Molecular Characterization of Avipox Viruses Circulating in Assam, India

Abstract

The Avipoxvirus infection continues to be a serious threat to the poultry production and avain biodiversity across the globe. The present study was undertaken to characterize Avipoxvirus isolates from fowl, pigeon, and duck origin from Assam, India, and to assess their genetic stability following adaptation in chicken embryo fibroblast (CEF) cell culture. The isolates were revived through chorioallantoic membrane (CAM) route in embryonated chicken eggs and confirmed by PCR of the highly conserved 4b gene. Nucleotide and amino acid differences between revived and CEF-adapted isolates were determined through sequencing and bioinformatic analysis. The comparison of the nucleotide sequences of isolates by pair wise analysis showed that there was high identity between the corresponding isolates suggesting a low variation in the cell culture adaptation process. Multiple alignment of deduced amino acid sequences revealed few substitutions with more being diverged in duck and pigeon isolates than the reference fowl pox strain (HP444). Host-associated clustering of isolates was indicated by phylogenetic analysis. The results have shown that the Avipoxvirus isolates are relatively stable in terms of genetic changes over a short period of in vitro adaptation but also host-specific differences exist. On-going genomic monitoring and prolonged passage experiments are required in order to be in a better position to comprehend the viral evolution and host adaptation.