Feasibility of UV-inactivated vaccinia virus in the modification of tumor cells for augmentation of their immunogenicity.

We compared the immunity induced by tumor cells modified with UV-inactivated purified vaccinia virus (UV-VV) and with live purified vaccinia virus (L-VV). C3H/HeN mice were inoculated i.p. with UV-VV or L-VV after whole-body irradiation with 150 rads of X-rays (priming). After 3 weeks the mice were immunized i.p. 3 times at weekly intervals with syngeneic X5563 or MH134 cells that had been absorbed in vitro with UV-VV or infected with L-VV and subsequently irradiated with 10(4) rads of X-rays. Then 1 week after the last immunization, the mice were challenged s.c. with X5563 viable tumor cells or challenged i.p. with MH134 viable tumor cells. The 50% lethal dose (TLD50) of X5563 in mice primed and immunized with UV-VV (UV-VV group) on s.c. challenge (10(6.06)) was the same as for mice treated with L-VV (L-VV group), whereas the TLD50 of unprimed or nonimmunized mice (control group) was 10(2.61). The TLD50 of MH134 in the UV-VV treated group on i.p. challenge (10(6.48)) was similar to that of the L-VV treated group (10(6.54)), while the TLD50 of the control group was 10(1.00). The difference between the TLD50 values of X5563 on s.c. challenge of mice primed and immunized with UV-VV or L-VV and control mice was 10(3.4). The difference between the TLD50 values of MH134 on i.p. challenge of primed and immunized mice and control mice was 10(5.5). These results indicate that the in vivo helper function of UV-VV is similar to that of L-VV and that the augmenting effect of this protocol depends on the kind of tumor.