Presentation of neutralizing epitopes by engineered rotavirus VP7's expressed by recombinant vaccinia viruses

Previous studies showed that a calcium-dependent neutralization domain forms on the rotavirus glycoprotein VP7 during assembly into particles. Here, we demonstrate that expressed, recombinant VP7 is capable of forming this neutralization domain in the absence of other rotavirus proteins, but that the domain is unstable. High calcium environments, incorporation into particles, and binding of neutralizing antibodies stabilize the neutralization domain on expressed VP7. A chimeric, cell surface-anchored molecule, VP7sc, has an enhanced ability to react with neutralizing antibodies. This may explain why immunization of mice with expressed native VP7 has had limited success while immunization with VP7sc efficiently induced neutralizing antibodies and passively protected pups from diarrhea. A model of VP7 folding consistent with these results is presented.