Type I strain of Toxoplasma gondii from chicken induced different immune responses with that from human, cat and swine in chicken

In this study, four strains of Toxoplasma gondii with the same genetic type (Type I) originated from chicken, human, cat and swine were used to compare the immune responses in resistant chicken host to investigate the relationships between the parasite origins and the pathogenicity in certain host. A total of 300, 10-day-old chickens were allocated randomly into five groups which named JS (from chicken), CAT (from cat), CN (from swine), RH (from human) and a negative control group (-Ve) with 60 birds in each group. Tachyzoites of four different T. gondii strains (JS, CAT, CN and RH) were inoculated intraperitoneally with the dose of 1×107 in the four designed groups, respectively. The negative control (-Ve) group was mockly inoculated with phosphate-buffered saline (PBS) alone. Blood and spleen samples were obtained on the day of inoculation (day 0) and at days 4, 11, 25, 39 and 53 post-infection to screen the immunopathological changes. The results demonstrated some different immune characters of T. gondii infected chickens with that of mice or swine previous reported. These differences included up-regulation of major histocompatibility complex class II (MHC II) molecules in the early stage of infection, early peak expressions of interleukin (IL)-12 (IL-12) and -10 (IL-10) and long keep of IL-17. These might partially contribute to the resistance of chicken to T. gondii infection. Comparisons to chickens infected with strains from human, cat and swine, chickens infected with strain from chicken showed significant high levels of CD4+ and CD8+ T cells, interferon gamma (IFN-γ), IL-12 and IL-10. It suggested that the strain from chicken had different ability to stimulate cellular immunity in chicken.