Application of Flow Cytometry in the Diagnostics Pipeline of Primary Immunodeficiencies Underlying Disseminated Talaromyces marneffei Infection in HIV-Negative Children.

Pamela P Lee,Xiaodong Zhao,Muthita Trakultivakorn,Lin Kui,Koon-Wing Chan,Haiyan Ma,Mongkol Lao-Araya,Lim-Cho Pei,Wanling Yang,Yu-Lung Lau,Jing Yang,Huawei Mao

doi:10.3389/fimmu.2019.02189

Abstract

Talaromyces (Penicillium) marneffei is an AIDS-defining infection in Southeast Asia and is associated with high mortality. It is rare in non-immunosuppressed individuals, especially children. Little is known about host immune response and genetic susceptibility to this endemic fungus. Genetic defects in the interferon-gamma (IFN-γ)/STAT1 signaling pathway, CD40/CD40 ligand- and IL12/IL12-receptor-mediated crosstalk between phagocytes and T-cells, and STAT3-mediated Th17 differentiation have been reported in HIV-negative children with talaromycosis and other endemic mycoses such as histoplasmosis, coccidioidomycosis, and paracoccidioidomycosis. There is a need to design a diagnostic algorithm to evaluate such patients. In this article, we review a cohort of pediatric patients with disseminated talaromycosis referred to the Asian Primary Immunodeficiency Network for genetic diagnosis of PID. Using these illustrative cases, we propose a diagnostics pipeline that begins with immunoglobulin pattern (IgG, IgA, IgM, and IgE) and enumeration of lymphocyte subpopulations (T-, B-, and NK-cells). The former could provide clues for hyper-IgM syndrome and hyper-IgE syndrome. Flow cytometric evaluation of CD40L expression should be performed for patients suspected to have X-linked hyper-IgM syndrome. Defects in interferon-mediated JAK-STAT signaling are evaluated by STAT1 phosphorylation studies by flow cytometry. STAT1 hyperphosphorylation in response to IFN-α or IFN-γ and delayed dephosphorylation is diagnostic for gain-of-function STAT1 disorder, while absent STAT1 phosphorylation in response to IFN-γ but normal response to IFN-α is suggestive of IFN-γ receptor deficiency. This simple and rapid diagnostic algorithm will be useful in guiding genetic studies for patients with disseminated talaromycosis requiring immunological investigations.

Highlights

Talaromyces marneffei is a pathogenic fungus indigenous to Southeast Asia [1,2,3,4,5]
CD40 Ligand (CD40L) expression on CD3+ T-cells activated by phorbol myristate acetate (PMA) and ionomycin was absent in the patient, and normal in both parents (Figure 1)
Human penicilliosis is believed to be initiated by inhalation of conidia which are subsequently phagocytosed by alveolar macrophages

Summary

Introduction

Talaromyces marneffei (previously known as Penicillium marneffei) is a pathogenic fungus indigenous to Southeast Asia [1,2,3,4,5]. Before the human immunodeficiency virus (HIV) epidemic, T. marneffei was an extremely rare pathogen in humans [1]. Since the late 1980s, talaromycosis emerged as a clinically important opportunistic infection following the exponential growth in the incidence of HIV in Southeast Asia, especially in Northern Thailand, Vietnam, Guangxi, and Guangdong in Southern China [2,3,4,5,6]. T. marneffei infection is classified as an acquired immunodeficiency syndrome (AIDS)-defining illness and listed as one of the HIV clinical stage 4 conditions [6]. The close relationship between disease manifestation and severity with CD4+ cell count confirms the central importance of cell-mediated immunity against endemic fungi

Methods

Results

Conclusion