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Rv3539 (PPE63) of Mycobacterium Tuberculosis Promotes Survival of Mycobacterium Smegmatis in Human Macrophages Cell
Pradeep K Anand1, Jagdeep Kaur2
1Department of Biotechnology, Panjab University, BMS Block-1, South Campus, Chandigarh, 160014, India.
Abstract:
The modulation of host's immune response plays an important role in the intracellular survival of Mycobacterium tuberculosis. The intracellular pathogen counteracts environmental stresses with help of the expression of several genes. The M. tuberculosis genome encodes several immune-modulatory proteins including PE (proline-glutamic acid)/PPE (proline-proline-glutamic acid) superfamily proteins. It is unclear how the unique PE/PPE proteins superfamily contributes to survival under different stress and pathophysiology conditions. Previously, we showed that PPE63 (Rv3539) has C-terminal esterase extension and was localized as a membrane attached and in extracellular compartment. Therefore, the probability of these proteins interacting with the host to modulate the host immune response cannot be ruled out. The physiological role of PPE63 was characterized by expressing the PPE63 in the M. smegmatis, a non-pathogenic strain intrinsically deficient of PPE63. The recombinant M. smegmatis expressing PPE63 altered the colony morphology, lipid composition, and integrity of the cell wall. It provided resistance to multiple hostile environmental stress conditions and several antibiotics. MS_Rv3539 demonstrated higher infection and intracellular survival in comparison to the MS_Vec in the PMA-differentiated THP-1 cells. The decreased intracellular level of ROS, NO, and expression of iNOS was observed in THP-1 cells upon infection with MS_Rv3539 in comparison to MS_Vec. Further, the decrease in expression of pro-inflammatory cytokines like IL-6, TNF-α, and IL-1β and enhanced anti-inflammatory cytokines like IL-10, pointed toward its role in immune modulation. Overall this study suggested the role of Rv3539 in enhanced intracellular survival of M. smegmatis via cell wall modulation and altered immune response of host.
Insights
Mycobacterium tuberculosis PPE63 (Rv3539) enhances intracellular survival by altering host immune responses and cell wall integrity. This study reveals Rv3539
Area of Science:
- Microbiology
- Immunology
- Molecular Biology
Background:
- Mycobacterium tuberculosis modulates host immunity for intracellular survival.
- The PE/PPE protein superfamily's role in M. tuberculosis stress response and pathophysiology is largely unknown.
- PPE63 (Rv3539) is a potential immune-modulating protein with extracellular and membrane localization.
Purpose of the Study:
- To characterize the physiological role of PPE63 (Rv3539).
- To investigate Rv3539's impact on host immune response and M. tuberculosis survival.
Main Methods:
- Expressing PPE63 in a non-pathogenic M. smegmatis strain (MS_Rv3539).
- Assessing changes in colony morphology, cell wall, and stress resistance.
- Evaluating intracellular survival and immune responses (ROS, NO, cytokines) in PMA-differentiated THP-1 cells.
Main Results:
- MS_Rv3539 exhibited altered cell wall integrity and increased resistance to stress and antibiotics.
- MS_Rv3539 showed enhanced infection and intracellular survival in THP-1 cells.
- Infection with MS_Rv3539 led to decreased pro-inflammatory cytokines (IL-6, TNF-α, IL-1β) and increased anti-inflammatory cytokine (IL-10).
Conclusions:
- Rv3539 contributes to M. tuberculosis intracellular survival.
- PPE63 modulates host immune responses, promoting a less inflammatory environment.
- Rv3539's effects on cell wall and host immunity are key to M. tuberculosis survival.
