AIDS-associated Talaromyces marneffei central nervous system infection in patients of southwestern China

An unusual Toll/MyD88-mediated Drosophila host defence against Talaromyces marneffei

Talaromycosis, caused by Talaromyces marneffei (T. marneffei, formerly known as Penicillium marneffei), is an opportunistic invasive mycosis endemic in tropical and subtropical areas of Asia with high mortality rate. Despite various infection models established to study the immunological interaction between T. marneffei and the host, the pathogenicity of this fungus is not yet fully understood. So far, Drosophila melanogaster, a well-established genetic model organism to study innate immunity, has not been used in related research on T. marneffei. In this study, we provide the initial characterization of a systemic infection model of T. marneffei in the D. melanogaster host. Survival curves and fungal loads were tested as well as Toll pathway activation was quantified by RT-qPCR of several antimicrobial peptide (AMP) genes including Drosomycin, Metchnikowin, and Bomanin Short 1. We discovered that whereas most wild-type flies were able to overcome the infection, MyD88 or Toll mutant flies failed to prevent fungal dissemination and proliferation and ultimately succumbed to this challenge. Unexpectedly, the induction of classical Toll pathway activation readouts, Drosomycin and Bomanin Short 1, by live or killed T. marneffei was quite limited in wild-type flies, suggesting that the fungus largely escapes detection by the systemic immune system. This unusual situation of a poor systemic activation of the Toll pathway and a strong susceptibility phenotype of MyD88/Toll might be accounted for by a requirement for this host defence in only specific tissues, a hypothesis that remains to be rigorously tested.

Emerging Fungal Infections of the Central Nervous System in the Past Decade: A Literature Review

INTRODUCTION

Invasive fungal infections affecting the central nervous system (CNS) are a major health concern worldwide associated with high mortality rates. Their increased incidence is largely due to an increase in the vulnerable immunocompromised population, changing environmental factors, and development of more accurate diagnostic methods. The aim of this article is to identify fungal causes of CNS infections that are recently emerging or have the potential to become emerging pathogens in the near future, as well as their clinical characteristics, including: Candida auris, Trichosporon spp., Blastomyces spp., Sporothrix spp., Talaromyces marneffei, Lomentospora prolificans, and Scedosporium spp.

METHODS

A review of the literature in PubMed in the last ten years was conducted to identify central nervous system infections caused by each of these fungi.

RESULTS

The review identified 10 cases caused by C. auris, 5 cases by Trichosporon spp., 82 cases by Blastomyces spp., 36 cases by Sporothrix spp., 21 cases by T. marneffei, 22 cases by Lomentospora prolificans, and 42 cases by Scedosporium spp.

DISCUSSION

The exact burden of these diseases remains difficult to ascertain, but their apparent rise underscores the urgent need for improved diagnostic, treatment, and management strategies against CNS fungal pathogens to improve outcomes against these life-threatening infections.

Advances in the understanding of talaromycosis in HIV-negative patients (especially in children and patients with hematological malignancies): A comprehensive review

Talaromyces marneffei (T. marneffei) stands out as the sole thermobiphasic fungus pathogenic to mammals, including humans, within the fungal community encompassing Ascomycota, Eurotium, Eurotiumles, Fungiaceae, and Cyanobacteria. Thriving as a saprophytic fungus in its natural habitat, it transitions into a pathogenic yeast phase at the mammalian physiological temperature of 37°C. Historically, talaromycosis has been predominantly associated with human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS), classified among the three primary opportunistic infections linked with AIDS, alongside tuberculosis and cryptococcosis. As advancements are made in HIV/AIDS treatment and control measures, the incidence of talaromycosis co-infection with HIV is declining annually, whereas the population of non-HIV-infected talaromycosis patients is steadily increasing. These patients exhibit diverse risk factors such as various types of immunodeficiency, malignant tumors, autoimmune diseases, and organ transplantation, among others. Yet, a limited number of retrospective studies have centered on the clinical characteristics and risk factors of HIV-negative talaromycosis patients, especially in children and patients with hematological malignancies, resulting in an inadequate understanding of this patient cohort. Consequently, we conducted a comprehensive review encompassing the epidemiology, pathogenesis, risk factors, clinical manifestations, diagnosis, treatment, and prognosis of HIV-negative talaromycosis patients, concluding with a prospectus of the disease's frontier research direction. The aim is to enhance comprehension, leading to advancements in the diagnosis and treatment rates for these patients, ultimately improving their prognosis.

The microbial damage and host response framework: lesson learned from pathogenic survival trajectories and immunoinflammatory responses of Talaromyces marneffei infection

The adverse outcomes of fungal infection in mammalian hosts depend on the complex interactions between the host immune system and pathogen virulence-associated traits. The main clinical problems arise when the host response is either too weak to effectively eliminate the pathogen or overly aggressive, resulting in host tissue damage rather than protection. This article will highlight current knowledge regarding the virulence attributions and mechanisms involved in the dual-sided role of the host immune system in the immunopathogenesis of the thermally dimorphic fungus Talaromyces marneffei through the lens of the damage response framework (DRF) of microbial pathogenesis model.

Coexisting of Primary Central Nervous System Lymphoma and Talaromyces marneffei Brain Abscess in an AIDS Patient, A Case Report and Review of the Literature

Background

Talaromyces marneffei is prevalent in South Asia. Latent Talaromyces marneffei infection of travellers make the diagnosis difficult. There are similarities in clinical manifestations between Talaromyces marneffei infection and lymphoma. Brain abscess is a rare form of Talaromyces marneffei infection.

Case Presentation

We reported a very rare case of a 19-year-old man with HIV infection who suffered from a brain mass and lymphadenopathy. His blood culture, bone marrow culture and sputum culture all grew Talaromyces marneffei. One month after treatment with voriconazole, the symptoms improved except brain mass. Surgical incision of the brain mass showed a compact mass, and pathological analysis showed the coexisting Talaromyces marneffei abscess and lymphoma. The patient is currently in a stable condition after receiving antifungal therapy and chemotherapy.

Conclusion

Based on a case report of a traveller who suffered from a brain mass of Talaromyces marneffei abscess and lymphoma after a visit to an endemic area, this review summarized the cases where there was confusion between lymphoma and the brain abscess of Talaromyces marneffei. Talaromyces marneffei infection can be found globally due to the increasing number of international travels. Talaromyces marneffei infection and lymphoma had similar characteristics which is easy to misdiagnose in clinic. Infection may also be accompanied by tumors, especially in patients infected with HIV. The manifestations and imaging of brain abscess of Talaromyces marneffei were not characteristic in different patients.

Talaromyces marneffei Infection: Virulence, Intracellular Lifestyle and Host Defense Mechanisms

Talaromycosis (Penicilliosis) is an opportunistic mycosis caused by the thermally dimorphic fungus Talaromyces (Penicillium) marneffei. Similar to other major causes of systemic mycoses, the extent of disease and outcomes are the results of complex interactions between this opportunistic human pathogen and a host’s immune response. This review will highlight the current knowledge regarding the dynamic interaction between T. marneffei and mammalian hosts, particularly highlighting important aspects of virulence factors, intracellular lifestyle and the mechanisms of immune defense as well as the strategies of the pathogen for manipulating and evading host immune cells.

Serum Exosomal microRNA Profiling in AIDS Complicated with Talaromyces marneffei Infection

Introduction

In order to find the early diagnostic markers of AIDS combined with TM infection, we detected and analyzed the serum exosomal miRNAs of AIDS patients with or without TM infection.

Materials and Methods

We profiled the expression levels of miRNAs via RNA sequencing in serum exosomes from the pooled samples of 17 AIDS patients combined without TM infection and 15 AIDS combined with TM infection patients. For external validation, we validated these results using real-time quantification polymerase chain reaction (qRT-PCR) in an independent cohort of 35 AIDS patients combined without TM infection and 33 AIDS combined with TM infection patients. Finally, bioinformatics was used to predict the target genes and pathways of meaningful miRNAs.

Results

A total of 131 serum exosomal miRNAs including 73 up-regulated and 59 down-regulated miRNAs were found to be differentially expressed (log2FC≥1 and FDR <0.01) in the two groups. A validation analysis revealed that three miRNAs (miR-192-5p, miR-194-5p and miR-1246) were upregulated in exosomes from AIDS combined with TM infection patients. ROC analyses showed that the AUC in combined diagnosis of the three miRNAs was 0.742, and the diagnostic sensitivity and specificity were 0.568 and 0.861, respectively. In the biological process analysis, all the 3 miRNAs were involved in transcription, DNA-templated and positive regulation of transcription from RNA polymerase II promoter. At the same time, the related pathways were involved in TGF-β signaling pathway, AMPK signaling pathway, Wnt signaling pathway, MAPK signaling pathway, cGMP-PKG and cAMP signaling pathway, etc.

Conclusion

miR-192-5p, miR-194-5p and miR-1246 in serum exosomes might be a potential biomarker for AIDS combined with TM infection patients, which may be involved in TGF-β signaling pathway, AMPK signaling pathway, Wnt signaling pathway, MAPK signaling pathway, cGMP-PKG and cAMP signaling pathway, etc. Further research is needed on the biological functions and mechanisms of these miRNAs.

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

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.

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. Although laboratory culture remains a gold standard diagnostic method, it lacks sensitivity and is time-consuming, which results in delayed patient’s treatment and needed care. In this study, 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. Our data showed that the assay exhibited high sensitivity (89.47%) and specificity (100%), with its result available within 30 minutes. In addition, this diagnostic assay is inexpensive, reproducible, and simple to perform. Therefore, the T. marneffei ICT should be considered for clinical application in the context of rapid and affordable point-of-care diagnostic test to reduce the burden of talaromycosis mortality in patients in low resource countries.

The Effect of Talaromyces marneffei Infection on CD86 Expression in THP-1 Cells

Background

Talaromyces marneffei (T. marneffei) is a destructive opportunistic dimorphic fungal which can cause lethiferous Talaromycosis, but the clearance of T. marneffei mainly depends on the innate immune response.

Objective

To investigate whether T. marneffei can inhibit the expression of CD86 in THP-1 cells after infection and discuss the potential mechanisms.

Methods

Western blot and immunoelectron microscopy were used to detect the CD86 expression on T. marneffei cultured on BHI medium at 37°C. Western blot, enzyme-linked immunoassay and immunofluorescence were used to detect the change of CD86 expression on macrophages incubating with T. marneffei. Enzyme-linked immunoassay was used to detect the content of CD86 in supernatant in the co-culture system. Immunohistochemistry and immunoelectron microscopy were used to detect the expression of CD86 on T. marneffei incubating with macrophages.

Results

T. marneffei did not express CD86 when cultured separately at 37°C detected by Western blot and immunoelectron microscopy, but it did express CD86 when incubated with macrophages detected by immunohistochemistry and immunoelectron microscopy. The CD86 expression of macrophages significantly decreased at 72 hours when infected with T. marneffei while the content of CD86 in supernatant significantly increased at 72 hours compared with the control group which were detected by Western blot, enzyme-linked immunoassay and immunofluorescence.

Conclusion

1) After T. marneffei infection, CD86 expression on THP-1 decreased, and with the progression of infection, insufficient polarization of M1 macrophages gradually appeared; 2) T. marneffei may adsorb or uptake CD86 in supernatant produced by macrophages during the contact with THP-1 cells, thus leading to the consumption of CD86 in macrophages.