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Updated: May 9, 2026
Separation and Fractionation of Cell Wall and Cell Membrane Proteins from Mycobacterium tuberculosis for Downstream Protein Analysis
Published on: September 26, 2025
Proteomic analysis of purified protein derivative of Mycobacterium tuberculosis
Thottethodi Subrahmanya Keshava Prasad1, Renu Verma, Satish Kumar
1Institute of Bioinformatics, International Tech Park, Whitefield, Bangalore 560 066, India. keshav@ibioinformatics.org.
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.
Insights
High-resolution mass spectrometry reveals the complex protein composition of Purified Protein Derivative (PPD) diagnostic reagents. This proteomic analysis aids in identifying key antigens for developing more accurate tuberculosis infection tests.
Area of Science:
- Proteomics
- Immunology
- Microbiology
Background:
- Purified Protein Derivative (PPD) has been a long-standing diagnostic antigen for tuberculosis infection via delayed-type hypersensitivity.
- The exact composition of PPD remains ill-defined despite its widespread use.
- Understanding PPD's complexity is crucial for improving tuberculosis diagnostics.
Purpose of the Study:
- To characterize the complex protein components of Purified Protein Derivative (PPD) using high-resolution mass spectrometry.
- To compare proteomic profiles of different PPD preparations to identify key diagnostic antigens.
- To inform the development of more potent and less complex diagnostic reagents for tuberculosis.
Main Methods:
- High-resolution mass spectrometry (LTQ-Orbitrap Velos) was employed to analyze PPD-CT68, a M. tuberculosis-derived tuberculin.
- Proteomic analysis identified 265 distinct proteins within the PPD-CT68 preparation.
- Comparative analysis was performed against PPD M. bovis, PPD M. avium, and PPD-S2 from prior studies.
Main Results:
- A total of 265 proteins were identified in PPD-CT68.
- 142 proteins were common between PPD-CT68 and PPD-S2.
- Cross-reactivity potential was indicated by shared epitopes between PPD-CT68 proteins and those from 24 lung-infecting bacteria.
Conclusions:
- Proteomic and bioinformatics analyses delineate common and distinct proteins across various PPD preparations.
- This detailed protein information can guide the selection of specific antigens for improved diagnostic tests.
- The findings support the development of simpler, more sensitive, and specific skin test antigens for tuberculosis detection.
