Evaluation of replicon particle vaccines for porcine reproductive and respiratory syndrome virus

Abstract

Porcine reproductive and respiratory syndrome (PRRS) causes significant economic, food production, and animal welfare problems for the world swine industry. The immune factors responsible for prevention of PRRS virus (PRRSV) infection are poorly understood. Further exploration of the factors responsible for PRRSV’s evasion of host defenses may contribute to improved vaccine design. We hypothesized that vaccination of pigs with a replicon particle (RP) derived from Venezuelan equine encephalitis virus (strain, TC-83) would interfere with the natural progression of PRRSV viremia due to the robust innate immune responses induced by the replicon system immediately after RP injection. To test this, we vaccinated young pigs with an RP vaccine against swine influenza virus and challenged with PRRSV at 24 or 72 hours post-vaccination. Compared to placebo, RP-vaccinated pigs had reduced viremia at various time points post-challenge, as well as a reduction in total viral load. The use of RP to modulate the immune system may prove useful for further study of PRRSV and other pathogens.