A Limited Number of Antibody Specificities Mediate Broad and Potent Serum Neutralization in Selected HIV-1 Infected Individuals

A protective vaccine against HIV-1 will likely require the elicitation of a broadly neutralizing antibody (bNAb) response. Although the development of an immunogen that elicits such antibodies remains elusive, a proportion of HIV-1 infected individuals evolve broadly neutralizing serum responses over time, demonstrating that the human immune system can recognize and generate NAbs to conserved epitopes on the virus. Understanding the specificities that mediate broad neutralization will provide insight into which epitopes should be targeted for immunogen design and aid in the isolation of broadly neutralizing monoclonal antibodies from these donors. Here, we have used a number of new and established technologies to map the bNAb specificities in the sera of 19 donors who exhibit among the most potent cross-clade serum neutralizing activities observed to date. The results suggest that broad and potent serum neutralization arises in most donors through a limited number of specificities (1–2 per donor). The major targets recognized are an epitope defined by the bNAbs PG9 and PG16 that is associated with conserved regions of the V1, V2 and V3 loops, an epitope overlapping the CD4 binding site and possibly the coreceptor binding site, an epitope sensitive to a loss of the glycan at N332 and distinct from that recognized by the bNAb 2G12 and an epitope sensitive to an I165A substitution. In approximately half of the donors, key N-linked glycans were critical for expression of the epitopes recognized by the bNAb specificities in the sera

Pentavalent HIV-1 vaccine protects against simian-human immunodeficiency virus challenge

The RV144 Thai trial HIV-1 vaccine of recombinant poxvirus (ALVAC) and recombinant HIV-1 gp120 subtype B/subtype E (B/E) proteins demonstrated 31% vaccine efficacy. Here we design an ALVAC/Pentavalent B/E/E/E/E vaccine to increase the diversity of gp120 motifs in the immunogen to elicit a broader antibody response and enhance protection. We find that immunization of rhesus macaques with the pentavalent vaccine results in protection of 55% of pentavalent-vaccine-immunized macaques from simian–human immunodeficiency virus (SHIV) challenge. Systems serology of the antibody responses identifies plasma antibody binding to HIV-infected cells, peak ADCC antibody titres, NK cell-mediated ADCC and antibody-mediated activation of MIP-1β in NK cells as the four immunological parameters that best predict decreased infection risk that are improved by the pentavalent vaccine. Thus inclusion of additional gp120 immunogens to a pox-prime/protein boost regimen can augment antibody responses and enhance protection from a SHIV challenge in rhesus macaques

Cell biology of virus entry: a review of selected topics from the 3rd International Frederick meeting

AbstractFollowing the first two Frederick meetings on virus entry in 1997 [Cell 91 (1997) 721]11[1]. and in 2000 [Cell 101 (2000) 697]22[2]., 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

Crystal Structure of Human Antibody 2909 Reveals Conserved Features of Quaternary Structure-Specific Antibodies That Potently Neutralize HIV-1▿ † §

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

Simulation of salt and water movement and estimation of water productivity of rice crop irrigated with saline water

The HYDRUS-ID model was experimentally tested for water balance and salt build up in soil under rice crop irrigated with different salinity water (ECiw) of 0.4, 2, 4,6,8 and 10 dS m-1 in micro-lysimeters filled with sandy loam soil. Differences of means between measured (M) and HYDRUS-1D predicted (P) values of bottom flux (Qo) and leachate EC as tested by paired t test were not found significant at P = 0.05 and a close agreement between RMSE values showed the applicability of the HYDRUS-1D to simulate percolation and salt concentration in the micro-lysimeters under rice crop. Potential ET values of rice as obtained from CROPWAT matched well with model predicted and measured one at all ECiw treatments. The model predicted root water uptake varied from 66.1 to 652.7 mm and the maximum daily salt concentration in the root zone was 0.46, 2.3, 4.5, 6.7, 8.4 and 10.2 me cm-3 in 0.4, 2, 4, 6, 8 and 10 dS m-1 ECiw treatments, respectively. The grain production per unit evapotranspiration (WPETa) value of 2.56 in ECiw of 0.4 dS m-1 treatment declined to 1.31 with ECiw of 2 dS m-1. The WPETa reduced to one-fifth when percolation was included in the productivity determination. Similarly, the water productivity in respect of total dry matter production (TDM) was also reduced in different treatments. Therefore, the model predicted values of water balance can be effectively utilized to calculate the water productivity of rice crop. © Springer-Verlag 2010.V. Phogat, A. K. Yadav, R. S. Malik, Sanjay Kumar, Jim Co

Recombinant HIV-1 vaccine candidates based on replication-defective flavivirus vector

Multiple approaches utilizing viral and DNA vectors have shown promise in the development of an effective vaccine against HIV. In this study, an alternative replication-defective flavivirus vector, RepliVax (RV), was evaluated for the delivery of HIV-1 immunogens. Recombinant RV-HIV viruses were engineered to stably express clade C virus Gag and Env (gp120TM) proteins and propagated in Vero helper cells. RV-based vectors enabled efficient expression and correct maturation of Gag and gp120TM proteins, were apathogenic in a sensitive suckling mouse neurovirulence test, and were similar in immunogenicity to recombinant poxvirus NYVAC-HIV vectors in homologous or heterologous prime-boost combinations in mice. In a pilot NHP study, immunogenicity of RV-HIV viruses used as a prime or boost for DNA or NYVAC candidates was compared to a DNA prime/NYVAC boost benchmark scheme when administered together with adjuvanted gp120 protein. Similar neutralizing antibody titers, binding IgG titers measured against a broad panel of Env and Gag antigens, and ADCC responses were observed in the groups throughout the course of the study, and T cell responses were elicited. The entire data demonstrate that RV vectors have the potential as novel HIV-1 vaccine components for use in combination with other promising candidates to develop new effective vaccination strategies.The study was funded by the Bill & Melinda Gates Foundation (project nr OPP1040705) and we thank Dr. Pervin Amklesaria and Dr. Nina Russell (Gates Foundation) for their guidance of this study. We thank the Poxvirus T-cell Vaccine Discovery Consortium funded by the Bill & Melinda Gates Foundation (OPP38599) for the development and provision of NYVAC and DNA vectors; support for the ICS and antibody immune monitoring assays was provided by the Vaccine Immune Monitoring Centers (OPP1032325 & OPP1032144), and support for the statistical analysis from the Vaccine Immunology Statistical Center (OPP1032317), all part of the Collaboration for AIDS Vaccine Discovery

Replication-Competent NYVAC-KC Yields Improved Immunogenicity to HIV-1 Antigens in Rhesus Macaques Compared to Nonreplicating NYVAC

© 2019 Kibler et al.As part of the continuing effort to develop an effective HIV vaccine, we generated a poxviral vaccine vector (previously described) designed to improve on the results of the RV144 phase III clinical trial. The construct, NYVAC-KC, is a replication-competent, attenuated recombinant of the vaccinia virus strain NYVAC. NYVAC is a vector that has been used in many previous clinical studies but is replication deficient. Here, we report a side-by-side comparison of replication-restricted NYVAC and replication-competent NYVAC-KC in a nonhuman primate study, which utilized a prime-boost regimen similar to that of RV144. NYVAC-C and NYVAC-C-KC express the HIV-1 antigens gp140, and Gag/Gag-Pol-Nef-derived virus-like particles (VLPs) from clade C and were used as the prime, with recombinant virus plus envelope protein used as the boost. In nearly every T and B cell immune assay against HIV-1, including neutralization and antibody binding, NYVAC-C-KC induced a greater immune response than NYVAC-C, indicating that replication competence in a poxvirus may improve upon the modestly successful regimen used in the RV144 clinical trial.IMPORTANCE Though the RV144 phase III clinical trial showed promise that an effective vaccine against HIV-1 is possible, a successful vaccine will require improvement over the vaccine candidate (ALVAC) used in the RV144 study. With that goal in mind, we have tested in nonhuman primates an attenuated but replication-competent vector, NYVAC-KC, in direct comparison to its parental vector, NYVAC, which is replication restricted in human cells, similar to the ALVAC vector used in RV144. We have utilized a prime-boost regimen for administration of the vaccine candidate that is similar to the one used in the RV144 study. The results of this study indicate that a replication-competent poxvirus vector may improve upon the effectiveness of the RV144 clinical trial vaccine candidate.This investigation was funded by the Bill & Melinda Gates Foundation Poxvirus T Cell Vaccine Discovery Consortium (PTVDC) (38599). The Vaccine Immune Monitoring Centers (OPP1032144 and OPP1032325) and the Vaccine Immunology Statistical Center (OPP1032317), as part of the Collaboration for AIDS Vaccine Discovery (CAVD), were funded by the Bill & Melinda Gates Foundation. Novartis Vaccines received support for this work under contract number HHSN266200500007C from DAIDS-NIAID-NIH