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Prospects for a Globally Effective HIV-1 Vaccine

November 30, 2015
MHRP researchers provide an overview of current HIV vaccine strategies and lessons learned from past efficacy studies

A commentary in the December issues of American Journal of Preventive Medicine and Vaccine make the case for the development of a globally cost-effective HIV-1 vaccine that would protect against the many HIV-1 strains and varied routes of transmission.

The authors, including MHRP deputy director Dr. Merlin Robb, reviewed different HIV-1 vaccine approaches currently being pursued and the lessons learned from clinical trials, including the Army-led RV144 trial and the Step (HVTN 502/Merck 023) and Phambili (HVTN 503) studies.

Multiple non-human studies suggest that Env is a necessary component for successful protection from SIV acquisition, and two vaccine approaches are currently being pursued to elicit Env-specific antibody-mediated protection:

1) Vaccines that induce potent and broadly reactive neutralizing antibodies (bNAbs) which act against vast array of viruses common in human transmission.

2) Vaccines like RV144 that induce antibodies that neutralize only lab adapted and less commonly transmitted HIV strains, but may block HIV-1 infection by non-neutralizing mechanisms.

Based on the findings of their review, authors outline a broad agenda for future vaccine research. Newer prime-boost mosaic and conserved sequence immunization strategies aimed at inducing immune responses of greater breadth and depth as well as the development of immunogens inducing broadly neutralizing antibodies should be actively pursued.

Although Non-Human Primate (NHP) studies may guide vaccine development, human efficacy trials remain key to answer the critical questions leading to the development of a global HIV-1 vaccine for licensure.

According to Dr. Merlin Robb, “RV144 showed us that a safe and effective HIV vaccine is possible. The results of that study, along with other HIV vaccine clinical studies that did not show efficacy, have answered some critical questions and have accelerated research efforts towards a more effective HIV vaccine.”