PPE11 of Mycobacterium tuberculosis can alter host inflammatory response and trigger cell death

Area of Science:

• Microbiology
• Immunology
• Pathogenesis

Background:

• Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is a major global health issue.
• The Mtb PE/PPE protein family is implicated in modulating host immune responses during infection.
• The specific role of PPE11 (Rv0453) in Mtb pathogenesis remains largely unknown.

Purpose of the Study:

• To investigate the function and mechanism of the Mtb PE/PPE protein PPE11 in host-pathogen interactions.
• To determine PPE11's role in bacterial survival and virulence.

Main Methods:

• Heterologous expression of PPE11 in Mycobacterium smegmatis.
• Assessing bacterial viability under various stress conditions (lysozyme, H2O2, acid).
• Evaluating bacterial survival and replication in macrophages and mouse tissues.
• Measuring host cytokine production (IL-1β, IL-6, TNF-α, IL-10) and host cell death.

Main Results:

• Overexpression of PPE11 improved M. smegmatis survival against lysozyme, hydrogen peroxide, and acid stress.
• PPE11 enhanced early survival of M. smegmatis in macrophages and increased bacterial load in mouse tissues.
• Infected macrophages and mice showed elevated pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) and increased host cell death.
• A decrease in the anti-inflammatory cytokine IL-10 was observed early in infection.

Conclusions:

• PPE11 contributes to bacterial stress resistance and enhances survival within host environments.
• PPE11 promotes Mtb virulence by disrupting inflammatory balance and inducing host cell death.
• PPE11 is a potential virulence factor for Mycobacterium tuberculosis.