Effect of Jun N-terminal kinase 1 and 2 on the replication of Penicillium marneffei in human macrophages

Antibody screening reveals antigenic proteins involved in Talaromyces marneffei and human interaction

Talaromycosis is a fungal infection that generally affects immunocompromised hosts and is one of the most frequent systemic mycoses in HIV patients, especially in endemic areas such as Southeast Asia. Talaromyces marneffei, the causative agent of talaromycosis, grows as a mold in the environment but adapts to the human body and host niches by transitioning from conidia to yeast-like cells. Knowledge of the human host and T. marneffei interaction has a direct impact on the diagnosis, yet studies are still lacking. The morbidity and mortality rates are high in taloromycosis patients if the diagnosis and treatments are delayed. Immunogenic proteins are excellent candidates for developing detection tools. Previously, we identified antigenic proteins that were recognized by antibodies from talaromycosis sera. Three of these identified proteins have been previously characterized in detail, while the others have not been explored. To expedite the progress of antigen discovery, the complete list of antigenic proteins and their features was fully reported in this study. Functional annotation and Gene Ontology examination revealed that these proteins showed a high association with membrane trafficking. Further bioinformatics analyses were performed to search for antigenic protein characteristics, including functional domains, critical residues, subcellular localization, secretory signals, and epitope peptide sequences. Expression profiling of these antigenic encoding genes was investigated using quantitative real-time PCR. The results demonstrated that most genes were expressed at low levels in the mold form, but were highly upregulated in the pathogenic yeast phase, consistent with the antigenic role of these genes during the human-host interaction. Most transcripts accumulated in the conidia, suggesting a role during phase transition. The collection of all antigen-encoding DNA sequences described here is freely accessible at GenBank, which could be useful for the research community to develop into biomarkers, diagnostic tests, research detection tools, and even vaccines.

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.

Talaromyces marneffei promotes M2-like polarization of human macrophages by downregulating SOCS3 expression and activating the TLR9 pathway

Little is known about how Talaromyces marneffei, a thermally dimorphic fungus that causes substantial morbidity and mortality in Southeast Asia, evades the human immune system. Polarization of macrophages into fungal-inhibiting M1-like and fungal-promoting M2-like types has been shown to play an important role in the innate immune response against fungal pathogens. This mechanism has not been defined for T. marneffei. Here, we demonstrated that T. marneffei promotes its survival in human macrophages by inducing them toward M2-like polarization. Our investigations of the mechanism revealed that T. marneffei infection led to SOCS3 protein degradation by inducing tyrosine phosphorylation, thereby relieving the inhibitory effect of SOCS3 on p-STAT6, a key factor for M2-like polarization. Our SOCS3-overexpression experiments showed that SOCS3 is a positive regulator of M1-like polarization and plays an important role in limiting M2-like polarization. Furthermore, we found that inhibition of the TLR9 pathway partially blocked T. marneffei-induced M2-like polarization and significantly enhanced the killing activity of macrophages against T. marneffei. Collectively, these results reveal a novel mechanism by which T. marneffei evades the immune response of human macrophages.

Talaromycosis in a renal transplant recipient returning from South China

Talaromycosis is a fungal infection endemic in Southeast Asia. We report a case of a renal transplant recipient who developed infection after a trip to South China. She presented with constitutional symptoms and was found to have an FDG-avid lung mass. Histopathology demonstrated small yeast cells and culture grew Talaromyces marneffei. The patient was treated with 2 weeks of liposomal amphotericin B followed by itraconazole. The dose of tacrolimus was significantly reduced because of the interaction with itraconazole. Mycophenolate mofetil was discontinued. After 12 months of treatment, the mass had completely resolved. Talaromycosis has mainly been reported in patients with AIDS and is uncommon among solid organ transplant recipients. The immune response against T. marneffei infection is mediated predominantly by T cells and macrophages. The diagnosis may not be suspected outside of endemic areas. We propose a therapeutic approach in transplant patients by extrapolating the evidence from the HIV literature and following practices applied to other endemic mycoses.

Activation of autophagy and IL-10 production are regulated by Jun N-terminal kinase 1 and 2 and p38 mitogen activated protein kinase signaling pathways during Talaromyces marneffei infection within dendritic cells

Previous study have shown that Talaromyces marneffei (T. marneffei) induced activation of autophagy. Therefore, we explore signaling pathway that regulates activation of autophagy by intracellular signaling mechanisms during T. marneffei infection. Further, we examine c-Jun N-terminal kinase 1 and 2 (JNK1/2) and p38 signaling pathways that regulate IL-1β and IL-10 production and activation of autophagy during T. marneffei infection in human dendritic cells (DCs). We found that T. marneffei induced activation of JNK1/2 and p38 in human DCs. Furthermore, the inhibition of JNK1/2 and p38 increased activation of autophagy and decreased the replication of T. marneffei in T. marneffei-infected human DCs. Moreover, IL-1β secretion in T. marneffei-infected human DCs was dependent on JNK1/2 and autophagy pathways, whereas IL-10 secretion was dependent on JNK1/2, p38 and autophagy pathways. These data suggest that JNK1/2 and p38 pathways play critical roles in activation of autophagy, the multiplication of T. marneffei and subsequent cytokine production during T. marneffei infection.

Evaluation of a real-time impedance analysis platform on fungal infection

End-point assays of in vitro cell proliferation and death have been employed to study the mechanisms of fungal pathogenesis and have shown the responses of host cells at individual time points. A new cell analysis technology has been developed that allows for the continuous measurement and quantification of cell activities, thus enabling the dynamic assessment of electrical impedance when various pathogens are cultured in vitro. In this study, this system was evaluated to determine the response of the cell line RAW264.7 to infection by several clinically relevant fungi in vitro, including Aspergillus fumigatus, Candida albicans, and melanized and albino mutant strains of Fonsecaea monophora. The results showed that infection resulted in rounding of the host cells with a loss of contact between individual cells and a decline in the electrical impedance of all test groups. However, changes in the electrical impedance were variable. Aspergillus fumigatus caused initial increases and later significant decreases in the electrical impedance, while for C. albicans and F. monophora, the effect was reduced. The melanized strain of F. monophora caused a faster change in the electrical impedance than the albino strain. Our data proved that this system can be used as an efficient tool for monitoring cellular responses to fungal infection.

Activation of ERK1/2 and TNF-α production are regulated by calcium/calmodulin signaling pathway during Penicillium marneffei infection within human macrophages

Previous study have shown that Penicillium marneffei (P. marneffei)-induced TNF-α production via an extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase-dependent mechanism is an important host defence mechanism against P. marneffei in human macrophages. Therefore, we explore signaling pathway that regulates TNF-α secretion and activation of ERK1/2 by intracellular signaling mechanisms during P. marneffei infection. We found that ERK1/2 activation was dependent on the calcium/calmodulin/calmodulin kinase Ⅱ pathway in P. marneffei-infected human macrophages. In contrast, P. marneffei-induced p38 MAPK activation was negatively regulated by calcium/calmodulin/calmodulin kinase Ⅱ signaling pathway. Furthermore, TNF-α production in P. marneffei-infected human macrophages was also dependent on Ca(2+)/calmodulin/calmodulin kinase Ⅱ pathway. These data suggest that Ca(2+)/calmodulin/calmodulin kinase Ⅱ pathway plays vital regulatory roles in macrophage activation and subsequent cytokine production during P. marneffei infection.