Differentiation of the Emerging Human Pathogens Trichosporon asahii and Trichosporon asteroides from Other Pathogenic Yeasts and Moulds by Using Species-Specific Monoclonal Antibodies

Genna E Davies,Christopher R Thornton,Kirsten Nielsen

doi:10.1371/journal.pone.0084789

Abstract

The fungal genus Trichosporon contains emerging opportunistic pathogens of humans, and is the third most commonly isolated non-candidal yeast from humans. Trichosporon asahii and T. asteroides are the most important species causing disseminated disease in immunocompromised patients, while inhalation of T. asahii spores is the most important cause of summer-type hypersensitivity pneumonitis in healthy individuals. Trichosporonosis is misdiagnosed as candidiasis or cryptococcosis due to a lack of awareness and the ambiguity of diagnostic tests for these pathogens. In this study, hybridoma technology was used to produce two murine monoclonal antibodies (MAbs), CA7 and TH1, for detection and differentiation of Trichosporon from other human pathogenic yeasts and moulds. The MAbs react with extracellular antigens from T. asahii and T. asteroides, but do not recognise other related Trichosporon spp., or unrelated pathogenic yeasts and moulds including Candida, Cryptococcus, Aspergillus, Fusarium, and Scedosporium spp., or the etiologic agents of mucormycosis. Immunofluorescence and Western blotting studies show that MAb CA7, an immunoglobulin G1 (IgG1), binds to a major 60 kDa glycoprotein antigen produced on the surface of hyphae, while TH1, an immunoglobulin M (IgM), binds to an antigen produced on the surface of conidia. The MAbs were used in combination with a standard mycological growth medium (Sabouraud Dextrose Agar) to develop an enzyme-linked immunosorbent assay (ELISA) for differentiation of T. asahii from Candida albicans and Cryptococcus neoformans in single and mixed species cultures. The MAbs represent a major advance in the identification of T. asahii and T. asteroides using standard mycological identification methods.

Highlights

The genus Trichosporon contains approximately 50 species of basidiomycete yeasts found in a wide variety of habitats including soil and indoor environments [1,2,3]
This paper describes the use of hybridoma technology to develop two murine hybridoma cell lines (CA7 and TH1) producing monoclonal antibodies (MAbs) specific for Trichosporon asahii and the closely related species Trichosporon asteroides, the most important causes of trichosporonosis
Isotyping of the MAbs showed that CA7 belongs to immunoglobulin class G1 (IgG1) and TH1 to immunoglobulin class M (IgM)

Summary

Introduction

The genus Trichosporon contains approximately 50 species of basidiomycete yeasts found in a wide variety of habitats including soil and indoor environments [1,2,3]. As well as superficial infections, repeated inhalation of Trichosporon arthroconidia can cause summer-type hypersensitivity pneumonitis (SHP) [4,5], an immunologically induced lung disease. It is the most common form of hypersensitivity pneumonitis (HP) in Japan [4] and T. asahii is the most frequent cause of the disease [1,3]. High mortality rates are associated with trichosporonosis, with reports in the literature of between 50 and 80% in high-risk patient groups [2]

Methods

Results

Conclusion