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Novel Partitivirus Enhances Virulence of and Causes Aberrant Gene Expression in Talaromyces marneffei
Susanna K P Lau1,2,3,4,5, George C S Lo4, Franklin W N Chow4
1State Key Laboratory of Emerging Infectious Diseases, The University of Hong Kong, Hong Kong, China skplau@hkucc.hku.hk pcywoo@hkucc.hku.hk.
Abstract:
Talaromyces marneffei is the most important thermal dimorphic fungus causing systemic mycosis in Southeast Asia. We report the discovery of a novel partitivirus, Talaromyces marneffeipartitivirus-1 (TmPV1). TmPV1 was detected in 7 (12.7%) of 55 clinical T. marneffei isolates. Complete genome sequencing of the seven TmPV1 isolates revealed two double-stranded RNA (dsRNA) segments encoding RNA-dependent RNA polymerase (RdRp) and capsid protein, respectively. Phylogenetic analysis showed that TmPV1 occupied a distinct clade among the members of the genus Gammapartitivirus Transmission electron microscopy confirmed the presence of isometric, nonenveloped viral particles of 30 to 45 nm in diameter, compatible with partitiviruses, in TmPV1-infected T. marneffei Quantitative reverse transcription-PCR (qRT-PCR) demonstrated higher viral load of TmPV1 in the yeast phase than in the mycelial phase of T. marneffei Two virus-free isolates, PM1 and PM41, were successfully infected by purified TmPV1 using protoplast transfection. Mice challenged with TmPV1-infected T. marneffei isolates showed significantly shortened survival time (P < 0.0001) and higher fungal burden in organs than mice challenged with isogenic TmPV1-free isolates. Transcriptomic analysis showed that TmPV1 causes aberrant expression of various genes in T. marneffei, with upregulation of potential virulence factors and suppression of RNA interference (RNAi)-related genes. This is the first report of a mycovirus in a thermally dimorphic fungus. Further studies are required to ascertain the mechanism whereby TmPV1 enhances the virulence of T. marneffei in mice and the potential role of RNAi-related genes in antiviral defense in T. marneffeiIMPORTANCETalaromyces marneffei (formerly Penicillium marneffei) is the most important thermal dimorphic fungus in Southeast Asia, causing highly fatal systemic penicilliosis in HIV-infected and immunocompromised patients. We discovered a novel mycovirus, TmPV1, in seven clinical isolates of T. marneffei TmPV1 belongs to the genus Gammapartitivirus of the family Partitiviridae We showed that TmPV1 enhanced the virulence of T. marneffei in mice, with shortened survival time and higher fungal burden in the organs of mice challenged with TmPV1-infected T. marneffei isolates than in those of mice challenged with virus-free isogenic isolates. Transcriptomics analysis showed that TmPV1 altered the expression of genes involved in various cellular processes in T. marneffei, with upregulation of potential virulence factors and suppression of RNAi machinery which may be involved in antiviral defense. This is the first report of a mycovirus in a thermal dimorphic fungus. The present results offer insights into mycovirus-fungus interactions and pathogenesis of thermal dimorphic fungi.
Insights
A novel mycovirus, Talaromyces marneffei partitivirus-1 (TmPV1), was discovered in the fungus Talaromyces marneffei. This virus enhances fungal virulence in mice and alters gene expression, representing the first mycovirus found in a thermally dimorphic fungus.
Area of Science:
- Mycology
- Virology
- Pathogenomics
Background:
- Talaromyces marneffei is a significant thermal dimorphic fungus causing systemic mycosis in Southeast Asia.
- It poses a severe threat to immunocompromised individuals, particularly those with HIV.
- Understanding fungal-host interactions and virulence factors is crucial for disease management.
Purpose of the Study:
- To report the discovery and characterization of a novel partitivirus in Talaromyces marneffei.
- To investigate the impact of this mycovirus on the virulence of T. marneffei in a murine model.
- To explore the molecular mechanisms underlying the virus-fungus interaction.
Main Methods:
- Detection and isolation of the novel partitivirus (TmPV1) from clinical T. marneffei isolates.
- Genome sequencing and phylogenetic analysis of TmPV1.
- Transmission electron microscopy for viral particle visualization.
- Quantitative reverse transcription-PCR (qRT-PCR) for viral load assessment.
- Protoplast transfection for experimental infection.
- Murine infection models to assess virulence.
- Transcriptomic analysis to study gene expression changes.
Main Results:
- A novel partitivirus, TmPV1, was identified in 12.7% of clinical T. marneffei isolates.
- TmPV1 possesses two dsRNA segments encoding RdRp and capsid protein, placing it in the Gammapartitivirus genus.
- TmPV1-infected T. marneffei exhibited significantly increased virulence in mice, characterized by shortened survival and higher fungal burden.
- Transcriptomic analysis revealed TmPV1 upregulates potential virulence factors and suppresses RNA interference (RNAi)-related genes in T. marneffei.
Conclusions:
- This study reports the first mycovirus, TmPV1, identified in a thermally dimorphic fungus.
- TmPV1 significantly enhances the virulence of Talaromyces marneffei in a murine model.
- TmPV1 influences T. marneffei gene expression, potentially by suppressing antiviral RNAi pathways, offering new insights into fungal pathogenesis and mycovirus-fungus interactions.
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