Lack of evidence for superantigen activity of Toxoplasma gondii towards human T cells

Toxoplasma gondii is an obligatory intracellular parasite whose life cycle may include man as an intermediate host. More than 500 million people are i nfected with this parasite worldwide. It has been previously reported that T. gondii contains a superantigen activity. The purpose of the present stud y was to determine if the putative superantigen activity of T gondii would manifest towards human T cells. Peripheral blood mononuclear cells (PBMC) f rom individuals with no previous contact with the parasite were evaluated f or proliferation as well as specific V beta expansion after exposure to Tox oplasma antigens. Likewise, PBMC from individuals with the congenital infec tion were evaluated for putative V beta family deletions in their T cell re pertoire. We also evaluated, over a period of one year, the PBMC proliferat ion pattern in response to Toxoplasma antigens in patients with recently ac quired infection. Some degree of proliferation in response to T. gondii was observed in the PBMC from individuals never exposed to the parasite. accom panied by specific V beta expansion, suggesting a superantigen effect. Howe ver, we found no specific deletion of V beta (or V alpha) families in the b lood of congenitally infected individuals. Furthermore, PBMC from recently infected individuals followed up over a period of one year did not present a reduction of the V beta families that were originally expanded in respons e to the parasite antigens. Taken together, our data suggest that T. gondii does not have a strong superantigen activity on human T cells.