弓形虫和乙型肝炎病毒混合核酸疫苗的研究Ⅲ.pcDNA3-HBsAg-GRA1免疫小鼠的保护性观察

Cocktail DNA vaccine against Toxoplasma gondii and hepatitis B virus infections: Ⅲ.Observation on protective immunity induced by plasmid pcDNA3-HBsAg-GRA1 injection in mice

目的观察重组质粒pcDNA3HBsAgGRA1DNA接种诱导的保护性免疫应答。方法质粒DNA免疫BALB/c小鼠;ELISA法检测GRA1、HBsAg抗体及亚类水平;提取各免疫组小鼠肌肉组织DNA进行PCR检测;弓形虫RH强毒株攻击感染各免疫组小鼠。结果经pcDNA3HBsAgGRA1免疫组小鼠产生抗GRA1和HBsAg抗体,且抗GRA1的抗体水平明显高于GRA1单独和GRA1与HBsAg混合免疫组。弓形虫RH强毒株攻击感染pcDNA3HBsAgGRA1免疫组小鼠,其存活时间明显长于其他各组,结果提示HBsAg可能起免疫佐剂作用。结论将GRA1与HBsAg融合明显增强了GRA1的免疫原性和保护性。

To observe the immune response of mice induced by plasmid pcDNA3-HBsAg-GRA1 DNA. BALB/c mice were immunized with the recombinant eukaryotic expression plasmid pcDNA3-HBsAg-GRA1 intramuscularly.And the specific antibodies and their subtypes against GRA1 and HBsAg were measured. Antibody induction of Balb/c mice was analysed and compared after injection with plasmids encoding the complete GRA1 and HBsAg alone,GRA1 and HBsAg combination, and GRA1-HBsAg fusion respectively. DNA from mouse muscle tissue was isolated and detected by PCR. The vaccinated mice were also challenged with T.gondii RH strain tachyzoites and the survival time of the mice was monitored.It was shown that DNA vaccination with the chimeric HBsAg-GRA1 plasmid elicited high humoral responses against GRA1. In all mice immunized with pcDNA3-HBsAg-GRA1, pcDNA3-HBsAg, pcDNA3-GRA1 or co-injection of pcDNA3-HBsAg+pcDNA3-GRA1,showed a predominant Th1-specific response and the value of IgG2a/IgG1>1 was observed. Genes coding for GRA1 or HBsAg were specifically amplified from muscle tissues of immunized mice. The survival time of mice was longer in mice immunized with pcDNA3-HBsAg-GRA1 than in animals immunized with pcDNA3-GRA1 or pcDNA3-GRA1+pcDNA3-HBsAg after challenged with T.gondii RH strain tachyzoites, suggesting that HBsAg may act as a genetic vaccine adjuvant augmenting the cellular and humoral immune response against the challenge of T.gondii RH tachyzoites. It is concluded that the vaccination of chimeric pcDNA3-HBsAg-GRA1 plasmid DNA increase the protective immune reponse against GRA1 as compared to pcDNA3-GRA1 vaccination.