Immunogenicity of Whole Mycobacterium intracellulare Proteins and Fingding on the Cross-Reactive Proteins between M. intracellulare and M. tuberculosis.

OBJECTIVES: To evaluate the immunogenicity of Mycobacterium intracellulare proteins and determine the cross-reactive proteins between M. intracellulare and M. tuberculosis. METHODS: Protein extracts from M. intracellulare were used to immunize BALB/c mice. The antigens were evaluated using cellular and humoral immunoassays. The common genes between M. intracellular and M. tuberculosis were identified using genome-wide comparative analysis, and cross-reactive proteins were screened using immunoproteome microarrays. RESULTS: Immunization with M. intracellulare proteins induced significantly higher levels of the cytokines interferon-γ (IFN-γ), interleukin-2 (IL-2), interleukin-12 (IL-12), interleukin-6 (IL-6) and immunoglobulins IgG, IgG1, IgM, and IgG2a in mouse serum. Bone marrow-derived macrophages isolated from mice immunized with M. intracellulare antigens displayed significantly lower bacillary loads than those isolated from mice immunized with adjuvants. Whole-genome sequence analysis revealed 396 common genes between M. intracellulare and M. tuberculosis. Microchip hybridization with M. tuberculosis proteins revealed the presence of 478 proteins in the serum of mice immunized with M. intracellulare protein extracts. Sixty common antigens were found using both microchip and genomic comparative analyses. CONCLUSION: This is the advanced study to investigate the immunogenicity of M. intracellulare proteins and the cross-reactive proteins between M. intracellulare and M. tuberculosis. The results revealed the presence of a number of cross-reactive proteins between M. intracellulare and M. tuberculosis. Therefore, this study provides a new way of identifying immunogenic proteins for use in tuberculosis vaccines against both M. intracellulare and M. tuberculosis in future.