Progranulin aggravates lethal Candida albicans sepsis by regulating inflammatory response and antifungal immunity.

Candida albicans is the most frequent pathogen of fungal sepsis associated with substantial mortality in critically ill patients and those who are immunocompromised. Identification of novel immune-based therapeutic targets from a better understanding of its molecular pathogenesis is required. Here, we reported that the production of progranulin (PGRN) levels was significantly increased in mice after invasive C.albicans infection. Mice that lacked PGRN exhibited attenuated kidney injury and increased survival upon a lethal systemic infection with C. albicans. In mice, PGRN deficiency protected against systemic candidiasis by decreasing aberrant inflammatory reactions that led to renal immune cell apoptosis and kidney injury, and by enhancing antifungal capacity of macrophages and neutrophils that limited fungal burden in the kidneys. PGRN in hematopoietic cell compartment was important for this effect. Moreover, anti-PGRN antibody treatment limited renal inflammation and fungal burden and prolonged survival after invasive C. albicans infection. In vitro, PGRN loss increased phagocytosis, phagosome formation, reactive oxygen species production, neutrophil extracellular traps release, and killing activity in macrophages or neutrophils. Mechanistic studies demonstrated that PGRN loss up-regulated Dectin-2 expression, and enhanced spleen tyrosine kinase phosphorylation and extracellular signal-regulated kinase activation in macrophages and neutrophils. In summary, we identified PGRN as a critical factor that contributes to the immunopathology of invasive C.albicans infection, suggesting that targeting PGRN might serve as a novel treatment for fungal infection.

CXCL14 Protects against Polymicrobial Sepsis by Enhancing Antibacterial Functions of Macrophages.

Rapid and effective control of bacterial infection is critical for the treatment of bacterial sepsis. CXCL14 (CXC motif ligand 14) is an important chemokine involved in infection and immunity, which can bind to CXCR4. However, the contribution of the CXCL14/CXCR4 chemokine axis to bacterial clearance in sepsis remains unknown. Here, the impact of CXCL14/CXCR4 blockade or CXCL14 administration on sepsis was assessed using murine and cell models, as well as human samples. CXCL14 protein concentrations were elevated in mice after cecal ligation and puncture (CLP)-induced sepsis. In vivo, CXCL14 blockade using anti-CXCL14 antibody or CXCL14 knockdown by adeno-associated virus carrying-CXCL14 shRNA significantly increased mortality and bacterial burden, which was paralleled by significantly decreased macrophage influx and M2 macrophage polarization at the site of infection after CLP. Therapeutic administration of CXCL14 improved mortality and bacterial clearance after CLP in a CXCR4-dependent manner, and macrophages, but not neutrophils, were important for the protective effect of CXCL14 in sepsis. In vitro, CXCL14 directly enhanced bacterial phagocytosis and killing of macrophages, and it also increased phagosome formation and reactive oxygen species production in macrophages. Furthermore, inhibiting the activation of PI3K/Akt and NF-κB signaling pathways, but not STAT1 (signal transducer and activator of transcription 1), abrogated the enhanced antibacterial effects of CXCL14 on macrophages. Finally, circulating CXCL14 concentrations were significantly upregulated in patients with sepsis. CXCL14 could enhance bacterial phagocytosis and killing in human monocyte-derived macrophages, which was dependent on CXCR4. Therefore, our results indicate a previously undescribed role of the CXCL14/CXCR4 axis and suggest CXCL14 as a potential adjunct therapy in bacterial sepsis.

Differences in the Intestinal Flora of Patients with Inflammatory Bowel Disease in Southwest China.

To study changes in the intestinal flora associated with inflammatory bowel disease (IBD) in the Han population of southwest China, 48 participants were enrolled, 18 of whom had been diagnosed with IBD. Stool samples were collected from the participants. Sequencing of 16S rRNA gene was used to measure and identify the components of the intestinal flora. Diversity analysis and multivariate statistical analysis were conducted to study differences in intestinal flora between patients with IBD and healthy controls. The goods coverage, observed species, Shannon, and Simpson indices of alpha diversity were different (p < 0.05). Beta diversity analysis yielded significant differences between groups (R = 0.5668, p = 0.001 < 0.05). Compared with the composition of the intestinal flora in healthy controls, the relative abundances of Proteobacteria (18.56% vs. 3.56%, p = 0.001) and Fusobacterium (2.08% vs. 0.35%, p = 0.005) were higher in patients with IBD. Therefore, this study provides insight into the role of the microbiome in IBD. Supplementary Information: The online version contains supplementary material available at 10.1007/s12088-022-01014-z.

Elevated serum level of progranulin is associated with increased mortality in critically ill patients with candidemia.

Candidemia is a severe disease with high mortality in both intensive care unit (ICU) and non-ICU settings. Considering that progranulin (PGRN) is a potential therapeutic target for the candidemia caused by Candida albicans, we determined the serum level of PGRN after candidemia and evaluated its association with mortality. A retrospective discovery cohort (62 patients) and a validation cohort (70 patients) were enrolled. Blood was collected on day of first blood culture positivity for C. albicans, and serum PGRN levels were then measured. In the discovery cohort, all serum PGRN studied were expressed at higher levels in candidemia patients than in bacteremia patients and healthy volunteers, non-survivors presented with significantly higher serum PGRN concentrations when compared with survivors. Serum PGRN concentration was associated with 30-day mortality and patients at a higher risk of death showed higher serum PGRN levels. These results were confirmed in the independent validation cohort. Interestingly, in vitro study demonstrated that macrophages, neutrophils and lymphocytes may be the major source of PGRN production after C. albicans infection instead of epithelial cells. Our findings highlight that serum PGRN appears as a biomarker in candidemia patients and as a promising tool for mortality risk stratification in managing candidemia.

Absence of toll-like receptor 7 ameliorates survival and reduces intestinal injury in mice after Clostridium difficile infection.

Clostridioides difficile (CD) is a major cause of antibiotic-associated diarrhea and pseudomembranous enteritis. C. difficile infection (CDI) is increasingly present in the community and represents a significant burden on the healthcare system. Identification of novel immune-based therapeutic targets from a better understanding of their molecular pathogenesis is urgently required. Toll-like receptor 7 (TLR7) is an important pattern recognition receptor and function as an immune sensor that can trigger host defenses against pathogens, but the relationship between TLR7 and CDI remains unknown. Here, we reported that the expression levels of TLR7 increased significantly in patients and mice with CDI. Absence of TLR7 in mice with CDI demonstrated enhanced bacterial clearance of intestinal contents and reduced intestinal inflammation, edema, injury and prolonged the survival. TLR7 loss decreased the concentrations of tumor necrosis factor (TNF)-α, interferon (IFN)-γ and IFN-α1 in the intestine and improved tissue damage and inflammation. Flow cytometry and immunofluorescence results indicated that TLR7 enhanced leukocyte recruitment in the infected intestine. In-vitro results have shown that TLR7 impairs the phagocytosis and killing ability of macrophages to CD, prompts reactive oxygen species (ROS) production and accelerates apoptosis. To our knowledge, our study first identified TLR7 as a critical factor that contributes to the immunopathology of CDI, suggesting that targeting TLR7 might serve as a potential treatment for CDI.

Differences in the Distribution of Species, Carbapenemases, Sequence Types, Antimicrobial Heteroresistance and Mortality Rates Between Pediatric and Adult Carbapenemase-Producing Enterobacterales in Bloodstream Infections.

The dissemination of carbapenemase-producing Enterobacterales (CPE) is worrisome given their scarce treatment options. CPE bloodstream infections (BSIs) had a high mortality rate in adults, and there was little data on pediatric CPE-BSIs around the world. We comprehensively explored the differences in the clinical and microbiological characteristics between pediatric and adult CPE-BSIs. Forty-eight pediatric and 78 adult CPE-BSIs cases were collected. All-cause 30 day-mortality in children with CPE-BSIs (14.6%, 7/48) was significantly lower than that in adult patients (42.3%, 33/78, p = 0.001). The subgroup in adults empirically treated with tigecycline as an active drug displayed a significantly higher 30-days crude mortality (63.3%, 19/30) than the subgroup treated without tigecycline (29.2%, 14/48, p = 0.003). K. pneumoniae was the most prevalent species in both the pediatric (45.8%, 22/48) and adult populations (64.1%, 50/78), with discrepant carbapenemase genes in each population: 95.4% (21/22) of the pediatric K. pneumoniae isolates carried bla NDM, while 82.0% (41/50) of the adult strains harbored bla KPC. The ratio of E. coli in children (37.5%) was significantly higher than that in adults (12.8%, p = 0.002). In both populations, the majority of E. coli expressed bla NDM, particularly bla NDM-5. With statistical significance, bla NDM was much more common in children (95.8%, 46/48) than in adults (34.6%, 27/78). The rate of multiple-heteroresistance phenotypes in children was as high as 87.5%, which was much lower in adults (57.1%). Agar dilution checkboard experiment against one pediatric carbapenemase-producing E. coli isolates showed that the combination of amikacin and fosfomycin yielded an additive effect. Overall, K. pneumoniae was the most common CPE-BSIs pathogen in both populations, with NDM-producing K. pneumoniae and KPC-producing ST11 K. pneumoniae being the most prevalent species in children and adults, respectively. E. coli was more prevalent in children than in adults, yet bla NDM-5 was the most common carbapenem-resistant mechanism in E. coli in both populations. The wide range of multiple-heteroresistance combination traits found in different pathogen species from different host populations should provide a good foundation for future combination therapy design. Further investigations from more CPE isolates of various species are needed to evaluate the possible in vitro partial synergy of the amikacin and fosfomycin combination.

Absence of Toll-like receptor 7 protects mice against Pseudomonas aeruginosa pneumonia.

Toll-like receptor 7 (TLR7) is a sensor of microbial ssRNA that participates in the immune response process in many diseases. We herein sought to establish the role of TLR7 in Pseudomonas aeruginosa pneumonia. Pneumonia model was created by intratracheally injecting Pseudomonas aeruginosa and the effects of TLR7 on survival, bacterial burden, lung pathology, cytokine and chemokine production, and pulmonary leukocyte recruitment were measured after Pseudomonas aeruginosa challenge. TLR7 expression was significantly elevated in WT mice after Pseudomonas aeruginosa infection. TLR7-/- mice demonstrated enhanced survival, bacterial clearance, leukocyte infiltration, and macrophages phagocytic activity, and decreased pathology and capillary leakage. Besides, improved survival and bacterial clearance were observed in WT mice treated with TLR7 antagonist IRS661. More importantly, lack of TLR7 suppressed pro-inflammatory cytokine production and induced anti-inflammatory cytokine production in mice lungs. Finally, neutralized IL-10 damaged the bacterial clearance ability of TLR7 deficient mice, leading to decreased survival. Collectively, absence of TLR7 provided protective effects during Pseudomonas aeruginosa pneumonia and suggested that TLR7 could act as a novel immune target to treat clinical cases with Pseudomonas aeruginosa pneumonia.