evidence for enhancement of avian influenza virus H9N2 virulence by modulation of its hemagglutinin (HA) antigen function and stability during co-infection with infectious bronchitis virus in chickens.

Unlabelled: In the last few decades, frequent incidences of avian influenza (AI) H9N2 outbreaks have caused high mortality in poultry farms resulting in colossal economic losses in several countries. In Egypt, the co-infection of H9N2 with the infectious bronchitis virus (IBV) has been observed extensively during these outbreaks. However, the pathogenicity of H9N2 in these outbreaks remained controversial. The current study reports isolation and characterization of the H9N2 virus recovered from a concurrent IBV infected broiler chicken flock in Egypt during 2011. The genomic RNA was subjected to RT-PCR amplification followed by sequencing and analysis. The deduced amino acid sequences of the eight segments of the current study H9N2 isolate were compared with those of Egyptian H9N2 viruses isolated from healthy and diseased chicken flocks from 2011 to 2013. In the phylogenetic analysis, the current study isolate was found to be closely related to the other Egyptian H9N2 viruses. Notably, no particular molecular characteristic difference was noticed among all the Egyptian H9N2 isolates from apparently healthy, diseased or co-infected with IBV chicken flocks. Nevertheless, in-silico analysis, we noted modulation of stability and motifs structure of Hemagglutinin (HA) antigen among the co-infecting H9N2 AI and the IBV and isolates from the diseased flocks. The findings suggest that the putative factor for enhancement of the H9N2 pathogenicity could be co-infection with other respiratory pathogens such as IBV that might change the HA stability and function.

Supplementary Information: The online version contains supplementary material available at 10.1007/s13337-021-00688-1.