Talaromyces marneffei laccase modifies THP-1 macrophage responses
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Updated: Mar 20, 2026
Macrophage Differentiation and Polarization into an M2-Like Phenotype using a Human Monocyte-Like THP-1 Leukemia Cell Line
Published on: August 2, 2021
Ariya Sapmak1,2, Jutikul Kaewmalakul1, Joshua D Nosanchuk3
1a Department of Microbiology , Faculty of Medicine, Chiang Mai University , Chiang Mai , Thailand.
Abstract:
Talaromyces (Penicillium) marneffei is an emerging opportunistic pathogen associated with HIV infection, particularly in Southeast Asia and southern China. The rapid uptake and killing of T. marneffei conidia by phagocytic cells along with the effective induction of an inflammatory response by the host is essential for disease control. T. marneffei produces a number of different laccases linked to fungal virulence. To understand the role of the various laccases in T. marneffei, laccase-encoding genes were investigated. Targeted single, double and triple gene deletions of laccases encoding lacA, lacB, and lacC showed no significant phenotypic effects suggesting redundancy of function. When a fourth laccase-encoding gene, pbrB, was deleted in the ΔlacA ΔlacB ΔlacC background, the quadruple mutant displayed delayed conidiation and the conidia were more sensitive to H2O2, sodium dodecyl sulfate (SDS), and antifungal agents than wild-type and other transformants. Conidia of the quadruple mutant showed marked differences in their interaction with the human monocyte cell line, THP-1 such that phagocytosis was significantly higher when compared with the wild-type at one and 2 hours of incubation while the phagocytic index was significantly different from 15 to 120 minutes. In addition, killing of the quadruple mutant by THP-1 cells was more efficient at 2 and 4 hours of incubation. The levels of the proinflammatory cytokines TNF-α, IL-1β and IL-6 from THP-1 cells infected with the quadruple mutant were also significantly increased in comparison with wild-type. The results demonstrate that production of laccases by T. marneffei actually promotes the pathogen's resistance to innate host defenses.
Insights
Talaromyces marneffei laccase gene deletions reveal that fungal laccases promote pathogen resistance to host defenses. Quadruple mutants showed increased phagocytosis and inflammatory responses, indicating laccases aid T. marneffei survival.
Area of Science:
- Mycology
- Infectious Diseases
- Immunology
Background:
- Talaromyces marneffei is an opportunistic pathogen linked to HIV, prevalent in Southeast Asia.
- Effective host control relies on phagocytic cell clearance and inflammatory responses.
- Laccases are fungal enzymes implicated in T. marneffei virulence.
Purpose of the Study:
- To investigate the role of laccase-encoding genes (lacA, lacB, lacC, pbrB) in Talaromyces marneffei virulence.
- To understand how laccases affect fungal conidia interaction with host immune cells.
- To determine the impact of laccases on T. marneffei resistance to innate immunity.
Main Methods:
- Targeted gene deletion of laccase-encoding genes (lacA, lacB, lacC, pbrB) in T. marneffei.
- Phenotypic analysis of single, double, triple, and quadruple mutants.
- Assessment of conidial sensitivity to oxidative stress, SDS, and antifungal agents.
- In vitro interaction studies with the human monocyte cell line THP-1, including phagocytosis and killing assays.
- Quantification of pro-inflammatory cytokine (TNF-α, IL-1β, IL-6) production by infected THP-1 cells.
Main Results:
- Single, double, and triple laccase gene deletions showed no significant phenotypic changes, suggesting functional redundancy.
- A quadruple mutant (ΔlacA ΔlacB ΔlacC pbrB) exhibited delayed conidiation and increased sensitivity to H2O2, SDS, and antifungals.
- The quadruple mutant's conidia were phagocytosed more readily by THP-1 cells, with significantly altered phagocytic indices.
- THP-1 cells demonstrated more efficient killing of the quadruple mutant conidia.
- Infection with the quadruple mutant led to significantly elevated levels of TNF-α, IL-1β, and IL-6.
Conclusions:
- Talaromyces marneffei laccases contribute to the pathogen's resistance against host innate immune defenses.
- The absence of laccases enhances phagocytosis and inflammatory responses, making the fungus more susceptible to immune clearance.
- Laccases play a crucial role in T. marneffei virulence by promoting survival against host defenses.
