[Therapeutic effects and mechanisms of CpG oligodeoxynucleotides in mice infected with Mycobacterium tuberculosis].

OBJECTIVE: To investigate the protective effects and mechanisms of CpG oligodeoxynucleotides (CpG ODN) in mice infected with Mycobacterium tuberculosis. METHODS: Ninety-six female BALB/c mice were randomized into 4 groups, namely CpG ODN treatment (A group), control ODN treatment (B group), infection control (C group) and healthy control (D group) (n = 24 each). A group and B group were treated once with CpG ODN or control ODN (30 microg/mouse) intraperitoneally 2 weeks before infection with Mycobacterium tuberculosis. 1 x 10(6) bacili in a volume of 300 microl saline was injected into the tail vein of mice from A group, B group and C group. Twelve mice from each group were sacrificed at 3 weeks postinfection. Pathologic changes in lung tissues were observed. The expression of Toll-like receptor 9 (TLR9) mRNA and cytokine mRNA was detected by RT-PCR. The numbers of viable bacteria in lung and spleen were counted. The rest 12 mice from each group were monitored for 60 days to observe the mortality. RESULTS: CpG ODN was shown to increase the survival time of mice infected with Mycobacterium tuberculosis. The body weights of mice from A group [(20.37 +/- 1.12) g] were higher than those of B group [(17.50 +/- 0.62) g] and C group [(17.15 +/- 0.97) g, P < 0.01]. The lung weights of mice from A group [(0.25 +/- 0.02) g] were similar to those of B group [(0.27 +/- 0.34) g, P > 0.05], but less than those of C group [(0.28 +/- 0.26) g, P < 0.01]. The spleens of mice from A group [(0.63 +/- 0.37) g] were larger than those of B group [(0.39 +/- 0.05) g] and C group [(0.38 +/- 0.02) g, P < 0.01]. The inflammation in lung tissue of mice from A group was less than that of B group and C group. There was no mycobacterial outgrowth in lungs and spleens of mice from A group. The expression of TLR9 mRNA in lungs and spleens of mice from A group (0.61 +/- 0.29 and 0.72 +/- 0.48) was similar to that in B group (0.58 +/- 0.35 and 0.64 +/- 0.28) and C group (0.60 +/- 0.32 and 0.65 +/- 0.31, P > 0.05), but higher than that in D group (0.11 +/- 0.08 and 0.26 +/- 0.22, P < 0.01). CpG ODN did not affect the expression of TLR9 mRNA. The expression of IFN-gamma mRNA in lungs and spleens of mice from A group (0.44 +/- 0.07 and 0.76 +/- 0.09) was higher than that in B group (0.19 +/- 0.05 and 0.22 +/- 0.05) and C group (0.16 +/- 0.04 and 0.18 +/- 0.08, P < 0.01). The expression of IL-6 mRNA in lungs and spleens of mice from A group (1.56 +/- 0.29 and 8.21 +/- 0.82) was higher than that in B group (0.86 +/- 0.55 and 0.16 +/- 0.09) and C group (0.78 +/- 0.21 and 0.06 +/- 0.04, P < 0.01). The expression of IL-4 mRNA in lungs and spleens of mice from A group (0.18 +/- 0.05 and 0.06 +/- 0.02) was lower than that in B group (0.31 +/- 0.06 and 1.22 +/- 0.01) and C group (0.35 +/- 0.04 and 1.31 +/- 0.31, P < 0.01). The expression of IL-10 mRNA in spleens of mice from A group (0.05 +/- 0.02) was lower than that in B group (0.57 +/- 0.09) and C group (0.65 +/- 0.15, P < 0.01). CONCLUSION: CpG ODN could increase the immunity of mice against tuberculosis through up-regulation of Th1 immunity and down-regulation of Th2 immunity.