Expression of capsid proteins and non-structural proteins of waterfowl parvoviruses in Escherichia coli and their use in serological assays.

While there are a number of methods available for detection of antibodies against waterfowl parvoviruses, none is able to differentiate responses against the capsid and non-structural proteins. To enable this, the capsid and non-structural proteins of goose parvovirus (GPV) and Muscovy duck parvovirus (MDPV) were expressed in Escherichia coli. These proteins were purified and used as antigens in western blotting assays of antibodies against GPV and MDPV. The results showed that 94.7% of the goose and 90.0% of the duck sera collected from the field contained antibodies against GPV or MDPV. Moreover, these sera could be classified into distinct groups based on differences in patterns of western blot reactivity. These different patterns might indicate different stages in infection. Western blotting assays of sera collected from experimentally infected ducks showed that antibodies against the non-structural protein appeared first after infection, followed by antibodies against the capsid protein. It was concluded that the recombinant capsid and non-structural proteins might serve as useful antigens for assays for antibodies against GPV and MDPV. Moreover, because these assays could discriminate between antibodies against the non-structural protein and those against the capsid protein, they may be useful in differentiating vaccinated from infected birds when recombinant capsid protein is used as the vaccine.