Lessons from the RV144 Thai phase III HIV-1 vaccine trial and the search for correlates of protection

Primary Human B Cells at Different Differentiation and Maturation Stages Exhibit Distinct Susceptibilities to Vaccinia Virus Binding and Infection

Vaccinia virus (VACV), the prototypical member of the poxvirus family, was used as a live-virus vaccine to eradicate smallpox worldwide and has recently received considerable attention because of its potential as a prominent vector for the development of vaccines against infectious diseases and as an oncolytic virus for cancer therapy. Studies have demonstrated that VACV exhibits an extremely strong bias for binding to and infection of primary human antigen-presenting cells (APCs), including monocytes, macrophages, and dendritic cells. However, very few studies have assessed the interactions of VACV with primary human B cells, a main type of professional APCs. In this study, we evaluated the susceptibility of primary human peripheral B cells at various differentiation and maturation stages to VACV binding, infection, and replication. We found that plasmablasts were resistant to VACV binding, while other B subsets, including transitional, mature naive, memory, and plasma cells, were highly susceptible to VACV binding. VACV binding preference was likely associated with differential expression of chemokine receptors, particularly CXCR5. Infection studies showed that plasmablast, plasma, transitional, and mature naive B cells were resistant to VACV infection, while memory B cells were preferentially infected. VACV infection in ex vivo B cells was abortive, which occurred at the stage of late viral gene expression. In contrast, activated B cells were permissive to productive VACV infection. Thus, primary human B cells at different differentiation stages exhibit distinct susceptibilities to VACV binding and infection, and the infections are abortive and productive in ex vivo and activated B cells, respectively.IMPORTANCE Our results provide critical information to the field of poxvirus binding and infection tropism. We demonstrate that VACV preferentially infects memory B cells that play an important role in a rapid and vigorous antibody-mediated immune response upon reinfection by a pathogen. Additionally, this work highlights the potential of B cells as natural cellular models to identify VACV receptors or dissect the molecular mechanisms underlying key steps of the VACV life cycle, such as binding, penetration, entry, and replication in primary human cells. The understanding of VACV biology in human primary cells is essential for the development of a safe and effective live-virus vector for oncolytic virus therapy and vaccines against smallpox, other pathogens, and cancer.

A Sample-Sparing Multiplexed ADCP Assay

Antibodies serve as the primary correlate of protection following most clinically approved vaccines and are thought to confer protection in part through their ability to block (neutralize) infection. Increasingly, studies have shown that beyond their blocking activities, the ability of antibodies to leverage the innate immune response may serve a vital role in protection from infection. Specifically, antibodies can drive phagocytosis, complement activation, and cellular cytotoxicity by interacting with Fc-receptors found on all innate immune cells. Measuring the capacity of antibodies to induce these functions has become critical for the identification of correlates of protection in large-scale vaccine trials. Therefore, there is a growing need to develop robust, high throughput assays able to interrogate the functional capacity of innate immune recruiting antibodies. However, in many instances, only small sample volumes are available. Nevertheless, profiling antibody functions across many pathogen-associated antigens or across global intra-pathogen variants is in high demand, making sample sparing approaches to perform this antibody evaluation critical. Here we describe the development of an approach to interrogate the functional activity of antibodies in serum against up to 5 antigen targets simultaneously. A single bead-based cellular assay was adapted to accommodate 5 different fluorescently colored beads, allowing for the concurrent investigation of antibody responses directed against multiple antigens in a single well. The multiplexed assay was as sensitive, specific, and accurate as the single antigen assay and robustly able to assess functional differences mediated by antibodies across different samples. These findings show multiplexing allows for accurate and more efficient analysis of antibody-mediated effector profiles.

Induction of a Robust Humoral Response using HIV-1 VLPMPER-V3 as a Novel Candidate Vaccine in BALB/c Mice

Background:

Several approaches have not been successful to suppress HIV (Human immunodeficiency virus) infection among infected individuals or to prevent it yet. In order to expand strong HIV specific humoral and cellular responses, Virus-like particles (VLPs) as potential vaccines show significant increase in neutralizing antibodies secretion, T-cell count and also secretion of cytokines.

Objective:

This study aimed at immunological evaluation of VLPs harboring high copy of MPERV3 in BALB/c mice.

Methods:

Female BALB/c mice were immunized with homologous and heterologous primeboosting regimens of HIV-1 VLPMPER-V3. Their immune responses were evaluated for humoral responses (Total IgG and IgG isotyping) and cellular responses (IFN-γ, IL-5 secretion, in vitro CTL assay and T cell proliferation) and compared in immunized mice.

Results:

The data showed robust induction of humoral response in mice groups which received different regimens of VLP. Furthermore, analysis of cytokine profile indicated that the highest IL-5 secretion was related to VLP+M50 group and confirmed the dominance of Th2 immunity in this group.

Conclusion:

This study showed that VLP MPER-V3 as a potential vaccine candidate has the potency as an effective prophylactic vaccine and this finding guarantees further investigations to achieve a promising HIV-1 vaccine candidate.

HIV Research for Prevention 2018: From Research to Impact Conference Summary and Highlights

The HIV Research for Prevention (HIVR4P) conference is dedicated to advancing HIV prevention research, responding to a growing consensus that effective and durable prevention will require a combination of approaches as well as unprecedented collaboration among scientists, practitioners, and community workers from different fields and geographic areas. The conference theme in 2018, "From Research to Impact," acknowledged an increasing focus on translation of promising research findings into practical, accessible, and affordable HIV prevention options for those who need them worldwide. HIVR4P 2018 was held in Madrid, Spain, on 21-25 October, with >1,400 participants from 52 countries around the globe, representing all aspects of HIV prevention research and implementation. The program included 137 oral and 610 poster presentations. This article presents a brief summary of highlights from the conference. More detailed information, complete abstracts as well as webcasts and daily Rapporteur summaries may be found on the conference website.

Polysaccharide Nanoparticles Can Efficiently Modulate the Immune Response against an HIV Peptide Antigen

The development of an effective HIV vaccine continues to be a major health challenge since, so far, only the RV144 trial has demonstrated a modest clinical efficacy. Recently, the targeting of the 12 highly conserved protease cleavage sites (PCS1-12) has been presented as a strategy seeking to hamper the maturation and infectivity of HIV. To pursue this line of research, and because peptide antigens have low immunogenicity, we have included these peptides in engineered nanoparticles, aiming at overcoming this limitation. More specifically, we investigated whether the covalent attachment of a PCS peptide (PCS5) to polysaccharide-based nanoparticles, and their coadministration with polyinosinic:polycytidylic acid (poly(I:C)), improved the generated immune response. To this end, PCS5 was first conjugated to two different polysaccharides (chitosan and hyaluronic acid) through either a stable or a cleavable bond and then associated with an oppositely charged polymer (dextran sulfate and chitosan) and poly(I:C) to form the nanoparticles. Nanoparticles associating PCS5 by ionic interactions were used in this study as the control formulation. In vivo, all nanosystems elicited high anti-PCS5 antibodies. Nanoparticles containing PCS5 conjugated and poly(I:C) seemed to induce the strongest activation of antigen-presenting cells. Interestingly, T cell activation presented different kinetics depending on the prototype. These findings show that both the nanoparticle composition and the conjugation of the HIV peptide antigen may play an important role in the generation of humoral and cellular responses.

The Antibodiome-Mapping the Humoral Immune Response to HIV

PURPOSE OF REVIEW

The design of an HIV vaccine remains an elusive but top priority. Data from the non-human primate model and the first moderately protective HIV vaccine trial (RV144) point to a role for qualitative changes in humoral immune functions in protection from infection. Here, we review the current understanding of the antibody response throughout HIV infection, the known correlates of protection, and current strategies to manipulate antibodies to put an end to the epidemic.

RECENT FINDINGS

Recent studies point to innate immune-recruiting antibody function in preventing infection as well as controlling viremia following infection. These data have begun to inform next-generation design of HIV vaccines and antibody therapies by uncovering new viral targets and antibody architectures to improve potency and breadth. Emerging data illustrate a role for innate immune recruiting-antibodies in conferring protection against HIV infection as well as promoting viral control and clearance, offering an unprecedented opportunity to modulate and improve antibody function to fight HIV more effectively.

Clade C HIV-1 Envelope Vaccination Regimens Differ in Their Ability To Elicit Antibodies with Moderate Neutralization Breadth against Genetically Diverse Tier 2 HIV-1 Envelope Variants

The goals of preclinical HIV vaccine studies in nonhuman primates are to develop and test different approaches for their ability to generate protective immunity. Here, we compared the impact of 7 different vaccine modalities, all expressing the HIV-1 1086.C clade C envelope (Env), on (i) the magnitude and durability of antigen-specific serum antibody responses and (ii) autologous and heterologous neutralizing antibody capacity. These vaccination regimens included immunization with different combinations of DNA, modified vaccinia virus Ankara (MVA), soluble gp140 protein, and different adjuvants. Serum samples collected from 130 immunized monkeys at two key time points were analyzed using the TZM-bl cell assay: at 2 weeks after the final immunization (week 40/41) and on the day of challenge (week 58). Key initial findings were that inclusion of a gp140 protein boost had a significant impact on the magnitude and durability of Env-specific IgG antibodies, and addition of 3M-052 adjuvant was associated with better neutralizing activity against the SHIV1157ipd3N4 challenge virus and a heterologous HIV-1 CRF01 Env, CNE8. We measured neutralization against a panel of 12 tier 2 Envs using a newly described computational tool to quantify serum neutralization potency by factoring in the predetermined neutralization tier of each reference Env. This analysis revealed modest neutralization breadth, with DNA/MVA immunization followed by gp140 protein boosts in 3M-052 adjuvant producing the best scores. This study highlights that protein-containing regimens provide a solid foundation for the further development of novel adjuvants and inclusion of trimeric Env immunogens that could eventually elicit a higher level of neutralizing antibody breadth.IMPORTANCE Despite much progress, we still do not have a clear understanding of how to elicit a protective neutralizing antibody response against HIV-1 through vaccination. There have been great strides in the development of envelope immunogens that mimic the virus particle, but less is known about how different vaccination modalities and adjuvants contribute to shaping the antibody response. We compared seven different vaccines that were administered to rhesus macaques and that delivered the same envelope protein through various modalities and with different adjuvants. The results demonstrate that some vaccine components are better than others at eliciting neutralizing antibodies with breadth.

HIV Vaccine Efficacy Trials: RV144 and Beyond

Despite progress in antiretroviral therapy, pre-exposure prophylaxis, microbicides, and other preventive strategies, a vaccine to prevent HIV-1 infection remains desperately needed. Development of an effective vaccine is challenged by several immunologic features of HIV-1 evidenced by the failure of five of the six HIV-1 candidate vaccine efficacy trials to date. This chapter reviews these efficacy trials with a focus on the Phase 3 RV144 trial in Thailand, the only HIV-1 vaccine efficacy trial to show a moderate protective effect of 31% with respect to placebo administration. Although modest, this protection has allowed for the study of potential immunologic correlates of protection to improve development of future HIV-1 pox-protein and other vaccine strategies. Trials in Thailand and South Africa have built upon the RV144 framework to provide additional immunologic insights which enable current and future efficacy testing of related vaccine candidates.

Harnessing Antibody-Dependent Cellular Cytotoxicity To Control HIV-1 Infection

Passive administration of broadly neutralizing anti-human immunodeficiency virus type 1 (HIV-1) antibodies (bNAbs) has been recently suggested as a promising alternative therapeutic approach for HIV-1 infection. Although the success behind the studies that used this approach has been attributed to the potency and neutralization breadth of anti-HIV-1 antibodies, several lines of evidence support the idea that specific antibody-dependent effector functions, particularly antibody-dependent cellular cytotoxicity (ADCC), play a critical role in controlling HIV-1 infection. In this review, we showed that there is a direct association between the activation of ADCC and better clinical outcomes. This, in turn, suggests that ADCC could be harnessed to control HIV-1 infection. To this end, we addressed the passive administration of bNAbs capable of selectively activating ADCC responses to HIV-1 patients. Finally, we summarized the potential barriers that may impede the optimal activation of ADCC during HIV-1 infection and provided strategic solutions to overcome these barriers.

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

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.

The adjuvant AlhydroGel elicits higher antibody titres than AddaVax when combined with HIV-1 subtype C gp140 from CAP256

With the HIV-1 epidemic in southern Africa still rising, a prophylactic vaccine against the region’s most prolific subtype (subtype C) would be a significant step forward. In this paper we report on the effect of 2 different adjuvants, AddaVax and AlhydroGel, formulated with HIV-1 subtype C gp140, on the development of binding and neutralising antibody titres in rabbits. AddaVax is a squalene-based oil-in-water nano-emulsion (similar to MF59) which can enhance both cellular and humoral immune responses, whilst AlhydroGel (aluminium hydroxide gel) mainly drives a Th2 response. The gp140 gene tested was derived from the superinfecting virus (SU) from participant CAP256 in the CAPRISA 002 Acute infection cohort. The furin cleavage site of the Env protein was replaced with a flexible linker and an I559P mutation introduced. Lectin affinity purified soluble Env protein was mainly trimeric as judged by molecular weight using BN-PAGE and contained intact broadly neutralising epitopes for the V3-glycan supersite (monoclonal antibodies PGT128 and PGT135), the CD4 binding site (VRC01) and the V2-glycan (PG9) but not for the trimer-specific monoclonal antibodies PG16, PGT145 and CAP256-VRC26_08. When this soluble Env protein was tested in rabbits, AlhydroGel significantly enhanced soluble Env and V1V2 binding antibodies when compared to AddaVax. Finally, AlhydroGel resulted in significantly higher neutralization titres for a subtype C Tier 1A virus (MW965.26) and increased neutralization breadth to Tier 1A and 1B viruses. However, no autologous Tier 2 neutralisation was observed. These data suggest that adjuvant selection is critical for developing a successful vaccine and AlhydroGel should be further investigated. Additional purification of trimeric native-like CAP256 Env and/or priming with DNA or MVA might enhance the induction of neutralizing antibodies and possible Tier 2 HIV-1 neutralisation.

Defensive Driving: Directing HIV-1 Vaccine-Induced Humoral Immunity to the Mucosa with Chemokine Adjuvants

A myriad of pathogens gain access to the host via the mucosal route; thus, vaccinations that protect against mucosal pathogens are critical. Pathogens such as HIV, HSV, and influenza enter the host at mucosal sites such as the intestinal, urogenital, and respiratory tracts. All currently licensed vaccines mediate protection by inducing the production of antibodies which can limit pathogen replication at the site of infection. Unfortunately, parenteral vaccination rarely induces the production of an antigen-specific antibody at mucosal surfaces and thus relies on transudation of systemically generated antibody to mucosal surfaces to mediate protection. Mucosa-associated lymphoid tissues (MALTs) consist of a complex network of immune organs and tissues that orchestrate the interaction between the host, commensal microbes, and pathogens at these surfaces. This complexity necessitates strict control of the entry and exit of lymphocytes in the MALT. This control is mediated by chemoattractant chemokines or cytokines which recruit immune cells expressing the cognate receptors and adhesion molecules. Exploiting mucosal chemokine trafficking pathways to mobilize specific subsets of lymphocytes to mucosal tissues in the context of vaccination has improved immunogenicity and efficacy in preclinical models. This review describes the novel use of MALT chemokines as vaccine adjuvants. Specific attention will be placed upon the use of such adjuvants to enhance HIV-specific mucosal humoral immunity in the context of prophylactic vaccination.

Molecular epidemiology of a primarily MSM acute HIV-1 cohort in Bangkok, Thailand and connections within networks of transmission in Asia

INTRODUCTION

Thailand plays a substantial role in global HIV-1 transmission of CRF01_AE. Worldwide, men who have sex with men (MSM) are at elevated risk for HIV-1 infection. Hence, understanding HIV-1 diversity in a primarily Thai MSM cohort with acute infection, and its connections to the broader HIV-1 transmission network in Asia is crucial for research and development of HIV-1 vaccines, treatment and cure.

METHODS

Subtypes and diversity of infecting viruses from individuals sampled from 2009 to 2015 within the RV254/SEARCH 010 cohort were assessed by multiregion hybridization assay (MHAbce), multiregion subtype-specific PCR assay (MSSPbce) and full-length single-genome sequencing (SGS). Phylogenetic analysis was performed by maximum likelihood. Pairwise genetic distances of envelope gp160 sequences obtained from the cohort and from Asia (Los Alamos National Laboratory HIV Database) were calculated to identify potential transmission networks.

RESULTS

MHAbce/MSSPbce results identified 81.6% CRF01_AE infecting strains in RV254. CRF01_AE/B recombinants and subtype B were found at 7.3% and 2.8% respectively. Western subtype B strains outnumbered Thai B' strains. Phylogenetic analysis revealed one C, one CRF01_AE/CRF02_AG recombinant and one CRF01_AE/B/C recombinant. Asian network analysis identified one hundred and twenty-three clusters, including five clusters of RV254 participants. None of the RV254 sequences clustered with non-RV254 sequences. The largest international cluster involved 15 CRF01_AE strains from China and Vietnam. The remaining clusters were mostly intracountry connections, of which 31.7% included Thai nodes and 43.1% included Chinese nodes.

CONCLUSION

While the majority of strains in Thailand are CRF01_AE and subtype B, emergence of unique recombinant forms (URFs) are found in a moderate fraction of new HIV-1 infections. Approaches to vaccine design and immunotherapeutics will need to monitor and consider the expanding proportion of recombinants and the increasing genetic diversity in the region. Identified HIV-1 transmission networks indicate ongoing spread of HIV-1 among MSM. As HIV-1 epidemics continue to expand in other Asian countries, transmission network analyses can inform strategies for prevention, intervention, treatment and cure.

Improving the Breadth of the Host's Immune Response to Lassa Virus

In 2017, the global Coalition for Epidemic Preparedness (CEPI) declared Lassa virus disease to be one of the world's foremost biothreats. In January 2018, World Health Organization experts met to address the Lassa biothreat. It was commonly recognized that the diversity of Lassa virus (LASV) isolated from West African patient samples was far greater than that of the Ebola isolates from the West African epidemic of 2013⁻2016. Thus, vaccines produced against Lassa virus disease face the added challenge that they must be broadly-protective against a wide variety of LASV. In this review, we discuss what is known about the immune response to Lassa infection. We also discuss the approaches used to make broadly-protective influenza vaccines and how they could be applied to developing broad vaccine coverage against LASV disease. Recent advances in AIDS research are also potentially applicable to the design of broadly-protective medical countermeasures against LASV disease.

Antibodies and Antibody Derivatives: New Partners in HIV Eradication Strategies

Promptly after primoinfection, HIV generates a pool of infected cells carrying transcriptionally silent integrated proviral DNA, the HIV-1 reservoir. These cells are not cleared by combined antiretroviral therapy (cART), and persist lifelong in treated HIV-infected individuals. Defining clinical strategies to eradicate the HIV reservoir and cure HIV-infected individuals is a major research field that requires a deep understanding of the mechanisms of seeding, maintenance and destruction of latently infected cells. Although CTL responses have been classically associated with the control of HIV replication, and hence with the size of HIV reservoir, broadly neutralizing antibodies (bNAbs) have emerged as new players in HIV cure strategies. Several reasons support this potential role: (i) over the last years a number of bNAbs with high potency and ability to cope with the extreme variability of HIV have been identified; (ii) antibodies not only block HIV replication but mediate effector functions that may contribute to the removal of infected cells and to boost immune responses against HIV; (iii) a series of new technologies have allowed for the in vitro design of improved antibodies with increased antiviral and effector functions. Recent studies in non-human primate models and in HIV-infected individuals have shown that treatment with recombinant bNAbs isolated from HIV-infected individuals is safe and may have a beneficial effect both on the seeding of the HIV reservoir and on the inhibition of HIV replication. These promising data and the development of antibody technology have paved the way for treating HIV infection with engineered monoclonal antibodies with high potency of neutralization, wide coverage of HIV diversity, extended plasma half-life in vivo and improved effector functions. The exciting effects of these newly designed antibodies in vivo, either alone or in combination with other cure strategies (latency reversing agents or therapeutic vaccines), open a new hope in HIV eradication.

Correlates of GLA family adjuvants' activities

Lipopolysaccharide (LPS) is a well-defined agonist of Toll-like receptor (TLR) 4 that activates innate immune responses and influences the development of the adaptive response during infection with Gram-negative bacteria. Many years ago, Dr. Edgar Ribi separated the adjuvant activity of LPS from its toxic effects, an effort that led to the development of monophosphoryl lipid A (MPL). MPL, derived from Salmonella minnesota R595, has progressed through clinical development and is now used in various product-enabling formulations to support the generation of antigen-specific responses in several commercial and preclinical vaccines. We have generated several synthetic lipid A molecules, foremost glucopyranosyl lipid adjuvant (GLA) and second-generation lipid adjuvant (SLA), and have advanced these to clinical trial for various indications. In this review we summarize the potential and current positioning of TLR4-based adjuvant formulations in approved and emerging vaccines.

Modified Newcastle Disease virus as an improved vaccine vector against Simian Immunodeficiency virus

SIV infection in macaques is a relevant animal model for HIV pathogenesis and vaccine study in humans. To design a safe and effective vaccine against HIV, we evaluated the suitability of naturally-occurring avirulent Newcastle disease virus (NDV) strains and several modified versions of NDV as vectors for the expression and immunogenicity of SIV envelope protein gp160. All the NDV vectors expressed gp160 protein in infected cells. The gp160 expressed by these vectors formed oligomers and was incorporated into the NDV envelope. All the NDV vectors expressing gp160 were attenuated in chickens. Intranasal immunization of guinea pigs with modified NDV vectors such as rNDV-APMV-2CS/gp160 and rNDV-APMV-8CS/gp160 (NDV strain LaSota containing the cleavage site sequences of F protein of avian paramyxovirus (APMV) serotype 2 and 8, respectively), and rNDV-BC-F-HN/gp160 (NDV strain BC containing LaSota F cleavage site and LaSota F and HN genes) elicited improved SIV-specific humoral and mucosal immune responses compared to other NDV vectors. These modified vectors were also efficient in inducing neutralizing antibody responses to tier 1 A SIVmac251.6 and tier 1B SIVmac251/M766 strains. This study suggests that our novel modified NDV vectors are safe and immunogenic and can be used as vaccine vector to control HIV.

Distinct, IgG1-driven antibody response landscapes demarcate individuals with broadly HIV-1 neutralizing activity

Kadelka et al. show that parameters linked with HIV-1 broadly neutralizing antibody (bnAb) development shape HIV-1–binding antibody responses in an antigen and IgG subclass dependent manner. Identified HIV-1 antibody signature landscapes reveal a shift toward IgG1-driven responses in bnAb developers.

Understanding pathways that promote HIV-1 broadly neutralizing antibody (bnAb) induction is crucial to advance bnAb-based vaccines. We recently demarcated host, viral, and disease parameters associated with bnAb development in a large HIV-1 cohort screen. By establishing comprehensive antibody signatures based on IgG1, IgG2, and IgG3 activity to 13 HIV-1 antigens in 4,281 individuals in the same cohort, we now show that the same four parameters that are significantly linked with neutralization breadth, namely viral load, infection length, viral diversity, and ethnicity, also strongly influence HIV-1–binding antibody responses. However, the effects proved selective, shaping binding antibody responses in an antigen and IgG subclass–dependent manner. IgG response landscapes in bnAb inducers indicated a differentially regulated, IgG1-driven HIV-1 antigen response, and IgG1 binding of the BG505 SOSIP trimer proved the best predictor of HIV-1 neutralization breadth in plasma. Our findings emphasize the need to unravel immune modulators that underlie the differentially regulated IgG response in bnAb inducers to guide vaccine development.

Intragastric Administration of Lactobacillus plantarum and 2,2'-Dithiodipyridine-Inactivated Simian Immunodeficiency Virus (SIV) Does Not Protect Indian Rhesus Macaques from Intrarectal SIV Challenge or Reduce Virus Replication after Transmission

A major obstacle to development of an effective AIDS vaccine is that along with the intended beneficial responses, the immunization regimen may activate CD4+ T cells that can facilitate acquisition of human immunodeficiency virus (HIV) by serving as target cells for the virus. Lu et al. (W. Lu et al., Cell Rep 2:1736-1746, 2012, https://doi.org/10.1016/j.celrep.2012.11.016) reported that intragastric administration of chemically inactivated simian immunodeficiency virus SIVmac239 and Lactobacillus plantarum (iSIV-L. plantarum) protected 15/16 Chinese-origin rhesus macaques (RMs) from high-dose intrarectal SIVmac239 challenge at 3 months postimmunization. They attributed the observed protection to induction of immune tolerance, mediated by "MHC-Ib/E-restricted CD8+ regulatory T cells that suppressed SIV-harboring CD4+ T cell activation and ex vivo SIV replication in 15/16 animals without inducing SIV-specific antibodies or cytotoxic T." J.-M. Andrieu et al. (Front Immunol 5:297, 2014, https://doi.org/10.3389/fimmu.2014.00297) subsequently reported protection from infection in 23/24 RMs immunized intragastrically or intravaginally with iSIV and Mycobacterium bovis BCG, L. plantarum, or Lactobacillus rhamnosus, which they ascribed to the same tolerogenic mechanism. Using vaccine materials obtained from our coauthors, we conducted an immunization and challenge experiment with 54 Indian RMs and included control groups receiving iSIV only or L. plantarum only as well as unvaccinated animals. Intrarectal challenge with SIVmac239 resulted in rapid infection in all groups of vaccinated RMs as well as unvaccinated controls. iSIV-L. plantarum-vaccinated animals that became SIV infected showed viral loads similar to those observed in animals receiving iSIV only or L. plantarum only or in unvaccinated controls. The protection from SIV transmission conferred by intragastric iSIV-L. plantarum administration reported previously for Chinese-origin RMs was not observed when the same experiment was conducted in a larger cohort of Indian-origin animals.IMPORTANCE Despite an increased understanding of immune responses against HIV, a safe and effective AIDS vaccine is not yet available. One obstacle is that immunization may activate CD4+ T cells that may act as target cells for acquisition of HIV. An alternative strategy may involve induction of a tolerance-inducing response that limits the availability of activated CD4+ T cells, thus limiting the ability of virus to establish infection. In this regard, exciting results were obtained for Chinese-origin rhesus macaques by using a "tolerogenic" vaccine, consisting of intragastric administration of Lactobacillus plantarum and 2,2'-dithiodipyridine-inactivated SIV, which showed highly significant protection from virus transmission. In the present study, we administered iSIV-L. plantarum to Indian-origin rhesus macaques and failed to observe any protective effect on virus acquisition in this experimental setting. This work is important because it contributes to the overall assessment of the clinical potential of a new candidate AIDS vaccine platform based on iSIV-L. plantarum.

Natural Immunity to HIV: A Template for Vaccine Strategies

Africa accounts for the majority of global human immunodeficiency virus (HIV) infections, most of which affect women through heterosexual intercourse. Currently, there is no cure for HIV and the development of vaccines and microbicides remains the best solution to eradicate the pandemic. We and others have identified HIV highly-exposed seronegative (HESN) individuals among African female commercial sex workers (CSWs). Analyses of genital samples from HESNs have demonstrated potent innate and anti-inflammatory conditions, HIV-specific CD4⁺ and CD8⁺ T-cells as well as immunoglobulins (Igs), and increased regulatory cell populations, all of which support a delicate balance between strength and control against HIV intrusion. Moreover, we have recently shown that frequencies of innate marginal zone (MZ) B-cells are decreased in the blood of HESNs when compared to HIV-uninfected non-CSW women, suggesting their recruitment to peripheral sites. This coincides with the fact that levels of B lymphocyte stimulator (BLyS/BAFF), known to shape the MZ pool and whose overexpression leads to MZ deregulation in HIV-infected progressors, are significantly lower in the blood of HESNs when compared to both HIV-infected CSWs and HIV-uninfected non-CSW women. Interestingly, MZ B-cells can bind HIV gp120 and produce specific IgG and IgA, and have a propensity for B regulatory potential, which could help both the fight against HIV and maintenance of low inflammatory conditions in HESNs. HESN individuals provide an exceptional opportunity to identify important clues for the development of protective devices, and efforts should aim at soliciting immune responses observed in the context of their natural immunity to HIV.

HIV Vaccination: A Roadmap among Advancements and Concerns

Since the identification of the Human Immunodeficiency Virus type 1 (HIV-1) as the etiologic agent of AIDS (Acquired Immunodeficiency Syndrome), many efforts have been made to stop the AIDS pandemic. A major success of medical research has been the development of the highly active antiretroviral therapy and its availability to an increasing number of people worldwide, with a considerable effect on survival. However, a safe and effective vaccine able to prevent and eradicate the HIV pandemic is still lacking. Clinical trials and preclinical proof-of-concept studies in nonhuman primate (NHP) models have provided insights into potential correlates of protection against the HIV-1 infection, which include broadly neutralizing antibodies (bnAbs), non-neutralizing antibodies targeting the variable loops 1 and 2 (V1V2) regions of the HIV-1 envelope (Env), polyfunctional antibody, and Env-specific T-cell responses. In this review, we provide a brief overview of different HIV-1 vaccine approaches and discuss the current understanding of the cellular and humoral correlates of HIV-1 immunity.

The development of HIV vaccines targeting gp41 membrane-proximal external region (MPER): challenges and prospects

A human immunodeficiency virus type-1 (HIV-1) vaccine which is able to effectively prevent infection would be the most powerful method of extinguishing pandemic of the acquired immunodeficiency syndrome (AIDS). Yet, achieving such vaccine remains great challenges. The membrane-proximal external region (MPER) is a highly conserved region of the envelope glycoprotein (Env) gp41 subunit near the viral envelope surface, and it plays a key role in membrane fusion. It is also the target of some reported broadly neutralizing antibodies (bNAbs). Thus, MPER is deemed to be one of the most attractive vaccine targets. However, no one can induce these bNAbs by immunization with immunogens containing the MPER sequence(s). The few attempts at developing a vaccine have only resulted in the induction of neutralizing antibodies with quite low potency and limited breadth. Thus far, vaccine failure can be attributed to various characteristics of MPER, such as those involving structure and immunology; therefore, we will focus on these and review the recent progress in the field from the following perspectives: (1) MPER structure and its role in membrane fusion, (2) the epitopes and neutralization mechanisms of MPER-specific bNAbs, as well as the limitations in eliciting neutralizing antibodies, and (3) different strategies for MPER vaccine design and current harvests.

HIV-Specific T Cells Generated from Naive T Cells Suppress HIV In Vitro and Recognize Wide Epitope Breadths

The Berlin Patient represents the first and only functional HIV cure achieved by hematopoietic stem cell transplant (HSCT). In subsequent efforts to replicate this result, HIV rebounded post-HSCT after withdrawal of antiretroviral therapy. Providing HIV-specific immunity through adoptive T cell therapy may prevent HIV rebound post-HSCT by eliminating newly infected cells before they can seed systemic infection. Adoptive T cell therapy has demonstrated success in boosting Epstein-Barr virus and cytomegalovirus-specific immunity post-HSCT, controlling viral reactivation. However, T cell immunotherapies to boost HIV-specific immunity have been limited by single-epitope specificity and minimal persistence or efficacy in vivo. To improve this strategy, we sought to generate allogeneic HIV-specific T cells from human leukocyte antigen (HLA)-A02+ HIV-negative adult or cord blood donors. We focused on HLA-A02+ donors due to well-characterized epitope restrictions observed in HIV+ populations. We show that multi-antigen HIV-specific T cells can be generated from naive T cells of both cord blood and adults using a reproducible good manufacturing practice (GMP)-grade protocol. This product lysed antigen-pulsed targets and suppressed active HIV in vitro. Interestingly, these cells displayed broad epitope recognition despite lacking recognition of the common HLA-A02-restricted HIV epitope Gag SL9. This first demonstration of functional multi-antigen HIV-specific T cells has implications for improving treatment of HIV through allogeneic HSCT.

HIV Universal Vaccine

BACKGROUND

For many deadly viruses, there are no preventive and / or therapeutic vaccines approved by health authorities World-wide (e.g., HIV, Ebola, Dengue, and many others). Although, for some viruses, prophylactic vaccines are very effective (e.g., HBV, and many others).In this realm, we design, manufacture, test, and streamline into the clinics novel viral universal vaccines (VUV). VUV have such unique features, that medical vaccination or natural infection induced immunity against some viruses (e.g., HBV) upon the VUV's administration to the infected with other, different viruses patients, is redirected against these other, newly infecting viruses (e.g., HIV).

SPECIFIC AIM

The specific aim of this work was biomolecular engineering of the HIV universal vaccine comprising the two main functional domains: CD4 or anti-gp120 - as the HIV tagging domain and HBsAg - as the immune response eliciting domain, so that upon its administration the HBV medical immunization or natural infection induced immunity would be redirected, accelerated, and amplified to fight the HIV infection.

HEALTHY DONORS AND PATIENTS

Per the Institutional Review Board approval and in compliance with the Declaration of Helsinki, all healthy donors and patients were presented with the Patients' Bill of Rights and provided Patient Informed Consent. All the procedures were pursued by the licensed medical doctors.

METHODS & RESULTS

We have biomolecularly engineered HIV universal vaccine (HIVUV) comprising human CD4 or anti-gp120 and HBsAg of HBV. By immunoblotting and magnetic activated molecular sorting, we have demonstrated high specificity of this vaccine in binding HIV. By flow cytometry and nuclear magnetic resonance, we have demonstrated high efficacy of these vaccines to engage HBV immunized patients' immune system against HIV. Administration of HIVUV to blood or lymph of the HIV+ patients resulted in rapid reduction of the HIV viremia down to undetectable. It also resulted in protection of populations of CD4+ cells against HIV caused decline.

CONCLUSIONS

We have demonstrated the proof of concept for high efficacy of VUV, specifically HIVUV, in annihilating HIV. Nevertheless, the same compositions, processes, and methods, for persons skilled in biotechnology, pharmacogenomics, and molecular medicine, are adaptable for other deadly viral infections, which we vigorously pursue.

Advances in HIV-1 Vaccine Development

An efficacious HIV-1 vaccine is regarded as the best way to halt the ongoing HIV-1 epidemic. However, despite significant efforts to develop a safe and effective vaccine, the modestly protective RV144 trial remains the only efficacy trial to provide some level of protection against HIV-1 acquisition. This review will outline the history of HIV vaccine development, novel technologies being applied to HIV vaccinology and immunogen design, as well as the studies that are ongoing to advance our understanding of vaccine-induced immune correlates of protection.

Transcriptomic signatures of NK cells suggest impaired responsiveness in HIV-1 infection and increased activity post-vaccination

Natural killer (NK) cells limit viral replication by direct recognition of infected cells, antibody-dependent cellular cytotoxicity (ADCC), and releasing cytokines. Although growing evidence supports NK cell antiviral immunity in HIV-1 infection, further knowledge of their response is necessary. Here we show that NK cells responding to models of direct cell recognition, ADCC, and cytokine activation have unique transcriptional fingerprints. Compared with healthy volunteers, individuals with chronic HIV-1 infection have higher expression of genes commonly associated with activation, and lower expression of genes associated with direct cell recognition and cytokine stimulation in their NK cells. By contrast, NK cell transcriptional profiles of individuals receiving a modified vaccinia Ankara (MVA) vectored HIV-1 vaccine show upregulation of genes associated with direct cell recognition. These findings demonstrate that targeted transcriptional profiling provides a sensitive assessment of NK cell activity, which helps understand how NK cells respond to viral infections and vaccination.

Natural killer (NK) cells are important for eliminating cells under stress or infected by virus, and may have a function in anti-HIV immunity. Here the authors show that different NK-activating stimuli induce distinct transcriptional fingerprints in human NK cells that are analogous to changes caused by HIV vaccination or chronic infection.

Fundamental challenges to the development of a preventive HIV vaccine

There is consensus that only a preventive vaccine can contain the HIV/AIDS pandemic. After 30 years still there is no preventive HIV vaccine. This article examines fundamental challenges to the development of a preventive HIV vaccine. They include the initially erroneous but powerful perception of the natural history of HIV disease, as an acute rather than a chronic illness even in the absence of therapy, the lack of appreciation of the quasispecies biology of HIV and the abandonment of principles of immunology theory caused by the allure of technological prowess. In addition two other important aspects are discussed: vaccines directed against transmitted/founder viruses (T/F) and the reconsideration of HIV inactivation as a viable means to obtain a preventive HIV vaccine using novel safe methods of inactivation not available during the early years of the pandemic.

Vaccination route can significantly alter the innate lymphoid cell subsets: a feedback between IL-13 and IFN-γ

This study demonstrates that the fate of a vaccine is influenced by the cytokines produced by the innate lymphoid cells (ILC) recruited to the vaccination site, and it is vaccine route and adjuvant dependent. Intranasal virus vaccination induced ST2/IL-33R⁺ ILC2 in lung, while intramuscular vaccination induced exclusively IL-25R⁺ ILC2 in muscle. Interestingly, a larger proportion of IL-13⁺ ILC2s were detected in muscle following i.m. viral vector vaccination compared to lung post i.n. delivery. These observations revealed that ILC2 were the main source of IL-13 at the vaccination site (24 h post vaccination) responsible for inducing T cells of varying avidities. Moreover, recombinant fowlpox viral vector-based vaccines expressing adjuvants that transiently block IL-13 signalling at the vaccination site using different mechanisms (IL-4R antagonist or IL-13Rα2 adjuvants), revealed that the level of IL-13 present in the milieu also significantly influenced IFN-γ, IL-22 or IL-17A expression by ILC1/ILC3. Specifically, an early IL-13 and IFN-γ co-dependency at the ILC level may also be associated with shaping the downstream antibody responses, supporting the notion that differentially regulating IL-13 signalling via STAT6 or IL-13Rα2 pathways can modify ILC function and the resulting adaptive T- and B-cell immune outcomes reported previously. Moreover, unlike chronic inflammatory or experimentally induced conditions, viral vector vaccination induced uniquely different ILC profiles (i.e., expression of CD127 only on ILC2 not ILC1/ILC3; expression of IFN-γ in both NKP46⁺ and NKp46^- ILCs). Collectively, our data highlight that tailoring a vaccine vector/adjuvant to modulate the ILC cytokine profile according to the target pathogen, may help design more efficacious vaccines in the future.

Predominant envelope variable loop 2-specific and gp120-specific antibody-dependent cellular cytotoxicity antibody responses in acutely SIV-infected African green monkeys

Background

The initial envelope (Env)-specific antibody response in acutely HIV-1-infected individuals and simian immunodeficiency virus (SIV)-infected rhesus monkeys (RMs) is dominated by non-neutralizing antibodies targeting Env gp41. In contrast, natural primate SIV hosts, such as African green monkeys (AGMs), develop a predominant Env gp120-specific antibody response to SIV infection. However, the fine-epitope specificity and function of SIV Env-specific plasma IgG, and their potential role on autologous virus co-evolution in SIV-infected AGMs and RMs remain unclear.

Results

Unlike the dominant linear gp41-specific IgG responses in RMs, SIV-infected AGMs demonstrated a unique linear variable loop 2 (V2)-specific plasma IgG response that arose concurrently with high gp120-directed antibody-dependent cellular cytotoxicity (ADCC) activity, and SIVsab-infected cell binding responses during acute infection. Moreover, SIV variants isolated from SIV-infected AGMs exhibited high amino acid mutation frequencies within the Env V1V2 loop compared to those of RMs. Notably, the linear V2-specific IgG epitope in AGMs overlaps with an analogous region of the HIV V2 loop containing the K169 mutation epitope identified in breakthrough viruses from RV144 vaccinees.

Conclusion

Vaccine-elicited Env V2-specific IgG responses have been proposed as an immune correlate of reduced risk in HIV-1/SIV acquisition in humans and RMs. Yet the pathways to elicit these potentially-protective V2-specific IgG responses remain unclear. In this study, we demonstrate that SIV-infected AGMs, which are the natural hosts of SIV, exhibited high plasma linear V2-specific IgG binding responses that arose concurrently with SIV Env gp120-directed ADCC-mediating, and SIV-infected cell plasma IgG binding responses during acute SIV infection, which were not present in acutely SIV-infected RMs. The linear V2-specific antibody response in AGMs targets an overlapping epitope of the proposed site of vaccine-induced immune pressure defined in the moderately protective RV144 HIV-1 vaccine trial. Identifying host factors that control the early elicitation of Env V2-specific IgG and ADCC antibody responses in these natural SIV hosts could inform vaccination strategies aimed at rapidly inducing potentially-protective HIV-1 Env-specific responses in humans.

Electronic supplementary material

The online version of this article (10.1186/s12977-018-0406-5) contains supplementary material, which is available to authorized users.

Whither vaccines?

Currently used vaccines have had major effects on eliminating common infections, largely by duplicating the immune responses induced by natural infections. Now vaccinology faces more complex problems, such as waning antibody, immunosenescence, evasion of immunity by the pathogen, deviation of immunity by the microbiome, induction of inhibitory responses, and complexity of the antigens required for protection. Fortunately, vaccine development is now incorporating knowledge from immunology, structural biology, systems biology and synthetic chemistry to meet these challenges. In addition, international organisations are developing new funding and licensing pathways for vaccines aimed at pathogens with epidemic potential that emerge from tropical areas.

Multi-Envelope HIV-1 Vaccine Development: Two Targeted Immune Pathways, One Desired Protective Outcome

In 2016, there were more than 30 million individuals living with HIV-1, ∼1.8 million new HIV-1 infections, and ∼1 million HIV-1-related deaths according to UNAIDS ( unaids.org ). Hence, a preventive HIV-1 vaccine remains a global priority. The variant envelopes of HIV-1 present a significant obstacle to vaccine development and the vaccine field has realized that immunization with a single HIV-1 envelope protein will not be sufficient to generate broadly neutralizing antibodies. Here we describe two nonmutually exclusive, targeted pathways with which a multi-envelope HIV-1 vaccine may generate protective immune responses against variant HIV-1. Pathways include (i) the induction of a polyclonal immune response, comprising a plethora of antibodies with subset-reactive and cross-reactive specificities, together able to neutralize diverse HIV-1 (termed Poly-nAb in this report) and (ii) the induction of one or a few monoclonal antibodies, each with a broadly neutralizing specificity (bnAb). With each pathway in mind, we describe challenges and strategies that may ultimately support HIV-1 vaccine success.

Loading dendritic cells with gold nanoparticles (GNPs) bearing HIV-peptides and mannosides enhance HIV-specific T cell responses

Gold nanoparticles (GNPs) decorated with glycans ameliorate dendritic cells (DC) uptake, antigen-presentation and T-cells cross-talk, which are important aspects in vaccine design. GNPs allow for high antigen loading, DC targeting, lack of toxicity and are straightforward prepared and easy to handle. The present study aimed to assess the capacity of DC to process and present HIV-1-peptides loaded onto GNPs bearing high-mannoside-type oligosaccharides (P1@HM) to autologous T-cells from HIV-1 patients. The results showed that P1@HM increased HIV-specific CD4⁺ and CD8⁺ T-cell proliferation and induced highly functional cytokine secretion compared with HIV-peptides alone. P1@HM elicits a highly efficient secretion of pro-T_H1 cytokines and chemokines, a moderate production of pro-T_H2 and significant higher secretion of pro-inflammatory cytokines such as TNF-α and IL-1β. Thus, co-delivery of HIV-1 antigens and HM by GNPs is an excellent vaccine delivery system inducing HIV-specific cellular immune responses in HIV+ patients, being a promising approach to improve anti-HIV-1 vaccines.

Safety and vaccine-induced HIV-1 immune responses in healthy volunteers following a late MVA-B boost 4 years after the last immunization

Background

We have previously shown that an HIV vaccine regimen including three doses of HIV-modified vaccinia virus Ankara vector expressing HIV-1 antigens from clade B (MVA-B) was safe and elicited moderate and durable (1 year) T-cell and antibody responses in 75% and 95% of HIV-negative volunteers (n = 24), respectively (RISVAC02 study). Here, we describe the long-term durability of vaccine-induced responses and the safety and immunogenicity of an additional MVA-B boost.

Methods

13 volunteers from the RISVAC02 trial were recruited to receive a fourth dose of MVA-B 4 years after the last immunization. End-points were safety, cellular and humoral immune responses to HIV-1 and vector antigens assessed by ELISPOT, intracellular cytokine staining (ICS) and ELISA performed before and 2, 4 and 12 weeks after receiving the boost.

Results

Volunteers reported 64 adverse events (AEs), although none was a vaccine-related serious AE. After 4 years from the 1^st dose of the vaccine, only 2 volunteers maintained low HIV-specific T-cell responses. After the late MVA-B boost, a modest increase in IFN-γ T-cell responses, mainly directed against Env, was detected by ELISPOT in 5/13 (38%) volunteers. ICS confirmed similar results with 45% of volunteers showing that CD4+ T-cell responses were mainly directed against Env, whereas CD8+ T cell-responses were similarly distributed against Env, Gag and GPN. In terms of antibody responses, 23.1% of the vaccinees had detectable Env-specific binding antibodies 4 years after the last MVA-B immunization with a mean titer of 96.5. The late MVA-B boost significantly improved both the response rate (92.3%) and the magnitude of the systemic binding antibodies to gp120 (mean titer of 11460). HIV-1 neutralizing antibodies were also enhanced and detected in 77% of volunteers. Moreover, MVA vector-specific T cell and antibody responses were boosted in 80% and 100% of volunteers respectively.

Conclusions

One boost of MVA-B four years after receiving 3 doses of the same vaccine was safe, induced moderate increases in HIV-specific T cell responses in 38% of volunteers but significantly boosted the binding and neutralizing antibody responses to HIV-1 and to the MVA vector.

Trial registration

ClinicalTrials.gov NCT01923610.

Impact of Poxvirus Vector Priming, Protein Coadministration, and Vaccine Intervals on HIV gp120 Vaccine-Elicited Antibody Magnitude and Function in Infant Macaques

Despite success in reducing vertical HIV transmission by maternal antiretroviral therapy, several obstacles limit its efficacy during breastfeeding, and breast-milk transmission is now the dominant mode of mother-to-child transmission (MTCT) of HIV in infants. Thus, a pediatric vaccine is needed to eradicate oral HIV infections in newborns and infants. Utilizing the infant rhesus macaque model, we compared 3 different vaccine regimens: (i) HIV envelope (Env) protein only, (ii) poxvirus vector (modified vaccinia virus Ankara [MVA])-HIV Env prime and HIV Env boost, and (iii) coadministration of HIV Env and MVA-HIV Env at all time points. The vaccines were administered with an accelerated, 3-week-interval regimen starting at birth for early induction of highly functional HIV Env-specific antibodies. We also tested whether an extended, 6-week immunization interval using the same vaccine regimen as in the coadministration group would enhance the quality of antibody responses. We found that pediatric HIV vaccines administered at birth are effective in inducing HIV Env-specific plasma IgG. The vaccine regimen consisting of only HIV Env protein induced the highest levels of variable region 1 and 2 (V1V2)-specific antibodies and tier 1 neutralizing antibodies, whereas the extended-interval regimen induced both persistent Env-specific systemic IgG and mucosal IgA responses. Antibody-dependent cell-mediated cytotoxicity (ADCC) antibodies in plasma were elicited by all vaccine regimens. These data suggest that infant immunizations beginning at birth are effective for the induction of functional HIV Env-specific antibodies that could potentially protect against breast milk transmission of HIV and set the stage for immunity prior to sexual debut.

Combining biomedical preventions for HIV: Vaccines with pre-exposure prophylaxis, microbicides or other HIV preventions

Biomedical preventions for HIV, such as vaccines, microbicides or pre-exposure prophylaxis (PrEP) with antiretroviral drugs, can each only partially prevent HIV-1 infection in most human trials. Oral PrEP is now FDA approved for HIV-prevention in high risk groups, but partial adherence reduces efficacy. If combined as biomedical preventions (CBP) an HIV vaccine could provide protection when PrEP adherence is low and PrEP could prevent vaccine breakthroughs. Other types of PrEP or microbicides may also be partially protective. When licensed, first generation HIV vaccines are likely to be partially effective. Individuals at risk for HIV may receive an HIV vaccine combined with other biomedical preventions, in series or in parallel, in clinical trials or as part of standard of care, with the goal of maximally increasing HIV prevention. In human studies, it is challenging to determine which preventions are best combined, how they interact and how effective they are.

Animal models can determine CBP efficacy, whether additive or synergistic, the efficacy of different products and combinations, dose, timing and mechanisms. CBP studies in macaques have shown that partially or minimally effective candidate HIV vaccines combined with partially effective oral PrEP, vaginal PrEP or microbicide generally provided greater protection than either prevention alone against SIV or SHIV challenges. Since human CBP trials will be complex, animal models can guide their design, sample size, endpoints, correlates and surrogates of protection. This review focuses on animal studies and human models of CBP and discusses implications for HIV prevention.

Phenotypic and Functional Characterization of Circulatory, Splenic, and Hepatic NK Cells in Simian Immunodeficiency Virus-Controlling Macaques

NK cells are key components of the immune system because of their rapid response potential and their ability to mediate cytotoxic and immunomodulatory functions. Additionally, NK cells have recently been shown to persist for long periods in vivo and to have the capacity to establish immunologic memory. In the current study, we assessed the phenotype and function of circulatory and tissue-resident NK cells in a unique cohort of SIV-controlling rhesus macaques that maintained low to undetectable levels of viremia in the chronic phase of infection. By contrasting NK responses of these macaques with those observed in SIV-noncontrolling and uninfected macaques, we aimed to identify markers and activities of NK subpopulations associated with disease control. We show in this article that most differences among NK cells of the three groups of macaques were observed in tissue-resident cells. Although SIV infection resulted in NK cell dysfunction, double-negative NK cells and those expressing CXCR3, NKG2D, and IL-18Rα were associated with viremia control, as was Ab-dependent cytotoxic function. Our results suggest several novel targets for therapeutic intervention.

In vitro inhibition of HIV-1 replication in autologous CD4+ T cells indicates viral containment by multifactorial mechanisms

HIV-1-specific cytotoxic T lymphocytes (CTLs) and neutralizing antibodies (NAbs) are present during chronic infection, but the relative contributions of these effector mechanisms to viral containment remain unclear. Here, using an in vitro model involving autologous CD4⁺ T cells, primary HIV-1 isolates, HIV-1-specific CTLs, and neutralizing monoclonal antibodies, we show that b12, a potent and broadly neutralizing monoclonal antibody to HIV-1, was able to block viral infection when preincubated with virus prior to infection, but was much less effective than CTLs at limiting virus replication when added to infected cell cultures. However, the same neutralizing antibody was able to contain viruses by antibody-dependent cell-mediated virus inhibition in vitro, which was mediated by natural killer cells (NKs) and dependent on an Fc-Fc receptor interaction. Meanwhile, bulk CTLs from HIV-1 controllers were more effective in suppression of virus replication than those from progressors. These findings indicate that control of HIV-1 replication in activated CD4⁺ T cells is ineffectively mediated by neutralizing antibodies alone, but that both CTLs and antibody-dependent NK-mediated immune mechanisms contribute to viral containment. Our study systemically compared three major players in controlling HIV-1 infection, CTLs, NAbs, and NKs, in an autologous system and highlighted the multifactorial mechanisms for viral containment and vaccine success.

Increased, Durable B-Cell and ADCC Responses Associated with T-Helper Cell Responses to HIV-1 Envelope in Macaques Vaccinated with gp140 Occluded at the CD4 Receptor Binding Site

Strategies are needed to improve the immunogenicity of HIV-1 envelope (Env) antigens (Ag) for more long-lived, efficacious HIV-1 vaccine-induced B-cell responses. HIV-1 Env gp140 (native or uncleaved molecules) or gp120 monomeric proteins elicit relatively poor B-cell responses which are short-lived. We hypothesized that Env engagement of the CD4 receptor on T-helper cells results in anergic effects on T-cell recruitment and consequently a lack of strong, robust, and durable B-memory responses. To test this hypothesis, we occluded the CD4 binding site (CD4bs) of gp140 by stable cross-linking with a 3-kDa CD4 miniprotein mimetic, serving to block ligation of gp140 on CD4⁺ T cells while preserving CD4-inducible (CDi) neutralizing epitopes targeted by antibody-dependent cellular cytotoxicity (ADCC) effector responses. Importantly, immunization of rhesus macaques consistently gave superior B-cell (P < 0.001) response kinetics and superior ADCC (P < 0.014) in a group receiving the CD4bs-occluded vaccine compared to those of animals immunized with gp140. Of the cytokines examined, Ag-specific interleukin-4 (IL-4) T-helper enzyme-linked immunosorbent spot (ELISpot) assays of the CD4bs-occluded group increased earlier (P = 0.025) during the inductive phase. Importantly, CD4bs-occluded gp140 antigen induced superior B-cell and ADCC responses, and the elevated B-cell responses proved to be remarkably durable, lasting more than 60 weeks postimmunization.

IMPORTANCE Attempts to develop HIV vaccines capable of inducing potent and durable B-cell responses have been unsuccessful until now. Antigen-specific B-cell development and affinity maturation occurs in germinal centers in lymphoid follicles through a critical interaction between B cells and T follicular helper cells. The HIV envelope binds the CD4 receptor on T cells as soluble shed antigen or as antigen-antibody complexes, causing impairment in the activation of these specialized CD4-positive T cells. We proposed that CD4-binding impairment is partly responsible for the relatively poor B-cell responses to HIV envelope-based vaccines. To test this hypothesis, we blocked the CD4 binding site of the envelope antigen and compared it to currently used unblocked envelope protein. We found superior and durable B-cell responses in macaques vaccinated with an occluded CD4 binding site on the HIV envelope antigen, demonstrating a potentially important new direction in future design of new HIV vaccines.

Immunogenicity and efficacy of DNA/MVA HIV vaccines in rhesus macaque models

INTRODUCTION

Despite 30 years of research on HIV, a vaccine to prevent infection and limit disease progression remains elusive. The RV144 trial showed moderate, but significant protection in humans and highlighted the contribution of antibody responses directed against HIV envelope as an important immune correlate for protection. Efforts to further build upon the progress include the use of a heterologous prime-boost regimen using DNA as the priming agent and the attenuated vaccinia virus, Modified Vaccinia Ankara (MVA), as a boosting vector for generating protective HIV-specific immunity. Areas covered: In this review, we summarize the immunogenicity of DNA/MVA vaccines in non-human primate models and describe the efficacy seen in SIV infection models. We discuss immunological correlates of protection determined by these studies and potential approaches for improving the protective immunity. Additionally, we describe the current progress of DNA/MVA vaccines in human trials. Expert commentary: Efforts over the past decade have provided the opportunity to better understand the dynamics of vaccine-induced immune responses and immune correlates of protection against HIV. Based on what we have learned, we outline multiple areas where the field will likely focus on in the next five years.

Modeling HIV vaccine trials of the future

PURPOSE OF REVIEW

Models of implementation of known-effective interventions for HIV prevention indicate that an efficacious vaccine to prevent HIV infection would be critical for controlling the HIV pandemic. Key issues in the design of future HIV vaccine trials are: first, how to develop reliable immunological correlates of vaccine efficacy, second, how to down-select candidate vaccine regimens into efficacy trials, and third, how to learn about vaccine efficacy in the context of the evolving HIV prevention landscape.

RECENT FINDINGS

Whereas in the past phase-I/-II HIV vaccine trials have addressed the first and second points using a small set of immunological assays and readouts, recently they have used a battery of assays with highly multivariate readouts. In addition, systems vaccinology studies of other pathogens measuring PBMC transcriptomics and other immunological features pre- and postfirst vaccination are demonstrating value, for example, providing discoveries that preimmunization and early postimmunization cell population markers can predict the influenza-specific antibody titer that is a correlate of vaccine protection. The HIV prevention landscape continues to evolve, and the design and analysis of vaccine trials is evolving alongside, to accommodate increasingly dynamic and regional standards of HIV prevention.

SUMMARY

Development of interpretable and robust functional assays, in addition to the associated bioinformatics and statistical analytic tools, is needed to improve the assessment of correlates of protection in efficacy trials and the down-selection of candidate vaccine regimens into efficacy trials. Moreover, high-priority trials should integrate systems vaccinology, including the analysis of prevaccination and early postvaccination markers.

Lessons from HIV-1 vaccine efficacy trials

PURPOSE OF REVIEW

Only four HIV-1 vaccine concepts have been tested in six efficacy trials with no product licensed to date. Several scientific and programmatic lessons can be learned from these studies generating new hypotheses and guiding future steps.

RECENT FINDINGS

RV144 [ALVAC-HIV (canarypox vector) and AIDSVAX B/E (bivalent gp120 HIV-1 subtype B and CRF01_AE)] remains the only efficacy trial that demonstrated a modest vaccine efficacy, which led to the identification of immune correlates of risk. Progress on subtype-specific, ALVAC (canarypox vector) and gp120 vaccine prime-boost approaches has been slow, but we are finally close to the launch of an efficacy study in Africa in 2016. The quest of a globally effective HIV-1 vaccine has led to the development of new approaches. Efficacy studies of combinations of Adenovirus type 26 (Ad26)/Modified Vaccinia Ankara (MVA)/gp140 vaccines with mosaic designs will enter efficacy studies mid-2017 and cytomegalovirus (CMV)-vectored vaccines begin Phase I studies at the same time. Future HIV-1 vaccine efficacy trials face practical challenges as effective nonvaccine prevention programs are projected to decrease HIV-1 incidence.

SUMMARY

An HIV-1 vaccine is urgently needed. Increased industry involvement, mobilization of resources, expansion of a robust pipeline of new concepts, and robust preclinical challenge studies will be essential to accelerate efficacy testing of next generation HIV-1 vaccine candidates.

Randomized, Double-Blind Evaluation of Late Boost Strategies for HIV-Uninfected Vaccine Recipients in the RV144 HIV Vaccine Efficacy Trial

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.

Three-Year Durability of Immune Responses Induced by HIV-DNA and HIV-Modified Vaccinia Virus Ankara and Effect of a Late HIV-Modified Vaccinia Virus Ankara Boost in Tanzanian Volunteers

We explored the duration of immune responses and the effect of a late third HIV-modified vaccinia virus Ankara (MVA) boost in HIV-DNA primed and HIV-MVA boosted Tanzanian volunteers. Twenty volunteers who had previously received three HIV-DNA and two HIV-MVA immunizations were given a third HIV-MVA immunization 3 years after the second HIV-MVA boost. At the time of the third HIV-MVA, 90% of the vaccinees had antibodies to HIV-1 subtype C gp140 (median titer 200) and 85% to subtype B gp160 (median titer 100). The majority of vaccinees had detectable antibody-dependent cellular cytotoxicity (ADCC)-mediating antibodies, 70% against CRF01_AE virus-infected cells (median titer 239) and 84% against CRF01_AE gp120-coated cells (median titer 499). A high proportion (74%) of vaccinees had IFN-γ ELISpot responses, 63% to Gag and 42% to Env, 3 years after the second HIV-MVA boost. After the third HIV-MVA, there was an increase in Env-binding antibodies and ADCC-mediating antibodies relative to the response seen at the time of the third HIV-MVA vaccination, p < .0001 and p < .05, respectively. The frequency of IFN-γ ELISpot responses increased to 95% against Gag or Env and 90% to both Gag and Env, p = .064 and p = .002, respectively. In conclusion, the HIV-DNA prime/HIV-MVA boost regimen elicited potent antibody and cellular immune responses with remarkable durability, and a third HIV-MVA immunization significantly boosted both antibody and cellular immune responses relative to the levels detected at the time of the third HIV-MVA, but not to higher levels than after the second HIV-MVA.

Engineered Expression of Broadly Neutralizing Antibodies Against Human Immunodeficiency Virus

This review discusses recent progress made in developing a vaccine and novel treatments for human immunodeficiency virus (HIV). It highlights the shortcomings of the RV144 vaccination trial [ALVAC-HIV (vCP1521) and AIDSVAX B/E] and the current standard of care and proposes that engineered expression of broadly neutralizing antibodies (bNAbs) against HIV-1 could overcome these shortcomings. Current developments in three major lines of research on HIV prevention and treatment using bNAbs are reviewed: firstly, the use of sequential immunogens to activate B cells to express bNAbs; secondly, the delivery of novel and extremely potent bNAbs through passive administration; and finally, the use of gene transfer using adeno-associated viral vectors to deliver bNAbs.

Stabilization and Sustained Release of HIV Inhibitors by Encapsulation in Silk Fibroin Disks

Topical microbicides have the potential to provide effective protection against sexual transmission of HIV. Challenges in developing microbicides include their application in resource-poor settings with high temperatures and a lack of refrigeration, and low user adherence to a rigorous daily regimen. Several protein-based HIV inhibitors show great promise as microbicides, being highly specific and not expected to lead to resistance that would affect the efficacy of current antiretroviral treatments. We show that four potent protein HIV inhibitors, 5P12-RANTES, 5P12-RANTES-L-C37, Grft, and Grft-L-C37 can be formulated into silk fibroin (SF) disks and remain functional for 14 months at 25, 37, and 50 °C. These HIV inhibitor-encapsulated SF disks show excellent inhibition properties in PBMC and in human colorectal and cervical tissue explants, and do not induce inflammatory cytokine secretion. Further, the SF provides a mechanically robust matrix with versatile material formats for this type of application. Finally, a formulation was developed to allow sustained release of functional Grft for 4 weeks at levels sufficient to inhibit HIV transmission. This work establishes the suitability of HIV inhibitor-encapsulated SF disks as topical HIV microbicides that can be further developed to allow easy insertion for extended protection.

Assessment of Anti-HIV-1 Antibodies in Oral and Nasal Compartments of Volunteers From 3 Different Populations

In this study, we assessed the feasibility of collecting standardized nasal and salivary samples at centers in Nairobi (Kenya), Kigali (Rwanda), and London (United Kingdom) using different collection devices and media (synthetic absorptive matrices versus flocked swabs, and Salimetrics oral swabs versus whole oral fluid collection). We detected anti-Gag (p24) and envelope (gp140) antibodies in both nasal fluid and salivary collections from all HIV-infected individuals, and cross-reactive anti-p24 antibodies were detected in 10% of HIV-uninfected individuals enrolled at one site. Collections from the nasal turbinates were comparable with samples collected deeper in the nasopharyngeal tract, and the yield of anti-p24 IgA in the whole oral fluid samples was higher than in samples collected from the parotid gland. We noted a trend toward reduced levels of anti-HIV antibody in the volunteers receiving anti-retroviral therapy. Levels of antibodies were stable over multiple collection visits. Overall, this study shows that nasal and salivary samples can be collected in a standardized manner over repeated visits in both low- and high-resource settings. These methods may be used in support for future HIV vaccine clinical trials.