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Background: The RV144 ALVAC-HIV prime, AIDSVAX B/E boost afforded 60% efficacy against human immunodeficiency virus (HIV) acquisition at 1 year, waning to 31.2% after 3.5 years. We hypothesized that additional vaccinations might augment immune correlates of protection.Methods: In a randomized placebo-controlled double-blind study of 162 HIV-negative RV144 vaccine recipients, we evaluated 2 additional boosts, given 6-8 years since RV144 vaccination, for safety and immunogenicity, at weeks 0 and 24. Study groups 1-3 received ALVAC-HIV+AIDSVAX B/E, AIDSVAX B/E, and ALVAC-HIV, respectively, or placebo.Results: Vaccines were well tolerated. For groups 1 and 2, plasma immunoglobulin (Ig) G, IgA, and neutralizing antibody responses at week 2 were all significantly higher than 2 weeks after the last RV144 vaccination. IgG titers against glycoprotein (gp) 70V1V2 92TH023 increased 14-fold compared with 2 weeks after the last RV144 vaccination (14069 vs 999; P < .001). Groups 1 and 2 did not differ significantly from each other, whereas group 3 was similar to placebo recipients. Responses in groups 1 and 2 declined by week 24 but were boosted by the second vaccination, albeit at lower magnitude than for week 2.Conclusions: In RV144 vaccinees, AIDSVAX B/E with or without ALVAC-HIV 6-8 years after initial vaccination generated higher humoral responses than after RV144, but these responses were short-lived, and their magnitude did not increase with subsequent boost.Clinical Trials Registration: NCT01435135. [ABSTRACT FROM AUTHOR]

Broadly neutralizing antibodies against highly variable viral pathogens are much sought after to treat or protect against global circulating viruses. Here we probed the neutralizing antibody repertoires of four human immunodeficiency virus (HIV)-infected donors with remarkably broad and potent neutralizing responses and rescued 17 new monoclonal antibodies that neutralize broadly across clades. Many of the new monoclonal antibodies are almost tenfold more potent than the recently described PG9, PG16 and VRC01 broadly neutralizing monoclonal antibodies and 100-fold more potent than the original prototype HIV broadly neutralizing monoclonal antibodies. The monoclonal antibodies largely recapitulate the neutralization breadth found in the corresponding donor serum and many recognize novel epitopes on envelope (Env) glycoprotein gp120, illuminating new targets for vaccine design. Analysis of neutralization by the full complement of anti-HIV broadly neutralizing monoclonal antibodies now available reveals that certain combinations of antibodies should offer markedly more favourable coverage of the enormous diversity of global circulating viruses than others and these combinations might be sought in active or passive immunization regimes. Overall, the isolation of multiple HIV broadly neutralizing monoclonal antibodies from several donors that, in aggregate, provide broad coverage at low concentrations is a highly positive indicator for the eventual design of an effective antibody-based HIV vaccine. [ABSTRACT FROM AUTHOR]

The conserved surface of the HIV-1 gpl20 envelope glycoprotein that binds to the HIV-1 coreceptor is protected from humoral recognition by multiple layers of camouflage. Here we present sequence and genomic analyses for 12 antibodies that pierce these defenses and determine the crystal structures of 5. The data reveal mechanisms and atomic-level details for three unusual immune features: posttranslational mimicry of coreceptor by tyrosine sulfation of antibody, an alternative molecular mechanism controlling such sulfation, and highly selective VH-gene usage. When confronted by extraordinary viral defenses, the immune system unveils novel adaptive capabilities, with tyrosine sulfation enhancing the vocabulary of antigen recognition. [ABSTRACT FROM AUTHOR]

The ability to readily elicit broadly neutralizing antibodies to HIV-1 remains elusive. We and others have hypothesized that interaction of the viral envelope glycoprotein (Env, gp120-gp41) with its receptor molecules could enhance the exposure of conserved epitopes that may facilitate the elicitation of broadly neutralizing antibodies. The Env-CD4-coreceptor complexes mediate HIV-1 entry into cells and serve as a major target for inhibitors of this process. To begin to evaluate their potential also as vaccine immunogens we produced relatively large amounts of complexes of purified recombinant soluble truncated Env, gp14089.6 or gp12089.6, with CD4 and CCR5 or CXCR4. We found that gp140(gp120)-CD4-CCR5 complexes are stable and immunogenic in mice transgenic for human CD4 and CCR5. They elicited anti-gp120 and anti-gp140 antibodies that inhibited an heterologous primary HIV-1 isolate (JR-FL) with two- to threefold higher neutralizing activity than those elicited by gp120 and gp140. The antibodies elicited by the complexes competed better with the antibodies X5 and CG10 but not with b12 for binding to gp120 and gp120-CD4 complexes compared to those elicited with gp140(120) alone. These findings suggest that stable purified Env-CD4-CCR5(CXCR4) complexes can be produced in relatively large amount sufficient for their further characterization that may help in the development of novel vaccines candidates. [Copyright &y& Elsevier]

Following the first two Frederick meetings on virus entry in 1997 [Cell 91 (1997) 721]11. and in 2000 [Cell 101 (2000) 697]22., further developments in our understanding of the multifactorial and multistage process of virus entry, and possible biomedical implications were presented and discussed in a lively fashion by leading scientists from around the world at the third Frederick meeting on the Cell Biology of Viral Entry (May 7–10, Frederick, MD) organized by R. Blumenthal (NCI-Frederick, NIH, Frederick) and E. Hunter (University of Alabama, Birmingham). Unlike the previous two meetings, non-enveloped viruses were not discussed this time, and the focus was how envelope glycoproteins (Envs) mediate entry into cells. Major topics included Env structure, virus receptors, entry intermediates, membrane fusion, fusion kinetics, and rafts. Virus envelope structures will be described in more detail here because the other topics are extensively discussed in the other chapters of this volume. [Copyright &y& Elsevier]

Examines the binding of the HIV-1 glycoprotein (gp) to CD4 and coreceptors. Inhibition of cell-cell fusion immunoglobulin G1 b12; Infection of the peripheral blood mononuclear cells by HIV-1; Occurrence of X5 epitope binding to cell-surface-associated oligomeric envelope gp.

Describes the method for design of recombinant envelope (Env) glycoprotein (gp) for gp 120-gp 41 stabilization. Initiation of gp41 exposure intermediates; Induction of intermediate Env conformation by the coreceptors; Utilization of gp 120 complexes in immunogens and neutralizing antibodies.

The first evidence in humans that a safe and effective preventive vaccine for HIV is possible came from the phase III HIV clinical trial RV144 in Thailand. This trial was based on a prime/boost combination of a recombinant canarypox vaccine and two glycoprotein 120 proteins (ALVAC-HIV and AIDSVAX B/E). A pivotal phase IIb/III trial has recently commenced in the Republic of South Africa, for which the infectious titer assay was applied as the quantitative release test for the ALVAC-HIV vaccine. The infectious titer assay measures the ability of the vaccine vector to infect target permissive cells, but does not indicate if the vaccine transgenes are expressed. We have developed a high-throughput biological activity assay that provides results in agreement with the infectious titer assay. This assay uses flow cytometry to quantify expression of ALVAC-HIV encoded proteins gp120 and p24 in human cells. This transgene expression is detected by two cross-clade-reactive, biologically functional human anti-gp120 monoclonal antibodies isolated from clinical trial participants and a commercial mouse anti-p24 monoclonal antibody. The relative biological activity of the vaccine test sample is calculated by comparison of the test sample dose-response curve against that of a reference standard. We show that the novel biological activity assay is specific, accurate, precise, stability-indicating, and robust. The assay is being used for characterization of ALVAC-HIV (vCP2438) product, the efficacy of which is being evaluated in the pivotal phase IIb/III clinical trial HVTN702. The biological activity assay has the potential to indicate vaccine consistency and quality as a complement to the infectious titer assay. [ABSTRACT FROM AUTHOR]

Monoclonal antibody 2909 belongs to a class of potently neutralizing antibodies that recognize quaternary epitopes on HIV-1. Some members of this class, such as 2909, are strain specific, while others, such as antibody PG16, are broadly neutralizing; all, however, recognize a region on the gp120 envelope glycoprotein that includes two loops (V2 and V3) and forms appropriately only in the oligomeric HIV-1 spike (gp1203/gp413). Here we present the crystal structure of 2909 and report structure-function analysis with antibody chimeras composed of 2909 and other members of this antibody class. The 2909 structure was dominated by a heavy-chain third-complementarity-determining region (CDR H3) of 21 residues, which comprised 36% of the combining surface and formed a β-hairpin club extending ∼20 Å beyond the rest of the antibody. Sequence analysis and mass spectrometry identified sites of tyrosine sulfation at the middle and top of CDR H3; substitutions with phenylalanine either ablated (middle substitution) or substantially diminished (top substitution) neutralization. Chimeric antibodies composed of heavy and light chains, exchanged between 2909 and other members of the class, indicated a substantial lack of complementation. Comparison of 2909 to PG16 (which is tyrosine sulfated and the only other member of the class for which a structure has previously been reported) showed that both utilize protruding, anionic CDR H3s for recognition. Thus, despite some diversity, members of this class share structural and functional similarities, with conserved features of the CDR H3 subdomain likely reflecting prevalent solutions by the human immune system for recognition of a quaternary site of HIV-1 vulnerability. [ABSTRACT FROM AUTHOR]