Evidence brief

Broad Immunity from Naturally Occurring Influenza Antibodies The findings indicate that broadly neutralizing human antibodies can target conserved epitopes in the HA head, not just the stem, broadening the conceptual space for “universal” influenza vaccine design and for monoclonal antibody–based prophylaxis. The authors used large phage display libraries from B lymphocytes of adult donors to map naturally occurring human neutralizing antibodies against influenza A. From a donor born in 1974, they identified 18 unique anti HA monoclonal antibodies, including four related clones with remarkably broad reactivity. Two, F045 092 and F026 427, were characterized in detail and shown to bind the HA head (HA1) and neutralize multiple subtypes. F045 092 strongly neutralized diverse H3N2 strains and, with lower potency, selected H1N1, H2N2, and H5N1 viruses. Both antibodies displayed hemagglutination inhibition activity, indicating neutralization via blockade of HA–sialic acid binding rather than the stem targeting mechanism described for previously known group 1 specific...