Heterologous prime-boost vaccination strategies for HIV-1: augmenting cellular immune responses.

Cellular immune responses, specifically those mediated by CD8+ cytotoxic T-lymphocytes and CD4+ helper T-lymphocytes, are needed to control HIV-1 in vivo and to mediate viral clearance. Vaccines capable of inducing cellular immune responses are, therefore, widely considered as necessary for controlling the spread of HIV-1. Numerous different vaccine delivery formats designed to induce cellular immune responses have been evaluated in animal models and clinical trials. These include adjuvant-supplemented peptide- or protein-based formulations, DNA vaccines and viral vectors. While none of the current generation vaccine delivery technologies have proved potent enough for stand-alone use against HIV-1-infection, mixed delivery vaccine formats, vaccination schemes known as heterologous prime-boost, have proved to be significantly potent methods for inducing cellular immune responses. Different forms of heterologous prime-boost vaccines are currently being tested in numerous clinical trials and hold significant promise.