A HIV-1 Gp41 Peptide-Liposome Vaccine Elicits Neutralizing Epitope-Targeted Antibody Responses in Healthy Individuals

Background

HIV-1 vaccine development is a global health priority. Broadly neutralizing antibodies (bnAbs) which target the HIV-1 gp41 membrane-proximal external region (MPER) have some of the highest neutralization breadth. An MPER peptide-liposome vaccine has been found to expand bnAb precursors in monkeys.

Methods

The HVTN133 phase 1 clinical trial (NCT03934541) studied the MPER-peptide liposome immunogen in 24 HIV-1 seronegative individuals. Participants were recruited between 15 July 2019 and 18 October 2019 and were randomized in a dose-escalation design to either 500 mcg or 2000 mcg of the MPER-peptide liposome or placebo. Four intramuscular injections were planned at months 0, 2, 6, and 12.

Results

The trial was stopped prematurely due to an anaphylaxis reaction in one participant ultimately attributed to vaccine-associated polyethylene glycol. The immunogen induced robust immune responses, including MPER+ serum and blood CD4+ T-cell responses in 95% and 100% of vaccinees, respectively, and 35% (7/20) of vaccine recipients had blood IgG memory B cells with MPER-bnAb binding phenotype. Affinity purification of plasma MPER+ IgG demonstrated tier 2 HIV-1 neutralizing activity in two of five participants after 3 immunizations.

Conclusions

MPER-peptide liposomes induced gp41 serum neutralizing epitope-targeted antibodies and memory B-cell responses in humans despite the early termination of the study. These results suggest that the MPER region is a promising target for a candidate HIV vaccine.

Prophylactic HIV vaccine: vaccine regimens in clinical trials and potential challenges

Introduction: Ending the HIV epidemic will likely require an efficacious preventative HIV vaccine. As vaccine development progresses, new challenges emerge in the context of an evolving prevention landscape.Areas covered: The progress in HIV vaccine development including trial regimens, results, and impact of pre-exposure prophylaxis (PrEP) including trial design.Expert opinion: Building upon the modest RV144 efficacy results, a follow-up study was launched in South Africa using modified vaccine constructs, ALVAC-HIV vector and gp120 protein boosts (Clade C strains). An adjuvant, MF59, was used to improve durability. Another Phase 2b regimen using an Adenovirus-26 vector with multivalent mosaic antigen inserts and a Clade C gp140 boost advanced into efficacy testing. Current vaccine efficacy studies enroll participants at risk for HIV, offer robust prevention packages, and notably do not restrict PrEP usage. With increasingly efficacious prevention options, future clinical trial designs become more complex. While formally requiring PrEP in HIV vaccine trials (e.g. PrEP ± Vaccine) may maximize protection, it raises both ethical and incremental efficacy over PrEP. Increasing vaccine complexity may lead to persistent vaccine-induced seropositivity, which presents different challenges. Discussion with the community and broader stakeholder engagement will help create solutions to these challenges.

Preclinical development of BCG.HIVA2auxo.int, harboring an integrative expression vector, for a HIV-TB Pediatric vaccine. Enhancement of stability and specific HIV-1 T-cell immunity

One of the critical issues that should be addressed in the development of a BCG-based HIV vaccine is genetic plasmid stability. Therefore, to address this issue we have considered using integrative vectors and the auxotrophic mutant of BCG complemented with a plasmid carrying a wild-type complementing gene. In this study, we have constructed an integrative E. coli-mycobacterial shuttle plasmid, p2auxo.HIVA^int, expressing the HIV-1 clade A immunogen HIVA. This shuttle vector uses an antibiotic resistance-free mechanism for plasmid selection and maintenance. It was first transformed into a glycine auxotrophic E. coli strain and subsequently transformed into a lysine auxotrophic Mycobacterium bovis BCG strain to generate the vaccine BCG.HIVA^2auxo.int. Presence of the HIVA gene sequence and protein expression was confirmed. We demonstrated that the in vitro stability of the integrative plasmid p2auxo.HIVA^int was increased 4-fold, as compared with the BCG strain harboring the episomal plasmid, and was genetically and phenotypically characterized. The BCG.HIVA^2auxo.int vaccine in combination with modified vaccinia virus Ankara (MVA).HIVA was found to be safe and induced HIV-1 and Mycobacterium tuberculosis-specific interferon-γ-producing T-cell responses in adult BALB/c mice. We have engineered a more stable and immunogenic BCG-vectored vaccine using the prototype immunogen HIVA. Thus, the use of integrative expression vectors and the antibiotic-free plasmid selection system based on “double” auxotrophic complementation are likely to improve the mycobacterial vaccine stability in vivo and immunogenicity to develop not only recombinant BCG-based vaccines expressing second generation of HIV-1 immunogens but also other major pediatric pathogens to prime protective responses shortly following birth.

Safety and Immunogenicity of a Recombinant Adenovirus Serotype 35-Vectored HIV-1 Vaccine in Adenovirus Serotype 5 Seronegative and Seropositive Individuals

BACKGROUND

Recombinant adenovirus serotype 5 (rAd5)-vectored HIV-1 vaccines have not prevented HIV-1 infection or disease and pre-existing Ad5 neutralizing antibodies may limit the clinical utility of Ad5 vectors globally. Using a rare Ad serotype vector, such as Ad35, may circumvent these issues, but there are few data on the safety and immunogenicity of rAd35 directly compared to rAd5 following human vaccination.

METHODS

HVTN 077 randomized 192 healthy, HIV-uninfected participants into one of four HIV-1 vaccine/placebo groups: rAd35/rAd5, DNA/rAd5, and DNA/rAd35 in Ad5-seronegative persons; and DNA/rAd35 in Ad5-seropositive persons. All vaccines encoded the HIV-1 EnvA antigen. Antibody and T-cell responses were measured 4 weeks post boost immunization.

RESULTS

All vaccines were generally well tolerated and similarly immunogenic. As compared to rAd5, rAd35 was equally potent in boosting HIV-1-specific humoral and cellular immunity and responses were not significantly attenuated in those with baseline Ad5 seropositivity. Like DNA, rAd35 efficiently primed rAd5 boosting. All vaccine regimens tested elicited cross-clade antibody responses, including Env V1/V2-specific IgG responses.

CONCLUSIONS

Vaccine antigen delivery by rAd35 is well-tolerated and immunogenic as a prime to rAd5 immunization and as a boost to prior DNA immunization with the homologous insert. Further development of rAd35-vectored prime-boost vaccine regimens is warranted.

Project VOGUE: A partnership for increasing HIV knowledge and HIV vaccine trial awareness among House Ball leaders in Western New York

Men who sleep with men (MSM) and transgender individuals of color, the largest demographic in the House Ball community (HBC) are amongst the group at highest risk for HIV infection in the United States. The HBC have limited access to culturally appropriate HIV education. This study aimed to develop a partnership with HBC leaders to uncover strategies for increasing HIV prevention knowledge, including participation in HIV vaccine trials. To this end a research institution-community-HBC partnership was established. In-depth qualitative and quantitative data were collected from the 14 HBC leaders in western New York, revealing that knowledge of HIV and related vaccine trials was limited. Barriers to increasing HIV knowledge included fear of peer judgment, having inaccurate information about HIV, and lack of education. Among the HBC, community partnerships will further aid in the development of future HIV prevention programs and increase individuals' willingness to participate in future HIV vaccine trials.