Hiv/Aids Vaccine: Rumors and Insights on a T-Cell-Based Vaccine

Abstract

Evaluation of: Liu J, O’Brien KL, Lynch DM et al.: Immune control of an SIV challenge by a T-cell-based vaccine in rhesus monkeys. Nature 457(7225), 87–91 (2009). The generation of a vaccine against HIV/AIDS has turned out to be extremely challenging. In spite of enormous experience both in preclinical and clinical models, we still do not know what viral gene is essential for protective immunity, what the correlate(s) of protection are and what type of delivery system works better in term of safety, immunogenicity and efficacy. Recently, the STEP (double-blind, randomized trial HTVN502; Merck V520, protocol 023) vaccine failure in the scientific community raised the question as to whether a T-cell-based vaccine against HIV/AIDS is still feasible. Liu and colleagues demonstrated that a combination of serologically distinct adenoviral vectors expressing the SIV Gag protein elicited polyfunctional and broad T-cell responses that correlated with a durable but partial protection in macaques challenged with pathogenic SIV in the absence of homologous Env antigen (i.e., neutralizing antibodies). This, and other preclinical trials, are providing convincing evidence that T-cell-based vaccine strategies – while not able to elicit sterilizing immunity – could, however, be sufficient to control viral replication and lower viral transmission rate among individuals (secondary end point of HIV vaccine). These approaches, as long as they demonstrate their ability to elicit broad and antigen-specific polyfunctional activities in relevant animal models, have the potential to be studied further in clinical trials.