Characterization of a novel yeast phase-specific antigen expressed during in vitro thermal phase transition of Talaromyces marneffei

Talaromyces marneffei endocarditis initially detected by Next Generation Sequencing: A case report

BACKGROUND

Talaromyces marneffei (T. marneffei) is a thermal dimorphic fungus, which can cause lung or blood stream infection in patients, often life-threatening. However, endocarditis caused by T. marneffei has not been reported. For elderly patients with implanted cardiac devices or artificial valves, the prevention and treatment of infective endocarditis should not be ignored.

METHODS

This is a descriptive study of a T. marneffei endocarditis by joint detection of cardiac ultrasound examination, peripheral blood DNA metagenomics Next Generation Sequencing (mNGS), and in vitro culture.

RESULTS

We describe an 80-year-old female patient with an unusual infection of T. marneffei endocarditis. After intravenous drip of 0.2 g voriconazole twice a day for antifungal treatment, the patient showed no signs of improvement and their family refused further treatment.

CONCLUSION

Infective endocarditis is becoming more and more common in the elderly due to the widely use of invasive surgical procedures and implantation of intracardiac devices. The diagnosis and treatment of T. marneffei endocarditis is challenging because of its rarity. Here, we discussed a case of T. marneffei endocarditis, and emphasized the role of mNGS in early diagnosis, which is of great significance for treatment and survival rate of patients.

Identification and production of novel potential pathogen-specific biomarkers for diagnosis of histoplasmosis

IMPORTANCE

Histoplasmosis is considered one of the most important mycoses due to the increasing number of individuals susceptible to develop severe clinical forms, particularly those with HIV/AIDS or receiving immunosuppressive biological therapies, the high mortality rates reported when antifungal treatment is not initiated in a timely manner, and the limitations of conventional diagnostic methods. In this context, there is a clear need to improve the capacity of diagnostic tools to specifically detect the fungal pathogen, regardless of the patient's clinical condition or the presence of other co-infections. The proposed novel pathogen-specific biomarkers have the potential to be used in immunodiagnostic platforms and antifungal treatment monitoring in histoplasmosis. In addition, the bioinformatics strategy used in this study could be applied to identify potential diagnostic biomarkers in other models of fungal infection of public health importance.

Talaromyces marneffei suppresses macrophage inflammation by regulating host alternative splicing

Talaromyces marneffei (T. marneffei) immune escape is essential in the pathogenesis of talaromycosis. It is currently known that T. marneffei achieves immune escape through various strategies. However, the role of cellular alternative splicing (AS) in immune escape remains unclear. Here, we depict the AS landscape in macrophages upon T. marneffei infection via high-throughput RNA sequencing and detect a truncated protein of NCOR2 / SMRT, named NCOR2-013, which is significantly upregulated after T. marneffei infection. Mechanistic analysis indicates that NCOR2-013 forms a co-repression complex with TBL1XR1 / TBLR1 and HDAC3, thereby inhibiting JunB-mediated transcriptional activation of pro-inflammatory cytokines via the inhibition of histone acetylation. Furthermore, we identify TUT1 as the AS regulator that regulates NCOR2-013 production and promotes T. marneffei immune evasion. Collectively, these findings indicate that T. marneffei escapes macrophage killing through TUT1-mediated alternative splicing of NCOR2 / SMRT, providing insight into the molecular mechanisms of T. marneffei immune evasion and potential targets for talaromycosis therapy.

Evaluation of the yeast phase-specific monoclonal antibody 4D1 and Galanthus nivalis agglutinin sandwich ELISA to detect Talaromyces marneffei antigen in human urine

Talaromyces (Penicillium) marneffei (TM) is an important, but neglected, thermally dimorphic fungus. It is the pathogenic cause of talaromycosis, which is strongly associated with the immunodeficiency state present in individuals with advanced HIV disease. The purpose of this study was to develop a sandwich enzyme-linked immunosorbent assay (sandwich ELISA) for the detection of T. marneffei cytoplasmic yeast antigen (TM CYA) in human urine. Monoclonal antibody (MAb) 4D1 specifically binds to TM CYA. Galanthus nivalis agglutinin (GNA), a mannose -binding lectin, recognizes and binds to mannose residues of TM CYA. For the sandwich ELISA, the microplate was coated with GNA as the capturing molecule for absorbing immune complexes of MAb 4D1-TM CYA. The MAb 4D1-GNA sandwich ELISA did not detect a cross-reaction with other antigens from other fungi or bacteria. Seventy-four urine samples from patients with blood culture -confirmed talaromycosis and 229 urine samples from people without talaromycosis residing in the endemic area were subjected to the MAb 4D1-GNA sandwich ELISA. At an optical density (OD) cutoff value of 0.356, the sensitivity was 89.19% [95% confidence interval (CI): 79.80% -95.22%]; the specificity was 98.69% (95% CI: 96.22% -99.73%). The diagnostic performance of the MAb 4D1-GNA sandwich ELISA was highly consistent with those of blood culture and the Platelia Aspergillus galactomannan (GM) ELISA kit. Collectively, the MAb 4D1-GNA sandwich ELISA is a promising technique for the rapid diagnosis of T. marneffei infection, which would facilitate the early treatment of patients with talaromycosis and it may be used to monitor treatment responses.

Extracellular vesicles derived from Talaromyces marneffei contain immunogenic compounds and modulate THP-1 macrophage responses

Pathogenic eukaryotes including fungi release extracellular vesicles (EVs) which are composed of a variety of bioactive components, including peptides, nucleic acids, polysaccharides, and membrane lipids. EVs contain virulence-associated molecules suggesting a crucial role of these structures in disease pathogenesis. EVs derived from the pathogenic yeast phase of Talaromyces (Penicillium) marneffei, a causative agent of systemic opportunistic mycoses "talaromycosis," were studied for their immunogenic components and immunomodulatory properties. Some important virulence factors in EVs including fungal melanin and yeast phase specific mannoprotein were determined by immunoblotting. Furthermore, fluorescence microscopy revealed that T. marneffei EVs were internalized by THP-1 human macrophages. Co-incubation of T. marneffei EVs with THP-1 human macrophages resulted in increased levels of supernatant interleukin (IL)-1β, IL-6 and IL-10. The expression of THP-1 macrophage surface CD86 was significantly increased after exposed to T. marneffei EVs. These findings support the hypothesis that fungal EVs play an important role in macrophage "classical" M1 polarization. T. marneffei EVs preparations also increased phagocytosis, suggesting that EV components stimulate THP-1 macrophages to produce effective antimicrobial compounds. In addition, T. marneffei EVs stimulated THP-1 macrophages were more effective at killing T. marneffei conidia. These results indicate that T. marneffei EVs can potently modulate macrophage functions, resulting in the activation of these innate immune cells to enhance their antimicrobial activity.

Talaromyces marneffei infection and complicate manifestation of respiratory system in HIV-negative children

BACKGROUND

Respiratory symptoms are the earliest clinical manifestation of Talaromyces marneffei (TM) infection. In this study, we aimed to improve the early identification of TM infection in human immunodeficiency virus (HIV)-negative children with respiratory symptoms as the first manifestation, analyze the risk factors, and provide evidence for diagnosis and treatment.

METHODS

We retrospectively analyzed six cases of HIV-negative children with respiratory system infection symptoms as the first presentation.

RESULTS

All subjects (100%) had cough and hepatosplenomegaly, and five subjects (83.3%) had a fever; other symptoms and signs included lymph node enlargement, rash, rales, wheezing, hoarseness, hemoptysis, anemia, and thrush. Additionally, 66.7% of the cases had underlying diseases (three had malnutrition, one had severe combined immune deficiency [SCID]). The most common coinfecting pathogen was Pneumocystis jirovecii, which occurred in two cases (33.3%), followed by one case of Aspergillus sp. (16.6%). Furthermore, the value of β-D-glucan detection (G test) increased in 50% of the cases, while the proportion of NK decreased in six cases (100%). Five children (83.3%) were confirmed to have the pathogenic genetic mutations. Three children (50%) were treated with amphotericin B, voriconazole, and itraconazole, respectively; three children (50%) were treated with voriconazole and itraconazole. All children were tested for itraconazole and voriconazole plasma concentrations throughout antifungal therapy. Two cases (33.3%) relapsed after drug withdrawal within 1 year, and the average duration of antifungal treatment for all children was 17.7 months.

CONCLUSION

The first manifestation of TM infection in children is respiratory symptoms, which are nonspecific and easily misdiagnosed. When the effectiveness of anti-infection treatment is poor for recurrent respiratory tract infections, we must consider the condition with an opportunistic pathogen and attempt to identify the pathogen using various samples and detection methods to confirm the diagnosis. It is recommended the course for anti-TM disease be longer than one year for children with immune deficiency. Monitoring the blood concentration of antifungal drugs is important.

Expression of Cytokine Profiles in Human THP-1 Cells during Phase Transition of Talaromyces marneffei

Talaromyces marneffei, a dimorphic fungus, exhibits temperature-dependent growth, existing in a filamentous form at 25 °C and as a yeast at 37 °C. Several studies have highlighted the important roles of macrophages in defense against T. marneffei infection. However, the immune responses to the interaction of macrophages with T. marneffei cells during phase transition require further investigation. This study reports the expression of cytokine profiles in human THP-1 cells during infection by T. marneffei. THP-1 cells were infected with T. marneffei conidia at different multiplicity of infections (MOIs). Surviving conidia transformed into yeasts after phagocytosis by macrophages, and the number of yeasts gradually increased over 36 h. The transcription and secretion levels of pro- and anti-inflammatory cytokines were examined at different times by qRT-PCR and ELISA. Transcription levels of IL-8, IL-12, IL-1β, and TNF-α increased significantly at 12 or 24 h and then slightly decreased at 36 h. In contrast, the transcription levels of IL-6, IL-10, and TGF-β gradually increased at all MOIs. The levels of IL-6 and IL-10 secretion corresponded to their levels of transcription. These results indicated that as the number of intracellular yeasts increased, the infected macrophages first underwent slight M1 polarization before shifting to M2 polarization. This polarization transition was confirmed by the fungicidal ability and the expression of macrophage surface markers. By inducing the M2-type polarization of macrophages, the intracellular T. marneffei cells can successfully evade the immune response. Our study provides a novel insight into the immune characterization during the transition of T. marneffei infection and could further contribute to possible diagnostic and therapeutic interventions for this infection.

Overexpression of CD86 enhances the ability of THP-1 macrophages to defend against Talaromyces marneffei

BACKGROUND

Macrophages are the first line of defense against Talaromyces marneffei. CD86 is a surface molecule expressed on antigen-presenting cells, such as macrophages, that provide costimulatory signals necessary for T cell activation and survival. In a prior study, it was shown that as infection progressed, CD86 expression levels in macrophages considerably declined while CD86 concentrations in the supernatant significantly increased. Additionally, M1 macrophage polarization was insufficient and switched to M2 macrophage polarization. Besides costimulation, however, additional roles of CD86 are not known or well-studies. Therefore, we hypothesized that upregulating CD86 on macrophages might promote T. marneffei defense.

METHODS

A lentivirus vector, called Lenti-CD86, was used to infect THP-1 cells to overexpress secretory CD86. Through killing assay, nitric oxide detection, and cytokine detection, the capacity of THP-1 macrophages to phagocytose and kill T. marneffei was examined.

RESULTS

In the current study, Lenti-CD86 transfection of THP-1 cells resulted in a signifant expression of CD86. Additionally, the THP-1 macrophages stably transfected with Lenti-CD86 showed higher nitric oxide and IL-1β production, faster polarization, and stronger phagocytosis and killing capabilities than the non-transfected or control virus transfected cells.

CONCLUSION

Our study shows that lentivirus-mediated CD86 overexpression improves THP-1 macrophages' capacity to phagocytose and eliminate T. marneffei.

Interaction of Talaromyces marneffei with free living soil amoeba as a model of fungal pathogenesis

Talaromyces (Penicillium) marneffei is an important dimorphic mycosis endemic in Southeast Asia and Southern China, but the origin and maintenance of virulence traits in this organism remains obscure. Several pathogenic fungi, including Cryptococcus neoformans, Aspergillus fumigatus, Blastomyces dermatitidis, Sporothrix schenckii, Histoplasma capsulatum and Paracoccidioides spp. interact with free living soil amoebae and data suggests that fungal pathogenic strategies may emerge from environmental interactions of these fungi with ubiquitous phagocytic microorganisms. In this study, we examined the interactions of T. marneffei with the soil amoeba Acanthamoeba castellanii. T. marneffei was rapidly ingested by A. castellanii and phagocytosis of fungal cells resulted in amoeba death after 24 h of contact. Co-culture also resulted in a rapid transition for conidia to the fission-yeast form. In addition, well-established virulence factors such as melanin and a yeast specific mannoprotein of T. marneffei were expressed during interaction with A. castellanii at 37°C. Our findings support the assumption that soil amoebae environmental predators play a role in the selection and maintenance of particular features in T. marneffei that impart virulence to this clinically important dimorphic fungus in mammalian hosts.

Virus-like particles displaying conserved toxin epitopes stimulate polyspecific, murine antibody responses capable of snake venom recognition

Antivenom is currently the first-choice treatment for snakebite envenoming. However, only a low proportion of antivenom immunoglobulins are specific to venom toxins, resulting in poor dose efficacy and potency. We sought to investigate whether linear venom epitopes displayed on virus like particles can stimulate an antibody response capable of recognising venom toxins from diverse medically important species. Bioinformatically-designed epitopes, corresponding to predicted conserved regions of group I phospholipase A₂ and three finger toxins, were engineered for display on the surface of hepatitis B core antigen virus like particles and used to immunise female CD1 mice over a 14 weeks. Antibody responses to all venom epitope virus like particles were detectable by ELISA by the end of the immunisation period, although total antibody and epitope specific antibody titres were variable against the different epitope immunogens. Immunoblots using pooled sera demonstrated recognition of various venom components in a diverse panel of six elapid venoms, representing three continents and four genera. Insufficient antibody yields precluded a thorough assessment of the neutralising ability of the generated antibodies, however we were able to test polyclonal anti-PLA₂ IgG from three animals against the PLA₂ activity of Naja nigricollis venom, all of which showed no neutralising ability. This study demonstrates proof-of-principle that virus like particles engineered to display conserved toxin linear epitopes can elicit specific antibody responses in mice which are able to recognise a geographically broad range of elapid venoms.

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.

Fungicidal Activity of Recombinant Javanicin against Cryptococcus neoformans Is Associated with Intracellular Target(s) Involved in Carbohydrate and Energy Metabolic Processes

The occurrence of Cryptococcus neoformans, the human fungal pathogen that primarily infects immunocompromised individuals, has been progressing at an alarming rate. The increased incidence of infection of C. neoformans with antifungal drugs resistance has become a global concern. Potential antifungal agents with extremely low toxicity are urgently needed. Herein, the biological activities of recombinant javanicin (r-javanicin) against C. neoformans were evaluated. A time-killing assay was performed and both concentration- and time-dependent antifungal activity of r-javanicin were indicated. The inhibitory effect of the peptide was initially observed at 4 h post-treatment and ultimately eradicated within 36 to 48 h. Fungal outer surface alteration was characterized by the scanning electron microscope (SEM) whereas a negligible change with slight shrinkage of external morphology was observed in r-javanicin treated cells. Confocal laser scanning microscopic analysis implied that the target(s) of r-javanicin is conceivably resided in the cell thereby allowing the peptide to penetrate across the membrane and accumulate throughout the fungal body. Finally, cryptococcal cells coped with r-javanicin were preliminarily investigated using label-free mass spectrometry-based proteomics. Combined with microscopic and proteomics analysis, it was clearly elucidated the peptide localized in the intracellular compartment where carbohydrate metabolism and energy production associated with glycolysis pathway and mitochondrial respiration, respectively, were principally interfered. Overall, r-javanicin would be an alternative candidate for further development of antifungal agents.