Analysis of immunoprotectivity of the recombinant OmpA of Rickettsia heilongjiangensis.

A truncated gene ompA was amplified from Rickettsia heilongjiangensis isolated in China and a 56-kDa truncated OmpA protein was expressed in E. coli cells transformed with the ompA-recombined expression plasmid. High levels of serum antibodies to R. heilongjiangensis and proliferation of the splenic cells were found in mice immunized with the truncated OmpA. After challenge with R. heilongjiangensis or R. rickettsii, fever and pathological damages of the guinea pigs immunized with the truncated OmpA were significantly slighter as compared with those of nonimmunized guinea pigs. These results suggest that the truncated OmpA of R. heilongjiangii is immunogenic for effectively inducing humoral and cell-mediated immune responses against homologous and heterologous species in the spotted fever group.