Evidence for superantigenic activity during murine malaria infection

TCR V beta usage was examined in C57BL/6 mice infected with Plasmodiumyoelii. In addition to a polyclonal T cell activation, already described, asuperantigenic-like activity was observed during the acute infection. Thissuperantigenic activity induces a preferential deletion without priorexpansion of CD4+ and CD8+ T cells bearing the TCR V beta 9 segment. Thesuperantigen could be released by the parasite at different stages of itsdevelopment since the deletion of V beta 9+ T cells was observed in bloodand lymph nodes of mice infected either with sporozoites or witherythrocytic stages. Injection of sporozoite or parasitized erythrocytes tonewborn mice led to a deletion and anergy of peripheral V beta 9+ T cells,without affecting thymic T cell populations. These observations suggestthat the superantigen is released at very low concentrations duringparasite development. The role of such parasite superantigenic activity ininfectivity can be underlined by the observation that congenic BALB.D2Mis1a mice lacking V beta 9 T cells are more susceptible to infection by P.yoelii.