Appropriate amount of W protein of avian avulavirus 1 benefits viral replication and W shows strain-dependent subcellular localization.

In order to confirm the existence of W protein in Avian avulavirus 1 (AAvV-1) infected cells, two monoclonal antibodies were prepared. The presence of W protein in cells infected with lentogenic genotype II strain La Sota or velogenic genotype VII strain SG10 was confirmed with immunofluorescence and western blotting assays. WSG10 localized to the cytoplasm, whereas WLa Sota localized to the nucleus. The influence of W protein was investigated in vitro and in vivo with two AAvV-1 strains defective in the W C-terminus. The growth kinetic curves and pathogenicity tests in 3-week-old SPF chickens both showed that the replication abilities of strains with C-terminally deleted W proteins were lower than that of the parental strain. Restoring the appropriate dose of W protein increased the viral titers of these strains. The expression validation and functional exploration of W protein will facilitate our understanding of pathogenic mechanism of AAvV-1.