Murine Macrophage Requires CD11b to Recognize Talaromyces marneffei

Talaromycosis from Wuhan: two-case report and literature review

Background

Talaromycosis is a serious opportunistic infectious disease caused by Talaromyces marneffei, which mostly occurs in immunocompromised patients. The disease is mainly prevalent in tropical countries and regions of Southeast Asia and South Asia, but non-endemic areas also have patients with Talaromycosis. The disease has no characteristic clinical manifestations and is difficult to diagnose. Delayed diagnosis often leads to death.

Case presentation

Both patients had cellular immunodeficiency. Case 1 had a history of acquired immune deficiency syndrome, and case 2 had a history of renal transplantation and glucose-6-phosphate dehydrogenase deficiency. They all had fever, anemia, fatigue, and skin lesions. Case 1 had gastrointestinal bleeding, enlarged lymph nodes, and hepatosplenomegaly. Case 2 had cough and dyspnea. Both patients had thrombocytopenia and hypoalbuminemia; an increased neutrophil ratio, procalcitonin, and C-reactive protein; and abnormal liver function and coagulation dysfunction. Case 1 sputum culture, blood culture, and bronchoalveolar lavage fluid were positive for T. marneffei. T. marneffei was detected in the blood culture of case 2, with infection of Candida parapsilosis and Pneumocystis jirovecii. Chest computed tomography scan mainly showed pulmonary exudative lesions. Although these two patients were actively treated, they died of poor efficacy.

Conclusion

Talaromycosis has an insidious onset, long course, atypical clinical symptoms, imaging performance and laboratory results, difficult diagnosis, and high mortality. Therefore, it is important to promptly consider and treat Talaromycosis in immunocompromised patients upon infection in order to reduce mortality.

In Vitro Anti-Inflammatory Activity and Structural Characteristics of Polysaccharides Extracted from Lobonema smithii Jellyfish

Crude polysaccharides were extracted from the white jellyfish (Lobonema smithii) using water extraction and fractionated using ion-exchange chromatography to obtain three different fractions (JF1, JF2, and JF3). The chemical characteristics of four polysaccharides were investigated, along with their anti-inflammatory effect in LPS-stimulated RAW264.7 cells. All samples mainly consisted of neutral sugars with minor contents of proteins and sulphates in various proportions. Glucose, galactose, and mannose were the main constituents of the monosaccharides. The molecular weights of the crude polysaccharides and the JF1, JF2, and JF3 fractions were 865.0, 477.6, 524.1, and 293.0 kDa, respectively. All polysaccharides were able to decrease NO production, especially JF3, which showed inhibitory activity. JF3 effectively suppressed iNOS, COX-2, IL-1β, IL-6, and TNF-α expression, while IL-10 expression was induced. JF3 could inhibit phosphorylated ERK, JNK, p38, and NF-κB p65. Furthermore, flow cytometry showed the impact of JF3 on inhibiting CD11b and CD40 expression. These results suggest that JF3 could inhibit NF-κB and MAPK-related inflammatory pathways. The structural characterisation revealed that (1→3)-linked glucopyranosyl, (1→3,6)-linked galactopyranosyl, and (1→3,6)-linked glucopyranosyl residues comprised the main backbone of JF3. Therefore, L. smithii polysaccharides exhibit good anti-inflammatory activity and could thus be applied as an alternative therapeutic agent against inflammation.

An Overlooked and Underrated Endemic Mycosis-Talaromycosis and the Pathogenic Fungus Talaromyces marneffei

Talaromycosis is an invasive mycosis endemic in tropical and subtropical Asia and is caused by the pathogenic fungus Talaromyces marneffei. Approximately 17,300 cases of T. marneffei infection are diagnosed annually, and the reported mortality rate is extremely high (~1/3). Despite the devastating impact of talaromycosis on immunocompromised individuals, particularly HIV-positive persons, and the increase in reported occurrences in HIV-uninfected persons, diagnostic and therapeutic approaches for talaromycosis have received far too little attention worldwide. In 2021, scientists living in countries where talaromycosis is endemic raised a global demand for it to be recognized as a neglected tropical disease. Therefore, T. marneffei and the infectious disease induced by this fungus must be treated with concern. T. marneffei is a thermally dimorphic saprophytic fungus with a complicated mycological growth process that may produce various cell types in its life cycle, including conidia, hyphae, and yeast, all of which are associated with its pathogenicity. However, understanding of the pathogenic mechanism of T. marneffei has been limited until recently. To achieve a holistic view of T. marneffei and talaromycosis, the current knowledge about talaromycosis and research breakthroughs regarding T. marneffei growth biology are discussed in this review, along with the interaction of the fungus with environmental stimuli and the host immune response to fungal infection. Importantly, the future research directions required for understanding this serious infection and its causative pathogenic fungus are also emphasized to identify solutions that will alleviate the suffering of susceptible individuals worldwide.

Key thermally dimorphic fungal pathogens: shaping host immunity

Exposure to fungal pathogens from the environment is inevitable and with the number of at-risk populations increasing, the prevalence of invasive fungal infection is on the rise. An interesting group of fungal organisms known as thermally dimorphic fungi predominantly infects immunocompromised individuals. These potential pathogens are intriguing in that they survive in the environment in one form, mycelial phase, but when entering the host, they are triggered by the change in temperature to switch to a new pathogenic form. Considering the growing prevalence of infection and the need for improved diagnostic and treatment approaches, studies identifying key components of fungal recognition and the innate immune response to these pathogens will significantly contribute to our understanding of disease progression. This review focuses on key endemic dimorphic fungal pathogens that significantly contribute to disease, including Histoplasma, Coccidioides and Talaromyces species. We briefly describe their prevalence, route of infection and clinical presentation. Importantly, we have reviewed the major fungal cell wall components of these dimorphic fungi, the host pattern recognition receptors responsible for recognition and important innate immune responses supporting adaptive immunity and fungal clearance or the failure thereof.

Identification of Oleanolic Acid as Allosteric Agonist of Integrin αM by Combination of In Silico Modeling and In Vitro Analysis

Oleanolic acid is a widely distributed natural product, which possesses promising antitumor, antiviral, antihyperlipidemic, and anti-inflammatory activities. A heterodimeric complex formed by integrin α_M (CD11b) and integrin β₂ (CD18) is highly expressed on monocytes and macrophages. In the current study, we demonstrate that the I domain of α_M (α_M-I domain) might present a potential cellular target for oleanolic acid. In vitro data show that oleanolic acid induces clustering of α_M on macrophages and reduces their non-directional migration. In accordance with experimental data, molecular docking revealed that oleanolic acid binds to the α_M-I domain in its extended-open form, the dominant conformation found in α_M clusters. Molecular dynamics simulation revealed that oleanolic acid can increase the flexibility of the α7 helix and promote its movement away from the N-terminus, indicating that oleanolic acid may facilitate the conversion of the α_M-I domain from the extended-closed to the extended-open conformation. As demonstrated by metadynamics simulation, oleanolic acid can destabilize the local minimum of the α_M-I domain in the open conformation partially through disturbance of the interactions between α1 and α7 helices. In summary, we demonstrate that oleanolic acid might function as an allosteric agonist inducing clustering of α_M on macrophages by shifting the balance from the closed to the extended-open conformation. The molecular target identified in this study might hold potential for a purposeful use of oleanolic acid to modulate chronic inflammatory responses.

Cutaneous and subcutaneous fungal infections: recent developments on host-fungus interactions

The incidence of skin fungal infections is increasing at an alarming rate worldwide, presenting a major challenge to health professionals. Cutaneous and subcutaneous fungal infections are caused by pathogenic or opportunistic organisms varying from mold, yeasts, to dimorphic fungi. Recently, skin fungal have been increasingly reported and studied, giving rise to crucial breakthroughs in etiology and pathogenesis. This review aims to summarize recent insights into the clinical and etiological characteristics of common skin fungal infections according to different fungal species, as well as remarkable advances in the immune mechanisms. We hope it will be helpful to understand these diverse skin fungal infections, and bring about the latest developments that may facilitate novel diagnostic and therapeutic approaches to improve the outcomes in these patients.