title: Proteomic analysis of purified protein derivative of Mycobacterium tuberculosis.
abstract: BACKGROUND
  Purified protein derivative (PPD) has been used for more than half a century as an antigen for the diagnosis of tuberculosis infection based on delayed type hypersensitivity. Although designated as "purified," in reality, the composition of PPD is highly complex and remains ill-defined. In this report, high resolution mass spectrometry was applied to understand the complexity of its constituent components. A comparative proteomic analysis of various PPD preparations and their functional characterization is likely to help in short-listing the relevant antigens required to prepare a less complex and more potent reagent for diagnostic purposes.
  
  
  RESULTS
  Proteomic analysis of Connaught Tuberculin 68 (PPD-CT68), a tuberculin preparation generated from M. tuberculosis, was carried out in this study. PPD-CT68 is the protein component of a commercially available tuberculin preparation, Tubersol, which is used for tuberculin skin testing. Using a high resolution LTQ-Orbitrap Velos mass spectrometer, we identified 265 different proteins. The identified proteins were compared with those identified from PPD M. bovis, PPD M. avium and PPD-S2 from previous mass spectrometry-based studies. In all, 142 proteins were found to be shared between PPD-CT68 and PPD-S2 preparations. Out of the 354 proteins from M. tuberculosis-derived PPDs (i.e. proteins in either PPD-CT68 or PPD-S2), 37 proteins were found to be shared with M. avium PPD and 80 were shared with M. bovis PPD. Alignment of PPD-CT68 proteins with proteins encoded by 24 lung infecting bacteria revealed a number of similar proteins (206 bacterial proteins shared epitopes with 47 PPD-CT68 proteins), which could potentially be involved in causing cross-reactivity. The data have been deposited to the ProteomeXchange with identifier PXD000377.
  
  
  CONCLUSIONS
  Proteomic and bioinformatics analysis of different PPD preparations revealed commonly and differentially represented proteins. This information could help in delineating the relevant antigens represented in various PPDs, which could further lead to development of a lesser complex and better defined skin test antigen with a higher specificity and sensitivity.
authors.affiliation: Institute of Bioinformatics, International Tech Park, Whitefield, Bangalore 560 066, India. keshav@ibioinformatics.org.
authors.forename: Thottethodi Subrahmanya Keshava
authors.initials: TS
authors.lastname: Prasad
authors.forename: Renu
authors.initials: R
authors.lastname: Verma
authors.forename: Satish
authors.initials: S
authors.lastname: Kumar
authors.forename: Raja Sekhar
authors.initials: RS
authors.lastname: Nirujogi
authors.forename: Gajanan J
authors.initials: GJ
authors.lastname: Sathe
authors.forename: Anil K
authors.initials: AK
authors.lastname: Madugundu
authors.forename: Jyoti
authors.initials: J
authors.lastname: Sharma
authors.forename: Vinuth N
authors.initials: VN
authors.lastname: Puttamallesh
authors.forename: Anjali
authors.initials: A
authors.lastname: Ganjiwale
authors.forename: Vithal P
authors.initials: VP
authors.lastname: Myneedu
authors.forename: Aditi
authors.initials: A
authors.lastname: Chatterjee
authors.forename: Akhilesh
authors.initials: A
authors.lastname: Pandey
authors.forename: Hc
authors.initials: H
authors.lastname: Harsha
authors.forename: Jayasuryan
authors.initials: J
authors.lastname: Narayana