Mapping of antigenic sites on the major inner capsid protein of avian rotavirus using an Escherichia coli expression system.

The cDNA encoding the VP6 gene of avian rotavirus PO-13 strain was inserted into the bacterial expression vector pET-3a. Upon isopropyl-1-thio-beta-D-galactoside induction, the E. coli BL21 (DE3) harboring the vector containing cDNA of the VP6 gene produced an approximately 45-kDa polypeptide, which reacted with rabbit serum against PO-13 strain in Western blotting. To study the antigenic sites on VP6, various deletion mutants were constructed, expressed in E. coli and the reactivity with antigenic site I- and II-specific MAbs analyzed by Western blotting. Site I, which is shared with all group A mammalian and avian rotaviruses except for chicken rotavirus, was found to be located at amino acid positions 45 to 65, and site II, which probably contributes to an authentic group A antigen common to both mammalian and avian rotaviruses, at amino acid positions 134 to 142.