Effect of duck interferon-α and an anti-cap protein polyclonal antibody against duck circovirus.

Duck circovirus (DuCV) is one of the most prevalent viruses in the duck breeding industry, and causes persistent infection and severe immunosuppression. Currently, there is a serious lack of prevention and control measures and no commercial vaccine against DuCV. Therefore, effective antiviral drugs are important for treating DuCV infection. Interferon (IFN) is an important component of antiviral innate immunity, but it remains unclear whether duck IFN-α has a clinical effect against DuCV. Antibody therapy is an important way to treat viral infections. The DuCV structural protein (cap) is immunogenic, and it remains to be determined whether an anti-cap protein antibody can effectively block DuCV infection. In this study, the duck IFN-α gene and the DuCV structural protein cap gene were cloned, expressed and purified in Escherichia coli to prepare duck recombinant IFN-α and the cap protein. Then, rabbits were immunized with the recombinant cap protein to prepare a rabbit polyclonal antibody. This study investigated the antiviral effect of duck recombinant IFN-α and the anti-cap protein antibody and their combined effect on Cherry Valley ducks infected with DuCV. The results showed that the treatment significantly alleviated the clinical symptoms of immune organ atrophy and immunosuppression compared with the control. The histopathological damage of the target organs was alleviated, and replication of DuCV in the immune organs was significantly inhibited. The treatment also reduced the damage caused by DuCV to the liver and immune function, and increased the level of the DuCV antibody in the blood, thereby improving antiviral activity. Notably, the combination of duck IFN-α and the polyclonal antibody completely blocked DuCV infection after 13 days under the experimental conditions, showing a better inhibitory effect on DuCV infection than single treatments. These results showed that duck recombinant IFN-α and the anti-cap protein antibody can be used as antiviral drugs to clinically treat and control DuCV infection, particularly the vertical transmission of the virus in breeding ducks.