可表达结核分枝杆菌融合蛋白Ag85A-ESAT-6重组卡介苗免疫保护作用研究

Evaluation of protective efficacy conferred by a recombinant Mycobacterium bovis BCG strain expressing Ag85A-ESAT-6 fusion protein of Mycobacterium tuberculosis

目的以Balb/c小鼠为动物模型,评价重组卡介苗新型结核病疫苗rBCG-Ag85A-ESAT-6(rBC-AE)的免疫保护效应。方法将重组卡介苗rBCG-AE免疫动物10周后,结核分枝杆菌H37Rv尾静脉注射进行感染攻击,分别于感染攻击后3、6和9周,通过观察肺组织大体病变、脾肺组织细菌载荷量计数、肺组织抗酸染色、HE染色结合肺组织病理变化,综合评价该疫苗诱导的免疫保护作用。结果 rBCG-AE组脾肺组织细菌载荷量在各时间点均显著低于阴性对照组(PBST组,P<0.01),但明显高于卡介苗(BCG)组(P<0.01)。rBCG-AE组肺组织病变在感染攻击后6～9周逐渐改善,但其病理打分在各时间点均明显高于BCG组(P<0.01)。各组肺组织大体病变与组织病理打分变化相似。结论重组卡介苗rBCG-AE仅能诱导产生与BCG疫苗相当甚至较低的免疫保护作用。

We previously constructed a recombinant BCG strain（rBCG-AE） that could express a fusion protein of Ag85A-ESAT-6,and the study suggested that the rBCG vaccine was able to induce higher titer of antibody and elicit more long-lived and stronger Th1 type cellular immune responses than its parental BCG,or rBCG-A strain（expressing Ag85A）,or rBCG-E strain（expressing ESAT-6）.In this research,we aim to further investigate its protective efficacy against Mycobacterium tuberculosis（MTB） H37Rv infection in Balb/c mice through evaluation of organ bacterial loads,lung histopathology and acid-fast stain,using conventional BCG,rBCG-A and rBCG-E as controls.Results showed that the bacterial counts in tissues（including spleen and lung tissues） from the mice immunized with rBCG-AE were significantly lower than that in control group（PBST group）,but higher than that in BCG group from 3rd week to 9th week after challenge infection.The pathological changes in lung tissues from rBCG-AE group were gradually improved from 6th to 9th weeks after infection with MTB H37Rv,but the score of pathological changes was obviously higher than that in BCG group.Meanwhile,the result of general pathological changes of lung was consistent with lung pathological changes.The results illustrated that rBCG-AE could only confer similar and even lower protective efficacy against MTB H37Rv infection compared with BCG vaccine