耻垢分枝杆菌与卡介苗作为载体在鼠结核病治疗中的作用比较

Comparative Study on Roles of Mycobacterium smegmatis and BCG as Vectors in Treatment of Tuberculosis in Mouse Model

目的比较耻垢分枝杆菌(MS)与卡介苗(BCG)作为载体在鼠结核病治疗中的作用。方法分别以不同剂量的MS和BCG免疫BALB/c小鼠,观察二者的致病作用。以结核分枝杆菌H37Rv感染BALB/c小鼠4周后,分别用生理盐水、MS、GLS/IL-12、重组MS、BCG及GLS/IL-12重组BCG治疗6次,于第6次治疗后7d处死小鼠,检测肺、脾荷菌量、血清IL-12和IFN-γ水平、脾淋巴细胞IFN-γ和TNF-α的水平及肺、脾组织中颗粒溶素表达,并观察小鼠肺组织病理改变。结果重组MS和重组BCG组器官荷菌量明显低于MS和BCG组;重组MS和重组BCG组血清IL-12和IFN-γ水平明显高于MS和BCG组,MS和BCG组明显高于生理盐水组;重组MS和重组BCG组脾淋巴细胞IFN-γ和TNF-α的水平明显高于其他组;MS与BCG组比较,重组MS与重组BCG比较,荷菌量、病理变化、肺、脾中的IL-12和IFN-γ水平差异均无显著意义;淋巴细胞中的IFN-γ和TNF-α水平,MS与BCG组差异有显著意义,而重组MS与重组BCG组差异无显著意义;重组MS和重组BCG组在肺、脾中均有颗粒溶素表达;MS所致病变比相同剂量BCG轻。结论MS与BCG一样,可将要表达的基因靶向递送到相应的组织,并诱导特异性细胞免疫,同时其在体内的副作用低于BCG,因此可作为良好的有机载体。

Objective To explore the roles of Mycobacterium smegmatis （MS） and BCG as vectors in treatment of tuberculosis in mouse model. Methods Infect BALB/c mice with MS and BCG at various dosages and observe the pathogenic effects. Divide the BALB/c mice 4 weeks after infection with Mycobacterium tuberculosis H37Rv strain into 5 groups and treat with physiological saline, MS, granulysin （GLS）/IL-12 recombinant with MS （recombinant MS）, BCG and GLS/IL-12 recombinant with BCG （recombinant BCG） for 6 times respectively, Kill the mice 7 d after the 6th treatment and determine the bacterial loading quantity and expression level of GLS in lung and spleen, IL-12 and IFN-γ in sera as well as IFN-γ and TNF-α in splenic lymphocytes, and observe the pathological change of lung tissue. Results The pathological change caused by BCG was severer than that by MS at the same dosage. The bacterial loading quantities in lungs and spleens of mice in recombinant MS and recombinant BCG groups were signifi- cantly lower, while serum IL-12 and IFN-γ levels were significantly higher than those in MS and BCG groups. However, the serum IL-12 and IFN-γlevels of mice in MS and BCG groups were significantly higher than those in physiological saline group. The IFN-γ and TNF-α levels in splenic lymphocytes of mice in recombinant MS and recombinant BCG groups were significantly higher than those in other groups. No significant difference were observed in the bacterial loading quantity and IL-12 and IFN-γ levels in lung and spleen as well as pathological change in lung of mice in MS and BCG groups, or in recombinant MS and BCG groups. The IFN-γand TNF-α levels in splenic lymphocytes of mice showed significant difference in MS and BCG groups, while showed no significant difference in recombinant MS and recombinant BCG groups. The expression of GLS was observed in the lung and spleen of mice in recombinant MS and recombinant BCG groups. Conclusion Like BCG, MS could deliver the gene to be expressed to the target tissue and induce specific cellular immunity. However, the adverse reaction induced by MS was mild as compared with that by BCG. It proved that MS might be used as a satisfactory organic vector.