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. W localized to the cytoplasm, whereas W 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.