Scientific Publications by FDA Staff

J Virol 2016 Sep 29;90(20):9383-93

Antigenic fingerprinting of antibody response following highly pathogenic H7N7 avian influenza virus exposure in humans: Evidence for anti-PA-X antibodies.

Khurana S, Chung KY, Coyle EM, Meijer A, Golding H

Infections with H7 highly pathogenic avian influenza (HPAI) viruses remain a major public health concern. Adaptation of low pathogenic H7N7 to highly pathogenic H7N7 in Europe in 2015 raised further alarm for a potential pandemic. In-depth understanding of antibody responses to HPAI H7 virus following infection in humans could provide important insight into virus gene expression as well as define key protective and serodiagnostic targets. Here we used whole genome phage display libraries (GFPDL) expressing peptides of 15-350 amino acids across the complete genome of HPAI H7N7-A/Netherlands/33/03 virus. The hemagglutinin (HA) antibody epitope repertoires of fifteen H7N7 exposed humans identified clear differences between individuals with no hemagglutination inhibition (HI) titers (< 1:10) vs. those with HI >1:40. Several potentially protective H7N7 epitopes close to the HA receptor binding domain (RBD) and neuraminidase (NA) catalytic site were identified. Surface Plasmon Resonance (SPR) analysis identified a strong correlation between HA1 (but not HA2) binding antibodies and H7N7 HI titers. A proportion of HA1 binding in plasma was contributed by IgA antibodies. Antibodies against the N7 neuraminidase were less frequent but targeted sites close to the sialic acid binding site. Importantly, we identified strong antibody reactivity against PA-X, a putative virulence factor, in most H7N7 exposed individuals, providing the first evidence for in vivo expression of PA-X and its recognition by the immune system during human influenza A infection. This knowledge can help inform in the development and selection of the most effective countermeasures for prophylactic as well as therapeutic treatments of HPAI H7N7 avian influenza. IMPORTANCE: An outbreak of pathogenic H7N7 virus occurred in poultry farms in the Netherlands in 2003. Severe outcome included conjunctivitis, influenza-like illness, and one lethality. In the current study, we investigated convalescent sera from H7N7-exposed individuals using whole genome phage display library (H7N7-GFPDL) to explore the complete repertoire of post-H7N7 exposure antibodies.PA-X is a recently identified influenza virulence protein, generated by ribosomal frame shifting in segment 3 of influenza virus coding for PA. But PA-X expression during influenza infection in humans is unknown. We identified strong antibody reactivity against PA-X in most H7N7 exposed individuals (but not in unexposed adults), providing the first evidence for in vivo expression of PA-X and its recognition by the immune system during human infection with pathogenic H7N7 avian influenza.