77: Kinetics of Type I interferon responses determine either establishment of antiviral memory or no induction of adaptive immunity

Abstract

Many pathogens trigger type I interferon (IFN-I) responses early after infection that confer protection until adaptive immunity is induced. Upon infection with vesicular stomatitis virus (VSV) Toll-like receptor (TLR) and RIG-I-like helicase (RLH) signaling platforms are indispensable for the induction of protective IFN-I. Hence, TLR- and RLH-ablated MyTrCa −/− mice challenged with VSV do not mount IFN-I responses and are inevitably susceptible to lethal VSV infection. To study the impact of the kinetics of IFN-I responses on the induction of adaptive immunity, we infected MyTrCa −/− mice with VSV and treated them 4, 8, 16, and 24 h after infection with recombinant IFN- α (rIFN- α ) . Interestingly, under such conditions MyTrCa −/− mice mounted normal adaptive immune responses and approximately 76% of the mice survived. On the contrary, initiation of the rIFN- α treatment scheme 4 h before VSV infection significantly prolonged survival, whereas reduced VSV-specific cytotoxic T-lymphocytes and basically no VSV neutralizing antibody responses were induced and 100% of the mice finally died. Long-term rIFN- α treatment for 9 days initiated 4 h after VSV infection promoted 100% survival of MyTrCa −/− mice and protective immunity was induced normally as verified by 100% of the animals surviving even a VSV re-challenge 3 weeks after discontinuation of the rIFN- α treatment. Initiation of the 9 days rIFN- α regimen 4 h prior to infection also rescued 100% of the mice, however, no adaptive immunity developed and 100% of the animals succumbed to re-challenge. In conclusion, long-term rIFN- α treatment initiated before virus infection prevented induction of protective adaptive immunity, whereas initiation of rIFN- α treatment hours after infection supported development of normal adaptive immunity and protective memory response. These observations have implications for immunotherapies and vaccination strategies, in particular for patients under long-term IFN-I therapy who are treated with live attenuated vaccines.