Human Antibodies Found to Neutralize Measles Virus with Picomolar Potency

Measles virus (MeV) remains one of the most contagious pathogens known, capable of causing severe neurological complications and death, particularly in vulnerable populations such as infants and immunocompromised individuals. Despite an effective vaccine, measles outbreaks are re-emerging globally due to declining vaccination rates. There is currently no approved antiviral therapy, making the identification of potent neutralizing antibodies a high priority.

Researchers at the La Jolla Institute for Immunology, in collaboration with teams at Columbia University, Ohio State, and Dartmouth, isolated a large panel of human monoclonal antibodies (mAbs) derived from the memory B cells of an MMR-vaccinated donor. The antibodies were screened for specificity against two key surface proteins: hemagglutinin (H), which facilitates viral attachment to host cells, and fusion protein (F), which drives membrane fusion and viral entry.

Using high-resolution cryo-electron microscopy, the scientists mapped four major epitope clusters on the H protein and five on the F protein. Representative antibodies from each cluster were structurally characterized. The most protective antibodies bound to highly conserved regions of both proteins, suggesting they would be broadly effective across MeV strains. Many antibodies achieved neutralization at picomolar concentrations — an exceptionally high potency level.

In animal model experiments, these mAbs substantially reduced viral loads whether administered prophylactically or therapeutically after viral exposure, demonstrating real-world utility for both prevention and treatment scenarios.

These findings provide a detailed blueprint of the human antibody response to measles and lay the groundwork for developing passive immunization tools, post-exposure prophylaxis, and direct antiviral therapies. Potential applications include protection of unvaccinated infants too young for the MMR vaccine, immunocompromised patients who cannot be vaccinated, and outbreak response. Patent filings on the antibodies and stabilized F protein have been noted.