GENERATION OF THERAPEUTIC T-LYMPHOCYTES AFTER IN-VIVO TUMOR TRANSFECTION WITH AN ALLOGENEIC CLASS-I MAJOR HISTOCOMPATIBILITY COMPLEX GENE

In an effort to enhance the generation of tumor-reactive T-lymphocytes for adoptive immunotherapy, we examined the effects of in vivo transf ection of an allogeneic major histocompatibility complex (MHC) class I gene (H-2K(s)) of the poorly immunogenic B16BL6 (BL6) melanoma of H-2 (b) origin. Cells from lymph nodes (LNs) draining these tumors after t ransfection were assessed in adoptive immunotherapy experiments for tu mor reactivity after sequential activation with anti-CD3 monoclonal an tibody (mAb) followed by culture in interleukin (IL)-2. H-2K(s) lipofe ction of progressively growing BL6 subcutaneous tumors did not reduce tumorigenicity. However, in vivo lipofection of BL6 by intratumor inoc ulation or admixture of H-2K(s) cDNA/liposome complexes and tumor cell s prior to inoculation resulted in enhanced development of sensitized T-lymphocytes in the draining LN, which mediated the reduction of the numbers of established 3-day parental lung metastases in six of six ex periments. In subsequent studies, in vivo transfection of BL6 with nak ed H-2K(s) cDNA was found to be more effective than lipofection in eli citing sensitized T-cells in the draining LN. Admixture of liposomes a lone or control plasmid DNA did not have an adjuvant effect similar to H-2K(s) cDNA. Relative tumor transfection efficiency was assessed by an indirect assay with the chloramphenicol acetyltransferase (CAT) rep orter gene. BL6 tumors were more efficiently transfected by intratumor inoculation with naked cDNA compared with lipofection. In summary, in vivo allogenization of the poorly immunogenic BL6 tumor resulted in e nhanced generation of therapeutic T-cells effective in the treatment o f parental tumor.