Scientific Publications

Broadly neutralizing antibodies isolated from infected patients who are elite neutralizers have identified targets on HIV-1 envelope (Env) glycoprotein that are vulnerable to antibody neutralization; however, it is not known whether infection established by the majority of the circulating clade C strains in Indian patients elicit neutralizing antibody responses against any of the known targets. In the present study, we examined the specificity of a broad and potent cross-neutralizing plasma obtained from an Indian elite neutralizer infected with HIV-1 clade C. This plasma neutralized 53/57 (93%) HIV pseudoviruses prepared with Env from distinct HIV clades of different geographical origins. Mapping studies using gp120 core protein, single-residue knockout mutants, and chimeric viruses revealed that G37080 broadly cross-neutralizing (BCN) plasma lacks specificities to the CD4 binding site, gp41 membrane-proximal external region, N160 and N332 glycans, and R166 and K169 in the V1-V3 region and are known predominant targets for BCN antibodies. Depletion of G37080 plasma with soluble trimeric BG505-SOSIP.664 Env (but with neither monomeric gp120 nor clade C membrane-proximal external region peptides) resulted in significant reduction of virus neutralization, suggesting that G37080 BCN antibodies mainly target epitopes on cleaved trimeric Env. Further examination of autologous circulating Envs revealed the association of mutation of residues in the V1 loop that contributed to neutralization resistance. In summary, we report the identification of plasma antibodies from a clade C-infected elite neutralizer that mediate neutralization breadth via epitopes on trimeric gp120 not yet reported and confer autologous neutralization escape via mutation of residues in the V1 loop.

The Investment Framework Enhanced (IFE) proposed in 2013 by the Joint United Nations Programme on HIV/AIDS (UNAIDS) explored how maximizing existing interventions and adding emerging prevention options, including a vaccine, could further reduce new HIV infections and AIDS-related deaths in low- and middle-income countries (LMICs). This article describes additional modeling which looks more closely at the potential health impact and cost-effectiveness of AIDS vaccination in LMICs as part of UNAIDS IFE.

Recent technological advances in genomics, mass spectrometry, and epitope identification algorithms offer significant potential to identify novel antigenic targets for vaccine and immunotherapeutic development. On 30 April 2015, leading immunologists and bioinformatics scientists met to consider how best to utilize these advances towards deciphering the human antigenome and exploiting this information for prevention and control of infectious and neoplastic diseases.

Men who have sex with men are increasingly recognised as one of the most vulnerable HIV risk groups in Kenya. Sex between men is highly stigmatised in Kenya, and efforts to provide sexual health services to men who have sex with men require a deeper understanding of their lived experiences; this includes how such men in Kenya construct their sexual identities and how these constructions affect sexual decision-making. Adult self-identified men who have sex with men (n = 26) in Malindi, Kenya, participated in individual interviews to examine sociocultural processes influencing sexual identity construction and decision-making. Four key themes were identified: (1) tensions between perceptions of 'homosexuality' versus being 'African', (2) gender-stereotyped beliefs about sexual positioning, (3) socioeconomic status and limitations to personal agency and (4) objectification and commodification of non-normative sexualities. Findings from this analysis emphasise the need to conceive of same-sex sexuality and HIV risk as context-dependent social phenomena. Multiple sociocultural axes were found to converge and shape sexual identity and sexual decision-making among this population. These axes and their interactive effects should be considered in the design of future interventions and other public health programmes for men who have sex with men in this region.

At the end of 2013, the Government of Uganda issued guidance recommending provision of Anti-Retroviral Treatment (ART) to HIV-positive people in key populations, including female sex workers, regardless of CD4 cell count. We describe the implementation of this new guidance in a clinic serving women at high risk of HIV infection in Kampala. Between July and December 2015, we conducted repeat in-depth interviews with 15 women attending the clinic after the change in guidelines, to explore their perceptions regarding prompt ART initiation. The sample included some women who were HIV-negative and women who had both started and deferred ART. We conducted a data-led thematic analysis of the material from the interviews. A total of 257 of 445 eligible women had started ART; others were undecided or had not returned to the clinic after receiving the new information. Participants recounted varying experiences with the provision of prompt treatment. At an individual level, a history of treatment for opportunistic infections and other illnesses, coupled with relatively poor health, encouraged some to initiate ART promptly. However, knowledge of friends/relatives already on ART who had experienced side effects caused others to delay starting, fearing the same experience for themselves. A number of women questioned why they should start treatment when they were not sick. Situational factors such as work and residence (with many sharing single rooms) caused discomfort among newly diagnosed women who feared disclosure and stigma that would result from taking ART when they were not ill. Alcohol consumption and irregular working hours affected perceptions of future adherence, making prompt ART harder to embrace for some. Our findings show the challenges that influence the delay of treatment initiation, and/or the decision to defer receiving information on ART, with implications for the success of the test and treat programmes and guidelines.

Due to high viral diversity, an effective HIV-1 vaccine will likely require Envs derived from multiple subtypes to generate broadly neutralizing antibodies (bNAbs). Soluble Env mimics, like the native flexibly linked (NFL) and SOSIP trimers, derived from the subtype A BG505 Env, form homogeneous, stable native-like trimers. However, other Env sequences, such as JRFL and 16055 from subtypes B and C, do so to a lesser degree. The high-resolution BG505 SOSIP crystal structures permit the identification and redesign of Env elements involved in trimer stability. Here, we identified structure trimer-derived (TD) residues that increased the propensity of the subtype B JRFL and subtype C 16055 Env sequences to form well-ordered, homogenous, and highly stable soluble trimers. The generation of these spike mimics no longer required antibody-based selection, positive or negative. Using the redesigned subtype B and C trimer representatives as respective foundations, we further stabilized the NFL TD trimers by engineering an intraprotomer disulfide linkage in the prebridging sheet, I201C-A433C (CC), that locks the gp120 in the receptor nontriggered state. We demonstrated that this disulfide pair prevented CD4 induced-conformational rearrangements in NFL trimers derived from the prototypic subtype A, B, and C representatives. Coupling the TD-based design with the engineered disulfide linkage, CC, increased the propensity of Env to form soluble highly stable spike mimics that are resistant to CD4-induced changes. These advances will allow testing of the hypothesis that such stabilized immunogens will more efficiently elicit neutralizing antibodies in small-animal models and primates.

The envelope glycoprotein trimer mediates HIV-1 entry into cells. The trimer is flexible, fluctuating between closed and more open conformations and sometimes sampling the fully open, CD4-bound form. We hypothesized that conformational flexibility and transient exposure of non-neutralizing, immunodominant epitopes could hinder the induction of broadly neutralizing antibodies (bNAbs). We therefore modified soluble Env trimers to stabilize their closed, ground states. The trimer variants were indeed stabilized in the closed conformation, with a reduced ability to undergo receptor-induced conformational changes and a decreased exposure of non-neutralizing V3-directed antibody epitopes. In rabbits, the stabilized trimers induced similar autologous Tier-1B or Tier-2 NAb titers to those elicited by the corresponding wild-type trimers but lower levels of V3-directed Tier-1A NAbs. Stabilized, closed trimers might therefore be useful components of vaccines aimed at inducing bNAbs.

The high-mannose patch on the HIV-1 envelope (Env) glycoprotein is the epicenter for binding of the potent broadly neutralizing PGT121 family of antibodies, but strategies for generating such antibodies by vaccination have not been defined. We generated structures of inferred antibody intermediates by X-ray crystallography and electron microscopy to elucidate the molecular events that occurred during evolution of this family. Binding analyses revealed that affinity maturation was primarily focused on avoiding, accommodating, or binding the N137 glycan. The overall antibody approach angle to Env was defined very early in the maturation process, yet some variation evolved in the PGT121 family branches that led to differences in glycan specificities in their respective epitopes. Furthermore, we determined a crystal structure of the recombinant BG505 SOSIP.664 HIV-1 trimer with a PGT121 family member at 3.0 Å that, in concert with these antibody intermediate structures, provides insights to advance design of HIV vaccine candidates.

African men who have sex with men often sell sex to men, and MSM who sell sex (MSM-SW) often also have female partners. We compared sexual risk behaviour of MSM-SW who were sexually active with female partners (bisexual MSW) to MSM-SW with only male partners (exclusive MSW).

Mental health conditions can erode quality of life and interfere with health-related behaviours such as medication adherence. We aimed to determine the prevalence and correlates of depression and other psychosocial factors among self-identified men who have sex with men (MSM) in coastal Kenya.

Patients with acute HIV-1 infection (AHI) have elevated infectivity, but cannot be diagnosed using antibody-based testing. Approaches to screen patients for AHI are urgently needed to enable counselling and treatment to reduce onward transmission.