Advancing Toward HIV-1 Vaccine Efficacy through the Intersections of Immune Correlates

Interrogating immune correlates of infection risk for efficacious and non-efficacious HIV-1 vaccine clinical trials have provided hypotheses regarding the mechanisms of induction of protective immunity to HIV-1. To date, there have been six HIV-1 vaccine efficacy trials (VAX003, Vaxgen, Inc., San Francisco, CA, USA), VAX004 (Vaxgen, Inc.), HIV-1 Vaccine Trials Network (HVTN) 502 (Step), HVTN 503 (Phambili), RV144 (sponsored by the U.S. Military HIV Research Program, MHRP) and HVTN 505). Cellular, humoral, host genetic and virus sieve analyses of these human clinical trials each can provide information that may point to potentially protective mechanisms for vaccine-induced immunity. Critical to staying on the path toward development of an efficacious vaccine is utilizing information from previous human and non-human primate studies in concert with new discoveries of basic HIV-1 host-virus interactions. One way that past discoveries from correlate analyses can lead to novel inventions or new pathways toward vaccine efficacy is to examine the intersections where different components of the correlate analyses overlap (e.g., virus sieve analysis combined with humoral correlates) that can point to mechanistic hypotheses. Additionally, differences in durability among vaccine-induced T- and B-cell responses indicate that time post-vaccination is an important variable. Thus, understanding the nature of protective responses, the degree to which such responses have, or have not, as yet, been induced by previous vaccine trials and the design of strategies to induce durable T- and B-cell responses are critical to the development of a protective HIV-1 vaccine.