Structural basis for antibody-mediated neutralization of Lymphocytic choriomeningitis virus

The mammarenavirus Lymphocytic choriomeningitis virus (LCMV) is a globally distributed zoonotic pathogen that can be lethal in immunocompromised patients and cause severe birth defects if acquired during pregnancy. Despite the fundamental importance of LCMV for studying immunobiology, the structure of the trimeric surface glycoprotein, essential for entry, vaccine design and antibody neutralization, remains unknown. In this study, we present the cryoEM structure of the LCMV surface glycoprotein (GP) in its trimeric prefusion assembly both alone and in complex with a rationally engineered monoclonal neutralizing antibody termed 18.5C-M28 (M28). Additionally, we show that passive administration of M28 protects mice from LCMV clone 13 (LCMVcl13) challenge when administered as either a prophylactic or therapeutic. Our study illuminates not only the overall structural organization of LCMV GP and the mechanism for its inhibition by M28, but also presents a promising therapeutic candidate to prevent severe or fatal disease in individuals who are at risk of infection by a virus that poses a threat worldwide. Highlights ### Competing Interest Statement The authors have declared no competing interest.