HIV Vaccine Development Research Articles

Strategies for induction of HIV-1 envelope-reactive broadly neutralizing antibodies.

IntroductionA primary focus of HIV‐1 vaccine development is the activation of B cell receptors for naïve or precursor broadly neutralizing antibodies (bnAbs), followed by expansion and maturation of bnAb B cell lineage intermediates leading to highly affinity‐matured bnAbs. HIV‐1 envelope (Env) encodes epitopes for bnAbs of different specificities. Design of immunogens to induce bnAb precursors of different specificities and mature them into bnAb status is a goal for HIV‐1 vaccine development. We review vaccine strategies for bnAb lineages development and highlight the immunological barriers that these strategies must overcome to generate bnAbs.MethodsWe provide perspectives based on published research articles and reviews.DiscussionThe recent Antibody Mediated Protection (AMP) trial that tested the protective efficacy of one HIV‐1 Env bnAb specificity demonstrated that relatively high levels of long‐lasting serum titers of multiple specificities of bnAbs will be required for protection from HIV‐1 transmission. Current vaccine efforts for induction of bnAb lineages are focused on immunogens designed to expand naïve HIV‐1 bnAb precursor B cells following the recent success of vaccine‐induction of bnAb precursor B cells in macaques and humans. BnAb precursor B cells serve as templates for priming‐immunogen design. However, design of boosting immunogens for bnAb maturation requires knowledge of the optimal immunogen design and immunological environment for bnAb B cell lineage affinity maturation. BnAb lineages acquire rare genetic changes as mutations during B cell maturation. Moreover, the immunological environment that supports bnAb development during HIV‐1 infection is perturbed with an altered B cell repertoire and dysfunctional immunoregulatory controls, suggesting that in normal settings, bnAb development will be disfavoured. Thus, strategies for vaccine induction of bnAbs must circumvent immunological barriers for bnAb development that normally constrain bnAb B cell affinity maturation.ConclusionsA fully protective HIV‐1 vaccine needs to induce durable high titers of bnAbs that can be generated by a sequential set of Env immunogens for expansion and maturation of bnAb B cell lineages in a permitted immunological environment. Moreover, multiple specificities of bnAbs will be required to be sufficiently broad to prevent the escape of HIV‐1 strains during transmission.

Structure-guided envelope trimer design in HIV-1 vaccine development: a narrative review.

IntroductionThe development of a human immunodeficiency virus 1 (HIV‐1) vaccine remains a formidable challenge. An effective vaccine likely requires the induction of broadly neutralizing antibodies (bNAbs), which likely involves the use of native‐like HIV‐1 envelope (Env) trimers at some or all stages of vaccination. Development of such trimers has been very difficult, but much progress has been made in the past decade, starting with the BG505 SOSIP trimer, elucidation of its atomic structure and implementing subsequent design iterations. This progress facilitated understanding the weaknesses of the Env trimer, fuelled structure‐guided HIV‐1 vaccine design and assisted in the development of new vaccine designs. This review summarizes the relevant literature focusing on studies using structural biology to reveal and define HIV‐1 Env sites of vulnerability; to improve Env trimers, by creating more stable versions; understanding antibody responses in preclinical vaccination studies at the atomic level; understanding the glycan shield; and to improve “on‐target” antibody responses versus “off‐target” responses.MethodsThe authors conducted a narrative review of recently published articles that made a major contribution to HIV‐1 structural biology and vaccine design efforts between the years 2000 and 2021.DiscussionThe field of structural biology is evolving at an unprecedented pace, where cryo‐electron microscopy (cryo‐EM) and X‐ray crystallography provide complementary information. Resolving protein structures is necessary for defining which Env surfaces are accessible for the immune system and can be targeted by neutralizing antibodies. Recently developed techniques, such as electron microscopy‐based polyclonal epitope mapping (EMPEM) are revolutionizing the way we are analysing immune responses and shed light on the immunodominant targets on new vaccine immunogens. Such information accelerates iterative vaccine design; for example, by reducing undesirable off‐target responses, while improving immunogens to drive the more desirable on‐target responses.ConclusionsResolving high‐resolution structures of the HIV‐1 Env trimer was instrumental in understanding and improving recombinant HIV‐1 Env trimers that mimic the structure of viral HIV‐1 Env spikes. Newly emerging techniques in structural biology are aiding vaccine design efforts and improving immunogens. The role of structural biology in HIV‐1 vaccine design has indeed become very prominent and is unlikely to diminish any time soon.

The importance of partnerships in accelerating HIV vaccine research and development.

The importance of partnerships in accelerating HIV vaccine research and development.

Current approaches to HIV vaccine development: a narrative review.

IntroductionThe development of an effective vaccine to protect against HIV is a longstanding global health need complicated by challenges inherent to HIV biology and to the execution of vaccine efficacy testing in the context of evolving biomedical prevention interventions. This review describes lessons learnt from previous efficacy trials, highlights unanswered questions, and surveys new approaches in vaccine development addressing these gaps.MethodsWe conducted a targeted peer‐reviewed literature search of articles and conference abstracts from 1989 through 2021 for HIV vaccine studies and clinical trials. The US National Library of Medicine's Clinical Trials database was accessed to further identify clinical trials involving HIV vaccines. The content of the review was also informed by the authors’ own experience and engagement with collaborators in HIV vaccine research.DiscussionThe HIV vaccine field has successfully developed multiple vaccine platforms through advanced clinical studies; however, the modest efficacy signal of the RV144 Thai trial remains the only demonstration of HIV vaccine protection in humans. Current vaccine strategies include prime‐boost strategies to improve elicitation of immune correlates derived from RV144, combination mosaic antigens, novel viral vectors, antigens designed to elicit broadly neutralizing antibody, new nucleic acid platforms and potent adjuvants to enhance immunogenicity across multiple classes of emerging vaccine candidates.ConclusionsHIV vaccine developers have applied lessons learnt from previous successes and failures to innovative vaccine design approaches. These strategies have yielded novel mosaic antigen constructs now in efficacy testing, produced a diverse pipeline of early‐stage immunogens and novel adjuvants, and advanced the field towards a globally effective HIV vaccine.

Fitting a vaccine into the HIV prevention landscape.

Fitting a vaccine into the HIV prevention landscape.

The Role of HIV-1 genome on biological mechanisms, Molecular function, Interactions between viral and host cell components, Mechanisms of viral entry, Chromosomal integration, and Transcription as potential target for new Preventive HIV-1 Vaccine Development

The human immunodeficiency virus (HIV) genome encodes a total of three structural proteins, two envelope proteins, three enzymes, and six accessory proteins. Three-dimensional molecular structures can provide detailed information on biological mechanisms and, for cases in which the molecular function affects human health, can significantly aid in the development of therapeutic interventions.

Structural and Biochemical Characterization of Cysteinylation in Broadly Neutralizing Antibodies to HIV-1

Antibodies with exceptional breadth and potency have been elicited in some individuals during natural HIV-1 infection. Elicitation and affinity maturation of broadly neutralizing antibodies (bnAbs) is therefore the central goal of HIV-1 vaccine development. The functional properties of bnAbs also make them attractive as immunotherapeutic agents, which has led to their production and optimization for passive immunotherapy. This process requires in vitro manufacturing and monitoring of any heterogeneous expression, especially when subpopulations of antibodies are produced with varying levels of biological activity. Post-translational modification (PTM) of antibodies can contribute to heterogeneity and is the focus of this study. Specifically, we have investigated cysteinylation in a bnAb lineage (PCDN family) targeting the N332-glycan supersite on the surface envelope glycoprotein (Env) of HIV-1. This PTM is defined by capping of unpaired cysteine residues with molecular cysteine. Through chromatography and mass spectrometry, we were able to characterize subpopulations of cysteinylated and non-cysteinylated antibodies when expressed in mammalian cells. The crystal structures of two PCDN antibodies represent the first structures of a cysteinylated antibody and reveal that the cysteinylation in this case is located in CDRH3. Biophysical studies indicate that cysteinylation of these HIV-1 antibodies does not interfere with antigen binding, which has been reported to occur in other cysteinylated antibodies. As such, these studies highlight the need for further investigation of cysteinylation in anti-HIV and other bnAbs.

Current Status of HIV-1 Vaccines.

HIV-1 infection and its progression to AIDS remains a significant global health challenge, particularly for low-income countries. Developing a vaccine to prevent HIV-1 infections has proven to be immensely challenging with complex biological acquisition and infection, unforeseen clinical trial disappointments, and funding issues. This paper discusses important landmarks of progress in HIV-1 vaccine development, various vaccine strategies, and clinical trials.

Phage display as a tool for identifying HIV-1 broadly neutralizing antibodies.

Combinatorial biology methods offer a good solution for targeting interactions of specif ic molecules by a high-throughput screening and are widely used for drug development, diagnostics, identif ication of novel monoclonal antibodies, search for linear peptide mimetics of discontinuous epitopes for the development of immunogens or vaccine components. Among all currently available techniques, phage display remains one of the most popular approaches. Despite being a fairly old method, phage display is still widely used for studying protein-protein, peptide-protein and DNA-protein interactions due to its relative simplicity and versatility. Phage display allows highly representative libraries of peptides, proteins or their fragments to be created. Each phage particle in a library displays peptides or proteins fused to its coat protein and simultaneously carries the DNA sequence encoding the displayed peptide/protein in its genome. The biopanning procedure allows isolation of specif ic clones for almost any target, and due to the physical link between the genotype and the phenotype of recombinant phage particles it is possible to determine the structure of selected molecules. Phage display technology continues to play an important role in HIV research. A major obstacle to the development of an effective HIV vaccine is an extensive genetic and antigenic variability of the virus. According to recent data, in order to provide protection against HIV infection, the so-called broadly neutralizing antibodies that are cross-reactive against multiple viral strains of HIV must be induced, which makes the identif ication of such antibodies a key area of HIV vaccinology. In this review, we discuss the use of phage display as a tool for identif ication of HIV-specif ic antibodies with broad neutralizing activity. We provide an outline of phage display technology, brief ly describe the design of antibody phage libraries and the affinity selection procedure, and discuss the biology of HIV-1-specif ic broadly neutralizing antibodies. Finally, we summarize the studies aimed at identif ication of broadly neutralizing antibodies using various types of phage libraries.

Polyclonal antibody responses to HIV Env immunogens resolved using cryoEM

Engineered ectodomain trimer immunogens based on BG505 envelope glycoprotein are widely utilized as components of HIV vaccine development platforms. In this study, we used rhesus macaques to evaluate the immunogenicity of several stabilized BG505 SOSIP constructs both as free trimers and presented on a nanoparticle. We applied a cryoEM-based method for high-resolution mapping of polyclonal antibody responses elicited in immunized animals (cryoEMPEM). Mutational analysis coupled with neutralization assays were used to probe the neutralization potential at each epitope. We demonstrate that cryoEMPEM data can be used for rapid, high-resolution analysis of polyclonal antibody responses without the need for monoclonal antibody isolation. This approach allowed to resolve structurally distinct classes of antibodies that bind overlapping sites. In addition to comprehensive mapping of commonly targeted neutralizing and non-neutralizing epitopes in BG505 SOSIP immunogens, our analysis revealed that epitopes comprising engineered stabilizing mutations and of partially occupied glycosylation sites can be immunogenic.

The current and future role of nanovaccines in HIV-1 vaccine development

ABSTRACT Introduction: An efficacious vaccine for HIV-1 has been sought for over 30 years to eliminate the virus from the human population. Many challenges have occurred in the attempt to produce a successful immunogen, mainly caused by the basic biology of the virus. Immunogens have been developed focusing on inducing one or more of the following types of immune responses; neutralizing antibodies, non-neutralizing antibodies, and T-cell mediated responses. One way to better present and develop an immunogen for HIV-1 is through the use of nanotechnology and nanoparticles. Areas covered: This article gives a basic overview of the HIV-1 vaccine field, as well as nanotechnology, specifically nanovaccines. It then covers the application of nanovaccines made from biological macromolecules to HIV-1 vaccine development for neutralizing antibodies, non-neutralizing antibodies, and T-cell-mediated responses. Expert opinion: Nanovaccines are an area that is ripe for further exploration in HIV-1 vaccine field. Not only are nanovaccines capable of carrying and presenting antigens in native-like conformations, but they have also repeatedly been shown to increase immunogenicity over recombinant antigens alone. Only through further research can the true role of nanovaccines in the development of an efficacious HIV-1 vaccine be established.

Broadly neutralizing antibody responses in the longitudinal primary HIV-1 infection Short Pulse Anti-Retroviral Therapy at Seroconversion cohort.

Objective:Development of immunogens that elicit an anti-HIV-1 broadly neutralizing antibody (bnAb) response will be a key step in the development of an effective HIV-1 vaccine. Although HIV-1 bnAb epitopes have been identified and mechanisms of action studied, current HIV-1 envelope-based immunogens do not elicit HIV-1 bnAbs in humans or animal models. A better understanding of how HIV-1 bnAbs arise during infection and the clinical factors associated with bnAb development may be critical for HIV-1 immunogen design efforts.Design and methods:Longitudinal plasma samples from the treatment-naive control arm of the Short Pulse Anti-Retroviral Therapy at Seroconversion (SPARTAC) primary HIV-1 infection cohort were used in an HIV-1 pseudotype neutralization assay to measure the neutralization breadth, potency and specificity of bnAb responses over time.Results:In the SPARTAC cohort, development of plasma neutralization breadth and potency correlates with duration of HIV infection and high viral loads, and typically takes 3–4 years to arise. bnAb activity was mostly directed to one or two bnAb epitopes per donor and more than 60% of donors with the highest plasma neutralization having bnAbs targeted towards glycan-dependent epitopes.Conclusion:This study highlights the SPARTAC cohort as an important resource for more in-depth analysis of bnAb developmental pathways.

Structural and genetic convergence of HIV-1 neutralizing antibodies in vaccinated non-human primates.

A primary goal of HIV-1 vaccine development is the consistent elicitation of protective, neutralizing antibodies. While highly similar neutralizing antibodies (nAbs) have been isolated from multiple HIV-infected individuals, it is unclear whether vaccination can consistently elicit highly similar nAbs in genetically diverse primates. Here, we show in three outbred rhesus macaques that immunization with Env elicits a genotypically and phenotypically conserved nAb response. From these vaccinated macaques, we isolated four antibody lineages that had commonalities in immunoglobulin variable, diversity, and joining gene segment usage. Atomic-level structures of the antigen binding fragments of the two most similar antibodies showed nearly identical paratopes. The Env binding modes of each of the four vaccine-induced nAbs were distinct from previously known monoclonal HIV-1 neutralizing antibodies, but were nearly identical to each other. The similarities of these antibodies show that the immune system in outbred primates can respond to HIV-1 Env vaccination with a similar structural and genotypic solution for recognizing a particular neutralizing epitope. These results support rational vaccine design for HIV-1 that aims to reproducibly elicit, in genetically diverse primates, nAbs with specific paratope structures capable of binding conserved epitopes.

Safety and immunogenicity of an HIV-1 gp120-CD4 chimeric subunit vaccine in a phase 1a randomized controlled trial

A major challenge for HIV vaccine development is to raise anti-envelope antibodies capable of recognizing and neutralizing diverse strains of HIV-1. Accordingly, a full length single chain (FLSC) of gp120-CD4 chimeric vaccine construct was designed to present a highly conserved CD4-induced (CD4i) HIV-1 envelope structure that elicits cross-reactive anti-envelope humoral responses and protective immunity in animal models of HIV infection. IHV01 is the FLSC formulated in aluminum phosphate adjuvant. We enrolled 65 healthy adult volunteers in this first-in-human phase 1a randomized, double-blind, placebo-controlled study with three dose-escalating cohorts (75 µg, 150 µg, and 300 µg doses). Intramuscular injections were given on weeks 0, 4, 8, and 24. Participants were followed for an additional 24 weeks after the last immunization. The overall incidence of adverse events (AEs) was not significantly different between vaccinees and controls. The majority (89%) of vaccine-related AE were mild. The most common vaccine-related adverse event was injection site pain. There were no vaccine-related serious AE, discontinuation due to AE, intercurrent HIV infection, or significant decreases in CD4 count. By the final vaccination, all vaccine recipients developed antibodies against IHV01 and demonstrated anti-CD4i epitope antibodies. The elicited antibodies reacted with CD4 non-liganded Env antigens from diverse HIV-1 strains. Antibody-dependent cell-mediated cytotoxicity against heterologous infected cells or gp120 bound to CD4+ cells was evident in all cohorts as were anti-gp120 T-cell responses. IHV01 vaccine was safe, well tolerated, and immunogenic at all doses tested. The vaccine raised broadly reactive humoral responses against conserved CD4i epitopes on gp120 that mediates antiviral functions.

Vaccine development lessons between HIV and COVID-19

The SARS-CoV-2 pandemic has many parallels to the early days of the HIV epidemic. Both began with efforts to identify the causative pathogen, followed by rapid development of diagnostics, animal models, therapeutics, and preventive vaccines. After targeting of the gp120 and gp160 HIV envelope proteins proved ineffective, development of candidate vaccines to prevent HIV expanded to encompass DNA and viral vector vaccines, with the intent of inducing both humoral and cellular immunity. In recent years, mRNA has been harnessed as a newer platform for the development of candidate HIV vaccines.

The Role of Dendritic cells in B lymphocytes, T-cell tolerance, Regulatory T Cells, and HIV-1 Pathogenesis as potential target for new Preventive and Therapeutic HIV-1 Vaccine Development (Part Five)

Novel vaccination approaches are needed to prevent and control human immunodeficiency virus (HIV) infection.

The path to find an HIV vaccine.

The path to find an HIV vaccine.

Immunization by exposure to live virus (SIVmne/HIV-2287) during antiretroviral drug prophylaxis may reduce risk of subsequent viral challenge.

Rationale/Study designA major challenge in the development of HIV vaccines is finding immunogens that elicit protection against a broad range of viral strains. Immunity to a narrow range of viral strains may protect infants of HIV-infected women or partners discordant for HIV. We hypothesized that immunization to the relevant viral variants could be achieved by exposure to infectious virus during prophylaxis with antiretroviral drugs. To explore this approach in an animal model, macaques were exposed to live virus (SIVmne or HIV-2287) during prophylaxis with parenteral tenofovir and humoral and cellular immune responses were quantified. Subsequently, experimental animals were challenged with homologous virus to evaluate protection from infection, and if infection occurred, the course of disease was compared to control animals. Experimental animals uninfected with SIVmne were challenged with heterologous HIV-2287 to assess resistance to retroviral infection.Methodology/Principal findingsJuvenile female Macaca nemestrina (N = 8) were given ten weekly intravaginal exposures with either moderately (SIVmne) or highly (HIV-2287) pathogenic virus during tenofovir prophylaxis. Tenofovir protected all 8 experimental animals from infection, while all untreated control animals became infected. Specific non-neutralizing antibodies were elicited in blood and vaginal secretions of experimental animals, but no ELISPOT responses were detected. Six weeks following the cessation of tenofovir, intravaginal challenge with homologous virus infected 2/4 (50%) of the SIVmne-immunized animals and 4/4 (100%) of the HIV-2287-immunized animals. The two SIVmne-infected and 3 (75%) HIV-2287-infected had attenuated disease, suggesting partial protection.Conclusions/SignificanceRepeated exposure to SIVmne or HIV-2287, during antiretroviral prophylaxis that blocked infection, induced binding antibodies in the blood and mucosa, but not neutralizing antibodies or specific cellular immune responses. Studies to determine whether antibodies are similarly induced in breastfeeding infants and sexual partners discordant for HIV infection and receiving pre-exposure antiretroviral prophylaxis are warranted, including whether these antibodies appear to confer partial or complete protection from infection.

Assessment of the population coverage of an HIV-1 vaccine targeting sequences surrounding the viral protease cleavage sites in Gag, Pol, or all 12 protease cleavage sites

Development of an effective HIV-1 vaccine has been a great challenge faced by the research community. Recently a novel strategy targeting the viral protease cleavage sites (PCSs) has been tested and shown promising results. This T cell-based vaccine strategy depends on individuals expressing certain HLA class I molecules and since each population has unique distributions of HLA class I alleles, population coverage analysis is required to assess feasibility. Utilizing the validated CD8 T cell epitope data from previous studies we conducted coverage analysis of an HIV-1 vaccine targeting the sequences surrounding all 12-PCSs, Gag-PCSs, and Pol-PCSs. The population coverage, average epitope hit, and minimum number of epitopes recognized by 90% of the population (PC90) was compiled for 66 countries and 16 geographical regions using the web tool provided by “Immune Epitope Database and Analysis Resource”. Our analysis shows that the coverage for an HIV-1 vaccine targeting sequences surrounding all 12 PCSs, 5 PCSs in Gag or 6 PCSs in Pol can cover ~ 70% to ~ 100% of the populations analyzed. There was no statistical difference in population coverages for the majority of populations examined when comparing the CD8 T cell epitope sets (12-PCSs, Gag-PCSs, and Pol-PCSs). As expected, vaccines targeting more sequences will have more CD8 T cell epitopes, as the mean average epitope hit for the 12-PCSs, Gag-PCSs, and Pol-PCSs across all countries studied was 9.45, 4.76, and 4.74, respectively, and across all geographical regions was 9.76, 4.99, and 4.92, respectively. The average PC90 for the 12-PCSs, Gag-PCSs, and Pol-PCSs across all countries studied was 2.53, 1.31, and 1.41, respectively, and across all geographical regions was 2.24, 1.23, and 1.29, respectively. Thus, vaccines targeting sequences surrounding the HIV-1 PCSs can cover broad populations; however, whether targeting a subset of the PCSs is sufficient to prevent acquisition requires further preclinical investigation.

Highly Mutated Antibodies Capable of Neutralizing N276-Glycan Deficient HIV after a Single Immunization with an Env Trimer

Elicitation of broadly neutralizing antibodies (bnAbs) is a major challenge in HIV vaccine development, because unmutated precursors to bnAbs are rare and typically do not bind the wildtype HIV Envelope glycoprotein (Env) trimers. One strategy to initiate bnAb type responses is to use germline-targeting immunogens that have high affinity to bnAb-class precursor B cells, then shepherd affinity maturation with booster immunogens that successively look more similar to native Env. Here, we demonstrate in a rare VRC01gHL (inferred germline of bnAb VRC01) B cell precursor model in mouse, starting from a physiological 1 in 1 million VRC01 gHL precursor frequency, a single immunization with a germline targeting soluble Env trimer can generate a significant number of high affinity bnAb-class somatic hypermutations (SHM). Notably, deletions in the light chain complementarity determining region 1 were observed in multiple germinal center (GC) B cell clones after a single immunization. Many of the GC-derived VRC01gHL antibodies developed binding to the wildtype Env trimer without an N276 glycan. Antibodies elicited after a single priming immunization neutralized several N276 glycan-deficient tier-2 HIV strains. These results are encouraging for germline-targeting Env trimer vaccine designs, demonstrating it can be possible to accumulate substantial SHM, including indels, and functional bnAb features after a single immunization.