Abstract
When avian influenza viruses (AIVs) are transmitted from their reservoir hosts (wild waterfowl and shorebirds) to domestic bird species, they undergo genetic changes that have been linked to higher virulence and broader host range. Common genetic AIV modifications in viral proteins of poultry isolates are deletions in the stalk region of the neuraminidase (NA) and additions of glycosylation sites on the hemagglutinin (HA). Even though these NA deletion mutations occur in several AIV subtypes, they have not been analyzed comprehensively. In this study, 4,920 NA nucleotide sequences, 5,596 HA nucleotide and 4,702 HA amino acid sequences were analyzed to elucidate the widespread emergence of NA stalk deletions in gallinaceous hosts, the genetic polymorphism of the deletion patterns and association between the stalk deletions in NA and amino acid variants in HA. Forty-seven different NA stalk deletion patterns were identified in six NA subtypes, N1–N3 and N5–N7. An analysis that controlled for phylogenetic dependence due to shared ancestry showed that NA stalk deletions are statistically correlated with gallinaceous hosts and certain amino acid features on the HA protein. Those HA features included five glycosylation sites, one insertion and one deletion. The correlations between NA stalk deletions and HA features are HA-NA-subtype-specific. Our results demonstrate that stalk deletions in the NA proteins of AIV are relatively common. Understanding the NA stalk deletion and related HA features may be important for vaccine and drug development and could be useful in establishing effective early detection and warning systems for the poultry industry.
Highlights
Wild aquatic birds, such as Anseriformes and Charadriiformes are reservoir hosts for avian influenza viruses (AIV) [1,2,3]
The only length polymorphism that we did not count as stalk deletion pattern was a Serine at position 40 among N5 sequences that was present in all North American isolates and with no counterpart amino acid in any Eurasian isolate
Forty-seven different NA stalk deletion (SDNA) patterns were identified in six NA subtypes, N1–N3 and N5–N7
Summary
Wild aquatic birds, such as Anseriformes (ducks and swans) and Charadriiformes (gulls and shorebirds) are reservoir hosts for avian influenza viruses (AIV) [1,2,3]. One observation that has been reported in viruses isolated during separate poultry outbreaks is a deletion in the stalk region of the NA [18,19,20,21]. SDNA are often accompanied by observations of variants on the HA protein, such as the addition of glycosylation sites, presumably to maintain functional balance between HA and NA which is necessary for viral infectivity [30,31,32]. These HA variants could further influence viral antigenicity, virulence and pathogenicity [32,33]
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have