H7N9 influenza virus neutralizing antibodies that possess few somatic mutations

Abstract

Avian H7N9 influenza viruses are group 2 influenza A viruses that have been identified as the etiologic agent for a current major outbreak that began in China in 2013 and may pose a pandemic threat. Here, we examined the human H7-reactive antibody response in 75 recipients of a monovalent inactivated A/Shanghai/02/2013 H7N9 vaccine. After 2 doses of vaccine, the majority of donors had memory B cells that secreted IgGs specific for H7 HA, with dominant responses against single HA subtypes, although frequencies of H7-reactive B cells ranged widely between donors. We isolated 12 naturally occurring mAbs with low half-maximal effective concentrations for binding, 5 of which possessed neutralizing and HA-inhibiting activities. The 5 neutralizing mAbs exhibited narrow breadth of reactivity with influenza H7 strains. Epitope-mapping studies using neutralization escape mutant analysis, deuterium exchange mass spectrometry, and x-ray crystallography revealed that these neutralizing mAbs bind near the receptor-binding pocket on HA. All 5 neutralizing mAbs possessed low numbers of somatic mutations, suggesting the clones arose from naive B cells. The most potent mAb, H7.167, was tested as a prophylactic treatment in a mouse intranasal virus challenge study, and systemic administration of the mAb markedly reduced viral lung titers.

A human inferred germline antibody binds to an immunodominant epitope and neutralizes Zika virus

“…Low levels of SHM in Abs possessing neutralizing activity have been previously reported in mice and humans [53][54][55], supporting the idea that germline-encoded mAbs can indeed neutralize. Abs with low levels of SHM have also been reported during the acute phase of human DENV infection, but it was not clear that these Abs contributed to the antiviral neutralization activity [56].…”

Neutralizing human antibodies prevent Zika virus replication and fetal disease in mice

“…Total RNA was extracted from hybridoma cells and genes encoding the VH and VL domains were amplified in RT–PCR using IgExp primers 31 . The PCR products were directly cloned into antibody expression vectors containing the constant domains of wild-type γ1 chain, LALA mutant (leucine (L) to alanine (A) substitution at positions 234 and 235) γ1 chain for the VH domains, and wild-type κ chain for the VL domain in an isothermal amplification reaction (Gibson reaction) 32 .…”

Potent anti-influenza H7 human monoclonal antibody induces separation of hemagglutinin receptor binding head domains

“…Several H7-specific mAbs have been described recently, including H7.137, H7.167, and H7.169, which target highly conserved regions of the HA head adjacent to the RBS (10). Another antibody isolated in the same study, mAb H7.5, was shown to recognize an epitope that overlaps a portion of the H7.167 epitope and neutralize similar strains of human H7 virus, including those from mallards and chickens, but which binds at a different angle (10). The H7.5 mAb potently neutralizes human H7 strains of influenza virus including strains isolated in outbreaks from 2003-2013 in Shanghai, Netherlands, and New York (10).…”