| Research Abstract |
Antigen presentation of Toxoplasma gondii (T.gondii)-infected cells to T.gondii-infected cell- specific CD4^+CD8^- and CD4^+CD8^- cytotoxic T lymphocytes (CTL) has been analysed. T.gondii-infected melanoma presents T.gondii-infected cell-specific antigens to CD4^+CD8^- GTL while T.gondii-infected B lymphoma presents T.gondii-infected cell-specific antigens to CD4^+CD8^- CTL.The role of heat shock protein (HSP) 70, a molecular chaperon in peptide and protein transport between cell organellas, in antigen processing and presentation of T.gondii -infected cells to cytotoxic T lymphocytes (CTL) specific for T.gondii-infected cells was investigated. Human melanoma line, P36, pulsed with HSP70 of T.gondii- infected P36 cells as well as T.gondii-infected P36 cells were lysed by a CD4^+ CTL specific for T.gondii infected cells that was generated from peripheral blood lymphocytes of a patient with chronic toxoplasmosis. The lytic activity of the CTL against P36 cells pulsed with T.gondii-infecte
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d P36 cell- derived HSP70 was inhibited by anti-HSP70 mAbs indicating that HSP70 molecules of T.gondii-infected P36 play a role in antigen processing and presentation of T.gondii-infected P36 cells to CD4^+CTL.
Furthermore, we have established a stable T.gondii SAG1 (a major surface antigen of T.gondii)- gene transfectant by using RMA.S cells, a murine TAP molecule-deficient mutant lymphoma line, as a host to elicit T.gondii-infected cell-specific CD4^-CD8^+ CTL and to develope an ex-vivo gene vaccination to T.gondii-infection. RMA.S cells are unable to process self peptides from cytosol to endoplasmic reticulum (ER) lumen due to a defect of TAP transporters, so that MHC class I molecules of RMA.S dominantly bind peptides derived from the transfected SAG1gene product containig a signal sequence. Immunization of mice with the SAG1-transfected RMA.S induced CD4^-CD8^+ CTL specific for not only SAG1-transfected RMA.S but also T.gondii-infected RMA.S, and elicited protective responses to infection with a virulent T.gondii strain, RH.Establishment of gene vaccination with SAG1 and molecular chaperones by using professional antigen presenting cells (APC) such as Langerhans cells or dendritic cells as the targeting APC are underway Less
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