Validation of the novel GLAS algorithm as an aid in the detection of liver fibrosis and cirrhosis based on GP73, LG2m, age, and sex.

BACKGROUND: Diagnosis of liver disease at earlier stages can improve outcomes and reduce the risk of progression to malignancy. Liver biopsy is the gold standard for diagnosis of liver disease, but is invasive and sample acquisition errors are common. Serum biomarkers for liver function and fibrosis, combined with patient factors, may allow for noninvasive detection of liver disease. In this pilot study, we tested and validated the performance of an algorithm that combines GP73 and LG2m serum biomarkers with age and sex (GLAS) to differentiate between patients with liver disease and healthy individuals in two independent cohorts. METHODS: To develop the algorithm, prototype immunoassays were used to measure GP73 and LG2m in residual serum samples collected between 2003 and 2016 from patients with staged fibrosis and cirrhosis of viral or non-viral etiology (n = 260) and healthy subjects (n = 133). The performance of five predictive models using combinations of age, sex, GP73, and/or LG2m from the development cohort were tested. Residual samples from a separate cohort with liver disease (fibrosis, cirrhosis, or chronic liver disease; n = 395) and healthy subjects (n = 106) were used to validate the best performing model. RESULTS: GP73 and LG2m concentrations were higher in patients with liver disease than healthy controls and higher in those with cirrhosis than fibrosis in both the development and validation cohorts. The best performing model included both GP73 and LG2m plus age and sex (GLAS algorithm), which had an AUC of 0.92 (95% CI: 0.90-0.95), a sensitivity of 88.8%, and a specificity of 75.9%. In the validation cohort, the GLAS algorithm had an estimated an AUC of 0.93 (95% CI: 0.90-0.95), a sensitivity of 91.1%, and a specificity of 80.2%. In both cohorts, the GLAS algorithm had high predictive probability for distinguishing between patients with liver disease versus healthy controls. CONCLUSIONS: GP73 and LG2m serum biomarkers, when combined with age and sex (GLAS algorithm), showed high sensitivity and specificity for detection of liver disease in two independent cohorts. The GLAS algorithm will need to be validated and refined in larger cohorts and tested in longitudinal studies for differentiating between stable versus advancing liver disease over time.

Comparative analysis of sigma factors RpoS, FliA, and RpoN in Edwardsiella tarda.

Sigma factors are important regulators that bacteria employ to cope with environmental changes. Studies on the functions of sigma factors have uncovered their roles in many important cellular activities, such as growth, stress tolerance, motility, biofilm formation, and virulence. However, comparative analyses of sigma factors that examine their common and unique features or elucidate their cross-regulatory relationships have rarely been conducted for Edwardsiella tarda. Here, we characterized and compared motility and resistance to oxidative stress of E. tarda strains complemented with rpoS, fliA, and rpoN mutants. The results suggest that the sigma factors FliA and RpoN regulated motility, whereas RpoS exhibited no such function. RpoS and RpoN were essential for oxidative stress resistance, whereas FliA had no obvious impact under oxidative stress conditions. Furthermore, 2-dimensional gel electrophoresis based proteomics analysis combined with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry revealed 12 differentially expressed protein spots that represented 11 proteins between the mutant and wild-type strains. Quantification of the expression of target genes by quantitative reverse transcription PCR confirmed the results of our proteomics analysis. Collectively, these results suggest that these sigma factors are multifunctional mediators involved in controlling the expression of many metabolic pathway genes.

Impact of co-deficiency of RpoN and RpoS on stress tolerance, virulence and gene regulation in Edwardsiella tarda.

Edwardsiella tarda the etiological agent for edwardsiellosis, a devastating fish disease prevailing in worldwide aquaculture industries was subjected to a molecular genetic study. To research into the influence when RpoN (σ(54) ) and RpoS (σ(38) ) were deleted simultaneously, the double deletion mutant of RpoN (σ(54) ) and RpoS (σ(38) ), namely rnrs, was constructed. Firstly, RpoN and RpoS are both essential for H2 O2 , starvation, high osmotic pressure and acid resistance, which have synergistic effect. Secondly, virulence of rnrs reduces significantly compared to E. tarda EIB 202 WT, ΔrpoN mutant and ΔrpoS mutant. Furthermore, transcriptional control of rpoS by rpoN in stationary phase was observed through qRT-PCR, while rpoS had no influence on rpoN in the level of transcription. Meanwhile, regulation of flagellar sigma factor σ(F) (FliA) and other flagella-related genes including flgA, flgK, flgL, motA, and motB by rpoS, and rpoN was found. fliA and other flagella-related genes were controlled positively by rpoN, while negatively by rpoS. At last, two differential expression genes in transcriptional level of rnrs strain were detected by DD-RT-PCR, namely cheY and narK. This study therefore indicated interaction between sigma factors RpoN and RpoS, which modulates stress response, virulence, motility, and provides new insights into the regulatory networks of E. tarda.

Characterization of Edwardsiella tarda rpoN: roles in σ(70) family regulation, growth, stress adaption and virulence toward fish.

Edwardsiella tarda EIB202, a Gram-negative pathogen with strong virulence, is an opportunistic pathogen capable of causing edwardsiellosis with high mortality to fish. Alternative sigma factor 54 (RpoN) is an important regulator of virulence and stress resistance genes in many bacterial species and mainly responsible for transcription of genes in nitrogen utilization. In this study, the in-frame rpoN deletion mutant was constructed to analyze the function of RpoN in Edwardsiella tarda firstly. Compared to the wild-type and complemented strain rpoN (+), the ΔrpoN was impaired in terms of the ability to survive under oxidative stress, osmotic stress and acid resistance, as well as the growth in Luria-Bertani medium, demonstrating essential roles of RpoN in stress resistance and nitrogen utilization. In addition, the ΔrpoN displayed markedly decreased biofilm formation and chondroitinase activity and was attenuated in virulence reflected in the increased median lethal dose value and extended infection cycle. Real-time polymerase chain reaction revealed that the expression levels of σ(70) class changed in varying degrees in the rpoN mutant. Especially, the expression levels of rpoS and fliA were down-regulated 4.1-fold and 7.9-fold in stationary phase in comparison with the wild type, respectively. Furthermore, two differential expression genes, znuA and flhC, were detected in the wild type and ΔrpoN using the method of differential display reverse transcription PCR.