Functional interferon system is required for clearance of lassa virus

Lassa virus (LASV) is the causative agent of Lassa hemorrhagic fever (LF) in humans, a deadly disease endemic toWest Africa that results in 5,000 to 10,000 deaths annually. Here we present results demonstrating that functional type I and type II inter-feron (IFN) signaling is required for efficient control of LASV dissemination and clearance. Lassa virus (LASV), an arenavirus (family Arenaviridae), isenveloped and contains two single-stranded RNA segments of ambisense polarity encoding five proteins (1). LASV is the etiological agent of Lassa hemorrhagic fever (LF), a severe hu-man disease that is reported in up to 100,000 patients annually in regions where it is endemic. Mortality varies between 5% and 10 % for hospitalized patients (3). Individuals succumbing to LASV infection generate very limited or no anti-LASV hu-moral immune response, and histological examination of LF cases has revealed minimal immune cell infiltrates and tissue damage (14). These findings support the notion that morbidity and mortality associated with LASV infection are facilitated by the failure of the host’s innate defense mechanisms to limi