Zinc metalloprotease-1 from Bacillus Calmette-Guerin inhibits the processing of mycobacterial antigen in vivo

Abstract:

Objective：To observe the effect of Zinc metalloprotease-1（Zmp1） from Bacillus Calmette-Guerin（BCG） on processing Mycobacterium tuberculosis antigen PPE68 in mouse in vivo. Methods：BALB/c mice of 6 to 8 weeks were randomly divided into five groups：plasmid pBudCE4.1 control group（n=7），plasmid pBudCE4.1-PPE68p group expressing PPE68 peptide（n=9），plasmid pBudCE4.1-PPE68 group expressing PPE68 antigen（n=9），plasmid pBudCE4.1-PPE68-Zmp1 group co-expressing PPE68 antigen and Zmp1（n=10），and plasmid pBudCE4.1-PPE68p-Zmp1 group co-expressing PPE68 antigen and Zmp1（n=8）. Recombinant Salmonella was constructed through the electrotransformation of these plasmids to attenuated Salmonella strain SL7207. All mice were immunized with corresponding recombinant Salmonella for three weeks via gavage. Mice blood and douche fluid of lung and small in－testine were collected and ELISA was used to analyze the level of IL-12，IFN-γ and secretory IgA（sIgA）. Mice splenocytes were sep－arately cultivated and CCK8 was used to analyze the proliferation of splenic lymphocytes. Results：Compared with those of the PPE68 antigen group，levels of IFN-γ（117.29±16.86，P=0.034），IL-12（40.46±7.11，P=0.004），and lymphocyte stimulation index（SI）（3.30±0.49，P=0.004） were decreased in co-expressing group of PPE68 and Zmp1. Compared with those of the PPE68 peptide group，levels of IFN-γ（132.75±28.40，P=0.070），IL-12（55.43±11.78，P=0.198），and SI（4.70±1.57，P=0.124） were not signifi－cantly decreased in co-expressing group of PPE68 peptide and Zmp1. Conclusion：Zmp1 from BCG may have effects on the process－ing of Mycobacterium tuberculosis antigen PPE68 in mouse in vivo，which may be an important factor influencing BCG immune.