The study of extracellular vesicles derived from virus-infected Talaromyces marneffei

Abstract

Talaromyces marneffei is a thermally dimorphic fungus that causes a disease named Talaromycosis. T. marneffei infection is common in immunocompromised individuals especially the human immunodeficiency virus-infected and acquired immunodeficiency syndrome patients. However, the pathogenesis of this important opportunistic pathogen in the Pacific region is yet to be fully understood. In the last few years, emerging research on extracellular vesicles has opened up new arenas in studying the mechanisms of pathogenesis in infectious diseases. However, little is known about the potential role of EVs in Talaromycosis.

Some T. marneffei strains harbour the mycovirus, TmPV-1. Mycovirus-infected T. marneffei was previously demonstrated to be more virulent than uninfected T. marneffei in a mouse model. This raises questions if some strains of T. marneffei may be hypervirulent and associated with more severe infections in patients. Yet, the mechanism underlying the hypervirulence of virus-infected T. marneffei remains undetermined. Recently, our group also discovered EVs from T. marneffei and found that EVs of virus-free T. marneffei exhibit immunomodulatory effect in macrophage cells. Since both mycovirus and EVs can be identified in T. marneffei, it would be interesting to study if the two may interact to contribute to the pathogenesis of T. marneffei. Therefore, the aim of this study is to characterize the EVs derived from virus-infected T. marneffei and identify potential factors involved in such interaction. We also hypothesize that mycovirus may play a role in the immunomodulatory effect of T. marneffei during infection, which may involve EVs during the process.

EVs of isogenic virus-free and virus-infected T. marneffei were characterized by transmission electron microscopy, nanoparticle tracking analysis and proteomic analysis. Proteins associated with the EVs of virus-infected T. marneffei were more enriched than EVs of virus-free T. marneffei and were predominantly related to the metabolic and biosynthetic processes in mitochondria. FMP32 was identified exclusively in the EVs of virus-infected T. marneffei, and this protein is related to maintaining the redox balance in the mitochondria. Because transmission of mycovirus from virus-infected T. marneffei to virus-free T. marneffei through EVs was unsuccessful, these findings collectively suggest that EVs of virus-infected T. marneffei are more likely involved in maintaining metabolic processes than the dissemination of the mycovirus. By transcriptomic analysis of the hPBMC-derived macrophages treated with isogenic virus-free and virus-infected T. marneffei, virus-infected T. marneffei exerted more marked immunosuppression in hPBMC-derived macrophages than virus-free T. marneffei. The recovery rate of isogenic virus-free and virus-infected T. marneffei and their correlation with the immune response of the host during infection were evaluated. Virus-infected T. marneffei displayed higher suppression of the host immune genes and higher recovery rate in J774 than virus-free T. marneffei but the results were found statistically insignificant. This may suggest potential immunomodulatory ability of virus-infected T. marneffei, although more studies are needed to confirm this finding and verify the role of EVs in such immunomodulation. In conclusion, this study offered insights into the potential roles of virus-infected T. marneffei derived EVs and potential immunomodulatory ability associated with virus-infected T. marneffei that may attribute to its hypervirulence phenotype.