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BioMed Research International
Volume 2014 (2014), Article ID 416727, 10 pages
Research Article

Comparison of Host Immune Responses to Homologous and Heterologous Type II Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) Challenge in Vaccinated and Unvaccinated Pigs

1Department of Anatomy and Physiology, 228 Coles Hall, College of Veterinary Medicine, Kansas State University, 1600 Denison Ave, Manhattan, KS 66506, USA
2Intrexon Corporation, 108 TW Alexander Drive, Durham, NC 27709, USA
3Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, 1600 Denison Ave, Manhattan, KS 66506, USA
4The Scripps Research Institute, 130 Scripps Way No. 3B3, Jupiter, FL 33487, USA

Received 18 November 2013; Revised 5 January 2014; Accepted 8 January 2014; Published 26 February 2014

Academic Editor: Denis Archambault

Copyright © 2014 X. Li et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Porcine reproductive and respiratory syndrome (PRRS) is a high-consequence animal disease with current vaccines providing limited protection from infection due to the high degree of genetic variation of field PRRS virus. Therefore, understanding host immune responses elicited by different PRRSV strains will facilitate the development of more effective vaccines. Using IngelVac modified live PRRSV vaccine (MLV), its parental strain VR-2332, and the heterologous KS-06-72109 strain (a Kansas isolate of PRRSV), we compared immune responses induced by vaccination and/or PRRSV infection. Our results showed that MLV can provide complete protection from homologous virus (VR-2332) and partial protection from heterologous (KS-06) challenge. The protection was associated with the levels of PRRSV neutralizing antibodies at the time of challenge, with vaccinated pigs having higher titers to VR-2332 compared to KS-06 strain. Challenge strain did not alter the cytokine expression profiles in the serum of vaccinated pigs or subpopulations of T cells. However, higher frequencies of IFN-γ-secreting PBMCs were generated from pigs challenged with heterologous PRRSV in a recall response when PBMCs were re-stimulated with PRRSV. Thus, this study indicates that serum neutralizing antibody titers are associated with PRRSV vaccination-induced protection against homologous and heterologous challenge.