Immunotherapeutic Effects of BCG-Polysaccharide Nucleic Acid on Murine with Pulmnary Tuberculosis

Purpose To study the immunotherapeutic effects and its mechanism of BCG-Polysaccharide Nucleic Acid (BCG-PSN) on murine infection with mycobacterium tuberculosis. Methods Forty-eight BALB/c mice were randomized into 2 groups,A group treated with BCG-PSN,B group treated with saline (n=24). 1×106 bacili in a volume of 300 μL saline were injected into the tail vein of mice in A and B groups.The mice from both group were treated with BCG-PSN (10 mg/kg once a day for 7 days)and saline (10 mL/kg once a day for 7 days) intraperitoneally respectively 1 week postinfection.The animals were sacrificed at 3 weeks and 4 weeks postinfection respectively.The weight of body,lung and spleen were measured.Then the lung and spleen of mice were fixed in 10% buffered formalin,paraffin embedded,and processed for histological examination. The numbers of viable bacteria in lung and spleen were counted. The expression of IFN-γ mRNA,IL-10 mRNA and IL-4 mRNA in lung and spleens were detected by real-time PCR method. Results At 4 weeks postinfection,the body weight of mice in A group was higher than that in B group,the lung weight of mice in A group was lower than that in B group,the spleen weight of mice in A group was higher than that in B group. At 3 weeks and 4 weeks postinfection,the numbers of viable bacteria in lungs and spleens of mice from A group were lower than that in B group respectively.At 3 weeks and 4 weeks postinfection,the expression of IFN-γ mRNA in lung tissue of mice from A group was similar to that in B group,the expression of IL-10 mRNA and IL-4 mRNA were less than those in B group respectively. At 3 weeks postinfection,the expression of IFN-γ mRNA in spleen tissue of mice from A group was similar to that in B group,while at 4 weeks postinfection,the expression of IFN-γ mRNA in spleen tissue of mice from A group was more than that in B group. At 3 weeks and 4 weeks postinfection,the expression of IL-10 mRNA and IL-4 mRNA were less than those in B group respectively. Conclusions BCG-PSN could improve host defence against mycobacterium tuberculosis and reduce mycobacterial outgrowth during tuberculosis and were associated with a decrease in inflammation in lung tissue by activating the Th1 response.