Genomic characterization of two duck-origin picornaviruses with seven putative 2A peptides.

INTRODUCTION

The Picornaviridae family is a large group of viruses comprising 68 genera. Duck-origin picornaviruses are categorized into four genera, however, the taxonomic status of some recently identified strains remains to be determined.

METHODS

In this study, two virus strains isolated from breeding ducks experiencing reduced egg production were identified and characterized through viral metagenomic analysis.

RESULTS

Two viral strains (NC0246 and PX0394) exhibiting the typical picornavirus-like genomic structure were identified and characterized. Notably, both strains exhibit extended 2A sequences that each possesses seven distinct 2A polypeptides considered rare in Picornaviridae family. Specifically, NC0246 exhibits a deletion of 73 amino acids (aa) in the region corresponding to 2A4-2A5 when compared to PX0394 indicating the genetic diversity of picornaviruses. Homology analysis revealed that the P1 region of NC0246 was most closely related to duck aalivirus A1, with aa identity of 37.37%. Conversely, the P1 region of PX0394 was most closely related to duck egg-reducing syndrome virus (DERSV), with aa identity of 64.44%. Furthermore, the 2C and 3D proteins of NC0246 and PX0394 was most closely related to DERSV. Phylogenetic analyses indicate that NC0246 and PX0394 form a sister clade to DERSV and duck aalivirus A1 and display marked heterogeneity in the P1 protein. While NC0246 and PX0394 branch nearest to DERSV and duck aalivirus A1, duck hepatitis A virus types 1 and 3, sharing secondary homology, occupy a separate lineage.

CONCLUSION

Two picornaviruses were identified and characterized from breeding ducks that exhibited decreased egg production. Through genomic structure and homology analysis, these viruses were most closely related to DERSV and duck aalivirus A1. NC0246, PX0394, and the previously reported DERSV show a close evolutionary relationship with the genus Aalivirus based on genomic and phylogenetic analyses, suggesting a potential affiliation with this genus.