Passive transfer of antibodies protects immunocompetent and immunodeficient mice against lethal Ebola virus infection without complete inhibition of viral replication

Ebola hemorrhagic fever is a severe, usually fatal illness caused by Ebola virus, a member of the filovirus family. The use of nonhomologous immune se rum in animal studies and blood from survivors in two anecdotal reports of Ebola hemorrhagic fever in humans has shown promise, but the efficacy of th ese treatments has not been demonstrated definitively. We have evaluated th e protective efficacy of polyclonal immune serum in a mouse model of Ebola virus infection. Our results demonstrate that mice infected subcutaneously with live Ebola virus survive infection and generate high levels of anti-Eb ola virus immunoglobulin G (IgG). Passive transfer of immune serum from the se mice before challenge protected upto 100% of naive mice against lethal E bola virus infection. Protection correlated with the level of anti-Ebola vi rus IgG titers, and passive treatment with high-titer antiserum was associa ted with a delay in the peak of viral replication. Transfer of immune serum to SCID mice resulted in 100% survival after lethal challenge with Ebola v irus, indicating that antibodies alone can protect from lethal disease. Thu s antibodies suppress or delay viral growth, provide protection against let hal Ebola virus infection, and may not require participation of other immun e components for protection.