Cellular immune responses to cell wall peptidoglycan associated protein antigens in tuberculosis patients and healthy subjects
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N Dhiman1, I Verma, G K Khuller
1Department of Biochemistry, Postgraduate Institute of Medical Education and Research, Chandigarh, India.
Abstract:
We have isolated cell wall peptidoglycan associated proteins (CW-Pr) of Mycobacterium tuberculosis H37Ra by chemical treatment with trifluoromethanesulfonic acid:anisole (2:1), which further resolved into 71, 60 and 45 kDa proteins on SDS-PAGE. A study was carried out to investigate the immunoreactivity of these proteins with blood samples from 4 categories, including 15 tuberculous patients (TB), 5 tuberculous patients on ATT (TBT), 10 PPD non-reactive healthy controls (HPPD-) and 11 PPD reactive healthy controls (HPPD+). Comparing the proliferative responses to cell wall protein antigens, it was observed that the 71 kDa protein gave maximum stimulation with PBMCs from the TB and HPPD+ groups. The adherent PBMCs from the TB group also demonstrated enhanced phagocytosis, particularly in the presence of 71 and 45 kDa proteins, and the phagocytic index was significantly higher (P < 0.05) than the TBT group. However, PBMCs from of the groups recognized the 60 kDa cell wall antigen. Our results suggest that the 71 kDa protein from the cell wall of M. tuberculosis is highly immunogenic.
Insights
Researchers identified key Mycobacterium tuberculosis cell wall proteins (CW-Pr) that trigger immune responses. The 71 kDa protein showed significant immunogenicity in tuberculous patients and PPD-reactive healthy individuals, indicating its potential diagnostic value.
Area of Science:
- Immunology
- Microbiology
- Biochemistry
Background:
- Tuberculosis (TB) remains a global health challenge, necessitating novel diagnostic and therapeutic targets.
- Mycobacterium tuberculosis cell wall peptidoglycan-associated proteins (CW-Pr) are potential candidates for immune-based interventions.
- Understanding the immunogenic properties of specific CW-Pr is crucial for developing effective TB diagnostics and vaccines.
Purpose of the Study:
- To isolate and characterize cell wall peptidoglycan-associated proteins (CW-Pr) from Mycobacterium tuberculosis H37Ra.
- To investigate the immunoreactivity of isolated CW-Pr (71, 60, and 45 kDa) using blood samples from different human cohorts.
- To identify specific CW-Pr with high immunogenic potential for diagnostic or vaccine development.
Main Methods:
- Isolation of CW-Pr from M. tuberculosis H37Ra using chemical treatment (trifluoromethanesulfonic acid:anisole).
- Separation and identification of protein components by SDS-PAGE, yielding 71, 60, and 45 kDa fractions.
- Assessment of peripheral blood mononuclear cell (PBMC) proliferation and phagocytosis in response to CW-Pr antigens from tuberculous patients (TB), treated TB patients (TBT), and healthy controls (HPPD-, HPPD+).
Main Results:
- The 71 kDa CW-Pr fraction induced maximum PBMC proliferative responses in both TB patients and PPD-reactive healthy controls (HPPD+).
- Adherent PBMCs from TB patients showed enhanced phagocytosis in the presence of 71 and 45 kDa CW-Pr, with a significantly higher phagocytic index compared to the TBT group.
- The 60 kDa CW-Pr antigen was recognized by PBMCs across all tested groups, suggesting broader immune recognition.
Conclusions:
- The 71 kDa protein isolated from the M. tuberculosis cell wall is a highly immunogenic antigen.
- This 71 kDa protein holds significant potential as a biomarker for TB diagnosis and as a component in novel TB vaccines.
- Further research into the specific immune mechanisms elicited by these CW-Pr could lead to improved TB control strategies.