Submitted to: American Association of Veterinary Parasitologists Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 4/10/1997
Publication Date: N/A
Technical Abstract: Swine infected with low doses (200-1000 oocysts) of VEG strain of T. gondii have been analyzed for their immune responses to infection. Analyses of cell subsets have shown an early (day 6-8) increase in peripheral blood CD4+/CD8+ T cells that returns to normal levels by day 14 of infection. Levels of activated monocytic cells are also increased in the first week after infection. Analyses of cytokine mRNA expression in peripheral blood lymphocytes from infected pigs show increases in interferon-g (IFN-g) levels as compared to cells from uninfected pigs. Recent studies have been aimed at documenting a T. gondii vaccination model using irradiated oocysts. Preliminary studies showed that pigs vaccinated with ~10,000 VEG strain oocysts, irradiated with 0.3 kGy Cs137, were protected against challenge high (106) or low (103) dose T. gondii oocyst inocula, as determined by clinical signs and by recovery of viable parasite from tissues. Antibody levels were measured during the vaccination process and were found not to be predictive of the protection stimulated by the vaccination. Repeat vaccination studies are underway to determine the reproducibility of irradiated oocysts as a T. gondii vaccine for swine and to assess whether specific cell subsets or cytokines are preferentially stimulated during vaccination responses. These studies should verify whether use of irradiated oocysts is a good vaccine candidate for preventing toxoplasmosis in swine and whether in vitro assays, such as measurement of cytokine levels, are potential predictors of positive T. gondii vaccination responses.