Scientific Publications

The ability of HIV-1 vaccine candidates MRKAd5, VRC DNA/Ad5 and ALVAC/AIDSVAX to elicit CD8 T cells with direct antiviral function was assessed and compared with HIV-1-infected volunteers.

In Uganda, fisher folk have HIV prevalence rates, about four times higher than the national average, and are often coinfected with Schistosoma mansoni. We hypothesized that innate immune responses and HIV-specific Th1 immune responses might be downmodulated in HIV/S. mansoni-coinfected individuals compared with HIV+/S. mansoni-negative individuals. We stimulated whole blood with innate receptor agonists and analyzed supernatant cytokines by Luminex. We evaluated HIV-specific responses by intracellular cytokine staining for IFN-γ, IL-2, and TNF-α. We found that the plasma viral load and CD4 count were similar between the HIV+SM+ and HIV+SM- individuals. In addition, the TNF-α response to the imidazoquinoline compound CL097 and β-1, 3-glucan (curdlan), was significantly higher in HIV/S. mansoni-coinfected individuals compared with HIV only-infected individuals. The frequency of HIV-specific IFN-γ+IL-2-TNF-α- CD8 T cells and IFN-γ+IL-2-TNF-α+ CD4 T cells was significantly higher in HIV/S. mansoni-coinfected individuals compared with HIV only-infected individuals. These findings do not support the hypothesis that S. mansoni downmodulates innate or HIV-specific Th1 responses in HIV/S. mansoni-coinfected individuals.

The trimeric HIV-1 envelope glycoprotein (Env) is critical for host immune recognition and neutralization. Despite advances in trimer design, the roots of Env trimer metastability remain elusive. Here we investigate the contribution of two Env regions to metastability. First, we computationally redesign a largely disordered bend in heptad region 1 (HR1) of SOSIP trimers that connects the long, central HR1 helix to the fusion peptide, substantially improving the yield of soluble, well-folded trimers. Structural and antigenic analyses of two distinct HR1 redesigns confirm that redesigned Env closely mimics the native, prefusion trimer with a more stable gp41. Next, we replace the cleavage site between gp120 and gp41 with various linkers in the context of an HR1 redesign. Electron microscopy reveals a potential fusion intermediate state for uncleaved trimers containing short but not long linkers. Together, these results outline a general approach for stabilization of Env trimers from diverse HIV-1 strains.

Structures of BG505 SOSIP.664 trimer in complex with broadly neutralizing antibodies (bNAbs) have revealed the critical role of trimeric context for immune recognition of HIV-1. Presentation of trimeric HIV-1 antigens on nanoparticles may thus provide promising vaccine candidates. Here we report the rational design, structural analysis and antigenic evaluation of HIV-1 trimer-presenting nanoparticles. We first demonstrate that both V1V2 and gp120 can be presented in native-like trimeric conformations on nanoparticles. We then design nanoparticles presenting various forms of stabilized gp140 trimer based on ferritin and a large, 60-meric E2p that displays 20 spikes mimicking virus-like particles (VLPs). Particle assembly is confirmed by electron microscopy (EM), while antigenic profiles are generated using representative bNAbs and non-NAbs. Lastly, we demonstrate high-yield gp140 nanoparticle production and robust stimulation of B cells carrying cognate VRC01 receptors by gp120 and gp140 nanoparticles. Together, our study provides an arsenal of multivalent immunogens for HIV-1 vaccine development.

Passive administration of broadly neutralizing antibodies has been shown to protect against both vaginal and rectal challenge in the simian/human immunodeficiency virus (SHIV)/macaque model of HIV transmission. However, the relative efficacy of antibody against the two modes of exposure is unknown and, given differences in the composition and immunology of the two tissue compartments, this is an important gap in knowledge. To investigate the significance of the challenge route for antibody-mediated protection, we performed a comparative protection study in macaques using the highly potent human monoclonal antibody, PGT126.

Broadly neutralizing antibodies to HIV-1 elicited in infected individuals evolves through shifts in their molecular specificities to viral envelope (Env) in the disease course. Recently, we showed that resistance of circulating HIV-1 clade C to the autologous plasma obtained from one Indian elite neutralizer is associated with mutations in V1 loop. In the present study, we examined the genetic attributes associated with exceptional sensitivity of pseudoviruses expressing an env gene obtained from the follow up visit contemporaneous plasma of the same donor.

Human immunodeficiency virus (HIV) is the cause of one of the most lethal pandemics in human history, although in recent years access to highly effective anti-retroviral therapy has provided new hope worldwide. Transmission of HIV by sexual contact, childbirth and injection drug use has been reduced, but 2 million are newly infected each year, and much of the transmission is from people who do not know their status. In addition to known methods, a preventive vaccine is needed to end the pandemic. The extraordinary mutability and genetic diversity of HIV is an enormous challenge, but vaccines are being designed for broad coverage. Computer-aided design of mosaic immunogens, incorporating many epitopes from the entire genome or from conserved regions aim to induce CD8+ T cells to kill virus-infected cells or inhibit virus replication, while trimeric envelope proteins or synthetic mimics aim to induce broadly reactive neutralizing antibodies similar to those cloned from some infected patients. Induction of more potent and durable responses may require new adjuvants or replicating chimeric vectors chimeras that bear HIV genes. Passive or genetic delivery of broadly neutralizing antibodies may provide broad protection and/or lead to insights for vaccine designers. Proof-of-concept trials in non-human primates and in one human efficacy trial have provided scientific clues for a vaccine that could provide broad and durable protection against HIV. The use of vaccines to destroy HIV reservoirs as part of therapy or cure is now also being explored.

Oral vaccination with live-attenuated Salmonella Typhi strain Ty21a is modestly efficacious, but the mechanisms of protection are currently unknown. While humoral and cellular immune responses are well described in peripheral blood, the cellular response at the intestinal mucosa has never been directly assessed.

Human leukocyte antigen class I (HLA)-restricted CD8(+) T lymphocyte (CTL) responses are crucial to HIV-1 control. Although HIV can evade these responses, the longer-term impact of viral escape mutants remains unclear, as these variants can also reduce intrinsic viral fitness. To address this, we here developed a metric to determine the degree of HIV adaptation to an HLA profile. We demonstrate that transmission of viruses that are pre-adapted to the HLA molecules expressed in the recipient is associated with impaired immunogenicity, elevated viral load and accelerated CD4(+) T cell decline. Furthermore, the extent of pre-adaptation among circulating viruses explains much of the variation in outcomes attributed to the expression of certain HLA alleles. Thus, viral pre-adaptation exploits 'holes' in the immune response. Accounting for these holes may be key for vaccine strategies seeking to elicit functional responses from viral variants, and to HIV cure strategies that require broad CTL responses to achieve successful eradication of HIV reservoirs.

A major step toward an HIV-1 vaccine is an immunogen capable of inducing neutralizing antibodies. Envelope glycoprotein (Env) mimetics, such as the NFL and SOSIP designs, generate native-like, well-ordered trimers and elicit tier 2 homologous neutralization (SOSIPs). We reasoned that the display of well-ordered trimers by high-density, particulate array would increase B cell activation compared to soluble trimers. Here, we present the design of liposomal nanoparticles displaying well-ordered Env spike trimers on their surface. Biophysical analysis, cryo- and negative stain electron microscopy, as well as binding analysis with a panel of broadly neutralizing antibodies confirm a high-density, well-ordered trimer particulate array. The Env-trimer-conjugated liposomes were superior to soluble trimers in activating B cells ex vivo and germinal center B cells in vivo. In addition, the trimer-conjugated liposomes elicited modest tier 2 homologous neutralizing antibodies. The trimer-conjugated liposomes represent a promising initial lead toward the development of more effective HIV vaccine immunogens.

Community engagement, incorporating elements of the broader concepts of public and stakeholder engagement, is increasingly promoted globally, including for health research conducted in developing countries. In sub-Saharan Africa, community engagement needs and challenges are arguably intensified for studies involving gay, bisexual and other men who have sex with men, where male same-sex sexual interactions are often highly stigmatised and even illegal. This paper contextualises, describes and interprets the discussions and outcomes of an international meeting held at the Kenya Medical Research Institute-Wellcome Trust in Kilifi, Kenya, in November 2013, to critically examine the experiences with community engagement for studies involving men who have sex with men.

HIV employs multiple means to evade the humoral immune response, particularly the elicitation of and recognition by broadly neutralizing antibodies (bnAbs). Such antibodies can act antivirally against a wide spectrum of viruses by targeting relatively conserved regions on the surface HIV envelope trimer spike. Elicitation of and recognition by bnAbs are hindered by the arrangement of spikes on virions and the relatively difficult access to bnAb epitopes on spikes, including the proximity of variable regions and a high density of glycans. Yet, in a small proportion of HIV-infected individuals, potent bnAb responses do develop, and isolation of the corresponding monoclonal antibodies has been facilitated by identification of favorable donors with potent bnAb sera and by development of improved methods for human antibody generation. Molecular studies of recombinant Env trimers, alone and in interaction with bnAbs, are providing new insights that are fueling the development and testing of promising immunogens aimed at the elicitation of bnAbs.

The high-mannose patch on HIV Env is a preferred target for broadly neutralizing antibodies (bnAbs), but to date, no vaccination regimen has elicited bnAbs against this region. Here, we present the development of a bnAb lineage targeting the high-mannose patch in an HIV-1 subtype-C-infected donor from sub-Saharan Africa. The Abs first acquired autologous neutralization, then gradually matured to achieve breadth. One Ab neutralized >47% of HIV-1 strains with only ∼11% somatic hypermutation and no insertions or deletions. By sequencing autologous env, we determined key residues that triggered the lineage and participated in Ab-Env coevolution. Next-generation sequencing of the Ab repertoire showed an early expansive diversification of the lineage followed by independent maturation of individual limbs, several of them developing notable breadth and potency. Overall, the findings are encouraging from a vaccine standpoint and suggest immunization strategies mimicking the evolution of the entire high-mannose patch and promoting maturation of multiple diverse Ab pathways.