Hyperinflammatory environment drives dysfunctional myeloid cell effector response to bacterial challenge in COVID-19.

COVID-19 displays diverse disease severities and symptoms including acute systemic inflammation and hypercytokinemia, with subsequent dysregulation of immune cells. Bacterial superinfections in COVID-19 can further complicate the disease course and are associated with increased mortality. However, there is limited understanding of how SARS-CoV-2 pathogenesis and hypercytokinemia impede the innate immune function against bacterial superinfections. We assessed the influence of COVID-19 plasma hypercytokinemia on the functional responses of myeloid immune cells upon bacterial challenges from acute-phase COVID-19 patients and their corresponding recovery-phase. We show that a severe hypercytokinemia status in COVID-19 patients correlates with the development of bacterial superinfections. Neutrophils and monocytes derived from COVID-19 patients in their acute-phase showed an impaired intracellular microbicidal capacity upon bacterial challenges. The impaired microbicidal capacity was reflected by abrogated MPO and reduced NETs production in neutrophils along with reduced ROS production in both neutrophils and monocytes. Moreover, we observed a distinct pattern of cell surface receptor expression on both neutrophils and monocytes, in line with suppressed autocrine and paracrine cytokine signaling. This phenotype was characterized by a high expression of CD66b, CXCR4 and low expression of CXCR1, CXCR2 and CD15 in neutrophils and low expression of HLA-DR, CD86 and high expression of CD163 and CD11b in monocytes. Furthermore, the impaired antibacterial effector function was mediated by synergistic effect of the cytokines TNF-α, IFN-γ and IL-4. COVID-19 patients receiving dexamethasone showed a significant reduction of overall inflammatory markers in the plasma as well as exhibited an enhanced immune response towards bacterial challenge ex vivo. Finally, broad anti-inflammatory treatment was associated with a reduction in CRP, IL-6 levels as well as length of ICU stay and ventilation-days in critically ill COVID-19 patients. Our data provides insights into the transient functional dysregulation of myeloid immune cells against subsequent bacterial infections in COVID-19 patients and describe a beneficial role for the use of dexamethasone in these patients.

A Novel Single Cell RNA-seq Analysis of Non-Myeloid Circulating Cells in Late Sepsis.

Background: With the successful implementation of the Surviving Sepsis Campaign guidelines, post-sepsis in-hospital mortality to sepsis continues to decrease. Those who acutely survive surgical sepsis will either rapidly recover or develop a chronic critical illness (CCI). CCI is associated with adverse long-term outcomes and 1-year mortality. Although the pathobiology of CCI remains undefined, emerging evidence suggests a post-sepsis state of pathologic myeloid activation, inducing suboptimal lymphopoiesis and erythropoiesis, as well as downstream leukocyte dysfunction. Our goal was to use single-cell RNA sequencing (scRNA-seq) to perform a detailed transcriptomic analysis of lymphoid-derived leukocytes to better understand the pathology of late sepsis. Methods: A mixture of whole blood myeloid-enriched and Ficoll-enriched peripheral blood mononuclear cells from four late septic patients (post-sepsis day 14-21) and five healthy subjects underwent Cellular Indexing of Transcriptomes and Epitopes by Sequencing (CITE-seq). Results: We identified unique transcriptomic patterns for multiple circulating immune cell subtypes, including B- and CD4+, CD8+, activated CD4+ and activated CD8+ T-lymphocytes, as well as natural killer (NK), NKT, and plasmacytoid dendritic cells in late sepsis patients. Analysis demonstrated that the circulating lymphoid cells maintained a transcriptome reflecting immunosuppression and low-grade inflammation. We also identified transcriptomic differences between patients with bacterial versus fungal sepsis, such as greater expression of cytotoxic genes among CD8+ T-lymphocytes in late bacterial sepsis. Conclusion: Circulating non-myeloid cells display a unique transcriptomic pattern late after sepsis. Non-myeloid leukocytes in particular reveal a host endotype of inflammation, immunosuppression, and dysfunction, suggesting a role for precision medicine-guided immunomodulatory therapy.

Baseline characteristics and changes of biomarkers in disease course predict prognosis of patients with COVID-19.

The outbreak of coronavirus disease (COVID-19) has brought great challenges to the world. The objectives of this study were to describe the baseline characteristics and changes of biomarkers of these COVID-19 patients and identify predictive value of the above markers for patient death. Using patient death as the observational endpoints, clinical data of inpatients in a special ward for COVID-19 in Wuhan, China were retrospectively collected. Univariate and multivariate Cox regression analyses were used to evaluate prognostic value of baseline characteristics and laboratory data changes. This study included clinical data of 75 patients. Age, c-reactive protein (CRP) and interleukin-6 levels were independent predictors of patient death. Survivors were characterized as having declining neutrophil counts, D-dimer, N-terminal pronatriuretic peptide, troponin I (TnI) and c-reactive protein levels, while counts of lymphocyte gradually came back. Non-survivors were characterized with increasing white blood cell counts (WBC) and neutrophil counts. Changes of WBC, TnI and interleukin-6 were also independently associated with patient death. Older age, baseline CRP and IL-6 levels may be used as meaningful predictors to identify patients with poor prognosis. Changes of biomarkers should be closely monitored in the management of patients with COVID-19, while constantly increasing levels of WBC, TnI and interleukin-6 in the disease course also predict patient death.

Facilitating the gut brain axis by probiotic bacteria to modulate neuroimmune response on lead exposed zebra fish models

Unravelling the efficacy of gut biome has a major impact on health. An unbalanced microbiome composition is linked to many common illnesses such as gut dysbiosis, mental deformities and immunological imbalance. An optimistic influence on the gut biome can be made by consumingprobiotics. This would stimulate neuroprotection and immunomodulation intended by heavy metals pollution. Lead is a major source of neurotoxin that can induce neural deformities. Lactobacillusspecies isolated from curd were characterized to confirm its specificity. Zebra fish was reared at standard conditions and preclinical assessment on the intensity of induced neurotoxin lead was performed. The embryo toxic assay, immunomodulation effects and animal behavioural models endorsed the consequence of neurotoxicity. Different concentrations of bacterial isolate with standard antidepressant was considered for analysing the vigour of toxicity and its influence on cognitive behaviour by novel tank diving method. The restrain in the animal behaviour was also conferred by all the test samples with a decreased bottom dwelling time which was authenticated with haematology and histopathological studies. The alterations in morphology of the lymphocytes were balanced by the treated test samples. This study paves a twofold potential of probiotic as neuroprotectant and immune modulator against heavy metal toxicity.

T-bet-dependent ILC1- and NK cell-derived IFN-γ mediates cDC1-dependent host resistance against Toxoplasma gondii.

Host resistance against intracellular pathogens requires a rapid IFN-γ mediated immune response. We reveal that T-bet-dependent production of IFN-γ is essential for the maintenance of inflammatory DCs at the site of infection with a common protozoan parasite, Toxoplasma gondii. A detailed analysis of the cellular sources for T-bet-dependent IFN-γ identified that ILC1s and to a lesser degree NK, but not TH1 cells, were involved in the regulation of inflammatory DCs via IFN-γ. Mechanistically, we established that T-bet dependent innate IFN-γ is critical for the induction of IRF8, an essential transcription factor for cDC1s. Failure to upregulate IRF8 in DCs resulted in acute susceptibility to T. gondii infection. Our data identifies that T-bet dependent production of IFN-γ by ILC1 and NK cells is indispensable for host resistance against intracellular infection via maintaining IRF8+ inflammatory DCs at the site of infection.

DJ-1 (Park7) affects the gut microbiome, metabolites and the development of innate lymphoid cells (ILCs).

The proper communication between gut and brain is pivotal for the maintenance of health and, dysregulation of the gut-brain axis can lead to several clinical disorders. In Parkinson's disease (PD) 85% of all patients experienced constipation many years before showing any signs of motor phenotypes. For differential diagnosis and preventive treatment, there is an urgent need for the identification of biomarkers indicating early disease stages long before the disease phenotype manifests. DJ-1 is a chaperone protein involved in the protection against PD and genetic mutations in this protein have been shown to cause familial PD. However, how the deficiency of DJ-1 influences the risk of PD remains incompletely understood. In the present study, we provide evidence that DJ-1 is implicated in shaping the gut microbiome including; their metabolite production, inflammation and innate immune cells (ILCs) development. We revealed that deficiency of DJ-1 leads to a significant increase in two specific genera/species, namely Alistipes and Rikenella. In DJ-1 knock-out (DJ-1-/-) mice the production of fecal calprotectin and MCP-1 inflammatory proteins were elevated. Fecal and serum metabolic profile showed that malonate which influences the immune system was significantly more abundant in DJ-1-/- mice. DJ-1 appeared also to be involved in ILCs development. Further, inflammatory genes related to PD were augmented in the midbrain of DJ-1-/- mice. Our data suggest that metabolites and inflammation produced in the gut could be used as biomarkers for PD detection. Perhaps, these metabolites and inflammatory mediators could be involved in triggering inflammation resulting in PD pathology.

Intestinal microbiota-derived short-chain fatty acids regulation of immune cell IL-22 production and gut immunity.

Innate lymphoid cells (ILCs) and CD4+ T cells produce IL-22, which is critical for intestinal immunity. The microbiota is central to IL-22 production in the intestines; however, the factors that regulate IL-22 production by CD4+ T cells and ILCs are not clear. Here, we show that microbiota-derived short-chain fatty acids (SCFAs) promote IL-22 production by CD4+ T cells and ILCs through G-protein receptor 41 (GPR41) and inhibiting histone deacetylase (HDAC). SCFAs upregulate IL-22 production by promoting aryl hydrocarbon receptor (AhR) and hypoxia-inducible factor 1α (HIF1α) expression, which are differentially regulated by mTOR and Stat3. HIF1α binds directly to the Il22 promoter, and SCFAs increase HIF1α binding to the Il22 promoter through histone modification. SCFA supplementation enhances IL-22 production, which protects intestines from inflammation. SCFAs promote human CD4+ T cell IL-22 production. These findings establish the roles of SCFAs in inducing IL-22 production in CD4+ T cells and ILCs to maintain intestinal homeostasis.

Neutrophil-To-Lymphocyte Ratio and Systemic Immune-Inflammation Index-Biomarkers in Interstitial Lung Disease.

Background and objectives: The aims of the study were to evaluate the utility of neutrophil-to-lymphocyte ratio (NLR) and the systemic immune-inflammation index (SII) as inflammation markers and prognostic factors in patients with known interstitial lung disease secondary to connective tissue diseases (CTD-ILD) compared with idiopathic pulmonary fibrosis (IPF). Materials and Methods: Forty-two patients with known interstitial lung disease (21 with IPF and 21 with CTD-ILD) and 42 control matched healthy patients were included. The NLR was calculated as the absolute neutrophil count divided by the absolute lymphocyte count, and the SII was calculated as follows: SII = platelets × neutrophils/lymphocytes, with the data being obtained from the patients data charts at admission, before any treatment. Results: our hypothesis was that in patients with interstitial lung disease NLR and SII would have higher values compared with patients with CTD-ILD or control healthy patients. The mean NLR value was 3.01 (±1.35) among patients with idiopathic pulmonary fibrosis, and 2.38 (±1.08) among patients with CTD-ILD without significant statistical difference (p = 0.92). There was however a clinically significant statistical difference when compared with the control group, where NLR was 2.00 (±1.05) (p = 0.003). SII values were 619.37 (±329.51) in patients with IPF, 671.55 (±365.73) in CTD-ILD group and 569.73 (±326.67) in healthy subjects (p = 0.13) Conclusions: A mean NLR value of 2.8 and a SII value over 500 in patients with connective diseases can become a marker of pulmonary interstitial involvement. In the context of non-exacerbated interstitial lung disease, NLR and SII have reduced numerical values, without being statistically correlated with prognosis when we compared with patients with connective tissue diseases without exacerbation or with healthy people, the cut off being of 2.4. However subsequent studies in larger patient samples might provide changes in these cut-off values.

The microbial coinfection in COVID-19.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a novel ß-coronavirus, is the main pathogenic agent of the rapidly spreading pneumonia called coronavirus disease 2019 (COVID-19). SARS-CoV-2 infects much more people, especially the elder population, around the world than other coronavirus, such as SARS-CoV and MERS-CoV, which is challenging current global public health system. Beyond the pathogenesis of SARS-CoV-2, microbial coinfection plays an important role in the occurrence and development of SARS-CoV-2 infection by raising the difficulties of diagnosis, treatment, prognosis of COVID-19, and even increasing the disease symptom and mortality. We summarize the coinfection of virus, bacteria and fungi with SARS-CoV-2, their effects on COVID-19, the reasons of coinfection, and the diagnosis to emphasize the importance of microbial coinfection in COVID-19. KEY POINTS: • Microbial coinfection is a nonnegligible factor in COVID-19. • Microbial coinfection exacerbates the processes of the occurrence, development and prognosis of COVID-19, and the difficulties of clinical diagnosis and treatment. • Different virus, bacteria, and fungi contributed to the coinfection with SARS-CoV-2.

COX Inhibition Increases Alternaria-Induced Pulmonary Group 2 Innate Lymphoid Cell Responses and IL-33 Release in Mice.

The cyclooxygenase (COX) metabolic pathway regulates immune responses and inflammation. The effect of the COX pathway on innate pulmonary inflammation induced by protease-containing fungal allergens, such as Alternaria alternata, is not fully defined. In this study, we tested the hypothesis that COX inhibition augments Alternaria-induced pulmonary group 2 innate lymphoid cell (ILC2) responses and IL-33 release. Mice were treated with the COX inhibitors indomethacin, flurbiprofen, or vehicle and challenged intranasally with Alternaria extract for four consecutive days to induce innate lung inflammation. We found that indomethacin and flurbiprofen significantly increased the numbers of ILC2 and IL-5 and IL-13 expression by ILC2 in the lung. Indomethacin also increased ILC2 proliferation, the percentages of eosinophils, and mucus production in the lung. Both indomethacin and flurbiprofen augmented the release of IL-33 in bronchoalveolar lavage fluid after Alternaria challenge, suggesting that more IL-33 was available for ILC2 activation and that a COX product(s) inhibited IL-33 release. This is supported by the in vitro finding that the COX product PGE2 and the PGI2 analogs cicaprost decreased Alternaria extract-induced IL-33 release by human bronchial epithelial cells. Although contrasting effects of PGD2, PGE2, and PGI2 on ILC2 responses have been previously reported, the overall effect of the COX pathway on ILC2 function is inhibitory in Alternaria-induced innate airway inflammation.

Stromal Cells Covering Omental Fat-Associated Lymphoid Clusters Trigger Formation of Neutrophil Aggregates to Capture Peritoneal Contaminants.

The omentum is a visceral adipose tissue rich in fat-associated lymphoid clusters (FALCs) that collects peritoneal contaminants and provides a first layer of immunological defense within the abdomen. Here, we investigated the mechanisms that mediate the capture of peritoneal contaminants during peritonitis. Single-cell RNA sequencing and spatial analysis of omental stromal cells revealed that the surface of FALCs were covered by CXCL1+ mesothelial cells, which we termed FALC cover cells. Blockade of CXCL1 inhibited the recruitment and aggregation of neutrophils at FALCs during zymosan-induced peritonitis. Inhibition of protein arginine deiminase 4, an enzyme important for the release of neutrophil extracellular traps, abolished neutrophil aggregation and the capture of peritoneal contaminants by omental FALCs. Analysis of omental samples from patients with acute appendicitis confirmed neutrophil recruitment and bacterial capture at FALCs. Thus, specialized omental mesothelial cells coordinate the recruitment and aggregation of neutrophils to capture peritoneal contaminants.

Longitudinal cerebrospinal fluid assessment in a patient with tuberculous meningitis-A case report.

BACKGROUND: Dynamic assessment of cerebrospinal fluid (CSF) is essential for diagnosis, treatment, and prognosis of tuberculous meningitis, one of the most severe forms of central nervous system (CNS) infection. CASE PRESENTATION: A 45-year-old man sought care as he developed confusion, clonic convulsion, and coma. Longitudinal, comprehensive analyses of cytological, biochemical, and microbial changes in CSF specimen were assessed for this patient. On day 1 of hospitalization, modified Ziehl-Neelsen staining of CSF identified positive acid-fast bacilli, cytological analysis revealed neutrophilic-predominant pleocytosis (neutrophils 77%), and adenosine deaminase (ADA) was substantially elevated. Therefore, tuberculous meningitis was diagnosed and first-line standard anti-tuberculosis treatment was initiated. Interestingly, after 7-day treatment, the patient was greatly improved, and CSF disclosed a dominant percentage of lymphocytes (82%) as well as macrophages engulfing Mycobacterium tuberculosis. Later, the dose of dexamethasone was reduced, large number of neutrophils (57%) was present and protein level was immediately elevated in CSF specimen, indicating a possible relapse of tuberculous meningitis. Since the clinical condition of the patient was not worsening, the patient was stick to reduced dose of dexamethasone and standard anti-tuberculosis agents. He was discharged from the hospital on day 34, with 1-year continuation standard anti-tuberculosis therapy, and was clinically resolved from tuberculous meningitis. CONCLUSION: Detailed analyses of cellular composition, biochemical results, and microbial tests of CSF specimen provide the physician direct evidence of the immune surveillance status during tuberculous meningitis, which facilitates early diagnosis, optimal treatment, and improved prognosis.

Neutrophils Recirculate through Lymph Nodes to Survey Tissues for Pathogens.

The adaptive immune function of lymph nodes is dependent on constant recirculation of lymphocytes. In this article, we identify neutrophils present in the lymph node at steady state, exhibiting the same capacity for recirculation. In germ-free mice, neutrophils still recirculate through lymph nodes, and in mice cohoused with wild microbiome mice, the level of neutrophils in lymph nodes increases significantly. We found that at steady state, neutrophils enter the lymph node entirely via L-selectin and actively exit via efferent lymphatics via an S1P dependent mechanism. The small population of neutrophils in the lymph node can act as reconnaissance cells to recruit additional neutrophils in the event of bacterial dissemination to the lymph node. Without these reconnaissance cells, there is a delay in neutrophil recruitment to the lymph node and a reduction in swarm formation following Staphylococcus aureus infection. This ability to recruit additional neutrophils by lymph node neutrophils is initiated by LTB4. This study establishes the capacity of neutrophils to recirculate, much like lymphocytes via L-selectin and high endothelial venules in lymph nodes and demonstrates how the presence of neutrophils at steady state fortifies the lymph node in case of an infection disseminating through lymphatics.

Construction and development of FimH lectin domain for rising immune response after injection by uropathogenic E. coli.

Uropathogenic E. coli is one of the major agents of urinary tract infection. Today, no effective treatment or vaccine against this infection is exist. Accordingly, in the present study, a genetic constrruct for inducing of cellular immune system was designed. At first, fimH gene from E. coli 35218 was amplified using PCR. PCR product inserted into pET23a expression vector and the recombinant vector was analysed by sequencing. The vector was transformed to E. coli strain Origami and the protein was expressed under the 1 mM IPTG. FimH was purified with Ni-NTA column and the purified protein was used for immunization of BALB/c. Two weeks after the last injection, lymphocyte proliferation assay was carried out. In addition, IL-4 and IFN-γ cytokines, total antibody serum, IgG1 and IgG2a isotypes were quantified. Finally, protection ability of the vaccine in bladder and kidney infection of mice was evaluated.The results indicated that cellular immune response has a main protective role against UTI and FimH, as a vaccine candidate, significantly increase lymphocyte proliferation, IFN-γ response and total antibody amount. Immunization of mice with FimH conferred effective protection of kidney and bladder against urinary tract infection by uropathogenic E. coli (P< 0.002). It can be concluded that, the current FimH will be valuable for more trying to prepare a new vaccine against UTI.

The interaction of intestinal microbiota and innate lymphoid cells in health and disease throughout life.

Immunity is shaped by commensal microbiota. From early life onwards, microbes colonize mucosal surfaces of the body and thereby trigger the establishment of immune homeostasis and defense mechanisms. Recent evidence reveals that the family of innate lymphoid cells (ILCs), which are mainly located in mucosal tissues, are essential in the maintenance of barrier functions as well as in the initiation of an appropriate immune response upon pathogenic infection. In this review, we summarize recent insights on the functional interaction of microbiota and ILCs at steady-state and throughout life. Furthermore, we will discuss the interplay of ILCs and the microbiota in mucosal infections focusing on intestinal immunity.

Lactobacillus delbrueckii subsp. bulgaricus 2038 and Streptococcus thermophilus 1131 Induce the Expression of the REG3 Family in the Small Intestine of Mice via the Stimulation of Dendritic Cells and Type 3 Innate Lymphoid Cells.

Accumulating evidence clarifies that intestinal barrier function, for example, by the mucus layer, antimicrobial peptides, immune systems, and epithelial tight junctions, plays crucial roles in maintaining our health. We reported previously that yogurt fermented with Lactobacillus delbrueckii subsp. bulgaricus 2038 and Streptococcus thermophilus 1131 induced the gene expression of the regenerating family member 3 (REG3) family, which encodes antimicrobial peptides in the small intestine, although it was unclear how the yogurt activated the intestinal cells related to it. Here, we evaluated the cytokine production from the intestinal immune cells stimulated by these strains in vitro and in vivo to elucidate the mechanism for the induction of the REG3 family by the yogurt. The results showed that stimulation by both strains induced interleukin (IL)-23 production from bone marrow-derived dendritic cells (DCs) and IL-22 production from small intestinal lamina propria (LP) cells. In addition, oral administration of these strains to mice increased IL-23p19+ LPDCs and IL-22+ type 3 innate lymphoid cells and induced the expression of Reg3g in small intestinal tissue. Moreover, we showed that the activities for the induction of IL-23 by DCs were strain dependent on L. bulgaricus and S. thermophilus and that S. thermophilus 1131, which is the predominant species in the yogurt, exhibited relatively higher activity compared to the other strains of S. thermophilus. Our findings suggested that these yogurt starter strains, L. bulgaricus 2038 and S. thermophilus 1131, have the potential to maintain and improve intestinal barrier function by stimulating immune cells in the LP.

Riemerella anatipestifer infection in ducks induces IL-17A production, but not IL-23p19.

R. anatipestifer (RA) is one of the most harmful bacterial pathogens affecting the duck industry, and infection is associated with the production of proinflammatory cytokines, including IL-17A. Another proinflammatory cytokine, IL-23, is critical for the development of Th17 cells, which produce IL-17. However, IL-23 roles have not been studied in this infection. Here, we describe the identification and mRNA expression analysis of duck IL-23p19 (duIL-23p19) in splenic lymphocytes and macrophages stimulated with killed RA and in spleens of RA-infected ducks. Expression of duIL-23p19 transcript identified in this study was relatively high in livers of healthy ducks and was upregulated in mitogen-activated splenic lymphocytes as well as in splenic lymphocytes and macrophages stimulated with killed RA. In spleens of RA-infected ducks, expression levels of duIL-23p19 transcript were unchanged at all time points except on days 4 and 7 post-infection; however, duIL-17A and IL-17F expression levels were upregulated in both spleens of RA-infected ducks and splenic lymphocytes and macrophages stimulated with killed RA. In sera collected at 24 h after this infection, duIL-23p19 expression levels were unchanged, whereas IL-17A significantly upregulated. These results suggest that IL-23p19 does not play a critical role in the IL-17A response in early stages of RA-infected ducks.

Rapid Detection of Mycoplasma-Infected Cells by an ssDNA Aptamer Probe.

Mycoplasmas are unique cell wall-free bacteria. Because they lack a cell wall and have resistance to ß-lactam antibiotics, mycoplasma is the major pathogen that infects cultured cells in research laboratories. For rapid detection of mycoplasma-infected cells, we developed an ssDNA aptamer sequence composed of 40 nucleotides. Flow cytometry analysis showed that the synthetic aptamer probe selectively targeted mycoplasma-infected culture cells with high specificity identical to commercially available PCR-based assays. Additionally, fluorescent microscopy studies revealed that the aptamer probe rapidly stained mycoplasma-infected cells with higher sensitivity compared to Hoechst dye-mediated cellular DNA content stains. Moreover, confocal microscopy studies of trypsin-treated cells validated that the aptamer probes selectively targeted mycoplasma components on the surface of infected cells. Finally, preclinical studies of peripheral blood cells demonstrated that the aptamer probe was able to detect in vitro mycoplasma infection of primary lymphocytes. Taken together, these findings indicate that the aptamer probe will not only allow rapid detection of mycoplasma-infected culture cells for research purposes but also provide a simple method to monitor mycoplasma infection in primary cell products for clinical use.

Comparison of pleural effusion features and biomarkers between talaromycosis and tuberculosis in non-human immunodeficiency virus-infected patients.

BACKGROUND: Due to the similar clinical, lung imaging, and pathological characteristics, talaromycosis is most commonly misdiagnosed as tuberculosis. This study aimed to identify the characteristics of talaromycosis pleural effusion (TMPE) and to distinguish TMPE from tuberculosis pleural effusion (TPE). METHODS: We enrolled 19 cases each of TMPE and TPE from Guangxi, China. Patients' clinical records, pleural effusion tests, biomarker test results, and receiver operating characteristic curves were analyzed. RESULTS: In total, 39.8% (65/163) of patients exhibited serous effusion, of whom 61 were non-human immunodeficiency virus (HIV)-infected patients; 68.85% of the non-HIV-infected patients (42/61) had TMPE. Thoracentesis was performed only in 19 patients, all of whom were misdiagnosed with tuberculosis and received long-term anti-tuberculosis treatment. In four of these patients, interleukin (IL)-23, IL-27, and interferon-gamma (IFN-γ) measurements were not performed since pleural effusion samples could not be collected because the effusion had been drained prior to the study. In the remaining 15 patients, pleural effusion samples were collected. Talaromyces marneffei was isolated from the pleural effusion and pleural nodules. Most TMPEs were characterized by yellowish fluid, with marked elevation of protein content and nucleated cell counts. However, neutrophils were predominantly found in TMPEs, and lymphocytes were predominantly found in TPEs (both p < 0.05). Adenosine deaminase (ADA) and IFN-γ levels in TMPEs were significantly lower than those in TPEs (all p < 0.05) and provided similar accuracies for distinguishing TMPEs from TPEs. IL-23 concentration in TMPEs was significantly higher than that in TPEs (p < 0.05), and it provided similar accuracy for diagnosing TMPEs. IL-27 concentrations in TMPEs were significantly lower than those in TPEs (all p < 0.05) but was not useful for distinguishing TMPE from TPE. CONCLUSIONS: Talaromycosis can infringe on the pleural cavity via the translocation of T. marneffei into the pleural space. Nonetheless, this phenomenon is still commonly neglected by clinicians. TMPE is a yellowish fluid with exudative PEs and predominant neutrophils. Higher neutrophil counts and IL-23 may suggest talaromycosis. Higher lymphocyte counts, ADA activity, and IFN-γ concentration may suggest tuberculosis.