EVIDENCE FOR SUPERANTIGENIC ACTIVITY DURING MURINE MALARIA INFECTION

TCR V-beta usage was examined in C57BL/6 mice infected with Plasmodium yoelii. In addition to a polyclonal T cell activation, already descri bed, a superantigenic-like activity was observed during the acute infe ction, This superantigenic activity induces a preferential deletion wi thout prior expansion of CD4(+) and CD8(+) T cells bearing the TCR V(b eta)9 segment. The superantigen could be released by the parasite at d ifferent stages of its development since the deletion of V(beta)9(+) T cells was observed in blood and lymph nodes of mice infected either w ith sporozoites or with erythrocytic stages, Injection of sporozoite o r parasitized erythrocytes to newborn mice led to a deletion and anerg y of peripheral V(beta)9(+) T cells, without affecting thymic T cell p opulations, These observations suggest that the superantigen is releas ed at very low concentrations during parasite development. The role of such parasite superantigenic activity in infectivity can be underline d by the observation that congenic BALB.D2 Mls1(a) mice lacking V(beta )9 T cells are more susceptible to infection by P. yoelii.