A human commensal-pathogenic fungus suppresses host immunity via targeting TBK1

Area of Science:

• Immunology
• Microbiology
• Molecular Biology

Background:

• Candida albicans is a common human colonizer and a major cause of hospital-acquired fungemia.
• Fungal immune evasion strategies are critical for pathogenesis.
• Type I interferon (IFN-I) signaling plays a key role in host defense against fungal infections.

Purpose of the Study:

• To investigate the mechanism by which Candida albicans evades the host immune response.
• To identify specific fungal effector proteins involved in immune modulation.
• To understand the role of IFN-I signaling in C. albicans colonization and infection.

Main Methods:

• Investigated the translocation of fungal effector proteins into host cells.
• Utilized a cmi1 mutant strain of C. albicans.
• Assessed IFN-I responses in murine infection models and bone-marrow-derived macrophages.
• Analyzed the impact of Cmi1 on TANK-binding kinase 1 (TBK1) and IFN-regulatory factor 3 (IRF3) phosphorylation.
• Examined the role of the IFN-I receptor in host responses.

Main Results:

• C. albicans translocates the effector protein Cmi1 into host cells to block IFN-I signaling.
• Cmi1 inhibits TBK1, preventing IRF3 phosphorylation and suppressing the IFN-I cascade.
• Mice infected with a cmi1 mutant showed enhanced IFN-I responses, leading to faster fungal clearance and increased survival.
• Loss of CMI1 impaired gut commensalism and heightened IFN-I responses in colonic cells, effects reversed by IFN-I receptor depletion.

Conclusions:

• Fungal effector protein Cmi1 is essential for C. albicans immune evasion by inhibiting TBK1-mediated IFN-I signaling.
• TBK1 inhibition is a critical virulence mechanism for C. albicans.
• C. albicans manipulates host immunity via effector protein delivery, impacting both infection and commensal colonization.