Immune Response of Swine to Porcine Reproductive and Respiratory Syndrome Virus: Laboratory and Field Studies

129 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008.Porcine reproductive and respiratory syndrome virus (PRRSv) is an arterivirus that has had a significant economic impact on the pork industry in the past few decades. Our studies have focused on three major issues that concern alleviation of this problem. These include utilizing contact exposure to inoculated pigs as a strategy for acclimatization of pigs to autogenous (endemic) PRRSv strains; comparing protection against autogenous and heterogenous strains to better understand cross protection; and discovering T cell epitopes of PRRSv, which will be useful for designing epitope driven vaccines.The first study relates to the practice of "acclimatization", which is geared towards generation of immunity to locally circulating endemic strains. The study documents acclimatization to PRRSv via contact exposure to inoculated pigs, a novel procedure of acclimatization hitherto not described. Since early acclimatization to PRRSv is considered crucial to development of immunity, we evaluated acclimatization in two age groups and demonstrate that acclimatization to PRRSv via contact exposure may be practiced till pigs are 10.5 weeks of age to raise immunity against locally circulating endemic PRRSv strains.Cross protection is an important issue concerning constantly changing pathogens like PRRSv. Our second study evaluates cross protection by challenging PRRSv vaccinated pigs with autogenous and heterogenous PRRSv strains. The study demonstrates that: (1) The interaction between viral strains and the porcine immune system may not be stereotypic; (2) Long term protection provided by a strain may not correlate with the immediate cytopathic effects of a viral strain; (3) Cross protection may result not only from antigenic variability, but also from inter-strain variation in immunogenicity; and (4) Apart from viral load, other factors related to the inherent virulence of the viral strain may be responsible for disease outcome. Heterogenous viral strains albeit different, possibly have common epitopes that they use to interact with the host. In our third study, we determined the T cell epitopes of the two viral strains used for the second study and also attempted to see if there were any differences between the two strains.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD