Scientific Publications

The elicitation of broadly neutralizing antibodies (bNAbs) against the HIV-1 envelope glycoprotein (Env) trimer remains a major vaccine challenge. Most cross-conserved protein determinants are occluded by self-N-glycan shielding, limiting B cell recognition of the underlying polypeptide surface. The exceptions to the contiguous glycan shield include the conserved receptor CD4 binding site (CD4bs) and glycoprotein (gp)41 elements proximal to the furin cleavage site. Accordingly, we performed heterologous trimer-liposome prime:boosting in rabbits to drive B cells specific for cross-conserved sites. To preferentially expose the CD4bs to B cells, we eliminated proximal N-glycans while maintaining the native-like state of the cleavage-independent NFL trimers, followed by gradual N-glycan restoration coupled with heterologous boosting. This approach successfully elicited CD4bs-directed, cross-neutralizing Abs, including one targeting a unique glycan-protein epitope and a bNAb (87% breadth) directed to the gp120:gp41 interface, both resolved by high-resolution cryoelectron microscopy. This study provides proof-of-principle immunogenicity toward eliciting bNAbs by vaccination.

A preventive vaccine for HIV is a crucial public health need; adeno-associated virus (AAV)-mediated antibody gene delivery could be an alternative to immunisation to induce sustained expression of neutralising antibodies to prevent HIV. We assessed safety and tolerability of rAAV1-PG9DP, a recombinant AAV1 vector encoding the gene for PG9, a broadly neutralising antibody against HIV.

Fisherfolks (FF) and female sex workers (FSW) in Uganda could be suitable key populations for HIV vaccine efficacy trials because of the high HIV incidence and good retention in observational cohorts. However, the observed HIV incidence may differ in participants who enroll into a trial. We used simulated vaccine efficacy trials (SiVET) nested within observational cohorts in these populations to evaluate this difference.

Female sex workers (FSWs) were recruited from known hotspots in Kigali, Rwanda, and offered free, anonymous human immunodeficiency virus (HIV) counseling and testing, diagnosis and treatment of sexually transmitted infections (STIs) and long-acting reversible contraception (LARC). From September 2012 to March 2015, 1168 FSWs sought services, including 587 (50%) who were HIV-positive. More than 90% had previously tested for HIV, and 26% who reported previously testing negative had seroconverted. Of the 349 who already knew their HIV-positive status, 74% were on antiretroviral treatment. The prevalence of serologic syphilis was 43% in HIV-positive and 19% in HIV-negative FSWs (p  0.0001), and Trichomonas vaginalis was found in vaginal wet mounts in 21% of HIV-positive and 13% of HIV-negative FSWs (p  0.0001). Signs and symptoms of STIs were found in 35% of HIV-positive compared with 21% of HIV-negative FSWs (p  0.0001). Only one-third reported consistent condom use in the last month. Modern contraceptive use was reported by 43% of HIV-positive and 56% of HIV-negative FSWs (p  0.0001). Current pregnancy was reported by 4% of HIV-positive and 6% of HIV-negative FSWs (p = 0.0409). Despite Rwanda's successes with preventing 70% of new infections in the general population through nationwide couples' testing in antenatal clinics, prevention and timely treatment in key populations including FSWs are lacking. The prevalence of HIV - including many new cases - and STIs among FSWs in Kigali is high and condom and contraceptive use are low. Tailored and integrated HIV/STIs and family planning programs are urgently needed for FSWs.

Multiple antibody effector functions arise in HIV-1 infection that could be harnessed to protect against infection or clear the persistent reservoir. Here, we have investigated the genetic and functional memory B cell and antibody landscape present during early infection in six individuals infected with either subtype A, C, or an A/C recombinant HIV-1. These individuals demonstrated varying levels of plasma autologous neutralization (nAb) against the transmitted/founder envelope (T/F Env) pseudovirus and non-neutralizing Fc-mediated effector function (nnFc) antibody-dependent cell-mediated cytotoxicity (ADCC) against the T/F Env gp120 protein at ~7 months after infection. Genetic analysis of the immunoglobulin heavy (VH) and light (VL) chain variable domain gene segments from 352 autologous T/F Env gp120-specific single B cells recovered at this same 7-month time-point revealed an over-representation of the VH1-69 germline in five of six individuals. A defining feature of the VH1-69 utilizing gp120-specific antibodies was their significantly more hydrophobic complementarity-determining region-2 (CDRH2) regions compared to other VH CDRH2 sequences from each individual. While none of the VH1-69 antibodies possessed strong neutralizing activity against virions pseudotyped with the autologous T/F Env, almost a third were capable of mediating high ADCC activity, as assayed by intracellular granzyme B activity in CEM.NKr.CCR5 target cells coated with autologous T/F Env gp120. High ADCC mediating VH1-69 antibodies exhibited shorter complementarity-determining region-3 (CDRH3) lengths and a more neutral isoelectric point than antibodies lacking this function. In the individual that developed the highest autologous ADCC responses, the high granzyme B producing antibodies bound to surface expressed envelope in the absence of CD4 and were not enhanced by the addition of soluble CD4. Overall, VH1-69 utilizing antibodies are commonly induced against gp120 in diverse HIV-1 infections and a subset of these antibodies can mediate ADCC functions, serving as a bridge between the innate and adaptive immune response to HIV-1.

The N-terminal fusion peptide (FP) of the human immunodeficiency virus (HIV)-1 envelope glycoprotein (Env) gp41 subunit plays a critical role in cell entry. However, capturing the structural flexibility in the unbound FP is challenging in the native Env trimer. Here, FP conformational isomerism is observed in two crystal structures of a soluble clade B transmitted/founder virus B41 SOSIP.664 Env with broadly neutralizing antibodies (bNAbs) PGT124 and 35O22 to aid in crystallization and that are not specific for binding to the FP. Large rearrangements in the FP and fusion peptide proximal region occur around M530, which remains anchored in the tryptophan clasp (gp41 W623, W628, W631) in the B41 Env prefusion state. Further, we redesigned the FP at position 518 to reinstate the bNAb VRC34.01 epitope. These findings provide further structural evidence for the dynamic nature of the FP and how a bNAb epitope can be restored during vaccine design.

The induction of broadly neutralizing antibodies (bNAb) is a major goal in the development of an effective vaccine against HIV-1. A soluble, trimeric, germline (gI) bNAb-targeting variant of the HIV-1 envelope glycoprotein (termed BG505 SOSIP.v4.1-GT1.1 gp140, abbreviated to GT1.1) has recently been developed. Here, we have compared this new immunogen with the parental trimer from which it was derived, BG505 SOSIP.664 gp140. We used a comprehensive suite of biochemical and biophysical methods to determine physicochemical similarities and differences between the two trimers, and thereby assessed whether additional formulation development efforts were needed for the GT1.1 vaccine candidate. The overall higher order structure and oligomeric states of the two vaccine antigens were quite similar, as were their thermal, chemical, and colloidal stability profiles, as evaluated during accelerated stability studies. Overall, we conclude that the primary sequence changes made to create the gl bNAb-targeting GT1.1 trimer did not detrimentally affect its physicochemical properties or stability profiles from a pharmaceutical perspective. This developability assessment of the BG505 GT1.1 vaccine antigen supports using the formulation and storage conditions previously identified for the parental SOSIP.664 trimer and enables the development of GT1.1 for Phase I clinical studies.

People living in fishing communities around Lake Victoria may be suitable for enrolment in HIV prevention trials because of high HIV incidence. We assessed the ability to recruit and retain individuals from fishing communities into an HIV vaccine preparedness cohort study in Masaka, Uganda.

In vaccine design, arraying antigens in a multivalent nanoparticle form is often employed, but in vivo mechanisms underlying the enhanced immunity elicited by such vaccines remain poorly understood. Here we compared the fate of two different heavily glycosylated HIV antigens, a gp120-derived mini-protein and a large, stabilized envelope trimer, in protein nanoparticle or 'free' forms following primary immunization. Unlike monomeric antigens, nanoparticles were rapidly shuttled to the follicular dendritic cell (FDC) network and then concentrated in germinal centers in a complement-, mannose-binding lectin (MBL)-, and immunogen glycan-dependent manner. Loss of FDC localization in MBL-deficient mice or via immunogen deglycosylation significantly impacted antibody responses. These findings identify an innate immune-mediated recognition pathway promoting antibody responses to particulate antigens, with broad implications for humoral immunity and vaccine design.