Subtype-specific antibodies to type A influenza viruses in shorebirds at Delaware Bay

Type A influenza virus (AIV) infections in shorebirds at Delaware Bay have historically included most of the avian hemagglutinin (HA) and neuraminidase (NA) subtypes. In a given year, however, infections are characterized by a... [ view full abstract ]

Type A influenza virus (AIV) infections in shorebirds at Delaware Bay have historically included most of the avian hemagglutinin (HA) and neuraminidase (NA) subtypes. In a given year, however, infections are characterized by a limited number of HA and NA subtypes and a dominant HA subtype that generally represents >50% of all isolates. Predominant HA subtypes routinely shift between consecutive years. In addition, infection prevalence is consistently higher in ruddy turnstones (Arenaria interpres morinella) as compared to red knots (Calidris canutus rufa). The reason for these subtype patterns and species differences are not currently understood but may relate to within and between species differences in annual population immunity. To investigate a potential immunological basis for this phenomenon, a virus microneutralization (MN) assay was used to detect subtype-specific, neutralizing antibodies to H1 - H12 in serum samples collected from ruddy turnstones and red knots at Delaware Bay from 2012-2015. Neutralizing antibodies were detected in 29.5% of serum samples and all subtypes were represented. The composition of dominate antibodies varied annually but regularly included H6, H9, and H11. Antibodies to H4 and H8 were rarely detected. These results suggest that a low prevalence of HA-specific, neutralizing antibodies may be a driver in annual AIV infection patterns in shorebirds. Furthermore, they demonstrate the utility of a MN assay in detecting specific, functional antibodies in serologic investigations.