GENE-TRANSFER OF COSTIMULATORY MOLECULES B7-1 AND B7-2 INTO HUMAN MULTIPLE-MYELOMA CELLS BY RECOMBINANT ADENOASSOCIATED VIRUS ENHANCES THE CYTOLYTIC T-CELL RESPONSE

Gene transfer of the costimulatory molecules of B7-1 and B7-2 induces a potent antitumor immune response ina variety of tumor models. B cell neoplasms including multiple myeloma (MM) often show little or no exp ression of B7 antigens; they are therefore a potential target for this approach. To increase the expression of human B7 genes in MM cells, b oth genes and the neomycin phosphotransferase gene were packaged into recombinant adeno-associated virus vectors (rAAV). The resulting recom binant viruses rAAV/B7-1, rAA/B7-2 and rAAV/Neo were used to transduce the MM cell lines LP-1 and RPMI 8226. This allowed the transduction o f up to 80% of LP-1 cells 4 days after infection with purified rAAV pa rticles. The response of human allogenic T cells to rAAV/B7-1 an rAAV/ B7-2 transduced, gamma-irradiated LP-1 cells was assessed by [H-3]thym idine incorporation, by RT-PCR-based detection of immunostimulatory cy tokine transcripts and by ELISA quantification of cytokines in the sup ernatant. Stimulation of T cells with rAAV/B7-1 or rAAV/B7-2 transduce d LP-1 cells resulted in an up to 10-fold increase of T cell prolifera tion when compared with LP-1 cells transduced with rAAV/Neo. Similar r esults were obtained with RPMI 8226 cells. Both rAAV/B7-1 and rAAV/B7- 2 transduced LP-1 cells stimulated the T cell secretion of IL-2 and IF N-gamma. Furthermore, [Cr-51] release assays showed that rAAV/B7-1 or rAAV/B7-2 transduced LP-1 cells induced a cytoltic T cell (CTL) respon se, in contrast to LP-1 cells transduced with rAAV/Neo. In all assays, the effects of rAAV/BV-1 and rAAV/B7-2 were similar. Taken together, the results show that rAAV-mediated transfer of 87 genes into MM cell lines by is able to enhance the antitumor T cell response and to elici t a cytolytic T cell response.