Sequential immunization with domain Ⅲ of dengue envelope proteins induces immune responses against dengue virus / 中华微生物学和免疫学杂志

ABSTRACT

Objective To investigate whether a novel sequential immunization strategy was more superior to the traditional immunization strategy in eliciting immune responses by using domainⅢof dengue envelope proteins (EDⅢs) as immunogens. Methods EDⅢ subunit proteins of four serotypes of dengue viruses (DENVs) were expressed in a baculovirus expression system. SDS-PAGE and Western blot were performed to analyze the purity and specificity of purified recombinant proteins, respectively. In order to evaluate the immunogenicity of EDⅢ-based immunization strategies, female BALB/c mice were subcutane-ously immunized with PBS,tetravalent mixture of four EDⅢrecombinant proteins,or the four EDⅢproteins sequentially for four times with two weeks interval between each immunization. Two-week after the final im-munization,splenocytes were isolated and analyzed by ELISPOT assay to evaluate T cell responses and serum samples were collected for plaque reduction neutralization test(PRNT). Results Both immunization strate-gies of sequential EDⅢproteins and tetravalent EDⅢproteins could elicit stronger antigen-specific Th2(IL-4) cell responses in immunized mice than PBS did and the former was superior to the latter. Only the se-quential immunization strategy could induce Th2 cell responses in immunized mice against peptide segments of DENV2 EDⅢ. Tetravalent EDⅢ proteins performed better than the sequential immunization strategy in inducing higher levels of neutralizing antibodies against DENV-1,DENV-2 and DENV-3,while both immu-nization strategies failed to generate neutralizing antibodies against DENV-4. Conclusion Sequential immu-nization with DENV EDⅢ proteins induced stronger T cell responses, but weaker neutralizing antibody re-sponses against DENV than tetravalent EDⅢ proteins did.