIV-1 immune complexes are more efficiently internalized by monocytes from HH subjects compared with RR subjects, likely because of the presence of IgG2 in the complexes. Finally, the FcgammaRIIIa F/V gene polymorphism was not associated with progression of HIV infection, but, as demonstrated previously, did predict the risk of Kaposi's sarcoma. These results demonstrate the importance of FcgammaRs in AIDS pathogenesis and point toward a critical role for interactions between FcgammaRs and immune complexes in disease progression.
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Affiliation(s)
- Donald N Forthal
- Division of Infectious Diseases, Department of Medicine, University of California, Irvine School of Medicine, Irvine, CA 92697, USA.
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77
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Abstract
The authors discuss humoral immune responses to HIV and approaches to designing vaccines that induce viral neutralizing and other potentially protective antibodies.
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78
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Hessell AJ, Hangartner L, Hunter M, Havenith CEG, Beurskens FJ, Bakker JM, Lanigan CMS, Landucci G, Forthal DN, Parren PWHI, Marx PA, Burton DR. Fc receptor but not complement binding is important in antibody protection against HIV. Nature 2007; 449:101-4. [PMID: 17805298 DOI: 10.1038/nature06106] [Citation(s) in RCA: 737] [Impact Index Per Article: 43.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2007] [Accepted: 07/20/2007] [Indexed: 11/08/2022]
Abstract
Most successful vaccines elicit neutralizing antibodies and this property is a high priority when developing an HIV vaccine. Indeed, passively administered neutralizing antibodies have been shown to protect against HIV challenge in some of the best available animal models. For example, antibodies given intravenously can protect macaques against intravenous or mucosal SHIV (an HIV/SIV chimaera) challenge and topically applied antibodies can protect macaques against vaginal SHIV challenge. However, the mechanism(s) by which neutralizing antibodies afford protection against HIV is not understood and, in particular, the role of antibody Fc-mediated effector functions is unclear. Here we report that there is a dramatic decrease in the ability of a broadly neutralizing antibody to protect macaques against SHIV challenge when Fc receptor and complement-binding activities are engineered out of the antibody. No loss of antibody protective activity is associated with the elimination of complement binding alone. Our in vivo results are consistent with in vitro assays indicating that interaction of Fc-receptor-bearing effector cells with antibody-complexed infected cells is important in reducing virus yield from infected cells. Overall, the data suggest the potential importance of activity against both infected cells and free virus for effective protection against HIV.
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Affiliation(s)
- Ann J Hessell
- Department of Immunology and Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA
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79
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Forthal DN, Gilbert PB, Landucci G, Phan T. Recombinant gp120 vaccine-induced antibodies inhibit clinical strains of HIV-1 in the presence of Fc receptor-bearing effector cells and correlate inversely with HIV infection rate. THE JOURNAL OF IMMUNOLOGY 2007; 178:6596-603. [PMID: 17475891 DOI: 10.4049/jimmunol.178.10.6596] [Citation(s) in RCA: 147] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Nonneutralizing Abs may play a role in protecting animals and humans from lentiviral infections. We explored the Ab-dependent, cell-mediated virus inhibition (ADCVI) Ab response to recombinant gp120 (rgp120) vaccination in sera from 530 participants in the Vax 004 trial. Serum ADCVI activity was measured against a clinical R5 strain of HIV-1 using peripheral blood mononuclear effector cells from healthy donors. The level of vaccine-induced ADCVI activity correlated inversely with the rate of acquiring HIV infection following vaccination, such that for every 10% increase in ADCVI activity, there was a 6.3% decrease in the hazard rate of infection (p=0.019). Some vaccinated individuals also mounted an ADCVI response against two other clinical R5 strains of HIV-1. However, ADCVI activity correlated poorly with neutralizing or CD4-gp120-blocking Ab activity measured against laboratory strains. Finally, the degree to which the ADCVI Ab response predicted the rate of infection was influenced by polymorphisms at the FcgammaRIIa and FcgammaRIIIa gene loci. These data indicate that rgp120 vaccination can elicit Abs with antiviral activity against clinical strains of HIV-1. However, such activity requires the presence of FcR-bearing effector cells. Our results provide further evidence that ADCVI may play a role in preventing HIV infection.
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MESH Headings
- AIDS Vaccines/administration & dosage
- AIDS Vaccines/immunology
- Antibodies, Blocking/biosynthesis
- Antibodies, Blocking/metabolism
- Antibodies, Blocking/physiology
- Antibody-Dependent Cell Cytotoxicity/genetics
- Antigens, CD/genetics
- HIV Antibodies/biosynthesis
- HIV Antibodies/metabolism
- HIV Antibodies/physiology
- HIV Envelope Protein gp120/administration & dosage
- HIV Envelope Protein gp120/immunology
- HIV Infections/immunology
- HIV Infections/prevention & control
- HIV Infections/virology
- HIV-1/growth & development
- HIV-1/immunology
- Humans
- Immunity, Cellular/genetics
- Killer Cells, Natural/immunology
- Killer Cells, Natural/metabolism
- Killer Cells, Natural/virology
- Macrophages/immunology
- Macrophages/metabolism
- Macrophages/virology
- Male
- Neutralization Tests
- Receptors, Fc/genetics
- Receptors, Fc/metabolism
- Receptors, IgG/genetics
- Vaccines, Subunit/administration & dosage
- Vaccines, Subunit/immunology
- Vaccines, Synthetic/administration & dosage
- Vaccines, Synthetic/immunology
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Affiliation(s)
- Donald N Forthal
- Division of Infectious Diseases, Department of Medicine, University of California, Irvine, CA 92697, USA.
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80
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Van Rompay KKA, Johnson JA, Blackwood EJ, Singh RP, Lipscomb J, Matthews TB, Marthas ML, Pedersen NC, Bischofberger N, Heneine W, North TW. Sequential emergence and clinical implications of viral mutants with K70E and K65R mutation in reverse transcriptase during prolonged tenofovir monotherapy in rhesus macaques with chronic RT-SHIV infection. Retrovirology 2007; 4:25. [PMID: 17417971 PMCID: PMC1852805 DOI: 10.1186/1742-4690-4-25] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2007] [Accepted: 04/06/2007] [Indexed: 01/29/2023] Open
Abstract
BACKGROUND We reported previously on the emergence and clinical implications of simian immunodeficiency virus (SIVmac251) mutants with a K65R mutation in reverse transcriptase (RT), and the role of CD8+ cell-mediated immune responses in suppressing viremia during tenofovir therapy. Because of significant sequence differences between SIV and HIV-1 RT that affect drug susceptibilities and mutational patterns, it is unclear to what extent findings with SIV can be extrapolated to HIV-1 RT. Accordingly, to model HIV-1 RT responses, 12 macaques were inoculated with RT-SHIV, a chimeric SIV containing HIV-1 RT, and started on prolonged tenofovir therapy 5 months later. RESULTS The early virologic response to tenofovir correlated with baseline viral RNA levels and expression of the MHC class I allele Mamu-A*01. For all animals, sensitive real-time PCR assays detected the transient emergence of K70E RT mutants within 4 weeks of therapy, which were then replaced by K65R mutants within 12 weeks of therapy. For most animals, the occurrence of these mutations preceded a partial rebound of plasma viremia to levels that remained on average 10-fold below baseline values. One animal eventually suppressed K65R viremia to undetectable levels for more than 4 years; sequential experiments using CD8+ cell depletion and tenofovir interruption demonstrated that both CD8+ cells and continued tenofovir therapy were required for sustained suppression of viremia. CONCLUSION This is the first evidence that tenofovir therapy can select directly for K70E viral mutants in vivo. The observations on the clinical implications of the K65R RT-SHIV mutants were consistent with those of SIVmac251, and suggest that for persons infected with K65R HIV-1 both immune-mediated and drug-dependent antiviral activities play a role in controlling viremia. These findings suggest also that even in the presence of K65R virus, continuation of tenofovir treatment as part of HAART may be beneficial, particularly when assisted by antiviral immune responses.
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Affiliation(s)
- Koen KA Van Rompay
- California National Primate Research Center, University of California, Davis, USA
| | - Jeffrey A Johnson
- Division of HIV/AIDS Prevention, National Center for HIV, STD and Tuberculosis Prevention, Centers for Disease Control and Prevention, Atlanta, USA
| | - Emily J Blackwood
- California National Primate Research Center, University of California, Davis, USA
| | - Raman P Singh
- California National Primate Research Center, University of California, Davis, USA
| | - Jonathan Lipscomb
- Division of HIV/AIDS Prevention, National Center for HIV, STD and Tuberculosis Prevention, Centers for Disease Control and Prevention, Atlanta, USA
| | | | - Marta L Marthas
- California National Primate Research Center, University of California, Davis, USA
| | - Niels C Pedersen
- Department of Medicine and Epidemiology, School of Veterinary Medicine; University of California, Davis, USA
| | | | - Walid Heneine
- Division of HIV/AIDS Prevention, National Center for HIV, STD and Tuberculosis Prevention, Centers for Disease Control and Prevention, Atlanta, USA
| | - Thomas W North
- Center for Comparative Medicine, University of California, Davis, USA
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, USA
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81
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Demberg T, Florese RH, Heath MJ, Larsen K, Kalisz I, Kalyanaraman VS, Lee EM, Pal R, Venzon D, Grant R, Patterson LJ, Korioth-Schmitz B, Buzby A, Dombagoda D, Montefiori DC, Letvin NL, Cafaro A, Ensoli B, Robert-Guroff M. A replication-competent adenovirus-human immunodeficiency virus (Ad-HIV) tat and Ad-HIV env priming/Tat and envelope protein boosting regimen elicits enhanced protective efficacy against simian/human immunodeficiency virus SHIV89.6P challenge in rhesus macaques. J Virol 2007; 81:3414-27. [PMID: 17229693 PMCID: PMC1866031 DOI: 10.1128/jvi.02453-06] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We previously demonstrated that replication-competent adenovirus (Ad)-simian immunodeficiency virus (SIV) recombinant prime/protein boost regimens elicit potent immunogenicity and strong, durable protection of rhesus macaques against SIV(mac251). Additionally, native Tat vaccines have conferred strong protection against simian/human immunodeficiency virus SHIV(89.6P) challenge of cynomolgus monkeys, while native, inactivated, or vectored Tat vaccines have failed to elicit similar protective efficacy in rhesus macaques. Here we asked if priming rhesus macaques with replicating Ad-human immunodeficiency virus (HIV) tat and boosting with the Tat protein would elicit protection against SHIV(89.6P). We also evaluated a Tat/Env regimen, adding an Ad-HIV env recombinant and envelope protein boost to test whether envelope antibodies would augment acute-phase protection. Further, expecting cellular immunity to enhance chronic viremia control, we tested a multigenic group: Ad-HIV tat, -HIV env, -SIV gag, and -SIV nef recombinants and Tat, Env, and Nef proteins. All regimens were immunogenic. A hierarchy was observed in enzyme-linked immunospot responses (with the strongest response for Env, followed by Gag, followed by Nef, followed by Tat) and antibody titers (with the highest titer for Env, followed by Tat, followed by Nef, followed by Gag). Following intravenous SHIV(89.6P) challenge, all macaques became infected. Compared to controls, no protection was seen in the Tat-only group, confirming previous reports for rhesus macaques. However, the multigenic group blunted acute viremia by approximately 1 log (P = 0.017), and both the multigenic and Tat/Env groups reduced chronic viremia by 3 and 4 logs, respectively, compared to controls (multigenic, P = 0.0003; Tat/Env, P < 0.0001). The strikingly greater reduction in the Tat/Env group than in the multigenic group (P = 0.014) was correlated with Tat and Env binding antibodies. Since prechallenge anti-Env antibodies lacked SHIV(89.6P)-neutralizing activity, other functional anti-Env and anti-Tat activities are under investigation, as is a possible synergy between the Tat and Env immunogens.
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Affiliation(s)
- Thorsten Demberg
- Vaccine Branch, National Cancer Institute/NIH, 41 Medlars Drive, Building 41, Bethesda, MD 20892-5065, USA
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