Genetic characterization of chicken anemia viruses newly isolated from diseased chicks in Japan in 2020

Abstract

In this study, a total of nine chicken samples obtained from two broiler flocks in Oita and Tottori prefectures in 2020 were examined for Chicken anemia virus (CAV) infection. The samples were collected from clinically suspected flocks and diseased chickens. The CAV genome was detected in all nine samples tested by real-time PCR. Phylogenetic analyses and sequence comparisons of the full-length VP1 gene sequences indicated that all the Japanese CAV strains obtained in this study formed a similar cluster of genotype III and shared high nucleotide (99.62%-100%) identity. The current Japanese CAV strains were closely related to Chinese CAV strains but not related to vaccine strains. One positive selection site of VP1 was detected among the Japanese CAV strains.

Chicken anemia virus VP1 negatively regulates type I interferon via targeting interferon regulatory factor 7 of the DNA-sensing pathway

“…Furthermore, we confirmed that VP1 interacted with IRF7 by selectively binding to IRF7 with a DBD deletion (aa 143–492) which was reported to be essential for the dimerization and phosphorylation of IRF7 ( Wang et al., 2020 ). In our study, we found for the first time that CAV VP1 is a potent inhibitor of the crash-STING pathway that binds to IRF7 and disrupts IRF7 dimerization, which ultimately can reduce IFN-β production and weaken the innate antiviral response ( Christensen et al., 2016 ; Dong et al., 2022 ) ( Figure 7 ).

Figure 7 Schematic of the inhibitory effect of CAV VP1 on the cGAS-STING pathway.

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“…Chicken anemia virus ( CAV ), a nonenveloped small ssDNA virus, is a ubiquitous avian pathogen that causes an immunosuppressive infectious anemia disease. This virus represses the immune responses of the host and thus, infected chickens are more susceptible to other pathogens ( Wani et al., 2006 ; Schat, 2009 ; Dong et al., 2022 ). As a result, great economic loss has been caused by CAV in the poultry industry globally.…”