#02-127

Complete

Date Full Report Received

06/02/2003

Date Abstract Report Received

07/24/2006

Investigation

Institution:
Primary Investigator: , ,

PRRSV vaccine efficacy remains controversial. The currently available PRRSV vaccines, either modified live (MLV) or killed virus (KV) vaccines, often appear to provide insufficient protective immunity. Therefore, this study was designed to investigate if interleukin (IL) – 12, a protein known to induce a cell-mediated immune (CMI) response, added to the KV would enhance vaccine efficacy. Combining MLV and KV (2 doses of KV following MLV) was also investigated to determine if this vaccination strategy would induce stronger and more rapid immune responses. The results of this study suggest that adding IL-12 failed to enhance the protection against PRRSV challenge. Addition of IL-12 slightly enhanced the efficacy of KV with regard to induction of humoral and CMI responses as demonstrated by increases of ELISA titer and the number of IFN-? producing cells. It is noteworthy that administration of MLV followed by 2 doses of KV, 2 weeks apart, induced stronger humoral and CMI responses compared to vaccination with either vaccine alone. Pigs in the group receiving both vaccines displayed higher levels of serum neutralizing antibodies than pigs receiving either MLV or KV alone. However, no statistical difference was observed. The magnitude of T-lymphocyte proliferative responses was slightly higher in the group receiving both vaccines on 28 dpv and 7 dpi compared to the other vaccine groups. In addition, the magnitude and duration of viremia was observed following the administration of both vaccines was reduced.
The results of this study suggest that combining MLV and KV vaccination protocols may induce greater immune responses, resulting in reduced clinical disease and viremia compared to administration of either vaccine alone.