Immuno-protection efficacy of Mtb8.4 gene vaccine with signal peptide against TB in mice / 基础医学与临床

ABSTRACT

Objecticve To study the immunogenicity and protective effecacy of MTB8.4 with signal peptide gene vaccine against TB in mice.Methods C57BL/6N!mice were vaccinated with MTB8.4 with signal peptide(MS) gene vaccine three times at 3 weeks intervals.Four weeks after the final vaccination,three mice were sacrificed to assess cytokine response and CTL induction and the other five mice were challenged intravenously in a lateral tail vein with(1?10~(6)) CFU of virulent M.tuberculosis H37Rv.Spleen and the left lung were harvested from each mouse 4 weeks after(infection) and homogenized in sterile saline.Serial dilutions of organ homogenates were plated on (L-J agar) and incubated(37 ℃) until colonies were visible 4 weeks later. Protective efficacy in each experiment was expressed as(reduced) CFU and was compared with the negative control group.The right lung was obtained from each mouse and(inflated) with and stored in 10% formalin saline immediately.Tissues were embedded in paraffin,sec-tioned(and stained) with hematoxylin and eosin.Results MS gene vaccine induced the secretion of more of Th1 cytokines(IFN-?and IL-2),but not IL-4 and enhanced CTL activity while BCG induced the secretion of both types of cytokines(IFN-?,IL-2 and IL-4).Mice immunized with MS gene vaccine had fewer and smaller tubercles than those immunized with PBS or control plasmid DNA,but had more tubercles than the mice inoculated with BCG.Virable bacterial counts in the lungs and spleens of mice receiving DNA encoding MS were reduced as compared with mice injected with PBS or control plasmid DNA,while increased as compared with mice immunized with BCG.Conclusion MS gene vaccine can induce secretion of Th1 cytokines and the higher protective efficacy against TB in mice.