Evaluation of the efficacy of a trivalent vaccine mixture against a triple challenge with Mycoplasma hyopneumoniae, PCV2, and PRRSV and the efficacy comparison of the respective monovalent vaccines against a single challenge

Oh, Taehwan; Park, Kee Hwan; Yang, Siyeon; Jeong, Jiwoon; Kang, Ikjae; Park, Changhoon; Chae, Chanhee

Lastly, we compared the efficacy of trivalent vaccine mixture against PRRSV with that of the monovalent PRRS vaccine and unvaccinated positive control. Reduction in viremia and lung lesions, and induction of cell-mediated immunity, specifically PRRSV-specific IFN-γ-SC which are used for the assessment of antigen-specific T-cell responses in swine [15, 16] are important criteria for PRRSV vaccine evaluation. Despite the fact that the protective role of IFN-γ-SC is controversial [17] , correlation between activation of T cell responses and clearance of PRRSV in blood has been previously reported [18, 19] . These data suggest that T cell responses elicited by PRRSV MLV vaccine play a role in the reduction of PRRSV viremia in vaccinatedchallenged pigs. In our study vaccination with either trivalent vaccine mixture or monovalent PRRS vaccine, both resulted in the induction of T cell responses and a reduction in the viral load in the blood simultaneously. In addition, there was no statistical difference in the number of PRRSV-specific IFN-γ-SC, levels of PRRSV viremia, and lung lesion scores between trivalent vaccination and monovalent vaccination in pigs.