Penicillium marneffei fungaemia in an allogeneic bone marrow transplant recipient

Evolution of the ability to evade host innate immune defense by Talaromyces marneffei

Talaromyces (Penicillium) marneffei is an intracellular pathogenic fungus. Some strains of this fungus have been misidentified due to the similarity between Talaromyces and Penicillium. T. marneffei has mainly been found to afflict immunocompromised individuals, causing respiratory, skin, and systemic mycosis. Mp1p is a key virulence factor that can help T. marneffei evade clearance by the normally functioning immune system. Understanding how novel functions arise is an intriguing question in many fields of biology. Mp1p has two homologous domains (Mp1p-LBD1 and Mp1p-LBD2). Sequence similarity searches with Mp1p-LBD sequences revealed Mp1p homologs in many other pathogenic fungi. Integrated information on the taxonomic distribution, phylogenetic relationships, and sequence similarity of Mp1p domains revealed that the ancestor of Mp1p-LBDs was acquired through horizontal gene transfer (HGT). Additional evidence revealed that Mp1p homologs have undergone extensive gene duplications in T. marneffei. Mp1p might be a result of gene fusion following gene duplication. Furthermore, we propose a new method for identifying Talaromyces and identify 4 strains with misclassification errors. Our results characterize the evolutionary mechanism of T. marneffei evasion of host innate immune defense and clearly demonstrate the role of gene duplication and HGT in the evolution of host immune escape by T. marneffei.

A review of endemic mycoses after hematopoietic stem cell transplantation

BACKGROUND

Endemic mycoses after hematopoietic stem cell transplantation (HSCT) are rarely reported. We aimed to comprehensively review the clinical presentation and outcomes of endemic mycoses in this immunocompromised population.

METHODS

Multiple databases were reviewed from inception through May 31, 2023 using endemic fungi as keywords (e.g., coccidioides, histoplasma, blastomyces, talaromyces, and paracoccidioides). Only hematopoietic transplants were included.

RESULTS

There were 16 publications on endemic mycoses after HSCT that reported nine unique cases of histoplasmosis, seven coccidioidomycosis, and two talaromycosis. No cases of paracoccidioides and blastomycoses were identified. Fifteen cases were allogeneic hematopoietic transplant recipients and three were autologous. Many were male (14/18, 77.8%) and overall median age was 50 (range 21-75) years. Among the 16 patients with coccidiodomycosis or histoplasmosis, fever, cytopenias and disseminated disease were the most common clinical presentations, with median onset of 8 or 12 months after HSCT, respectively. Likewise, the two HSCT patients with talaromycosis presented with disseminated disease at 12 and 48 months after transplantation. The vast majority were not on effective azole prophylaxis at the time of presentation, and many had recent intensification of immunosuppression. Nine of 18 patients died (50%), and all deaths occurred among patients with disseminated endemic mycoses.

CONCLUSION

Endemic mycoses among HSCT are uncommon. Onset was late, after discontinuation of azole prophylaxis, or was associated with intensification of immunosuppression. Disseminated disease was a common presentation, manifested by fever and cytopenias. Attributable mortality was high, and emphasizes the need for a high index of clinical suspicion so that prompt diagnosis and treatment is provided.

Endemic or regionally limited parasitic and fungal infections in haematopoietic stem-cell transplantation recipients: a Worldwide Network for Blood and Marrow Transplantation (WBMT) Review

There is a scarcity of data on endemic and regionally limited fungal and parasitic infections in recipients of haematopoietic stem-cell transplantation (HSCT) outside western Europe and North America. This Worldwide Network for Blood and Marrow Transplantation (WBMT) Review is one of two papers aiming to provide guidance to transplantation centres worldwide regarding prevention, diagnosis, and treatment based on the currently available evidence and expert opinion. These recommendations were created and reviewed by physicians with expertise in HSCT or infectious disease, representing several infectious disease and HSCT groups and societies. In this paper, we review the literature on several endemic and regionally limited parasitic and fungal infections, some of which are listed as neglected tropical diseases by WHO, including visceral leishmaniasis, Chagas disease, strongyloidiasis, malaria, schistosomiasis, histoplasmosis, blastomycosis, and coccidioidomycosis.

Clinical Characteristics of Transplant Recipients Infected with Talaromyces Marneffei: 2 Case Reports and a Literature Review

Purpose

To summarize the clinical characteristics, treatment and outcomes of transplant recipients infected with Talaromyces marneffei (TM).

Materials and Methods

A retrospective analysis was performed on 2 patients with Talaromycosis marneffei (TSM) and transplants at the First Affiliated Hospital of Guangxi Medical University, and a systematic literature review was conducted simultaneously.

Results

This article reported two patients after kidney transplantation who developed fever, cough within 3-4 months. Their haemoglobin was decreased. Their chest computed tomography (CT) showed nodules. TM was detected in their blood or bronchoalveolar lavage fluid samples by next-generation sequencing (NGS). After antifungal treatment with voriconazole (VOR), one patient worsened, the other patient died. A total of 21 patients with TSM after transplants were reported in the literature review. Fourteen underwent kidney transplantation, 4 underwent liver transplantation, 2 underwent lung transplantation, and 1 underwent bone marrow transplantation. The median time from initiating the postoperative immunosuppressive therapy to the onset of symptoms or disease changes was 18 (0.5-140) months. Among them, 9 patients developed fever, 7 patients developed cough or expectoration and 4 patients developed dyspnoea. Haemoglobin was decreased in 10 patients. Pulmonary nodules were found in 7 patients. Among the 21 patients, 7 were diagnosed by positive culture, 6 by biopsy, 5 by culture and biopsy. Of the 21 patients, 13 patients improved by antifungal therapy, 8 patients worsened or died. Seven patients who received amphotericin B followed by itraconazole (ITR) therapy all improved. Regarding the use of immunosuppressants in 12 patients, 9 patients had to discontinue or reduce their medications (6 patients improved, 3 patients worsened or died).

Conclusion

Patients with TSM after transplant often have disseminated infections, involving the respiratory, hematopoietic and so on. Fever, cough, decreased haemoglobin and pulmonary nodules often occur approximately 18 months after surgery. The combined applications of culture, biopsy, NGS are helpful for an early diagnosis. Antifungal therapy with amphotericin B followed by itraconazole is recommended, and the dosage of the immunosuppressant should be adjusted timely.

Title of Paper: First case of subcutaneous infection by Talaromyces marneffei in a renal transplant recipient from India and review of literature

Talaromyces marneffei is one of the endemic mycoses prevalent in South-East Asian region. The infection, which was once considered to be opportunistic infection in HIV-positive patients, is establishing foothold in transplant and immunocompetent population. We report a case of a 41-year-old post-renal transplant female with a travel history to Assam two years back presenting with a subcutaneous lesion on right side of scalp associated with pain and blurring of vision in right eye. Fine-needle aspiration from the scalp lesion showed yeast cells with transverse septation in cytological examination and culture grew Talaromyces marneffei, which was confirmed by sequencing of ITS region. Patient was successfully managed with oral itraconazole 200 mg twice daily for ten months without subsequent recurrence. To our knowledge, this is the first case of subcutaneous infection by T. marneffei in a renal transplant recipient from India.

Disseminated Talaromyces marneffei Infection in a Non-HIV Infant With a Homozygous Private Variant of RELB

Objective

This study presents a relatively rare case of disseminated Talaromyces marneffei (T. marneffei) infection in an HIV-negative patient.

Methods

An 8-month-old girl was hospitalized because of uncontrollable fever and cough for 6 days. Routine laboratory tests, biochemical detection, immunological tests, pathogenic examination, and imaging inspection were performed. Genetic tests of trio whole genome sequencing (Trio-WES), trio copy number sequencing (Trio-CNVseq), and Sanger sequencing were conducted to identify pathogenic variants. In silico analysis of the sequence alignment and structural modeling results was carried out to study the possible pathogenicity of the identified variant. Western blotting was performed to investigate the expression of the identified gene at the protein level.

Results

Enhanced CT and MRI scanning demonstrated thymic dysplasia, diffuse pulmonary and liver nodules, and many balloon-like air sacs in both lungs. The white blood cell count, neutrophil count, and neutrophil ratio were normal or elevated. The patient was HIV-negative and bone marrow and blood culture showed T. marneffei infection. Total lymphocyte count, CD3+ T lymphocyte count, CD3+CD4+ T lymphocyte count, CD3+CD8+ T lymphocyte count, and NK cell count decreased, while the number of CD19 positive B cells increased. However, the ratio of CD3+CD4+:CD3+CD8+ T cells increased. Trio-WES identified a homozygous private variant of NM_006509: c.400_c.401insAGC/p.Lys134 delinsLysGln in RELB and Sanger sequencing validated the result. Structural modeling indicated that the variant may be pathogenic. Reverse transcription-polymerase chain reaction and Western blot analysis showed that the expression of RelB in the patient was lower than that in the healthy controls at mRNA and protein levels.

Conclusion

This is the first report on disseminated T. marneffei infection in a patient with a homozygous private variant of RELB.

Bioinformatic analysis of the pathogenic mechanism of talaromyces marneffei infection

BACKGROUND

Talaromyces marneffei (T marneffei), known as a significant pathogen in patients with AIDS in Southeast Asia, is a dimorphic fungus, which can cause deadly systematic infection in immunocompromised hosts. What is more, the dimorphic phase transition has been reported as a conspicuous process linked with virulence. Interestingly, the yeast form was found in infected individuals, representing the pathogenic phase. However, few researches were found to study the mechanism of dimorphic transition. Thus, a diverse insight into the dimorphic switch mechanism, is urgently needed and we are the first one to research the mechanism of dimorphism.

METHODS

Firstly, we investigated the microarray of T. marneffei in the Gene Expression Omnibus database (GEO) for differentially expressed genes (DEGs). Then Database for Annotation, Visualization and Integrated Discovery (DAVID) v6.8 was employed to analyze the underlying enrichment and pathway in biological process of DEGs. Meanwhile, protein-protein interaction (PPI) network was constructed using STRING database. On the strength of the theory that similar amino acid sequences share similar structures, which play a decisive role on the function of protein, three dimensional structures of hub-genes were predicted to further investigate the likely function of hub-genes.

RESULTS

GSE51109 was elected as the eligible series for the purpose of our research, including GSM1238923 (GSM23), GSM1238924 (GSM24), and GSM1238925 (GSM25). PMAA_012920, PMAA_028730, PMAA_068140, PMAA_092900, PMAA_032350 were the most remarkable genes in all of the three PPI networks, thus, were viewed as hub-genes. With regard to the three-dimensional construction, except that there was no significant prediction structure of PMAA_092900 with the criterion seq identify > 30%, GMQE: 0-1, QMEAN4: -4-0, the parallel templates for four structures were Crystal structure of Saccharomyces cerevesiae mitochondrial NADP(+)-dependent isocitrate dehydrogenase in complex with isocitrate, Organellar two-pore channels (TPCs), Yeast Isocitrate Dehydrogenase (Apo Form) and Crystal Structure Of ATP-Dependent Phosphoenolpyruvate Carboxykinase From Thermus thermophilus HB8 in order.

CONCLUSION

The dimorphic transition of T. marneffei was viewed as a pathogenic factor and DEGs were observed. In-depth study of the function and pathway of DEGs revealed that PMAA_012920, PMAA_028730, PMAA_068140, PMAA_092900, PMAA_032350 were most likely acting as the hub-genes and were likely taking effect through regulating energy metabolism.

Methylcitrate cycle gene MCD is essential for the virulence of Talaromyces marneffei

Talaromyces marneffei (T. marneffei), which used to be known as Penicillium marneffei, is the causative agent of the fatal systemic mycosis known as talaromycosis. For the purpose of understanding the role of methylcitrate cycle in the virulence of T. marneffei, we generated MCD deletion (ΔMCD) and complementation (ΔMCD+) mutants of T. marneffei. Growth in different carbon sources showed that ΔMCD cannot grow on propionate media and grew slowly on the valerate, valine, methionine, isoleucine, cholesterol, and YNB (carbon free) media. The macrophage killing assay showed that ΔMCD was attenuated in macrophages of mice in vitro, especially at the presence of propionate. Finally, virulence studies in a murine infection experiment revealed attenuated virulence of the ΔMCD, which indicates MCD is essential for T. marneffei virulence in the host. This experiment laid the foundation for the further study of the specific mechanisms underlying the methylcitrate cycle of T. marneffei and may provide suitable targets for new antifungals.

The decreased number and function of lymphocytes is associated with Penicillium marneffei infection in HIV-negative patients

BACKGROUND/PURPOSE

Penicillium marneffei (P. marneffei) infection, which has been traditionally considered as an indicator of immunosuppression, is one of the most common systemic opportunistic infections in patients with AIDS. Recently, more and more P. marneffei infections have been documented in HIV-negative patients without underlying diseases, which challenges the traditional view that P. marneffei infection is an indicator of immunosuppression. We aimed to evaluate the number and function of lymphocytes in HIV-negative patients with P. marneffei infection.

METHODS

15 HIV-negative P. marneffei-infected patients and 18 healthy controls were recruited and investigated. The number and function of lymphocytes were analyzed by flow cytometry.

RESULTS

Most laboratory tests were within the reference ranges, except for a significant increase in total IgE in P. marneffei-infected patients. Lymphocyte subset analysis showed that the number of CD4⁺ T cells and NK cells was significantly decreased in HIV-negative marneffei-infected patients compared with healthy controls. However, almost half of the marneffei-infected patients still had normal levels of lymphocytes. A further analysis of cell function showed that the activation and proliferation of CD4⁺ T cells, the cytotoxicity of CD8⁺ T cells and NK cells, and the cytokine secretion potential of CD4⁺ T cells and NK cells were all impaired, in comparison with healthy controls.

CONCLUSIONS

P. marneffei infection has to be regarded as an indicator of immunosuppression. A further investigation of cell function is required in patients with opportunistic infection, as the cell function may be impaired in this condition.

Rapid and robust identification of clinical isolates of Talaromyces marneffei based on MALDI-TOF mass spectrometry or dimorphism in Galleria mellonella

Talaromyces marneffei is a thermally dimorphic fungal pathogen that causes serious infections particularly in patients with human immunodeficiency virus (HIV). Although the mould form typically produces a characteristic red-diffusing pigment, and conidia from penicillate heads, several nonpathogenic Talaromyces/Penicillium species are morphologically and phenotypically similar. While those other species do not exhibit thermal dimorphism, conversion of T. marneffei to the distinctive fission yeast form in vitro is arduous and frequently incomplete. Here we show that T. marneffei can be rapidly and unambiguously discriminated from related nonpathogenic Talaromyces/Penicillium spp., either by matrix-assisted laser desorption ionisation time-of-flight (MALDI-TOF) mass spectrometry or conversion to fission yeast after introduction into Galleria mellonella. Conversion of T. marneffei conidia to the fission yeast form in G. mellonella larvae occurred as early as 24 h post inoculation at 37oC. Identification by MALDI-TOF was possible after supplementation of the commercial Bruker database with in-house mass spectral profiles created from either the yeast or mycelial phase of T. marneffei. In addition, we show that in-house generated mass spectral profiles could be successfully used to identify T. marneffei with a recently published on-line MALDI-TOF database, circumventing the need to create extensive in-house additional databases for rarely encountered fungal pathogens.

Novel Partitivirus Enhances Virulence of and Causes Aberrant Gene Expression in Talaromyces marneffei

Talaromyces marneffei is the most important thermal dimorphic fungus causing systemic mycosis in Southeast Asia. We report the discovery of a novel partitivirus, Talaromyces marneffeipartitivirus-1 (TmPV1). TmPV1 was detected in 7 (12.7%) of 55 clinical T. marneffei isolates. Complete genome sequencing of the seven TmPV1 isolates revealed two double-stranded RNA (dsRNA) segments encoding RNA-dependent RNA polymerase (RdRp) and capsid protein, respectively. Phylogenetic analysis showed that TmPV1 occupied a distinct clade among the members of the genus Gammapartitivirus Transmission electron microscopy confirmed the presence of isometric, nonenveloped viral particles of 30 to 45 nm in diameter, compatible with partitiviruses, in TmPV1-infected T. marneffei Quantitative reverse transcription-PCR (qRT-PCR) demonstrated higher viral load of TmPV1 in the yeast phase than in the mycelial phase of T. marneffei Two virus-free isolates, PM1 and PM41, were successfully infected by purified TmPV1 using protoplast transfection. Mice challenged with TmPV1-infected T. marneffei isolates showed significantly shortened survival time (P < 0.0001) and higher fungal burden in organs than mice challenged with isogenic TmPV1-free isolates. Transcriptomic analysis showed that TmPV1 causes aberrant expression of various genes in T. marneffei, with upregulation of potential virulence factors and suppression of RNA interference (RNAi)-related genes. This is the first report of a mycovirus in a thermally dimorphic fungus. Further studies are required to ascertain the mechanism whereby TmPV1 enhances the virulence of T. marneffei in mice and the potential role of RNAi-related genes in antiviral defense in T. marneffeiIMPORTANCETalaromyces marneffei (formerly Penicillium marneffei) is the most important thermal dimorphic fungus in Southeast Asia, causing highly fatal systemic penicilliosis in HIV-infected and immunocompromised patients. We discovered a novel mycovirus, TmPV1, in seven clinical isolates of T. marneffei TmPV1 belongs to the genus Gammapartitivirus of the family Partitiviridae We showed that TmPV1 enhanced the virulence of T. marneffei in mice, with shortened survival time and higher fungal burden in the organs of mice challenged with TmPV1-infected T. marneffei isolates than in those of mice challenged with virus-free isogenic isolates. Transcriptomics analysis showed that TmPV1 altered the expression of genes involved in various cellular processes in T. marneffei, with upregulation of potential virulence factors and suppression of RNAi machinery which may be involved in antiviral defense. This is the first report of a mycovirus in a thermal dimorphic fungus. The present results offer insights into mycovirus-fungus interactions and pathogenesis of thermal dimorphic fungi.

In Vitro Activity of Posaconazole against Talaromyces marneffei by Broth Microdilution and Etest Methods and Comparison to Itraconazole, Voriconazole, and Anidulafungin

We determined the susceptibilities of 57 Talaromyces marneffei strains to anidulafungin, itraconazole, voriconazole, and posaconazole with MICs of 2 to 8, 0.002 to 0.004, 0.016 to 0.063, and 0.001 to 0.002 μg/ml by broth microdilution and >32, ≤0.002 to 0.008, ≤0.002 to 0.008, and ≤0.002 μg/ml by Etest, respectively, at yeast phase; MICs at mycelial phase for anidulafungin and posaconazole were 1 to 2 and 0.004 to 0.063 μg/ml, respectively. The results suggest promising activities of posaconazole. Etest can be used for testing of azoles against T. marneffei.

First-in-man observation of Talaromyces marneffei-transmission by organ transplantation

A lung transplant recipient was diagnosed with penicilliosis due to Talaromyces marneffei, a fungus endemic in South-East Asia, which was acquired by donor transmission. This first case of Talaromyces marneffei-transmission by transplantation underscores that current globalisation of travelling necessitates increased vigilance for transmission of unusual pathogens in organ recipients.

Mp1p Is a Virulence Factor in Talaromyces (Penicillium) marneffei

Background

Talaromyces marneffei is an opportunistic dimorphic fungus prevalent in Southeast Asia. We previously demonstrated that Mp1p is an immunogenic surface and secretory mannoprotein of T. marneffei. Since Mp1p is a surface protein that can generate protective immunity, we hypothesized that Mp1p and/or its homologs are virulence factors.

Methodology/Principal Findings

We examined the pathogenic roles of Mp1p and its homologs in a mouse model. All mice died 21 and 30 days after challenge with wild-type T. marneffei PM1 and MP1 complemented mutant respectively. None of the mice died 60 days after challenge with MP1 knockout mutant (P<0.0001). Seventy percent of mice died 60 days after challenge with MP1 knockdown mutant (P<0.0001). All mice died after challenge with MPLP1 to MPLP13 knockdown mutants, suggesting that only Mp1p plays a significant role in virulence. The mean fungal loads of PM1 and MP1 complemented mutant in the liver, lung, kidney and spleen were significantly higher than those of the MP1 knockout mutant. Similarly, the mean load of PM1 in the liver, lung and spleen were significantly higher than that of the MP1 knockdown mutant. Histopathological studies showed an abundance of yeast in the kidney, spleen, liver and lung with more marked hepatic and splenic necrosis in mice challenged with PM1 compared to MP1 knockout and MP1 knockdown mutants. Likewise, a higher abundance of yeast was observed in the liver and spleen of mice challenged with MP1 complemented mutant compared to MP1 knockout mutant. PM1 and MP1 complemented mutant survived significantly better than MP1 knockout mutant in macrophages at 48 hours (P<0.01) post-infection. The mean fungal counts of Pichia pastoris GS115-MP1 in the liver (P<0.001) and spleen (P<0.05) of mice were significantly higher than those of GS115 at 24 hours post-challenge.

Conclusions/Significance

Mp1p is a key virulence factor of T. marneffei. Mp1p mediates virulence by improving the survival of T. marneffei in macrophages.

Talaromyces (Penicillium) marneffei is an opportunistic thermal dimorphic fungus most prevalent in Southeast Asia. Our team has previously shown that Mp1p, a protein encoded by the MP1 gene, is an immunogenic surface and secretory protein of T. marneffei. In this study, we showed that mice challenged with T. marneffei with the MP1 gene died but those challenged with T. marneffei without the MP1 gene did not die. There was also significantly higher fungal load and more necrosis in organs of mice challenged with T. marneffei with the MP1 gene than T. marneffei without the MP1 gene. Furthermore, T. marneffei with the MP1 gene survived better in macrophages than T. marneffei without the MP1 gene and Pichia pastoris with the MP1 gene survived in mice better than P. pastoris without the MP1 gene. Our data support that Mp1p is a key virulence factor of T. marneffei and Mp1p mediates virulence by improving the survival of T. marneffei in macrophages.

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry for rapid identification of mold and yeast cultures of Penicillium marneffei

BACKGROUND

Penicillium marneffei is the most important thermal dimorphic fungus causing systemic mycosis in HIV-infected and other immunocompromised patients in Southeast Asia. However, laboratory diagnosis of penicilliosis, which relies on microscopic morphology and mycelial-to-yeast conversion, is time-consuming and expertise-dependent, thus delaying diagnosis and treatment. Although matrix -assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) is useful for identification of various medically important fungi, its performance for identification of P. marneffei is less clear.

RESULTS

We evaluated the performance of the Bruker MALDI-TOF MS system for identification of mold and yeast cultures of 59 clinical strains and the type strain of P. marneffei using the direct transfer method, with results compared to four phylogenetically closely related species, P. brevi-compactum, P. chrysogenum, Talaromyces aurantiacus and T. stipitatus. Using the Bruker original database combined with BDAL v4.0.0.1 and Filamentous Fungi Library 1.0, MALDI-TOF MS failed to identify the 60 P. marneffei strains grown in mold and yeast phase (identified as P. funiculosum and P. purpurogenum with scores <1.7 respectively). However, when the combined database was expanded with inclusion of spectra from 21 P. marneffei strains in mold and/or yeast phase, all the remaining 39 P. marneffei strains grown in mold or phase were correctly identified to the species level with score >2.0. The MS spectra of P. marneffei exhibited significant difference to those of P. brevi-compactum, P. chrysogenum, T. aurantiacus and T. stipitatus. However, MALDI-TOF MS failed to identify these four fungi to the species level using the combined database with or without spectra from P. marneffei.

CONCLUSIONS

MALDI-TOF MS is useful for rapid identification of both yeast and mold cultures of P. marneffei and differentiation from related species. However, accurate identification to the species level requires database expansion using P. marneffei strains.

Talaromyces (Penicillium) marneffei infection in non-HIV-infected patients

Talaromyces (Penicillium) marneffei is an important pathogenic thermally dimorphic fungus causing systemic mycosis in Southeast Asia. The clinical significance of T. marneffei became evident when the human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome epidemic arrived in Southeast Asia in 1988. Subsequently, a decline in the incidence of T. marneffei infection among HIV-infected patients was seen in regions with access to highly active antiretroviral therapy and other control measures for HIV. Since the 1990s, an increasing number of T. marneffei infections have been reported among non-HIV-infected patients with impaired cell-mediated immunity. Their comorbidities included primary adult-onset immunodeficiency due to anti-interferon-gamma autoantibodies and secondary immunosuppressive conditions including other autoimmune diseases, solid organ and hematopoietic stem cell transplantations, T-lymphocyte-depleting immunsuppressive drugs and novel anti-cancer targeted therapies such as anti-CD20 monoclonal antibodies and kinase inhibitors. Moreover, improved immunological diagnostics identified more primary immunodeficiency syndromes associated with T. marneffei infection in children. The higher case-fatality rate of T. marneffei infection in non-HIV-infected than HIV-infected patients might be related to delayed diagnosis due to the lack of clinical suspicion. Correction of the underlying immune defects and early use of antifungals are important treatment strategies. Clinicians should be familiar with the changing epidemiology and clinical management of T. marneffei infection among non-HIV-infected patients.

Polyketides, toxins and pigments in Penicillium marneffei

Penicillium marneffei (synonym: Talaromyces marneffei) is the most important pathogenic thermally dimorphic fungus in China and Southeastern Asia. The HIV/AIDS pandemic, particularly in China and other Southeast Asian countries, has led to the emergence of P. marneffei infection as an important AIDS-defining condition. Recently, we published the genome sequence of P. marneffei. In the P. marneffei genome, 23 polyketide synthase genes and two polyketide synthase-non-ribosomal peptide synthase hybrid genes were identified. This number is much higher than those of Coccidioides immitis and Histoplasma capsulatum, important pathogenic thermally dimorphic fungi in the Western world. Phylogenetically, these polyketide synthase genes were distributed evenly with their counterparts found in Aspergillus species and other fungi, suggesting that polyketide synthases in P. marneffei did not diverge from lineage-specific gene duplication through a recent expansion. Gene knockdown experiments and ultra-high performance liquid chromatography-photodiode array detector/electrospray ionization-quadruple time of flight-mass spectrometry analysis confirmed that at least four of the polyketide synthase genes were involved in the biosynthesis of various pigments in P. marneffei, including melanin, mitorubrinic acid, mitorubrinol, monascorubrin, rubropunctatin, citrinin and ankaflavin, some of which were mycotoxins and virulence factors of the fungus.

The in vitro fungicidal activity of human macrophages against Penicillium marneffei is suppressed by dexamethasone

Penicillium marneffei (P. marneffei) is a pathogenic fungus that can persist in macrophages and cause a life-threatening systemic mycosis in immunocompromised hosts. To elucidate the mechanisms underlying this opportunistic fungal infection, we established the co-culture system of P. marneffei conidia and human monocyte-derived macrophages (MDM) for investigating the interactions between them. And, we impaired the immune state of MDM by the addition of dexamethasone (DEX). Compared with immunocompetent MDM without DEX treatment in response to P. marneffei, DEX could damage MDM function in initiating the innate immune response through decreasing TNF-α production and the proportion of P. marneffei conidia in mature phagolysosomes, while the red pigment secretion by P. marneffei conidia was promoted by DEX following MDM lysis. Our data provide the evidence that DEX-treated MDM have a low fungicidal activity against P. marneffei that causes penicilliosis in immunocompromised hosts.

Disseminated Infections with Talaromyces marneffei in Non-AIDS Patients Given Monoclonal Antibodies against CD20 and Kinase Inhibitors

Infections with the fungus Talaromyces (formerly Penicillium) marneffei are rare in patients who do not have AIDS. We report disseminated T. marneffei infection in 4 hematology patients without AIDS who received targeted therapy with monoclonal antibodies against CD20 or kinase inhibitors during the past 2 years. Clinicians should be aware of this emerging complication, especially in patients from disease-endemic regions.

Transplantation in the tropics: lessons on prevention and management of tropical infectious diseases

Tropical infectious diseases (IDs) remain a rare complication in transplant recipients even in tropical settings, but this topic has become increasingly important during the last decade due to multiple factors. Interestingly, non-tropical countries report most of the experiences with tropical diseases. The reported experience from non-endemic regions, however, does not always reflect the experience of endemic areas. Most of the guidelines and recommendations in the literature may not be applicable in tropical settings due to logistical difficulties, cost, and lack of proven benefit. In addition, certain post-transplant prevention measures, as prophylaxis and reducing exposure risk, are not feasible. Nonetheless, risk assessment and post-transplant management of tropical IDs in tropical areas should not be neglected, and clinicians need to have a higher clinical awareness for tropical ID occurring in this population. Herein, we review the more significant tropical ID in transplant patients, focusing on relevant experience reported by tropical settings.

The biosynthetic pathway for a thousand-year-old natural food colorant and citrinin in Penicillium marneffei

Monascorubrin and its derivatives are polyketides used as natural colorants for a wide range of food for more than one thousand years. Since the biosynthetic pathway for this ancient chemical compound is unknown and genome sequence unavailable for any Monascus species, monascorubrin production has relied on extraction from fungal cultures of Monascus species. In vitro synthesis and genetic manipulation are not possible. Here we report the polyketide gene cluster and pathway for monascorubrin biosynthesis in Penicillium marneffei, a diffusible red pigment-producing, thermal dimorphic fungus, taking advantage of available genome sequence and faster growth rate than Monascus species. We also documented that the red pigment of P. marneffei is a mixture of more than 16 chemical compounds, which are amino acid conjugates of monascorubrin and rubropunctatin, and showed that this polyketide gene cluster and pathway are also responsible for biosynthesis of ankaflavin and citrinin, a mycotoxin with nephrotoxic activity in mammals. The present study on elucidation of the biosynthetic pathway of monascorubrin is a proof-of-the-concept study that serves as a cornerstone for future studies on monascorubrin biosynthesis pathway dissection in Monascus species.

Proteome profiling of the dimorphic fungus Penicillium marneffei extracellular proteins and identification of glyceraldehyde-3-phosphate dehydrogenase as an important adhesion factor for conidial attachment

Despite being the most important thermal dimorphic fungus causing systemic mycosis in Southeast Asia, the pathogenic mechanisms of Penicillium marneffei remain largely unknown. By comparing the extracellular proteomes of P. marneffei in mycelial and yeast phases, we identified 12 differentially expressed proteins among which glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and heat shock protein 60 (HSP60) were found to be upregulated in mycelial and yeast phases respectively. Based on previous findings in other pathogens, we hypothesized that these two extracellular proteins may be involved in adherence during P. marneffei-host interaction. Using inhibition assays with recombinant GAPDH (rGAPDH) proteins and anti-rGAPDH sera, we demonstrated that adhesion of P. marneffei conidia to fibronectin and laminin was inhibited by rGAPDH or rabbit anti-rGAPDH serum in a dose-dependent manner. Similarly, a dose-dependent inhibition of conidial adherence to A549 pneumocytes by rGAPDH or rabbit anti-rGAPDH serum was observed, suggesting that P. marneffei GAPDH can mediate binding of conidia to human extracellular matrix proteins and pneumocytes. However, HSP60 did not exhibit similar inhibition on conidia adherence, and neither GAPDH norHSP60 exhibited inhibition on adherence to J774 or THP-1 macrophage cell lines. This report demonstrates GAPDH as an adherence factor in P. marneffei by mediating conidia adherence to host bronchoalveolar epithelium during the early establishment phase of infection.

Identification of microRNA-like RNAs in mycelial and yeast phases of the thermal dimorphic fungus Penicillium marneffei

Background

Penicillium marneffei is the most important thermal dimorphic fungus causing systemic mycosis in China and Southeast Asia. While miRNAs are increasingly recognized for their roles in post-transcriptional regulation of gene expression in animals and plants, miRNAs in fungi were less well studied and their potential roles in fungal dimorphism were largely unknown. Based on P. marneffei genome sequence, we hypothesize that miRNA-like RNAs (milRNAs) may be expressed in the dimorphic fungus.

Methodology/Principal Findings

We attempted to identify milRNAs in P. marneffei in both mycelial and yeast phase using high-throughput sequencing technology. Small RNAs were more abundantly expressed in mycelial than yeast phase. Sequence analysis revealed 24 potential milRNA candidates, including 17 candidates in mycelial and seven in yeast phase. Two genes, dcl-1 and dcl-2, encoding putative Dicer-like proteins and the gene, qde-2, encoding Argonaute-like protein, were identified in P. marneffei. Phylogenetic analysis showed that dcl-2 of P. marneffei was more closely related to the homologues in other thermal dimorphic pathogenic fungi than to Penicillium chrysogenum and Aspergillus spp., suggesting the co-evolution of dcl-2 among the thermal dimorphic fungi. Moreover, dcl-2 demonstrated higher mRNA expression levels in mycelial than yeast phase by 7 folds (P<0.001). Northern blot analysis confirmed the expression of two milRNAs, PM-milR-M1 and PM-milR-M2, only in mycelial phase. Using dcl-1^KO, dcl-2^KO, dcl^DKO and qde-2^KO deletion mutants, we showed that the biogenesis of both milRNAs were dependent on dcl-2 but not dcl-1 or qde-2. The mRNA expression levels of three predicted targets of PM-milR-M1 were upregulated in knockdown strain PM-milR-M1^KD, supporting regulatory function of milRNAs.

Conclusions/Significance

Our findings provided the first evidence for differential expression of milRNAs in different growth phases of thermal dimorphic fungi and shed light on the evolution of fungal proteins involved in milRNA biogenesis and possible role of post-transcriptional control in governing thermal dimorphism.

Penicillium marneffei is the most important thermal dimorphic pathogenic fungus in Southeast Asia. Despite findings on diverse genes and mechanisms involved in dimorphic switching, the key to signally pathways governing the switch is still unknown. Since miRNAs are important regulatory molecules in eukaryotes, we attempt to define if miRNAs are expressed in different growth phases of P. marneffei. Using high-throughput sequencing, we identified 24 potential milRNA candidates in P. marneffei, which were more abundantly expressed in mycelial than yeast phase. Two genes, dcl-1 and dcl-2, encoding Dicer-like proteins and the gene, qde-2, encoding Argonaute-like protein, were also identified. Phylogenetic analysis showed that dcl-2 of P. marneffei was more closely related to the homologues in other thermal dimorphic pathogenic fungi than to Penicillium chrysogenum and Aspergillus spp.. dcl-2 demonstrated higher mRNA levels in mycelial than yeast phase. Northern blot analysis confirmed expression of two milRNAs, PM-milR-M1 and PM-milR-M2, only in mycelial phase, whose expression was dependent on dcl-2 but not dcl-1 or qde-2. The mRNA levels of three predicted targets of PM-milR-M1 were upregulated in knockdown strain PM-milR-M1^KD, supporting its regulatory function. This study represents the first discovery of milRNAs in thermal dimorphic fungi, with differential expression in different growth phases.

First discovery of two polyketide synthase genes for mitorubrinic acid and mitorubrinol yellow pigment biosynthesis and implications in virulence of Penicillium marneffei

Background

The genome of P. marneffei, the most important thermal dimorphic fungus causing respiratory, skin and systemic mycosis in China and Southeast Asia, possesses 23 polyketide synthase (PKS) genes and 2 polyketide synthase nonribosomal peptide synthase hybrid (PKS-NRPS) genes, which is of high diversity compared to other thermal dimorphic pathogenic fungi. We hypothesized that the yellow pigment in the mold form of P. marneffei could also be synthesized by one or more PKS genes.

Methodology/Principal Findings

All 23 PKS and 2 PKS-NRPS genes of P. marneffei were systematically knocked down. A loss of the yellow pigment was observed in the mold form of the pks11 knockdown, pks12 knockdown and pks11pks12 double knockdown mutants. Sequence analysis showed that PKS11 and PKS12 are fungal non-reducing PKSs. Ultra high performance liquid chromatography-photodiode array detector/electrospray ionization-quadruple time of flight-mass spectrometry (MS) and MS/MS analysis of the culture filtrates of wild type P. marneffei and the pks11 knockdown, pks12 knockdown and pks11pks12 double knockdown mutants showed that the yellow pigment is composed of mitorubrinic acid and mitorubrinol. The survival of mice challenged with the pks11 knockdown, pks12 knockdown and pks11pks12 double knockdown mutants was significantly better than those challenged with wild type P. marneffei (P<0.05). There was also statistically significant decrease in survival of pks11 knockdown, pks12 knockdown and pks11pks12 double knockdown mutants compared to wild type P. marneffei in both J774 and THP1 macrophages (P<0.05).

Conclusions/Significance

The yellow pigment of the mold form of P. marneffei is composed of mitorubrinol and mitorubrinic acid. This represents the first discovery of PKS genes responsible for mitorubrinol and mitorubrinic acid biosynthesis. pks12 and pks11 are probably responsible for sequential use in the biosynthesis of mitorubrinol and mitorubrinic acid. Mitorubrinol and mitorubrinic acid are virulence factors of P. marneffei by improving its intracellular survival in macrophages.

Penicillium marneffei is the most important thermal dimorphic fungus causing respiratory, skin and systemic mycosis in China and Southeast Asia. Its genome possesses a large number of polyketide synthase (PKS) genes, which should be responsible for synthesis of secondary metabolites such as pigments, antibiotics and mycotoxins. Using state-of-the-art gene knockdown and ultra high performance liquid chromatography-photodiode array detector/electrospray ionization-quadruple time of flight-mass spectrometry technologies, we discovered that the yellow pigment of P. marneffei was composed of mitorubrinol and mitorubrinic acid and was synthesized by two PKS genes, named pks12 and pks11. This represents the first discovery of PKS genes responsible for mitorubrinol and mitorubrinic acid biosynthesis, in which pks12 and pks11 are probably responsible for sequential use in the biosynthesis of mitorubrinol and mitorubrinic acid. Using a mouse model and human and mouse macrophage cell line models for P. marneffei infection, we also discovered that mitorubrinol and mitorubrinic acid are virulence factors of P. marneffei by improving its intracellular survival in macrophages.

Recurrent hemoptysis with Penicillium marneffei and Stenotrophomonas maltophilia in Job's syndrome

Pulmonary infection caused by the opportunistic organisms Penicillium marneffei and Stenotrophomonas maltophilia in patients with Job's syndrome is rare and not well documented. The case of a 30-year-old man with Job's syndrome who developed recurrent pneumonia and lung abscesses caused by P. marneffei and S. maltophilia, complicated by massive hemoptysis, is described. Bronchial artery embolization was successful in controlling the hemoptysis; however, the infection proved fatal despite appropriate antimicrobial therapy. A brief review of the literature on Job's syndrome and its associated infective pulmonary manifestations is also presented.

Marrow penicilliosis: a readily missed diagnosis

Penicillium marneffei is a dimorphic fungus that causes one of the most common opportunistic infections in Asian patients with AIDS. The diagnosis is established by microbiologic culture, requiring at least several days. A presumptive diagnosis can be made by cytologic or histologic examination of biopsied or aspirated tissue. Bone marrow biopsy is often performed in the workup of patients with AIDS who have fever or hematologic abnormalities and can provide prompt diagnosis of opportunistic infection. We report the bone marrow findings in the largest series of patients with culture-proven P marneffei infection. In the bone marrow, the histiocytes can occur in large numbers and be easily recognized or may be extremely subtle. P marneffei infection is sometimes not accompanied by granuloma formation despite marked histiocytic proliferation. The histiocytes contain a few to many intracellular yeast-form cells that resemble cellular debris because of their small size and staining pattern. The characteristic septate forms and the absence of budding help distinguish the condition from histoplasmosis and toxoplasmosis. Routine performance of silver methenamine stain for fungi in marrow biopsy specimens of febrile patients with AIDS is recommended to detect a subtle infection.

Disseminated penicilliosis, recurrent bacteremic nontyphoidal salmonellosis, and burkholderiosis associated with acquired immunodeficiency due to autoantibody against gamma interferon

Acquired immunodeficiency due to autoantibody against gamma interferon has recently been associated with opportunistic nontuberculous mycobacteriosis, especially among Southeast Asians. We report another 8 cases, all except one apparently immunocompetent hosts who suffered from concomitant or sequential infections by other intracellular pathogens causing penicilliosis, extraintestinal nontyphoidal salmonellosis, and burkholderiosis. The only case with an underlying immunodeficiency syndrome had systemic lupus erythematosus that was quiescent throughout the multiple infective episodes. Eight out of 10 (80.0%) patients with serological evidence of penicilliosis, 5 out of 7 (71.4%) with culture-positive extraintestinal nontyphoidal salmonellosis, 5 out of 28 (17.9%) with serological evidence of melioidosis, and 7 out of 13 (53.8%) with culture-positive nontuberculous mycobacteriosis possessed autoantibody against gamma interferon, whereas only 1 out of 100 patients with systemic lupus erythematosus did. Our study represents the first and largest case series linking this emerging immunodeficiency syndrome with these atypical infections in apparently immunocompetent hosts. Thus, we advocate that any patient with unexplained recurrent or polymicrobial infections due to these intracellular pathogens should be screened for acquired immunodeficiency due to autoantibody against gamma interferon.

MP1 homologue-based multilocus sequence system for typing the pathogenic fungus Penicillium marneffei: a novel approach using lineage-specific genes

A highly reproducible and discriminative typing system is essential for better understanding of the epidemiology of Penicillium marneffei, the most important thermal dimorphic fungus causing respiratory, skin, and systemic mycosis in Southeast Asia. The sequences of 11 housekeeping genes were identical among 10 strains of P. marneffei, but those of MP1 and its 13 homologues, a novel superfamily of mannoproteins in the subdivision Pezizomycotina of Ascomycetes, mostly species of Penicillium and Aspergillus, showed significant variations. Therefore, a multilocus sequence typing (MLST) system for P. marneffei was constructed using MP1 (549 bp) and the four of its homologues (MPLP4 [337 bp], MPLP7 [347 bp], MPLP10 [546 bp], and MPLP13 [422 bp]) that showed the greatest variations. Among the 2,201 bp of the five loci, 183 polymorphic sites were observed in 44 strains of P. marneffei. The median number of alleles at each locus was five (range, 5 [MPLP4, MPLP7, and MPLP13] to 15 [MPLP10]). Four of the five genes had nonsynonymous substitution/synonymous substitution (d(n)/d(s)) ratios of >1. A total of 35 different sequence types (STs) were assigned to the 44 P. marneffei isolates, with 28 of the 35 STs identified only once. The discriminatory power was 0.9884. MP1 and its homologues were better than housekeeping genes for MLST in P. marneffei. Due to their more rapid evolutionary rates, lineage-specific genes may be better candidates than housekeeping genes for sequence-based typing, especially in microbes that evolve slowly or have evolved recently.

Detection of circulating galactomannan in serum samples for diagnosis of Penicillium marneffei infection and cryptococcosis among patients infected with human immunodeficiency virus

Galactomannan (GM) is a heteropolysaccharide in the cell walls of most Aspergillus and Penicillium species. Cross-reactivity of Cryptococcus neoformans galactoxylomannan in an Aspergillus GM test has also been reported. In this study, we used a Platelia Aspergillus enzyme immunoassay kit (Bio-Rad) to test serum samples obtained from 48 human immunodeficiency virus (HIV)-infected patients (15 with penicilliosis [7 with fungemia alone, 4 with cavitary lung lesions alone, 3 with both fungemia and cavitary lung lesions, and 1 with disseminated disease], 22 with cryptococcosis [11 with fungemia alone, 5 with cavitary lung lesions, 3 with both, and 3 with meningitis alone], and 11 without any invasive fungal infection [control]) for GM levels. None of the patients had aspergillosis or concurrent use of piperacillin-tazobactam or amoxicillin-clavulanate. The median time between diagnosis of fungal infection and collection of serum samples was 0 days for penicilliosis and 1.5 days for cryptococcosis. Of patients with penicilliosis, cryptococcosis, and controls, 73.3%, 13.6%, and 9%, respectively, had GM optical density (OD) indices of >0.5 (P = 0.0001). GM OD indices were higher for penicilliosis (median OD index, 4.419; range, 0.158 to >20) than for cryptococcosis (median, 0.247; range, 0.112 to 3.849) cases (P < 0.001). Patients with fungemic penicilliosis had higher OD indices (median, 10.628; range, 0.401 to >20) than patients with nonfungemic penicilliosis (median, 0.378; range, 0.158 to 4.419) and patients with cryptococcemia (median, 0.231; range, 0.112 to 1.168) (P < 0.001). Of the 15 patients with cavitary lung lesions, those with penicilliosis had higher antigen levels (median OD index, 1.641; range, 0.247 to >20) than those with cryptococcosis (median, 0.227; range, 0.112 to 3.849) (P = 0.011). This study showed that the GM OD index was significantly elevated for HIV patients with penicilliosis. The use of the GM antigen assay may facilitate earlier diagnosis of Penicillium marneffei infection for HIV-infected patients in areas of endemicity.

Emerging fungal pathogens in pulmonary disease

PURPOSE OF REVIEW

Invasive fungal infections of the lung have been increasing due to the increase of the population most at risk. This review aims to describe some of the emerging fungal pathogens and their complex management.

RECENT FINDINGS

With the increase in immunosuppressed populations, physicians are increasingly encountering uncommon fungal pathogens that historically have been difficult to identify and treat. Many of these fungal infections present with similar clinical features and often show similar histopathological changes. Treatment options are more complex because of an increasing number of antifungals that have become available for clinical use. The correct usage of these antifungals in addressing emerging fungal infections is unclear, however. Drawing from in-vitro and in-vivo susceptibility testing and case reports, some deductions may be made for the best empirical treatment of these deadly diseases. In general, the newer triazoles (voriconazole and posiconazole) and the use of combination therapy have shown promise.

SUMMARY

Invasive fungal infections are on the increase and contribute significantly to overall mortality, particularly among transplant recipients. With the lack of well designed controlled clinical studies, physicians will need to draw from previously described cases and in-vitro susceptibility testing to optimize therapy.

Isolation and properties of extracellular proteinases of Penicillium marneffei

Penicillium marneffei is a dimorphic fungus native to Southeast Asia. Disease caused by this organism, until recently a very rare condition, has increased dramatically in parallel with the increase in the number of individuals in the region immunocompromised by AIDS and other conditions. While much research has been performed on the control of dimorphic switching in P. marneffei, there is a relative dearth of information regarding the proteinases secreted by this pathogen. Our laboratory has purified and characterized two proteinases produced by this organism in liquid culture and cloned the gene of a third. Both the recombinant enzyme expressed from the cloned gene and one of those purified from culture supernatants have been identified as members of the eqolisin family, a group of pepstatin-insensitive acid proteinases. The other enzyme purified from a culture supernatant is a serine proteinase with activity in the neutral pH range. These enzymes appear to be differentially expressed, depending on culture conditions.

A novel approach for screening immunogenic proteins inPenicillium marneffeiusing the ΔAFMP1ΔAFMP2deletion mutant ofAspergillus fumigatus

Using serum from guinea-pigs immunized with a DeltaAFMP1DeltaAFMP2 deletion mutant of Aspergillus fumigatus to screen a cDNA library of A. fumigatus, we cloned a novel immunogenic 57-kDa protein in A. fumigatus. We also cloned its 55-kDa homologue in Penicillium marneffei, which was possibly related to amino acid biosynthesis and metabolism, with homologues present only in the subphylum Pezizomycotina of Ascomycota. The recombinant 55-kDa protein of P. marneffei reacted strongly with guinea-pig serum immunized with P. marneffei and with the sera of patients with P. marneffei infection. A similar approach could be applied to immunogenic protein screening in other microorganisms for serological diagnosis, epidemiological studies and the study of vaccines.

Genomic and experimental evidence for a potential sexual cycle in the pathogenic thermal dimorphic fungus Penicillium marneffei

All meiotic genes (except HOP1) and genes encoding putative pheromone processing enzymes, pheromone receptors and pheromone response pathways proteins in Aspergillus fumigatus and Aspergillus nidulans and a putative MAT-1 alpha box mating-type gene were present in the Penicillium marneffei genome. A putative MAT-2 high-mobility group mating-type gene was amplified from a MAT-1 alpha box mating-type gene-negative P. marneffei strain. Among 37 P. marneffei patient strains, MAT-1 alpha box and MAT-2 high-mobility group mating-type genes were present in 23 and 14 isolates, respectively. We speculate that P. marneffei can potentially be a heterothallic fungus that does not switch mating type.