トキソプラズマ原虫由来のhsp70に対する液性免疫

The cDNA for a member of stress induced 70-kDa protein family (hsp70) from Toxoplasma gondii was cloned. The deduced amino acid sequence revealed a 667 amino acid protein 70-80% homologous to other parasite and mammalian hsp70s. Southern blot analysis suggested that it is encoded by an intronless gene. A protein of ～77-kDa was identified in a lysate of T.gondii tachyzoites by mAbs generated against the recombinant hsp70 protein. Anti-human hsp70 mAb also cross-reacted with a T. gondii protein of the identical molecular weight. However, immunoprecipitation and Western blot analysis of these proteins indicated that it was distinct from the cloned hsp70 product, suggesting that T. gondii expresses another hsp70-like protein. Among 22 mice infected with a low virulence Fukaya strain of T. gondii, 6 mice exhibited significant humoral anti-hsp70 Ab responses. This Ab responses peaked at 1-2 weeks of infection, plateaued for 2-3 weeks and gradually declined to nearly undetectable levels at 6 weeks of infection. In contrast, the levels of serum Ab specific for soluble tachyzoite Ags continued to increase during the infection in all mice examined. These features suggest that pathogen-derived hsp70 may play a unique role in the induction and maintenance of the host irnmune responses