Divergent Effects of Circoviridae Capsid Proteins on Type I Interferon Signaling

Viruses in the Circoviridae family can infect both mammals and birds. Porcine circovirus type 2 (PCV2) significantly affects the livestock industry by causing porcine circovirus-associated diseases, such as postweaning multisystem wasting syndrome, respiratory disease complex, and dermatitis nephropathy syndrome. Additionally, beak and feather disease virus in parrots, canine circovirus in dogs, and columbid circovirus (pigeon circovirus) in racing pigeons induce immunosuppression, followed by secondary infections in these hosts. Although the PCV2 capsid protein has been demonstrated to inhibit type I interferon (IFN) signaling, the molecular mechanisms of Circoviridae-induced immunosuppression are largely unknown. In this study, we examined whether these functions are conserved across Circoviridae capsid proteins. Our results illustrated that although the nuclear localization of capsid proteins is conserved, their effects on IFN-β signaling vary by species, revealing the diverse roles of Circoviridae capsid proteins in modulating immune responses.