| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2002: ¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 2001: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Research Abstract |
Gp96 has useful properties as tumor vaccine for the generation of CD8 CTL independent of MHC restriction. We have developed a secreted form of gp96-Ig (gp96-Ig) by deleting the endoplasmic reticulum retention signal, KDEL, and replacing it with the Fc portion of murine IgG_1. Tumor cells transfected with and overexpressing gp96-Ig were less tumorigenic, compared to wild type tumors. Immunization of mice with the murine lymphoma E.G7 transfected with gp96-Ig (E.G7-gp96-Ig), but not with irradiated E.G7, induced immunity to subsequent challenge with E.G7. Depletion studies showed that CD8^+ cells were required for E.G7-gp96-Ig rejection throughout induction phase and effector phase, but not CD4^+ cells or macrophages. In this study, we examined the immunotherapeutical potency by gp96-Ig gene-transfected tumor cells. E.G7 was established in C57BL/6 mice for three days. Daily injections, beginning on day 4, of gp96-Ig-transduced tumor cells suppressed tumor growth remarkably when compared
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to PBS treatment or to treatment with control tumors treatment with control tumors secreting gp96-Ig. Beginning vaccination on day 5 after tumor transplantation, successful therapy required a vaccination schedule of two daily injections of E.G7-gp96-lg. In a Jung tumor model. LLC, LLC-gp96-Ig vaccines were equally effective as gp96 purified from LLC cells and comparable to IL-12-transduced tumor cells (LLC/1L12). There were no synergistic effects by a 1:1 mixture of LLC-gp96-Ig and LLC/IL12, suggesting that the two vaccines may act through similar cellular mechanisms. CD4^+ T cells were not required for vaccines by gp96-Ig-transduced tumor cells. CD8^+ cytotoxic activities specific for wild type tumor cells were induced by vaccines with gp96-Ig-transduced tumor cells. Moreover, adoptively transferred, ovalbumin specific T-cell receptor (TCR) transgenic CD8^+ cells (OT-1) responded with clonal expansion to the immunization with EG7-gp96-Ig. Our data suggest that tumors secreting gp96-Ig may be useful as potent anti tumor vaccines. Less
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