African Phase I HIV vaccine trial shows encouraging preliminary results

Preliminary analysis of the immunological trial results demonstrates the induction of high frequencies of broadly specific T cells that recognise functionally conserved regions on HIV-1 and are therefore more protective.

Not all T cells are equally protective, and the T cells induced by this vaccine candidate, also called killer T cells, are underutilized in natural HIV-1 infection. Furthermore, the killer T cells the vaccine candidate induced in this trial were capable of inhibiting four major global HIV clades: A, B, C and D. Further analyses are ongoing with the first results expected to be submitted for a publication later this year. All the components of the vaccine candidate were well tolerated by the participants with no serious adverse events reported.

Professor Tomáš Hanke, Professor of Vaccine Immunology at the Nuffield Department of Medicine's Jenner Institute, the consortium coordinator and lead researcher on the trial, said: 'Over the tenure of this consortium, the study team have evaluated a highly rational, bioinformatics-assisted vaccine design to address the enormous variability of HIV-1 – one of the greatest challenges to the development of an effective vaccine against HIV/AIDS. The analysis so far indicates the induction of strong and multi-specific T-cell responses that recognise several vulnerable parts of proteins common to most HIV variants in each individual at the same time – targeting HIV where it hurts.'

The goal of the HIV-CORE 006 is to evaluate the safety, tolerability, and immunogenicity of a novel mosaic HIV vaccine candidate, HIVconsvX, that has been designed to target a broad range of HIV-1 variants, making it potentially applicable for HIV strains in any geographical region. While most HIV vaccine candidates to date have aimed to generate antibody or T-cell responses against more variable HIV epitopes, HIVconsvX aims to induce the immune system’s killer T cells against a group of highly conserved regions, which obliterate the virus factories in the body.

Dr Vincent Muturi-Kioi, Senior Medical Director at IAVI said: 'This study represents an innovative hypothesis to harness the killer T cell arm of the immune system to prevent HIV infection from all major HIV subtypes. It’s important that we have a diversity of vaccine candidates in the pipeline to make sure we have the greatest chance of success in developing an effective HIV vaccine.'

HIV-CORE 006 took place at four vaccine trial sites in Kenya, Uganda and Zambia. First vaccinations were administered at the Center for Family Health Research in Lusaka, Zambia (CFHRZ) in August 2021 with the final volunteers enrolled at the KEMRI-Wellcome Trust Research Programme in December 2021. The last follow-up visits took place at the beginning of November 2022. A total of 88 participants were enrolled in the trial, of whom 72 received the vaccine candidate and 16 received a placebo. The participant retention rate and adherence to vaccination and follow-up visits exceeded 95%. This trial was made possible by six-and-a-half years of funding for the GREAT consortium from the European and Developing Countries Clinical Trials Partnership (EDCTP), which came to an end on 30 June this year.

Dr Paola Cicconi, chief investigator of the trial and Senior Clinical Researcher at NDM's Jenner Institute, said: 'The vaccines used in this trial have demonstrated a favourable safety profile and induction of immune responses in most of the participants. These are promising results, and an important step in developing an HIV vaccine that can protect people against HIV infection in all parts of the world. On behalf of the entire GREAT team, we extend our gratitude to all the participants for their huge commitment to the success of this trial.'

The GREAT team successfully completed planned capacity building activities with the four partnering clinical research centers (CRC) earlier this year. These activities focused on preparing the CRCs to participate in future HIV vaccine research and clinical trials. This included the training of personnel, procuring equipment, and updating and expanding clinical and laboratory infrastructure and establishing field-based clinical and laboratory capacity. Community and stakeholder engagement activities continue to support the dissemination of the forthcoming results.

Dr William Kilembe, project director at the Center for Family Health Research in Zambia (CFHRZ), said: 'The GREAT consortium has leveraged international partnerships in Africa and Europe to evaluate the novel HIVconsvX vaccine candidate in countries and communities where an HIV vaccine will ultimately have the greatest public health impact. Through this trial, the consortium members have contributed to strengthening the capacity of the partnering clinical research centers to conduct robust HIV vaccine research and clinical trials. Community engagement is key to this approach, and we look forward to continuing to work with community stakeholders as the final results become available.'

The next milestone will be reporting of the primary findings later this year followed by further in-depth analyses. The candidate HIVconsvX vaccines are tested in a comprehensive developmental clinical program encompassing trials in healthy uninfected individuals for prevention of HIV, such as in HIV-CORE 006, and in people already living with HIV-1 as a potential cure.