Induction of antiviral RNA interference by avian coronavirus IBV in PBMCs-Mφ

Infectious bronchitis virus (IBV), a member of the gammacoronavirus family, can easily mutate, resulting in different subtypes of strains. QX and M41, two subtypes of IBV, exhibit distinct characteristics in terms of their pathogenicity and infection site. Immunohistochemistry and qRT–PCR revealed differences in the replication of QX and M41 in different tissues. Interestingly, we found that the viral load of QX steadily increased in “PBMCs-Mφ” chicken macrophages, whereas the opposite phenomenon occurred in the M41 group. We also observed synergistic antiviral effects of interferon and RNA interference (RNAi) on PBMCs-Mφ. Moreover, high-throughput sequencing and vsiRNA analysis revealed only partially detectable vsiRNA (NSP10) in the IBV M41-stimulated group, which explains the above phenomenon. We constructed a PS-vsiRNA plasmid capable of efficiently expressing small RNAs, and the antiviral test results revealed that transfection with PS-M10 significantly reduced the M41 viral load. Moreover, PC-QX-NSP10 and PC-QX-NSP16 overexpression in PBMCs-Mφ showed that the complex of NSP10/NSP16 could effectively reduce the mRNA level of Dicer (an RNAi pathway core enzyme) and increase the viral load, which is a potential viral suppressor of the RNAi (VSR) protein. In summary, for the first time, this study explains the differences between QX and M41 on PBMCs-Mφ from the perspective of vsiRNA in RNAi, which is highly important for the subsequent development of therapeutic IBV vaccines.