Quantitative proteomics reveals that dormancy-related proteins mediate the attenuation in mycobacterium strains

Although members of the Mycobacterium tuberculosis complex (MTBC) exhibit high similarity, they are characterized by differences with respect to virulence, immune response, and transmissibility. To understand the virulence of these bacteria and identify potential novel therapeutic targets, we systemically investigated the total cell protein contents of virulent H37Rv, attenuated H37Ra, and avirulent M. bovis BCG vaccine strains at the log and stationary phases, based on tandem mass tag (TMT) quantitative proteomics. Data analysis revealed that we obtained deep-coverage protein identification and high quantification. Although 272 genetic variations were reported in H37Ra and H37Rv, they showed very little expression difference in log and stationary phase. Quantitative comparison revealed H37Ra and H37Rv had significantly dysregulation in log phase (227) compared with stationary phase (61). While BCG and H37Rv, and BCG and H37Ra showed notable differences in stationary phase (1171 and 1124) with respect to log phase (381 and 414). In the log phase, similar patterns of protein abundance were observed between H37Ra and BCG, whereas a more similar expression pattern was observed between H37Rv and H37Ra in the stationary phase. Bioinformatic analysis revealed that the upregulated proteins detected for H37Rv and H37Ra in log phase were virulence-related factors. In both log and stationary phases, the dysregulated proteins detected for BCG, which have also been identified as M. tuberculosis response proteins under dormancy conditions. We accordingly describe the proteomic profiles of H37Rv, H37Ra, and BCG, which we believe will potentially provide a better understanding of H37Rv pathogenesis, H37Ra attenuation, and BCG immuno protection.

Automated summary

Different strains of Mycobacterium tuberculosis complex (MTBC) exhibit high similarity but show differences in virulence, immune response, and transmissibility. Proteomic analysis of virulent H37Rv, attenuated H37Ra, and avirulent M. bovis BCG vaccine strains revealed minimal expression differences between H37Ra and H37Rv in different growth phases, while significant dysregulation was observed in H37Ra and H37Rv during log phase. Differences were also noted between BCG and H37Rv, as well as BCG and H37Ra during the stationary phase. Protein abundance patterns were similar between H37Ra and BCG, and between H37Rv and H37Ra in different growth phases. Upregulated proteins in H37Rv and H37Ra during log phase were found to be virulence-related, while dysregulated proteins in BCG were identified as M. tuberculosis response proteins under dormancy conditions. This study provides insights into the pathogenesis of H37Rv, attenuation of H37Ra, and immune protection of BCG.