La Jolla Institute for Immunology (LJI) researchers reported the characterization of human monoclonal antibodies that neutralize measles virus by blocking entry through binding to the virus’s hemagglutinin (H) and fusion (F) proteins. The team said infusion of the antibodies produced a 500-fold reduction in viral load in a rodent model of measles. The approach is designed for prophylaxis and treatment, including for people who cannot receive the live-attenuated MMR vaccine, such as immunocompromised patients and those too young for vaccination. In the work published in Cell Host & Microbe, the researchers derived antibodies from memory B cells of an individual vaccinated years earlier. LJI’s results raise the prospect of antibody-based measles therapy to complement vaccination strategies amid declining immunization coverage in multiple regions.