An in vitro infection model system to study proteins expressed during interaction of mycobacterium with murine macrophages

Resurgence of mycobacterial diseases particularly tuberculosis has caused a renewed interest to unravel the strategies employed by mycobacteria for intracellular survival. In spite of advancement in mycobacterial research, our knowledge about genes and their corresponding functional proteins involved during the interaction of mycobacterium with host’s macrophages is fragmentary. This study pertains to development of a suitable in vitro model using murine macrophages and Mycobacterium bovis BCG to study proteins expressed during macrophage-myco bacterium interactions. Peritoneal macrophages from BALB/c mice were infected with M. bovis BCG and intracellular replication was assessed by {3H} thymi- dine uptake assay which was maximal when macrophage to mycobacterium ratio was 1:10. SDS-PAGE was employed to study the proteins expressed and selected proteins were subjected to mass spectrometry. Seven proteins found to be upregulated during macrophage-mycobacterium interaction were identified by MALDI-TOF. The results indicate that the present in vitro infection model was able to support the growth of M. bovis BCG in murine macrophages and is an ideal model to determine the pattern of functions of gene expression during the interaction of mycobacterium with macrophages. The differentially expressed proteins will help in understanding the mycobacterial molecular basis of adaptation to intracellular macrophage environment.