Cellular immune responses to helper-free HSV-1 amplicon particles encoding HIV-1 gp120 are enhanced by DNA priming

A single inoculation of herpes simplex virus type-1 (HSV-1) amplicon vectors encoding human immunodeficiency virus type-1 gp120 (HSV:gp120) results in robust, specific immune responses to gp120. To explore further the utility of this novel vaccine delivery system, we examined the kinetics of the cellular immune response by tetramer staining, following a single intramuscular administration of HSV:gp120 particles, and found that it peaks at 9-28 days post-immunization, before declining to a stable memory response. We also examined the utility of prime-boost regimens using packaged amplicon particles and naked amplicon plasmid DNA (DNA:gp120). These experiments showed that two sequential immunizations with HSV:gp120 resulted in a 5-10-fold increase in gp120-specific cellular immune responses and that plasmid DNA priming, followed by amplicon particle boosting, imparted the strongest acute and memory T cell responses, as determined by tetramer analysis. Collectively, these results demonstrate the utility of HSV amplicon vectors in prime-boost regimens for HIV vaccine development.