Interleukin-10 and immune response in mice infected with the cyst strain of Toxoplasma gondii

Abstract

Early in vitro studies have shown that specific anti-Toxoplasma gondii antibodies are lytic for the parasite. However, it can persist in chronic latent infections, and it is suggested that parasite survival is dependent on induction of IL-10 in order to down regulate the host protective immune response. In the present study, Balb/c mice were infected orally with the cyst strain of T. gondii and the changes in the serum levels of interleukin-IO (IL-10) and anti-Toxoplasmosis antibodies were determined at weekly intervals throughout the 35 days post-infection, using a double sandwich ELISA and the indirect ELISA technique respectively. lgM peaked during early infection, while lgG peaked at the fourth week post-infection. IL- 10 peaked at 28 days post-infection. There was a strong positive correlation between lgG anti-Toxoplasma antibodies and IL-10 (r = 0.704, P < 0.05). Tissue cysts were detected in spleens that were enlarged at two weeks post-infection. Mortality was found to be dependant on the infective dose, this being highest in mice infected with I 0,000 cysts.