Assessment of the function of SUB6 in the pathogenic dermatophyte Trichophyton mentagrophytes

Area of Science:

• Medical Mycology
• Molecular Biology
• Immunology

Background:

• Trichophyton mentagrophytes is a pathogenic fungus causing infections in humans and animals.
• Subtilisins are crucial for T. mentagrophytes virulence, aiding invasion of the host's epidermal barrier.
• The SUB6 gene encodes a subtilisin protease, with its product Sub6 potentially being the allergen Tri r2, known to cause hypersensitivity reactions.

Purpose of the Study:

• To investigate the function of the SUB6 gene in T. mentagrophytes virulence.
• To analyze the impact of SUB6 disruption on the fungus's proteolytic activity and pathogenicity.
• To understand the role of SUB6 in modulating the host's immune response.

Main Methods:

• Agrobacterium tumefaciens-mediated transformation was used to create a SUB6 gene disruption mutant (SUB6::hph).
• Polymerase chain reaction and Southern blot analyses confirmed the gene disruption.
• In vitro and in vivo virulence assays were performed, including proteolytic activity measurements and analysis of host cytokine expression (IL-10, IFN-γ, TNF-α, IL-12) in infected animals.

Main Results:

• The SUB6 disruption mutant (SUB6::hph) exhibited significantly increased proteolytic activity in vitro.
• This increase in proteolytic activity correlated with elevated expression of MEP4 and SUB3 genes.
• In vivo, SUB6::hph-infected animals showed attenuated clinical symptoms and delayed/reduced increases in pro-inflammatory cytokines (IFN-γ, TNF-α, IL-12) due to sustained high levels of IL-10.

Conclusions:

• SUB6 disruption leads to attenuated virulence of T. mentagrophytes in vivo.
• The study suggests a genetically-linked regulatory mechanism responsible for increased proteolytic activity and residual pathogenicity in the mutant strain.
• SUB6 plays a significant role in modulating the host immune response during T. mentagrophytes infection.