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TOPLINE:

The experimental HIV vaccine regimen exhibited an acceptable safety profile and elicited robust immune responses in 99% of trial participants from sub-Saharan Africa. Its ability to induce broad T-cell responses makes it a promising tool for HIV-1 prevention and cure strategies.

METHODOLOGY:

• HIVconsvX is an experimental vaccine comprising six cross-clade conserved HIV immunogens, delivered in two stages using nonreplicating vectors — initially a chimpanzee adenovirus (ChAdOx1), followed by a modified vaccinia virus Ankara (MVA).
• Researchers conducted a phase 1 randomized clinical trial across clinical research centers in Uganda, Kenya, and Zambia to evaluate the safety and immunogenicity of the HIVconsvX T-cell vaccine, delivered in a regimen that included ChAdOx1.tHIVconsv1 (C1), MVA.tHIVconsv3 (M3), and MVA.tHIVconsv4 (M4).
• Overall, 88 healthy adults without HIV-1 (median age, 30 years; 65% men) were randomly assigned to receive either the vaccine (n = 72) or placebo (n = 16) from July 2021 to November 2022 and were followed up for 40 weeks.
• Participants in the vaccine group received a C1 prime dose on day 0, followed by M3 and M4 boosters on day 28; participants in the placebo group received placebo doses on days 0 and 28.
• The primary endpoint was vaccine safety, with solicited and unsolicited adverse events, including serious events, assessed until the end of the study period and measurement of HIVconsvX-specific T-cell responses.

TAKEAWAY:

• Overall, the vaccine regimen was well tolerated with no grade 3 solicited reactions after the C1 administration; 18% were grade 2, and only 2% were grade 3 after M3/M4.
• The vaccine regimen was highly immunogenic, inducing HIVconsvX-specific responses in 99% of participants who completed all vaccine doses (P < .0001).
• HIVconsvX-specific T cells peaked at a median of 2310 spots per million peripheral blood mononuclear cells. Men had significantly higher responses than women (P = .0451).
• Upon reexposure to the virus, the T cells proliferated and neutralized HIV-1 isolates from clades A, B, C, and D.

IN PRACTICE:

“We foresee the future development and use of the HIVconsvX vaccines as a potentially key component of a combined package of tools for cure and prevention,” the authors wrote.

SOURCE:

This study was led by Chama Chanda, MB ChB, Center for Family Health Research Zambia, Lusaka, Zambia. It was published online on May 16, 2025, in The Lancet Microbe.

LIMITATIONS:

This study looked at responses in peripheral blood mononuclear cells, whereas control of HIV-1 is primarily mediated in lymphoid organs and tissues, such as the gut.

DISCLOSURES:

This study was funded by the European and Developing Countries Clinical Trials Partnership. One author was a co-inventor of the HIVconsvX immunogens. Other authors declared having no competing interests.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.