Preliminary Study On Immunogenicity Of Respiratory Syncytial Virus F2 Recombinant Fusion Protein

Respiratory syncytial virus is the leading course of serious lower respiratory tract infections in infants, causes great threat to baby health. Previous vaccins have not been successful due to a type-2 immune response and immunopathological damage in human. Here, we expressed a fusion protein ESAT-6-F2 in E. coli and immunized with LT to elicit Thl/Th2 balance immune responses and respiratory mucosal protective antibody.Genes of F2 and ESAT-6 were fused by PCR. ESAT-6-F2 and ESAT-6 protein were expressed in E.coli in form of inclusion bodies with molecular weight 21kD and lOkD respectively. Western-blotting analysis proved the expressed proteins to be ESAT-6-F2 and ESAT-6. The expressed fusion protein were purified by Ni-NTA affinity chromatography under denaturing conditions and refolded by dialyzing in PBS buffer with 90% purity.BALB/c mice were divided into 5 groups with 5 mice per group, including PBS group; LT group; ESAT-6 group; ESAT-6-F2 group and ESAT-6-F2+LT group. The results showed that the total antibody titer of ES AT-6-F2+LT group、ESAT-6-F2 group and ESAT-6 groups were obvious higher than PBS group, it means that they all had a good immunogenicity, but appeared type-2 immune response. LT adjuvants weakened immune polarization phenomenon of ESAT-6-F2 protein.Two weeks following final immunization, mice were challenged with 5 X 105 pfu RSV for three days. The results suggested that after RSV infected, mice weight lost remarkably, but ESAT-6-F2+LT group had significant difference with PBS group, it means that formulation with ESAT-6-F2 and LT enhanced its protection. ESAT-6 group also had a serious Th2-type immune responses and pulmonary disease. Instead, ESAT-6-F2+LT induced a balanced immune responses and a little lung pathological, resulted in a better immune safety.In this paper, we evaluated immunogenicity of ESAT-6-F2, provides reference data for development of RSV vaccine.