Expression and characterization of canine distemper virus hemagglutinin protein in suspension mammalian cells.

Hundreds of millions of the domestic dogs worldwide are routinely inoculated with the modified live vaccines for canine distemper virus (CDV) every year. However, the corresponding serological diagnostic and detections are always lacking, thus, there is an urgent demand to establish its unique diagnostic technologies to produce high-quality antigenic biomolecules. In the present study, the ectodomain (et) of CDV hemagglutinin (H) protein was firstly expressed in a soluble and secreted forms by an Expi293F transient transfection system based on its antigenic secondary structure analysis. The yields of CDV H(et) protein was 2.6 g/L with purity over 95 % in supernatant of Expi293F cells. The CDV H(et) protein elicited comparative antibodies levels to the CDV virions in rabbit by ELISA and neutralization test. The purified polyclonal antibodies of immunized with CDV H(et) protein recognized both wild-type and vaccine CDV strains. More importantly, the purified polyclonal antibodies of CDV H(et) protein revealed significantly higher viral neutralizing activity than those from CDV-3 virions, which highlighted that the critical role of CDV H protein to elicit viral specific and protective neutralizing antibodies. Taken together, the CDV H(et) protein produced in mammalian expression systems was high-quality and good immunogenicity, and would be with great potential to serve as a serological diagnostic antigen or a novel CDV subunit vaccine in future.