Submitted to: International Immunology Congress
Publication Type: Abstract Only
Publication Acceptance Date: 8/15/1998
Publication Date: N/A
Technical Abstract: The major strategy for prevention of toxoplasmosis is the identification of resistance factors and/or specific vaccines which induce protective responses. Despite the extensive literature on immunity to T. gondii in mice, sheep and humans, little is known about the protective immune response in pigs. Serologic titers have been reported for swine but these are highly variable and, as with other species, have proven to be poor predictors of effective immunity. Two sets of recent studies will be presented. In the first series, pigs were vaccinated with irradiated T. gondii oocysts. After challenge, it was clear that the pigs were protected from clinical disease, however, T. gondii cysts could still be recovered in tissues from the vaccinated pigs. Thus, this vaccine would not completely prevent foodborne transmission of this protozoan parasite. In the second series, pigs of different swine leukocyte antigen (SLA) haplotypes were evaluated for their natural resistance to low level T. gondii infection (~500 T. gondii oocysts) to determine whether genetic background would influence resistance to this parasite. The immune response to infection was characterized by following changes in peripheral blood cell subsets and in the cytokines, specifically interferon- g (IFN-g), they produced. SLAdd pigs were able to respond with higher IFN-g production and lower T. gondii burden as compared with SLAcc and SLAaa pigs. An increase was also seen in the second week CD4+/CD8+ T cell populations and in SWC3+/SLA II+ cells. Thus, SLAdd pigs may express immune factors asociated with increased resistance to T. gondii infection.