The PPE18 of Mycobacterium tuberculosis interacts with TLR2 and activates IL-10 induction in macrophage

Area of Science:

• Immunology
• Microbiology
• Molecular Biology

Background:

• The functions of Mycobacterium tuberculosis PE/PPE proteins remain largely unknown.
• Understanding these proteins is crucial for developing targeted tuberculosis therapies.

Purpose of the Study:

• To investigate the role of PPE18 protein from Mycobacterium tuberculosis in modulating host immune responses.
• To elucidate the molecular mechanism by which PPE18 influences macrophage cytokine production.

Main Methods:

• Recombinant PPE18 protein was used to stimulate THP-1 macrophages.
• Interaction with Toll-like receptor 2 (TLR2) and activation of p38 MAPK were analyzed.
• In silico docking and mutation experiments were performed.
• Comparative infection studies using wild-type and mutant Mycobacterium tuberculosis strains, and overexpressing M. smegmatis.

Main Results:

• PPE18 stimulates macrophages to secrete Interleukin-10 (IL-10), promoting a Th2-biased response.
• PPE18 specifically binds to TLR2, leading to sustained p38 MAPK activation, critical for IL-10 induction.
• Mutation experiments identified the leucine-rich repeat 11-15 domain of TLR2 as the interaction site for PPE18.
• M. tuberculosis lacking PPE18 showed reduced IL-10 production, while M. smegmatis overexpressing PPE18 showed increased IL-10 production.

Conclusions:

• PPE18 protein from Mycobacterium tuberculosis plays a significant role in inducing IL-10 production.
• This suggests PPE18 may contribute to an anti-inflammatory response during M. tuberculosis infection.
• Targeting PPE18 could be a potential strategy for modulating host immune responses in tuberculosis.