Recombinant Adenovirus Vaccines Can Successfully Elicit CD8+ T Cell Immunity under Conditions of Extreme Leukopenia

We have examined the efficacy of vaccination with recombinant adenovirus under conditions of extreme leukopenia in lethally irradiated mice reconstituted with autologous bone marrow. The expansion of antigen-specific CD8(+) T cells following immunization of lethally irradiated hosts paralleled the recovery of total CD8(+) T cells. Surprisingly, the numbers of antigen-specific CD8(+) T cells in lethally irradiated mice beyond 6 weeks postimmunization were comparable to the numbers found in nonirradiated controls. CD8(+) T cells elicited in the lethally irradiated hosts were functionally indistinguishable from those elicited in normal hosts. Antigen expression and presentation persisted for a longer period of time in the draining lymph nodes of irradiated mice compared to those of nonirradiated animals, suggesting that antigen presentation mechanisms were intact during the reconstitution period. Experiments employing allogeneic bone marrow demonstrated that radioresistant host antigen-presenting cells were responsible for antigen presentation during the process of immune reconstitution. These results demonstrate clear compatibility of adenovirus vaccines and cytotoxic therapy. Furthermore, these observations provide novel insights into the mechanisms of CD8(+) T cell activation following adenovirus immunization.