Haemolysin Ahh1 secreted from Aeromonas dhakensis activates the NLRP3 inflammasome in macrophages and mediates severe soft tissue infection.

Severe soft tissue infections caused by Aeromonas dhakensis, such as necrotizing fasciitis or cellulitis, are prevalent in southern Taiwan and around the world. However, the mechanism by which A. dhakensis causes tissue damage remains unclear. Here, we found that the haemolysin Ahh1, which is the major virulence factor of A. dhakensis, causes cellular damage and activates the NLR family pyrin domain containing 3 (NLRP3) inflammasome signalling pathway. Deletion of ahh1 significantly downregulated caspase-1, the proinflammatory cytokine interleukin 1ß (IL-1ß) and gasdermin D (GSDMD) and further decreased the damage caused by A. dhakensis in THP-1 cells. In addition, we found that knockdown of the NLRP3 inflammasome confers resistance to A. dhakensis infection in both THP-1 NLRP3-/- cells and C57BL/6 NLRP3-/- mice. In addition, we demonstrated that severe soft-tissue infections treated with antibiotics combined with a neutralizing antibody targeting IL-1ß significantly increased the survival rate and alleviated the degree of tissue damage in model mice compared control mice. These findings show that antibiotics combined with therapies targeting IL-1ß are potential strategies to treat severe tissue infections caused by toxin-producing bacteria.

Reversibility of some oxidative stress markers in chronic hepatitis C patients after receiving direct-acting antiviral agents.

Introduction: Hepatitis C (HCV) is associated with extra-hepatic involvment, morbidity as well as metabolic changes. Whether these might be reversible if sustained virologic response (SVR) is achieved by direct-acting antiviral (DAA) therapy remains unknown. Methods: Chronic hepatitis C (CHC) individuals receiving DAA treatment with SVR were compared to those who underwent spontaneous clearance (SC) of HCV infection at the 2-year follow-up. Plasma oxidative stress markers (oxidized low-density lipoprotein (oxLDL), 8-hydroxy-2'-deoxyguanosine (8-OHdG), malondialdehyde (MDA) and ischemia-modified albumin (IMA)) as well as progression of liver fibrosis were evaluated. Results: Compared to SC individuals, those in the CHC group exhibited at baseline higher levels of oxLDL, 8-OHdG and IMA but not of MDA. In the SC group, 8-OHdG levels were elevated at 2-year post-SVR (p = 0.0409), while the DAA-treated CHC group showed decrease in oxLDL (p < 0.0001) and 8-OHdG (p = 0.0255) levels, approaching those of the SC group, but increased MDA (p = 0.0055) levels. Additionally, oxLDL levels were positively correlated with liver stiffness measurements at SVR (p = 0.017) and at 1 year post- SVR (p = 0.002). Conclusions: Plasma oxLDL showed post-SVR normalization after clearance of HCV viremia with DAAs and was associated with levels of hepatic fibrosis.

Antagonizing apolipoprotein J chaperone promotes proteasomal degradation of mTOR and relieves hepatic lipid deposition.

BACKGROUND AND AIMS: Overnutrition-induced activation of mammalian target of rapamycin (mTOR) dysregulates intracellular lipid metabolism and contributes to hepatic lipid deposition. Apolipoprotein J (ApoJ) is a molecular chaperone and participates in pathogen-induced and nutrient-induced lipid accumulation. This study investigates the mechanism of ApoJ-regulated ubiquitin-proteasomal degradation of mTOR, and a proof-of-concept ApoJ antagonist peptide is proposed to relieve hepatic steatosis. APPROACH AND RESULTS: By using omics approaches, upregulation of ApoJ was found in high-fat medium-fed hepatocytes and livers of patients with NAFLD. Hepatic ApoJ level associated with the levels of mTOR and protein markers of autophagy and correlated positively with lipid contents in the liver of mice. Functionally, nonsecreted intracellular ApoJ bound to mTOR kinase domain and prevented mTOR ubiquitination by interfering FBW7 ubiquitin ligase interaction through its R324 residue. In vitro and in vivo gain-of-function or loss-of-function analysis further demonstrated that targeting ApoJ promotes proteasomal degradation of mTOR, restores lipophagy and lysosomal activity, thus prevents hepatic lipid deposition. Moreover, an antagonist peptide with a dissociation constant (Kd) of 2.54 µM interacted with stress-induced ApoJ and improved hepatic pathology, serum lipid and glucose homeostasis, and insulin sensitivity in mice with NAFLD or type II diabetes mellitus. CONCLUSIONS: ApoJ antagonist peptide might be a potential therapeutic against lipid-associated metabolic disorders through restoring mTOR and FBW7 interaction and facilitating ubiquitin-proteasomal degradation of mTOR.

Establishment of quantitative and recovery method for detection of dengue virus in wastewater with noncognate spike control.

Wastewater-based epidemiology (WBE) represents an efficient approach for public pathogen surveillance as it provides early warning of disease outbreaks; however, it has not yet been applied to dengue virus (DENV), which might cause endemics via mosquito spread. In this study, a working platform was established to provide direct virus recovery and qPCR quantification from wastewater samples that were artificially loaded with target DENV serotypes I to IV and noncognate spike control viral particles. The results showed qPCR efficiencies of 91.2 %, 94.8 %, 92.6 % and 88.7 % for DENV I, II, III, and IV, respectively, and a broad working range over 6 orders of magnitude using the preferred primer sets. Next, the results revealed that the ultrafiltration method was superior to the skimmed milk flocculation method for recovering either DENV or control viral particles from wastewater. Finally, DENV-2 was loaded simultaneously with the noncognate spike control and could be recovered at comparable levels either in PBS or in wastewater, indicating the applicability of noncognate spike control particles to reflect the efficiency of experimental steps. In conclusion, our data suggest that DENV particles in wastewater could be recovered and quantitatively detected in absolute amounts, indicating the feasibility of DENV surveillance using the WBE approach.

Interdependence of glycemic and lipid modulation in cured chronic hepatitis C patients by direct-acting antiviral agents.

BACKGROUND: Chronic hepatitis C virus (HCV) infection causes various liver diseases and metabolic disorders. With direct-acting antiviral agents (DAAs), which effectively eradicate pan-genotypic HCV, hepatic and concomitant metabolic restorations are achieved. The study aims to evaluate the posttherapeutic benefits of lipid and glycemic homeostasis. METHODS: Nighty-five chronic hepatitis C patients who achieved sustained virological response (SVR) by using DAAs were enrolled to collect plasma samples and fractionated lipoproteins at baseline, SVR, and during the post-SVR follow-ups for 6 months (pS6m) and 1 year (pS1yr). The lipid and glycemic parameters were analyzed to establish muturally modulatory relationships. RESULTS: Plasma cholesterol (Chol) and glucose were elevated at SVR from baseline, whereas plasma Chol remained increased until pS1yr; however, glucose returned to the basal level. The post-SVR responses included a peak elevation of glycated hemoglobin at pS6m, a sustained elevation of triglyceride (Tg), and sustained declines in insulin, homeostasis model assessment (HOMA)-insulin resistance, and HOMA-beta levels until pS1yr. The changes in plasma Chol and high-density-lipoprotein Chol showed positive correlations, as did the plasma Tg with low-density-lipoprotein Tg and very-low-density-lipoprotein Tg per particle load. Very-low-density-lipoprotein was found to be loaded with increased Tg and Chol and underwent efficient Tg catabolism in the form of conversion into low-density-lipoprotein. Additionally, the posttherapeutic dynamics exhibited correlations of high-density-lipoprotein Chol with plasma glucose and HOMA-beta. CONCLUSION: Irrespective of the baseline metabolic status, the posttherapeutic interdependent modulation of blood glycemic and lipid metabolic parameters were revealed in chronic hepatitis C patients following clearance of HCV viremia by DAA treatment.

Iron Acquisition of Urinary Tract Infection Escherichia coli Involves Pathogenicity in Caenorhabditis elegans.

Uropathogenic Escherichia coli (UPEC) is a major bacterial pathogen that causes urinary tract infections (UTIs). The mouse is an available UTI model for studying the pathogenicity; however, Caenorhabditis elegans represents as an alternative surrogate host with the capacity for high-throughput analysis. Then, we established a simple assay for a UPEC infection model with C. elegans for large-scale screening. A total of 133 clinically isolated E. coli strains, which included UTI-associated and fecal isolates, were applied to demonstrate the simple pathogenicity assay. From the screening, several virulence factors (VFs) involved with iron acquisition (chuA, fyuA, and irp2) were significantly associated with high pathogenicity. We then evaluated whether the VFs in UPEC were involved in the pathogenicity. Mutants of E. coli UTI89 with defective iron acquisition systems were applied to a solid killing assay with C. elegans. As a result, the survival rate of C. elegans fed with the mutants significantly increased compared to when fed with the parent strain. The results demonstrated, the simple assay with C. elegans was useful as a UPEC infectious model. To our knowledge, this is the first report of the involvement of iron acquisition in the pathogenicity of UPEC in a C. elegans model.

OmpR coordinates the expression of virulence factors of Enterohemorrhagic Escherichia coli in the alimentary tract of Caenorhabditis elegans.

Enterohemorrhagic Escherichia coli (EHEC), an enteropathogen that colonizes in the intestine, causes severe diarrhea and hemorrhagic colitis in humans by the expression of the type III secretion system (T3SS) and Shiga-like toxins (Stxs). However, how EHEC can sense and respond to the changes in the alimentary tract and coordinate the expression of these virulence genes remains elusive. The T3SS-related genes are known to be regulated by the locus of enterocyte effacement (LEE)-encoded regulators, such as Ler, as well as non-LEE-encoded regulators in response to different environmental cues. Herein, we report that OmpR, which participates in the adaptation of E. coli to osmolarity and pH alterations, is required for EHEC infection in Caenorhabditis elegans. OmpR protein was able to directly bind to the promoters of ler and stx1 (Shiga-like toxin 1) and regulate the expression of T3SS and Stx1, respectively, at the transcriptional level. Moreover, we demonstrated that the expression of ler in EHEC is in response to the intestinal environment and is regulated by OmpR in C. elegans. Taken together, we reveal that OmpR is an important regulator of EHEC which coordinates the expression of virulence factors during gastrointestinal infection in vivo.

IGLR-2, a Leucine-Rich Repeat Domain Containing Protein, Is Required for the Host Defense in Caenorhabditis elegans.

Enterohemorrhagic Escherichia coli (EHEC), a human pathogen, also infects Caenorhabditis elegans. We demonstrated previously that C. elegans activates the p38 MAPK innate immune pathway to defend against EHEC infection. However, whether a C. elegans pattern recognition receptor (PRR) exists to regulate the immune pathway remains unknown. PRRs identified in other metazoans contain several conserved domains, including the leucine-rich repeat (LRR). By screening a focused RNAi library, we identified the IGLR-2, a transmembrane protein containing the LRR domain, as a potential immune regulator in C. elegans. Our data showed that iglr-2 regulates the host susceptibility to EHEC infection. Moreover, iglr-2 is required for pathogen avoidance to EHEC. The iglr-2 overexpressed strain, which was more resistant to EHEC originally, showed hypersusceptibility to EHEC upon knockdown of the p38 MAPK pathway. Together, our data suggested that iglr-2 plays an important role in C. elegans to defend EHEC by regulating pathogen-avoidance behavior and the p38 MAPK pathway.

UvrY is required for the full virulence of Aeromonas dhakensis.

Aeromonas dhakensis is an emerging human pathogen which causes fast and severe infections worldwide. Under the gradual pressure of lacking useful antibiotics, finding a new strategy against A. dhakensis infection is urgent. To understand its pathogenesis, we created an A. dhakensis AAK1 mini-Tn10 transposon library to study the mechanism of A. dhakensis infection. By using a Caenorhabditis elegans model, we established a screening platform for the purpose of identifying attenuated mutants. The uvrY mutant, which conferred the most attenuated toxicity toward C. elegans, was identified. The uvrY mutant was also less virulent in C2C12 fibroblast and mice models, in line with in vitro results. To further elucidate the mechanism of UvrY in controlling the toxicity in A. dhakensis, we conducted a transcriptomic analysis. The RNAseq results showed that the expression of a unique hemolysin ahh1 and other virulence factors were regulated by UvrY. Complementation of Ahh1, one of the most important virulence factors, rescued the pore-formation phenotype of uvrY mutant in C. elegans; however, complementation of ahh1 endogenous promoter-driven ahh1 could not produce Ahh1 and rescue the virulence in the uvrY mutant. These findings suggest that UvrY is required for the expression of Ahh1 in A. dhakensis. Taken together, our results suggested that UvrY controls several different virulence factors and is required for the full virulence of A. dhakensis. The two-component regulator UvrY therefore a potential therapeutic target which is worthy of further study.

Detection of Enterohemorrhagic Escherichia Coli Colonization in Murine Host by Non-invasive In Vivo Bioluminescence System.

Enterohemorrhagic E. coli (EHEC) O157:H7, which is a foodborne pathogen that causesdiarrhea, hemorrhagic colitis (HS), and hemolytic uremic syndrome (HUS), colonize to the intestinal tract of humans. To study the detailed mechanism of EHEC colonization in vivo, it is essential to have animal models to monitor and quantify EHEC colonization. We demonstrate here a mouse-EHEC colonization model by transforming the bioluminescent expressing plasmid to EHEC to monitor and quantify EHEC colonization in living hosts. Animals inoculated with bioluminescence-labeled EHEC show intense bioluminescent signals in mice by detection with a non-invasive in vivo imaging system. After 1 and 2 days post infection, bioluminescent signals could still be detected in infected animals, which suggests that EHEC colonize in hosts for at least 2 days. We also demonstrate that these bioluminescent EHEC locate to mouse intestine, specifically in the cecum and colon, from ex vivo images. This mouse-EHEC colonization model may serve as a tool to advance the current knowledge of the EHEC colonization mechanism.

A multi-omic analysis reveals the role of fumarate in regulating the virulence of enterohemorrhagic Escherichia coli.

The enteric pathogen enterohemorrhagic Escherichia coli (EHEC) is responsible for outbreaks of bloody diarrhea and hemolytic uremic syndrome (HUS) worldwide. Several molecular mechanisms have been described for the pathogenicity of EHEC; however, the role of bacterial metabolism in the virulence of EHEC during infection in vivo remains unclear. Here we show that aerobic metabolism plays an important role in the regulation of EHEC virulence in Caenorhabditis elegans. Our functional genomic analyses showed that disruption of the genes encoding the succinate dehydrogenase complex (Sdh) of EHEC, including the sdhA gene, attenuated its toxicity toward C. elegans animals. Sdh converts succinate to fumarate and links the tricarboxylic acid (TCA) cycle and the electron transport chain (ETC) simultaneously. Succinate accumulation and fumarate depletion in the EHEC sdhA mutant cells were also demonstrated to be concomitant by metabolomic analyses. Moreover, fumarate replenishment to the sdhA mutant significantly increased its virulence toward C. elegans. These results suggest that the TCA cycle, ETC, and alteration in metabolome all account for the attenuated toxicity of the sdhA mutant, and Sdh catabolite fumarate in particular plays a critical role in the regulation of EHEC virulence. In addition, we identified the tryptophanase (TnaA) as a downstream virulence determinant of SdhA using a label-free proteomic method. We demonstrated that expression of tnaA is regulated by fumarate in EHEC. Taken together, our multi-omic analyses demonstrate that sdhA is required for the virulence of EHEC, and aerobic metabolism plays important roles in the pathogenicity of EHEC infection in C. elegans. Moreover, our study highlights the potential targeting of SdhA, if druggable, as alternative preventive or therapeutic strategies by which to combat EHEC infection.

Mutation of the Enterohemorrhagic Escherichia coli Core LPS Biosynthesis Enzyme RfaD Confers Hypersusceptibility to Host Intestinal Innate Immunity In vivo.

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is an important foodborne pathogen causing severe diseases in humans worldwide. Currently, there is no specific treatment available for EHEC infection and the use of conventional antibiotics is contraindicated. Therefore, identification of potential therapeutic targets and development of effective measures to control and treat EHEC infection are needed. Lipopolysaccharides (LPS) are surface glycolipids found on the outer membrane of gram-negative bacteria, including EHEC, and LPS biosynthesis has long been considered as potential anti-bacterial target. Here, we demonstrated that the EHEC rfaD gene that functions in the biosynthesis of the LPS inner core is required for the intestinal colonization and pathogenesis of EHEC in vivo. Disruption of the EHEC rfaD confers attenuated toxicity in Caenorhabditis elegans and less bacterial colonization in the intestine of C. elegans and mouse. Moreover, rfaD is also involved in the control of susceptibility of EHEC to antimicrobial peptides and host intestinal immunity. It is worth noting that rfaD mutation did not interfere with the growth kinetics when compared to the wild-type EHEC cells. Taken together, we demonstrated that mutations of the EHEC rfaD confer hypersusceptibility to host intestinal innate immunity in vivo, and suggested that targeting the RfaD or the core LPS synthesis pathway may provide alternative therapeutic regimens for EHEC infection.