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Talaromyces marneffei Mp1p Is a Virulence Factor that Binds and Sequesters a Key Proinflammatory Lipid to Dampen Host
Kong-Hung Sze1, Wai-Hei Lam2, Hongmin Zhang3
1State Key Laboratory of Emerging Infectious Diseases, The University of Hong Kong, Hong Kong SAR, China; Department of Microbiology, The University of Hong Kong, Hong Kong SAR, China; Research Centre of Infection and Immunology, The University of Hong Kong, Hong Kong SAR, China; Carol Yu Centre for Infection, The University of Hong Kong, Hong Kong SAR, China.
Abstract:
Talaromyces (Penicillium) marneffei is one of the leading causes of systemic mycosis in immunosuppressed or AIDS patients in Southeast Asia. How this intracellular pathogen evades the host immune defense remains unclear. We provide evidence that T. marneffei depletes levels of a key proinflammatory lipid mediator arachidonic acid (AA) to evade the host innate immune defense. Mechanistically, an abundant secretory mannoprotein Mp1p, shown previously to be a virulence factor, does so by binding AA with high affinity via a long hydrophobic central cavity found in the LBD2 domain. This sequesters a critical proinflammatory signaling lipid, and we see evidence that AA, AA's downstream metabolites, and the cytokines interleukin-6 and tumor necrosis factor α are downregulated in T. marneffei-infected J774 macrophages. Given that Mp1p-LBD2 homologs are identified in other fungal pathogens, we expect that this novel class of fatty-acid-binding proteins sequestering key proinflammatory lipid mediators represents a general virulence mechanism of pathogenic fungi.
