Focusing HIV-1 Gag T cell responses to highly conserved regions by DNA vaccination in HVTN 119

BACKGROUNDAn HIV-1 DNA vaccine composed of 7 highly conserved, structurally important elements (conserved elements, CE) of p24Gag was tested in a phase I randomized, double-blind clinical trial (HVTN 119, NCT03181789) in people without HIV. DNA vaccination of CE prime/CE+p55Gag boost was compared with p55Gag.METHODSTwo groups (n = 25) received 4 DNA vaccinations (CE/CE+p55Gag or 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.RESULTSBoth regimens were safe and generally well tolerated. The p24CE vaccine was immunogenic and significantly boosted by CE+p55Gag (64% CD4+, P = 0.037; 42% CD8+, P = 0.004). CE+p55Gag induced responses to 5 of 7 CE, compared with only 2 CE by p55Gag DNA, with a higher response to CE5 in 30% of individuals (P = 0.006). CE+p55Gag induced significantly higher CD4+ CE T cell breadth (0.68 vs. 0.22 CE; P = 0.029) and a strong trend for overall T cell breadth (1.14 vs. 0.52 CE; P = 0.051). Both groups developed high cellular and humoral responses. p24CE vaccine-induced CD4+ CE T cell responses correlated (P = 0.007) with p24Gag antibody responses.CONCLUSIONThe CE/CE+p55Gag DNA vaccine induced T cell responses to conserved regions in p24Gag, increasing breadth and epitope recognition throughout p55Gag compared with p55Gag DNA. Vaccines focusing immune responses by priming responses to highly conserved regions could be part of a comprehensive HIV vaccine strategy.TRIAL REGISTRATIONClinical Trials.gov NCT03181789FUNDINGHVTN, NIAID/NIH.