Human Immunodeficiency Virus Env Research Articles

Mosaic and mixed HIV-1 glycoprotein nanoparticles elicit antibody responses to broadly neutralizing epitopes.

An effective human immunodeficiency virus 1 (HIV-1) vaccine will most likely have to elicit broadly neutralizing antibodies (bNAbs) to overcome the sequence diversity of the envelope glycoprotein (Env). So far, stabilized versions of Env, such as SOSIP trimers, have been able to induce neutralizing antibody (NAb) responses, but those responses are mainly strain-specific. Here we attempted to broaden NAb responses by using a multivalent vaccine and applying a number of design improvements. First, we used highly stabilized SOSIP.v9 trimers. Second, we removed any holes in the glycan shields and optimized glycan occupancy to avoid strain-specific glycan hole responses. Third, we selected five sequences from the same clade (B), as we observed previously that combining Env trimers from clade A, B and C did not improve cross-reactive responses, as they might have been too diverse. Fourth, to improve antibody (Ab) responses, the Env trimers were displayed on two-component I53-50 nanoparticles (NPs). Fifth, to favor activation of cross-reactive B cells, the five Env trimers were co-displayed on mosaic NPs. Sixth, we immunized rabbits four times with long intervals between vaccinations. These efforts led to the induction of cross-reactive B cells and cross-reactive binding Ab responses, but we only sporadically detected cross-neutralizing responses. We conclude that stabilized HIV-1 Env trimers that are not modified specifically for priming naive B cells are unable to elicit strong bNAb responses, and infer that sequential immunization regimens, most likely starting with specific germline-targeting immunogens, will be necessary to overcome Env's defenses against the induction of NAbs. The antigens described here could be excellent boosting immunogens in a sequential immunization regimen, as responses to bNAb epitopes were induced.

Impact of Recombinant VSV-HIV Prime, DNA-Boost Vaccine Candidates on Immunogenicity and Viremia on SHIV-Infected Rhesus Macaques.

Currently, no effective vaccine to prevent human immunodeficiency virus (HIV) infection is available, and various platforms are being examined. The vesicular stomatitis virus (VSV) vaccine vehicle can induce robust humoral and cell-mediated immune responses, making it a suitable candidate for the development of an HIV vaccine. Here, we analyze the protective immunological impacts of recombinant VSV vaccine vectors that express chimeric HIV Envelope proteins (Env) in rhesus macaques. To improve the immunogenicity of these VSV-HIV Env vaccine candidates, we generated chimeric Envs containing the transmembrane and cytoplasmic tail of the simian immunodeficiency virus (SIV), which increases surface Env on the particle. Additionally, the Ebola virus glycoprotein was added to the VSV-HIV vaccine particles to divert tropism from CD4 T cells and enhance their replications both in vitro and in vivo. Animals were boosted with DNA constructs that encoded matching antigens. Vaccinated animals developed non-neutralizing antibody responses against both the HIV Env and the Ebola virus glycoprotein (EBOV GP) as well as systemic memory T-cell activation. However, these responses were not associated with observable protection against simian-HIV (SHIV) infection following repeated high-dose intra-rectal SHIV SF162p3 challenges.

Cannabis Use Associates With Reduced Proviral Burden and Inflammatory Cytokine in Tissues From Men With Clade C HIV-1 on Suppressive Antiretroviral Therapy.

Human immunodeficiency virus 1 (HIV-1) tissue reservoirs remain the main obstacle against an HIV cure. Limited information exists regarding cannabis's effects on HIV-1 infections in vivo, and the impact of cannabis use on HIV-1 parenchymal tissue reservoirs is unexplored. To investigate whether cannabis use alters HIV-1 tissue reservoirs, we systematically collected 21 postmortem brain and peripheral tissues from 20 men with subtype C HIV-1 and with suppressed viral load enrolled in Zambia, 10 of whom tested positive for cannabis use. The tissue distribution and copies of subtype C HIV-1 LTR, gag, env DNA and RNA, and the relative mRNA levels of cytokines IL-1β, IL-6, IL-10, and TGF-β1 were quantified using PCR-based approaches. Utilizing generalized linear mixed models we compared persons with HIV-1 and suppressed viral load, with and without cannabis use. The odds of tissues harboring HIV-1 DNA and the viral DNA copies in those tissues were significantly lower in persons using cannabis. Moreover, the transcription levels of proinflammatory cytokines IL-1β and IL-6 in lymphoid tissues of persons using cannabis were also significantly lower. Our findings suggested that cannabis use is associated with reduced sizes and inflammatory cytokine expression of subtype C HIV-1 reservoirs in men with suppressed viral load.

A new look at the immunopathogenesis of infection caused by the human immunodeficiency virus

Thanks to the achievements of biotechnology and genetics, numerous features of reproduction of the human immunodeficiency virus and its immunopathogenesis have been established. Genetic studies have called into question the African origin of the virus. Thus, the number of individuals with mutational changes in the CCR5∆32 allele among the population providing genetic protection against human immunodeficiency virus is decreasing from north to south. The probability of adaptation of the great ape virus in the human population is characterized. New biological effects and their influence on the immunopathogenesis of infection of the well-known human immunodeficiency virus genes Gag (structural proteins), Pol (enzymes) and Env (envelope glycoproteins), the proteins encoded by them, as well as a number of additional proteins have been discovered. Thus, the main task of the Tat gene is to stimulate the transcription of proviral deoxyribonucleic acid and the transport of ribonucleic acid from the nucleus to the cytoplasm of the cell. Rev promotes the synthesis of viral structural proteins and enzymes, ensures the availability of full-sized genomic ribonucleic acid for inclusion in the reproduced viral progeny. Viruses with the absence of the vif gene are about 1000 times less virulent compared to wild strains. The APOBEC3G factor inhibits the reproduction of lentiviruses in primates, but in humans it is characterized by polymorphism of biological effects. Viral protein R affects the rate of reproduction of the virus in T-lymphocytes, contributes to their destruction. It also promotes proteasomal degradation and protein modification. Vpr targets may be a structurally specific endonuclease subunit SLX4, uracil-deoxynucleoacid glycosylase 2, and a helicase-like transcription factor. Vpu is a powerful inhibitor of teterin by type 1 immunodeficiency viruses of group M, and in group N viruses it shows low activity. Vpu, Nef, and Env proteins of most lentiviruses are characterized by higher tropicity to the CD4 receptor compared to teterin, serine incorporation proteins. These proteins are incorporated into viral particles and reduce their infectivity by inhibiting fusion with target cells. The protein containing the tripartite motif 5a, the protein of mixovirus activity 2/B constitute an ancient system of protection against retroviruses and are extremely variable in their effectiveness to disrupt the reproduction of viruses.

HIV-1 Env trimers asymmetrically engage CD4 receptors in membranes

Human immunodeficiency virus 1 (HIV-1) infection is initiated by binding of the viral envelope glycoprotein (Env) to the cell-surface receptor CD41–4. Although high-resolution structures of Env in a complex with the soluble domains of CD4 have been determined, the binding process is less understood in native membranes5–13. Here we used cryo-electron tomography to monitor Env–CD4 interactions at the membrane–membrane interfaces formed between HIV-1 and CD4-presenting virus-like particles. Env–CD4 complexes organized into clusters and rings, bringing the opposing membranes closer together. Env–CD4 clustering was dependent on capsid maturation. Subtomogram averaging and classification revealed that Env bound to one, two and finally three CD4 molecules, after which Env adopted an open state. Our data indicate that asymmetric HIV-1 Env trimers bound to one and two CD4 molecules are detectable intermediates during virus binding to host cell membranes, which probably has consequences for antibody-mediated immune responses and vaccine immunogen design.

Refining HIV envelope protein conformational data from different experimental sources using bias-resampling methods and information theory.

Human immunodeficiency virus (HIV) remains a global epidemic, and vaccine development has been challenging. This challenge is due in part to conflicting data regarding which conformational states of the envelope glycoprotein (Env) are effectively targeted by neutralizing antibodies. Env is known to undergo conformational change as part of its function. Identifying the conformations best bound by neutralizing antibodies will improve vaccine design. To this end, we use bias resampling ensemble refinement (BRER) to integrate and compare prior spectroscopic measurements of HIV Env conformation. By using both electron paramagnetic resonance and single-molecule FRET data as restraints in conformational ensemble refinement, we generate models for the sets of HIV Env conformations consistent with each set of measurements. Results show that the “hidden” conformational states identified via single-molecule FRET spectroscopy indeed show differences from reference cryo-EM structures. Further analysis shows that the “hidden” conformational states have different distance distributions for some residue pairs than those measured via DEER. We have developed information-theoretic techniques to identify DEER label sites that would best differentiate conformational states defined by single-molecule FRET. We hope that testing of these proposed DEER experiments will help resolve the discrepancy between observations using different spectroscopic techniques and better elucidate the conformational heterogeneity of HIV Env. Extension to datasets in the presence of bound neutralizing antibodies will help elucidate the key conformations recognized by broadly neutralizing anti-HIV antibodies and, we hope, further assist in vaccine design.

Long-primed germinal centres with enduring affinity maturation and clonal migration.

Germinal centres are the engines of antibody evolution. Here, using human immunodeficiency virus (HIV) Env protein immunogen priming in rhesus monkeys followed by a long period without further immunization, we demonstrate germinal centre B (BGC) cells that last for at least 6 months. A 186-fold increase in BGC cells was present by week 10 compared with conventional immunization. Single-cell transcriptional profiling showed that both light- and dark-zone germinal centre states were sustained. Antibody somatic hypermutation of BGC cells continued to accumulate throughout the 29-week priming period, with evidence of selective pressure. Env-binding BGC cells were still 49-fold above baseline at 29 weeks, which suggests that they could remain active for even longer periods of time. High titres of HIV-neutralizing antibodies were generated after a single booster immunization. Fully glycosylated HIV trimer protein is a complex antigen, posing considerable immunodominance challenges for B cells1,2. Memory B cells generated under these long priming conditions had higher levels of antibody somatic hypermutation, and both memory B cells and antibodies were more likely to recognize non-immunodominant epitopes. Numerous BGC cell lineage phylogenies spanning more than the 6-month germinal centre period were identified, demonstrating continuous germinal centre activity and selection for at least 191 days with no further antigen exposure. A long-prime, slow-delivery (12 days) immunization approach holds promise for difficult vaccine targets and suggests that patience can have great value for tuning of germinal centres to maximize antibody responses.

Vaccine-Induced, High-Magnitude HIV Env-Specific Antibodies with Fc-Mediated Effector Functions Are Insufficient to Protect Infant Rhesus Macaques against Oral SHIV Infection.

ABSTRACTImproved access to antiretroviral therapy (ART) and antenatal care has significantly reduced in utero and peripartum mother-to-child human immunodeficiency virus (HIV) transmission. However, as breast milk transmission of HIV still occurs at an unacceptable rate, there remains a need to develop an effective vaccine for the pediatric population. Previously, we compared different HIV vaccine strategies, intervals, and adjuvants in infant rhesus macaques to optimize the induction of HIV envelope (Env)-specific antibodies with Fc-mediated effector function. In this study, we tested the efficacy of an optimized vaccine regimen against oral simian-human immunodeficiency virus (SHIV) acquisition in infant macaques. Twelve animals were immunized with 1086.c gp120 protein adjuvanted with 3M-052 in stable emulsion and modified vaccinia Ankara (MVA) virus expressing 1086.c HIV Env. Twelve control animals were immunized with empty MVA. The vaccine prime was given within 10 days of birth, with booster doses being administered at weeks 6 and 12. The vaccine regimen induced Env-specific plasma IgG antibodies capable of antibody-dependent cellular cytotoxicity (ADCC) and phagocytosis (ADCP). Beginning at week 15, infants were exposed orally to escalating doses of heterologous SHIV-1157(QNE)Y173H once a week until infected. Despite the induction of strong Fc-mediated antibody responses, the vaccine regimen did not reduce the risk of infection or time to acquisition compared to controls. However, among vaccinated animals, ADCC postvaccination and postinfection was associated with reduced peak viremia. Thus, nonneutralizing Env-specific antibodies with Fc effector function elicited by this vaccine regimen were insufficient for protection against heterologous oral SHIV infection shortly after the final immunization but may have contributed to control of viremia.IMPORTANCE Women of childbearing age are three times more likely to contract HIV infection than their male counterparts. Poor HIV testing rates coupled with low adherence to antiretroviral therapy (ART) result in a high risk of mother-to-infant HIV transmission, especially during the breastfeeding period. A preventative vaccine could curb pediatric HIV infections, reduce potential health sequalae, and prevent the need for lifelong ART in this population. The results of the current study imply that the HIV Env-specific IgG antibodies elicited by this candidate vaccine regimen, despite a high magnitude of Fc-mediated effector function but a lack of neutralizing antibodies and polyfunctional T cell responses, were insufficient to protect infant rhesus macaques against oral virus acquisition.

Refining HIV envelope protein conformational data from different experimental sources using bias-resampling methods

Human immunodeficiency virus (HIV) continues to cause a global epidemic, and vaccine development has been challenging. This is in part because there exist conflicting data regarding which conformational states of the envelope glycoprotein (Env) are effectively targeted by neutralizing antibodies. Env is known to undergo conformational change as part of its function, but identifying the conformations best bound by neutralizing antibodies will improve vaccine design. Here, we use bias resampling ensemble refinement (BRER) to integrate and compare prior spectroscopic measurements of HIV Env conformation.

In silico design and in vitro expression of novel multiepitope DNA constructs based on HIV-1 proteins and Hsp70 T-cell epitopes.

ObjectivesEpitope-driven vaccines carrying highly conserved and immunodominant epitopes have emerged as promising approaches to overcome human immunodeficiency virus-1 (HIV-1) infection.MethodsTwo multiepitope DNA constructs encoding T cell epitopes from HIV-1 Gag, Pol, Env, Nef and Rev proteins alone and/or linked to the immunogenic epitopes derived from heat shock protein 70 (Hsp70) as an immunostimulatory agent were designed. In silico analyses were applied including MHC-I and MHC-II binding, MHC-I immunogenicity and antigen processing, population coverage, conservancy, allergenicity, toxicity and hemotoxicity. The peptide-MHC-I/MHC-II molecular docking and cytokine production analyses were carried out for predicted epitopes. The selected highly immunogenic T-cell epitopes were then used to design two multiepitope fusion constructs. Next, prediction of the physicochemical and structural properties, B cell epitopes, and constructs-toll-like receptors (TLRs) molecular docking were performed for each construct. Finally, the eukaryotic expression plasmids harboring totally 12 cytotoxic T Lymphocyte (CTL) and 10 helper T lymphocytes (HTL) epitopes from HIV-1 proteins (i.e., pEGFP-N1-gag-pol-env-nef-rev), and linked to 2 CTL and 2 HTL epitopes from Hsp70 (i.e., pEGFP-N1-hsp70-gag-pol-env-nef-rev) were generated and transfected into HEK-293 T cells for evaluating the percentage of multiepitope peptides expression using flow cytometry and western blotting.ResultsThe designed DNA constructs could be successfully expressed in mammalian cells. The expression rates of Gag-Pol-Env-Nef-Rev-GFP and Hsp70-Gag-Pol-Env-Nef-Rev-GFP were about 56–60% as the bands of ~ 63 and ~ 72 kDa confirmed in western blotting, respectively.ConclusionThe combined in silico/in vitro methods indicated two multiepitope constructs can be produced and used as probable effective immunogens for HIV-1 vaccine development.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10529-021-03143-9.

Targeting HIV Env immunogens to B cell follicles in nonhuman primates through immune complex or protein nanoparticle formulations

Following immunization, high-affinity antibody responses develop within germinal centers (GCs), specialized sites within follicles of the lymph node (LN) where B cells proliferate and undergo somatic hypermutation. Antigen availability within GCs is important, as B cells must acquire and present antigen to follicular helper T cells to drive this process. However, recombinant protein immunogens such as soluble human immunodeficiency virus (HIV) envelope (Env) trimers do not efficiently accumulate in follicles following traditional immunization. Here, we demonstrate two strategies to concentrate HIV Env immunogens in follicles, via the formation of immune complexes (ICs) or by employing self-assembling protein nanoparticles for multivalent display of Env antigens. Using rhesus macaques, we show that within a few days following immunization, free trimers were present in a diffuse pattern in draining LNs, while trimer ICs and Env nanoparticles accumulated in B cell follicles. Whole LN imaging strikingly revealed that ICs and trimer nanoparticles concentrated in as many as 500 follicles in a single LN within two days after immunization. Imaging of LNs collected seven days postimmunization showed that Env nanoparticles persisted on follicular dendritic cells in the light zone of nascent GCs. These findings suggest that the form of antigen administered in vaccination can dramatically impact localization in lymphoid tissues and provides a new rationale for the enhanced immune responses observed following immunization with ICs or nanoparticles.

Transmission of HIV and HCV within Former Soviet Union Countries.

Background Following the collapse of the Union of Soviet Socialist Republic (USSR) in 1991, trans-border mobility increased within the former Soviet Union (FSU) countries. In addition, drug-trafficking and injection drug use began to rise, leading to the propagation and transmission of blood-borne infections within and across the FSU countries. To examine the transmission of blood-borne infections within this region, we analyzed the phylogenetic relationship of publically available sequences of two blood-borne viruses, hepatitis C virus (HCV) and human immunodeficiency virus (HIV), from FSU countries. Methods We analysed 614 and 295 NS5B sequences from HCV genotypes 1b and 3a, respectively, from 9 FSU countries. From 13 FSU countries, we analysed 347 HIV gag and 1282 HIV env sequences. To examine transmission networks and the origins of infection, respectively, phylogenetic and Bayesian analyses were performed. Results Our analysis shows intermixing of HCV and HIV sequences, suggesting transmission of these viruses both within and across FSU countries. We show involvement of three major populations in transmission: injection drug user, heterosexual, and trans-border migrants. Conclusion This study highlights the need to focus harm reduction efforts toward controlling transmission of blood-borne infections among the abovementioned high-risk populations in the FSU countries.

Osteopontin and Integrin Mediated Modulation of Post-Synapses in HIV Envelope Glycoprotein Exposed Hippocampal Neurons.

The advent of Human Immunodeficiency Virus (HIV) antiretrovirals have reduced the severity of HIV related neurological comorbidities but they nevertheless remain prevalent. Synaptic degeneration due to the action of several viral factors released from infected brain myeloid and glia cells and inflammatory cytokines has been attributed to the manifestation of a range of cognitive and behavioral deficits. The contributions of specific pro-inflammatory factors and their interplay with viral factors in the setting of treatment and persistence are incompletely understood. Exposure of neurons to chemokine receptor-4(CXCR4)-tropic HIV-1 envelope glycoprotein (Env) can lead to post-synaptic degradation of dendritic spines. The contribution of members of the extracellular matrix (ECM) and specifically, of perineuronal nets (PNN) toward synaptic degeneration, is not fully known, even though these structures are found to be disrupted in post-mortem HIV-infected brains. Osteopontin (Opn, gene name SPP1), a cytokine-like protein, is found in abundance in the HIV-infected brain. In this study, we investigated the role of Opn and its ECM integrin receptors, β1- and β3 integrin in modifying neuronal synaptic sculpting. We found that in hippocampal neurons incubated with HIV-1 Env protein and recombinant Opn, post-synaptic-95 (PSD-95) puncta were significantly increased and distributed to dendritic spines when compared to Env-only treated neurons. This effect was mediated through β3 integrin, as silencing of this receptor abrogated the increase in post-synaptic spines. Silencing of β1 integrin, however, did not block the increase of post-synaptic spines in hippocampal cultures treated with Opn. However, a decrease in the PNN to βIII-tubulin ratio was found, indicating an increased capacity to support spine growth. From these results, we conclude that one of the mechanisms by which Opn counters the damaging impact of the HIV Env protein on hippocampal post-synaptic plasticity is through complex interactions between Opn and components of the ECM which activate downstream protective signaling pathways that help maintain the potential for effective post-synaptic plasticity.

Glycosylation of HIV Env Impacts IgG Subtype Responses to Vaccination.

The envelope protein (Env) is the only surface protein of the human immunodeficiency virus (HIV) and as such the exclusive target for protective antibody responses. Experimental evidences from mouse models suggest a modulating property of Env to steer antibody class switching towards the less effective antibody subclass IgG1 accompanied with strong TH2 helper responses. By simple physical linkage we were able to imprint this bias, exemplified by a low IgG2a/IgG1 ratio of antigen-specific antibodies, onto an unrelated antigen, namely the HIV capsid protein p24. Here, our results indicate the glycan moiety of Env as the responsible immune modulating activity. Firstly, in Card9−/− mice lacking specific C-Type lectin responsiveness, DNA immunization significantly increased the IgG2a/IgG1 ratio for the Env-specific antibodies while the antibody response against the F-protein of the respiratory syncytial virus (RSV) serving as control antigen remained unchanged. Secondly, sequential shortening of the Env encoding sequence revealed the C2V3 domain as responsible for the strong IgG1 responses and TH2 cytokine production. Removing all potential N-glycosylation sites from the C2V3 domain by site-specific mutagenesis reversed the vaccine-induced immune response towards a Th1-dominated T-cell response and a balanced IgG2a/IgG1 ratio. Accordingly, the stretch of oligomannose glycans in the C2V3 domain of Env might mediate a specific uptake and/or signaling modus in antigen presenting cells by involving interaction with an as yet unknown C-type lectin receptor. Our results contribute to a deeper understanding of the impact of Env glycosylation on HIV antigen-specific immune responses, which will further support HIV vaccine development.

Method to identify efficiently cleaved, membrane-bound, functional HIV-1 (Human Immunodeficiency Virus-1) envelopes

An ideal vaccine against HIV-1 will specifically elicit bNAbs (broadly neutralizing antibodies) which can cross-neutralize a wide spectrum of circulating viral strains belonging to different clades. The current paradigm for developing such a vaccine is to generate HIV-1 envelope (Env)-based immunogens which can specifically elicit bNAbs. For this purpose, it is necessary to identify Envs, belonging to different clades, suitable for immunogen design. Efficient cleavage of the HIV-1 Env precursor gp160 polypeptide into its constituent subunits determines its ability to selectively bind to bNAbs and poorly to non-NAbs (non-neutralizing antibodies), properties desirable in Env-based immunogens. Thus, efficiently cleaved HIV-1 Envs with desirable antigenic properties can be good candidates for developing immunogens. Here we describe in detail a six step method we have used in our laboratory to identify such efficiently cleaved Envs. Some of these protocols are optimizations of previously reported assays such as FACS-based cell surface antibody binding assay, pseudovirus neutralization assay and gp120 shedding assay. Other protocols like biotinylation-neutravidin-agarose pull-down assay and plasma membrane protein immunoprecipitation assay have been developed by taking inputs from reagent/kit manufacturer’s protocols and previous studies. These protocols will help the field in identifying more such Envs which can be used for immunogen development.•Six step process to identify efficiently cleaved, membrane-bound, functional HIV-1 Envs with high degree of repeatability.•Method applicable for characterizing any HIV-1 envelope protein.•New method of immunoprecipitation of plasma membrane fraction to validate efficiently cleaved HIV-1 envelopes.

Phylogenetic Methods Inconsistently Predict the Direction of HIV Transmission Among Heterosexual Pairs in the HPTN 052 Cohort.

We evaluated use of phylogenetic methods to predict the direction of human immunodeficiency virus (HIV) transmission. For 33 pairs of HIV-infected patients (hereafter, "index patients") and their partners who acquired genetically linked HIV infection during the study, samples were collected from partners and index patients close to the time when the partner seroconverted (hereafter, "SC samples"); for 31 pairs, samples collected from the index patient at an earlier time point (hereafter, "early index samples") were also available. Phylogenies were inferred using env next-generation sequences (1 tree per pair/subtype). The direction of transmission (DoT) predicted from each tree was classified as correct or incorrect on the basis of which sequences (those from the index patient or the partner) were closest to the root. DoT was also assessed using maximum parsimony to infer ancestral node states for 100 bootstrap trees. DoT was predicted correctly for both single-pair and subtype-specific trees in 22 pairs (67%) by using SC samples and in 23 pairs (74%) by using early index samples. DoT was predicted incorrectly for 4 pairs (15%) by using SC or early index samples. In the bootstrap analysis, DoT was predicted correctly for 18 pairs (55%) by using SC samples and for 24 pairs (73%) by using early index samples. DoT was predicted incorrectly for 7 pairs (21%) by using SC samples and for 4 pairs (13%) by using early index samples. Phylogenetic methods based solely on the tree topology of HIV env sequences, particularly without consideration of phylogenetic uncertainty, may be insufficient for determining DoT.

Characterization of the membrane-bound form of the chimeric, B/C recombinant HIV-1 Env, LT5.J4b12C.

Human immunodeficiency virus 1 (HIV-1) diversity is a significant challenge in developing a vaccine against the virus. B/C recombinants have been found in India and other places but are the predominant clade prevalent in China. HIV-1 envelopes (Envs) are the target of broadly neutralizing antibodies (bNAbs) which develop spontaneously in some HIV-1 infected patients. It has been previously reported with efficiently cleaved clade A, B and C Envs that preferential binding of Envs to bNAbs as opposed to non-NAbs, a desirable property for immunogens, is correlated with efficient cleavage of the Env precursor polypeptide into constituent subunits. These Envs are suitable for designing immunogens as soluble proteins, virus-like particles or for delivery by viral vectors/plasmid DNA. However, a B/C recombinant Env with similar properties has not been reported. Here we show that the chimeric, recombinant B/C clade Env LT5.J4b12C is efficiently cleaved on the plasma membrane and selectively binds to bNAbs.

Structure and Immune Recognition of the HIV Glycan Shield.

Vaccine design efforts against the human immunodeficiency virus (HIV) have been greatly stimulated by the observation that many infected patients eventually develop highly potent broadly neutralizing antibodies (bnAbs). Importantly, these bnAbs have evolved to recognize not only the two protein components of the viral envelope protein (Env) but also the numerous glycans that form a protective barrier on the Env protein. Because Env is heavily glycosylated compared to host glycoproteins, the glycans have become targets for the antibody response. Therefore, considerable efforts have been made in developing and validating biophysical methods to elucidate the complex structure of the Env-spike glycoprotein, with its combination of glycan and protein epitopes. We illustrate here how the application of robust biophysical methods has transformed our understanding of the structure and function of the HIV Env spike and stimulated innovation in vaccine design strategies that takes into account the essential glycan components.

Host and Viral Factors in HIV-Mediated Bystander Apoptosis.

Human immunodeficiency virus (HIV) infections lead to a progressive loss of CD4 T cells primarily via the process of apoptosis. With a limited number of infected cells and vastly disproportionate apoptosis in HIV infected patients, it is believed that apoptosis of uninfected bystander cells plays a significant role in this process. Disease progression in HIV infected individuals is highly variable suggesting that both host and viral factors may influence HIV mediated apoptosis. Amongst the viral factors, the role of Envelope (Env) glycoprotein in bystander apoptosis is well documented. Recent evidence on the variability in apoptosis induction by primary patient derived Envs underscores the role of Env glycoprotein in HIV disease. Amongst the host factors, the role of C-C Chemokine Receptor type 5 (CCR5), a coreceptor for HIV Env, is also becoming increasingly evident. Polymorphisms in the CCR5 gene and promoter affect CCR5 cell surface expression and correlate with both apoptosis and CD4 loss. Finally, chronic immune activation in HIV infections induces multiple defects in the immune system and has recently been shown to accelerate HIV Env mediated CD4 apoptosis. Consequently, those factors that affect CCR5 expression and/or immune activation in turn indirectly regulate HIV mediated apoptosis making this phenomenon both complex and multifactorial. This review explores the complex role of various host and viral factors in determining HIV mediated bystander apoptosis.

Transmission network characteristics based on env and gag sequences from MSM during acute HIV-1 infection in Beijing, China.

Molecular epidemiology can be used to identify human immunodeficiency virus (HIV) transmission clusters, usually using pol sequence for analysis. In the present study, we explored appropriate parameters to construct a simple network using HIV env and gag sequences instead of pol sequences for constructing a phylogenetic tree and a genetic transmission subnetwork, which were used to identify individuals with many potential transmission links and to explore the evolutionary dynamics of the virus among men who have sex with men (MSM) in Beijing. We investigated 70 acute HIV-1 infections, which consisted of HIV-1 subtype B (15.71%), the circulating recombinant forms CRF01_AE (47.14%), CRF07_BC (21.43%), CRF55_01B (1.43%), and CRF65_cpx (4.29%), and an unknown subtype (10.00%). By exploring the similarities and differences among HIV env, gag and pol sequences in describing the dynamics of the HIV-1 CRF01_AE transmission subnetwork among Beijing MSM, we found that four key points of the env sequences (strains E-2011_BJ.CY_16014, E-2011_BJ.FT_16017, E-2011_BJ.TZ_16064, and E-2011_BJ.XW_16035) contained more transmission information than gag sequences (three key points: strains G-2011_BJ.CY_16014, G-2011_BJ.FT_16017, and G-2011_BJ.XW_16035) and pol sequences (two key points: strains P-2011_BJ.CY_16014 and P-2011_BJ.XW_16035). Although the env and gag sequence results were similar to pol sequences in describing the dynamics of the HIV-1 CRF01_AE transmission subnetwork, we were able to obtain more precise information, allowing identification of key points of subnetwork expansion, based on HIV env and gag sequences instead of pol sequences. Taken together, the key points we found will improve our current understanding of how HIV spreads between MSM populations in Beijing and help to better target preventative interventions for promoting public health.