Isolation of broadly neutralizing antibodies from single human memory B cell against human influenza A viruses (TECH2P.922)

Abstract During the past five years, broadly neutralizing antibodies (BnAbs) represent promising prophylactic and therapeutic treatments against influenza. Here, we have developed a novel method to isolate broadly neutralizing antibodies against influenza A virus from human memory B cells. Antigen-specific memory B cells were isolated from human PBMCs using tetramerized H3 (A/Brisbane/10/2007) hemagglutinin (HA) trimers. The H3-reactive single memory B cells were sorted into plates and stimulated in vitro. More than 40% sorted B cells produced on average 200 ng/ml IgG in the supernatant after 14 days. Supernatants from the expanded B cells were measured for their heterosubtypic binding specificity and neutralizing activity by MSD or a highly sensitive neutralization assay. The selective clones were recovered by single cell RT-PCR. Through screening 2688 memory B clones from 7 individuals, 11% clonable memory B cells were reactive with H3 hemagglutinin. Among them, H3/H7, H3/H7/H1 and H3/H7/H1/influenza B heterosubtypic binding population were 16%, 6.9% and 0.35%, respectively. A new broadly neutralizing Ab, 3I14 encoded by the IGHV3-30 germline gene, was further characterized and shown to possess cross-reactive binding and neutralization activity against both group 1 and group 2 influenza A viruses. Epitope mapping and competition assay revealed a highly conserved epitope located in the HA stalk. Passive transfer of this antibody also conferred in vivoprotection.