A CTL epitope of respiratory syncytial virus fused with G protein fragment regulates specific immunoresponses / 中国免疫学杂志

ABSTRACT

Objective: To investigate the regulation of respiratory syncytial virus CTL epitope fused with G protein antigen fragment G1 to the specific immunoresponses. Methods: The recombinant plasmid pET-DsbA-G1 or pET-DsbA-G1F/M2 was transferred into E.coli BL21(DE3) and the fusion protein DsbA-G1F/M2 or DsbA-G1 was expressed.The expressing product was induced and purified by affinity chromatography. The two proteins were used to immunized BALB/c mice i.p, respectively. Serum and spleen cells were collected regularly. RSV-specific CTL responses were measured by MTT, IgG and IgG1 and IgG2a antibodies by ELISA, neutralizing antibodies by plaque reduction assay. Results: The recombinant proteins were expressed successfully and the purity was over 90% after purified by affinity chromatography. The protein DsbA-G1F/M2 induced significant RSV-specific CTL responses, while DsbA-G1 without CTL epitope did not induce detctable CTL responses. Strong IgG antibody responses were elicited,indicated by both. IgG1 and IgG2a titers induced by DsbA-G1F/M2, while only IgG1 was induced by DsbA-G1.The ratio of IgG1/IgG2a was downregulated significantly. Both antigens induced high level of neutralizing antibodies, but the latter was a little lower. Conclusion: DsbA-G1F/M2, the fusion protein of a CTL epitope and G protein fragment G1 can induce both cellular immunity and humoral immunity. The activation of CTLs downregulates the ratio of IgG1/IgG2a.The more balanced immunoresponse is advantageous for improving safety of the candidate vaccine.