Focusing HIV-1 Gag T-cell Responses to Highly Conserved Regions by DNA Vaccination in HVTN 119

An HIV-1 DNA vaccine composed of seven highly conserved, structurally important elements (Conserved Elements, CE) of HIV p24Gag was tested in a phase I randomized, double-blind clinical trial (HVTN 119, NCT03181789) in people without HIV. A CE prime- CE+full-length p55Gag boost DNA vaccine was compared to p55Gag DNA vaccination only. Two groups (n=25 each) received 4 DNA vaccinations [2xCE prime- 2xCE+p55Gag boost or 4x p55Gag] by intramuscular injection/electroporation, including IL-12 DNA adjuvant. The placebo group (n=6) received saline. Participants were followed for safety and tolerability. Immunogenicity was assessed for T cell and antibody responses. Both regimens were safe and generally well-tolerated. The p24CE vaccine was immunogenic (29% CD4+ and 4% CD8+ responders) and was significantly boosted by CE+p55Gag (64% CD4+, p=0.037; 42% CD8+, p=0.004). CE+p55Gag induced CD4+ responses to 5 of 7 CE, compared to only 2 CE by p55Gag DNA alone, with a higher reponse to CE5 in 30% of individuals (p=0.006). CE+p55Gag induced significantly higher mean CD4+ CE Tcell breadth (0.68 vs 0.22 CE; p=0.029) and a strong trend for increased CD4+ and CD8+ T-cell breadth (1.14 vs. 0.52 CE; p=0.051) compared to p55Gag alone. Both groups developed high p55Gag T-cell (91% each) and p24Gag antibody (91% vs. 80%) responses. p24CE vaccine-induced CD4+ CE T-cell responses correlated (p=0.007) with p24Gag antibody responses. The combination CE/CE+p55Gag DNA vaccine induced T-cell immune responses to conserved regions in p24Gag resulting in significant increases in breadth and epitope recognition throughout p55Gag. Vaccines able to focus immune responses by priming responses to highly conserved regions could be part of a comprehensive HIV vaccine strategy. gov NCT03181789 Study URL: https://www. gov/search?term=NCT03181789 FUNDING. HIV vaccine trial network (HVTN), NIAID/NIH.

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