SESSION TITLE: Chest Infections
SESSION TYPE: Original Investigation Slide
PRESENTED ON: Sunday, October 25, 2015 at 01:30 PM - 03:00 PM
PURPOSE: Tuberculosis remains the greatest bacterial cause of human mortality. An understanding of virulence factors that enable Mycobacterium tuberculosis (M. tb) can inform new strategies, such as targets for species-specific diagnostic assays. To date, the key virulence factors identified for M. tb are not unique to this organism, leaving an important fundamental and translational gap. Considerable similarities have been noted when comparing the genome of M.tb with that of the non-transmissible environmental organism, Mycobacterium kansasii (M.kan), including the conservation of the ESX1 system, responsible for secreting ESAT 6 and CFP 10, hence infection with M. kan can induce a false positive IGRA result. Given the genetic similarity of these species, which contrasts with their relative pathogenicity, we hypothesize that this difference in biology will be explained by variations in protein expression.
METHODS: M. tb and M. kan were grown in parallel, under identical conditions to derive secreted protein and whole cell preparations. Protein extracts were separated by 1D SDS PAGE prior to in-gel trypsin digestion. Peptides were analysed following nano-HPLC separation coupled to on-line mass spectrometry. Proteins were identified by MASCOT matching against an in-house proteome database generated from complete genome sequencing, with quantitation and comparison between strains performed with the Scaffold interface.
RESULTS: More than 1000 proteins were confidently identified in each species. Comparison of the protein repertoires of each species revealed similarities and differences, as well documenting relative abundance of similar proteins between the strains. This resulted in the definition of a smaller group of proteins which were present or increased in abundance only in M. tb, constituting a novel source of candidates for understanding pathogenesis of tuberculosis.
CONCLUSIONS: Comparison of the complete protein repertoires of the human pathogen M. tb, to its largely indolent relative M. kan, was able to map some differences that correlate with the discrepancy in the behaviour of these two species. Further functional characterization is required to assess the causality of these findings.
CLINICAL IMPLICATIONS: Tuberculosis remains a significant respiratory illness and future treatment will require deeper understanding of pathogenesis as well as novel therapeutics. We have defined a small cohort of proteins likely to be significant in disease-causing mechanisms other than the well characterized ESX1 secretion system.
DISCLOSURE: The following authors have nothing to disclose: Megan Rees, Marcel Behr
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