An inexpensive point-of-care immunochromatographic test for Talaromyces marneffei infection based on the yeast phase specific monoclonal antibody 4D1 and Galanthus nivalis agglutinin.

Kritsada Pruksaphon,Sirida Youngchim,Akarin Intaramat,Pavinee Simsiriwong,Kavi Ratanabanangkoon,Skorn Mongkolsuk,Anna Kaltsas,Joshua D Nosanchuk,Thuy Le

doi:10.1371/journal.pntd.0009058

Abstract

Talaromyces marneffei is a thermally dimorphic fungus that causes opportunistic systemic mycoses in patients with AIDS or other immunodeficiency syndromes. The purpose of this study was to develop an immunochromatographic strip test (ICT) based on a solid phase sandwich format immunoassay for the detection of T. marneffei antigens in clinical urine specimens. The T. marneffei yeast phase specific monoclonal antibody 4D1 (MAb4D1) conjugated with colloidal gold nanoparticle was used as a specific signal reporter. Galanthus nivalis Agglutinin (GNA) was adsorbed onto nitrocellulose membrane to serve as the test line. Similarly, a control line was created above the test line by immobilization of rabbit anti-mouse IgG. The immobilized GNA served as capturing molecule and as non-immune mediated anti-terminal mannose of T. marneffei antigenic mannoprotein. The MAb4D1–GNA based ICT showed specific binding activity with yeast phase antigen of T. marneffei, and it did not react with other common pathogenic fungal antigens. The limit of detection of this ICT for T. marneffei antigen spiked in normal urine was approximately 0.6 μg/ml. The diagnostic performance of the ICT was validated using 341 urine samples from patents with culture- confirmed T. marneffei infection and from a control group of healthy individuals and patients with other infections in an endemic area. The ICT exhibited 89.47% sensitivity, 100% specificity, and 97.65% accuracy. Our results demonstrate that the urine-based GNA–MAb4D1 based ICT produces a visual result within 30 minutes and that the test is highly specific for the diagnosis of T. marneffei infection. The findings validate the deployment of the ICT for clinical use.

Highlights

The thermally dimorphic fungus Talaromyces marneffei causes disseminated mycosis affecting immunocompromised patients living in endemic areas including Southeast Asia, China and the Indian subcontinent [1,2]
Talaromycosis (Penicilliosis marneffei) is a neglected disease that causes an opportunistic systemic mycoses in AIDS and other immune-deficient patients living in Southeast Asia, China and the Indian subcontinent
We develop an immunochromatographic strip test (ICT) by utilizing a yeast phase specific monoclonal antibody 4D1 and Galanthus nivalis agglutinin for detection of T. marneffei antigens in clinical urine specimens

Summary

Introduction

The thermally dimorphic fungus Talaromyces marneffei (previously Penicillium marneffei) causes disseminated mycosis affecting immunocompromised patients living in endemic areas including Southeast Asia, China and the Indian subcontinent [1,2]. In the context of clinical laboratory diagnosis, T. marneffei is usually diagnosed by microscopic identification of the fungus in various clinical specimens and by standard microbiological culture, based on its morphological characteristics and thermally dimorphic properties between 25oC (mycelium form) and 37oC (yeast form). These procedures are relatively time-consuming, requiring about 3-14 days [7,8], which can negatively affect clinical decisions and delay the initiation of appropriate therapy. False-negative or false positive results of these tests were often encountered [13]

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