TLR7 and infection: During early acute infection by intravenous inoculation with Friend virus (FV), which is a complex composed of Friend murine leukemia (F-MLV) helper virus and polycythemia-inducing spleen focus-forming virus, mice deficient in the ssRNA sensor TLR7 had higher levels of infectious virus in plasma which persisted until 14 days post infection (dpi), unlike wild-type (WT) controls, which had undetectable viremia at this time.