戊肝病毒Th表位肽免疫可增强其载体蛋白的体液免疫应答

Priming with an HEV Th Epitope Can Improve the Humoral Immunogenicity of Its Native Protein

摘要:

戊型肝炎病毒衣壳蛋白内包含一个强H-2^d限制性Th表位P34。以该表位肽免疫BALB/c鼠，其脾细胞能够在体外识别重组戊型肝炎病毒衣壳蛋白，剔除实验表明应答细胞几乎完全是CD4⁺ T细胞，证明P34表位肽能有效诱导产生特异性Th细胞。以P34肽初免小鼠，再以包含该表位的重组戊型肝炎病毒抗原（E2）免疫，结果表明，10μg、 20μg E2免疫组在免疫后第1周即有部分小鼠产生抗体，到第3周所有小鼠均能够产生抗体；而对照肽P18初免的小鼠，以20μg E2加强免疫亦无法诱导小鼠产生抗体。这表明，Th表位肽P34初免诱导产生的Th细胞能够有效促进小鼠对携带该表位的载体蛋白的体液免疫应答。

Abstract:

A dominant H-2^d restricted Th epitope P34 was found to be contained in recombinant particulate hepatitis E virus (HEV) vaccine HEV 239. In this paper, the cellular immune response induced in P34 immunized BALB/c mice were studied and the priming effect of P34 was characterized. Groups of BALB/c mice were subcutaneously (s.c.) immunized with P34, splenocytes were then stimulated with P34 and HEV 239 protein, cellular immune response was assayed by IFN-γ-ELISPOT, flow cytometry and T cell proliferation experiments. Results showed that P34 immunized BALB/c splenocytes responsed to P34 and HEV 239 protein stimulation in IFN-γ-ELISPOT, flow cytometry and T cell proliferation experiments. After depletion of the CD4⁺ T cells from the immunized splenocytes by magnetic separation, the response decreased to the background level while almost no influence was observed after CD8⁺ T cells depletion which showed that the cells responsible for IFN-γ secretion were mainly CD4⁺ T cells. Then mice were primed with P34 and boosted with its vector protein, E2, the E2 specific antibody titer were assayed. Results showed that after P34 priming, some of the 10μg, 20μg E2 boosted mice could develop anti-E2 antibody 1 week later and all the mice had detectable antibody 3 weeks after boosting. In the control peptide P18 priming group, even after boosting with 20μg E2, anti-E2 antibody couldn't be detected until the end of this experiment. The results showed that priming with P34 epitope could increase the immunogenicity of its vector protein, E2, in BALB/c mice.