Reproductive efficacy of a modified-live porcine reproductive and respiratory syndrome vaccine against Korean PRRSV-2 challenge in sows

Background Evaluation of the reproductive efficacy of a modified-live vaccine (MLV) based on porcine reproductive and respiratory syndrome virus-2 (PRRSV-2). Objective The objective of this study was to evaluate the efficacy of a MLV based on porcine PRRSV-2 against a heterologous Korean PRRSV-2 lineage 1 strain challenge in pregnant sows. Animals Twelve pregnant sows from PRRSV-free farms were randomly assigned to three groups (four sows per group). Methods Sows in the vaccinated-challenged group received a 2.0 mL intramuscular dose of PRRSV-2 MLV and were subsequently challenged intranasally with a heterologous PRRSV-2 strain. Results Vaccinated-challenged sows improved reproductive performance, including a higher number of live-born piglets and fewer stillbirths compared with unvaccinated-challenged sows. Viral genomic loads were lower in vaccinated-challenged sows and their offspring as well. Vaccinated-challenged sows also elicited a significantly higher frequency of PRRSV-2 specific interferon- γ secreting cells. Discussion These findings demonstrated that the PRRSV-2 MLV administered to pregnant sows provide protection against heterologous challenge through clinical, virological, and immunological evaluation.