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Lau R.W.T.,University of Hong Kong | Ho P.-L.,University of Hong Kong | Kao R.Y.T.,University of Hong Kong | Yew W.-W.,Tuberculosis and Chest Unit | And 6 more authors.
Antimicrobial Agents and Chemotherapy | Year: 2011

A PCR-sequencing assay was evaluated for direct detection of mutations in the quinolone resistance-determining region (QRDR) of gyrase A (gyrA) gene in fluoroquinolone-resistant Mycobacterium tuberculosis in respiratory specimens. As determined by gyrA QRDR analysis, complete concordance of genotypic and phenotypic fluoroquinolone resistance was demonstrated. Our results indicate that the assay is a rapid and reliable method for the diagnosis of fluoroquinolone-resistant tuberculosis, facilitating timely clinical management and public health control. Using the assay, we detected a novel gyrA Ala74Ser mutation in M. tuberculosis directly from sputum specimens. The functional effect of the Ala74Ser mutant was verified through the study of the DNA supercoiling inhibitory activity of fluoroquinolones against the recombinant gyrase. The drug-mediated gyrase-DNA cleavage complex model suggests perturbation of the gyrA-gyrA dimer interface caused by the Ala74Ser mutation probably disturbs the putative quinolone binding pocket and leads to the reduction of the drug binding affinity. A number of gyrA mutations (Glu21Gln, Ser95Thr, and Gly668Asp) were also characterized to be natural polymorphisms not associated with fluoroquinolone resistance. Copyright © 2011, American Society for Microbiology. All Rights Reserved. Source


Qiu Y.,Sun Yat Sen University | Qiu Y.,Jinan University | Chen J.,Shenzhen Third Peoples Hospital | Liao H.,Sun Yat Sen University | And 15 more authors.
PLoS Pathogens | Year: 2012

T-cell immune responses modulated by T-cell immunoglobulin and mucin domain-containing molecule 3 (Tim-3) during Mycobacterium tuberculosis (Mtb) infection in humans remain poorly understood. Here, we found that active TB patients exhibited increases in numbers of Tim-3-expressing CD4+ and CD8+ T cells, which preferentially displayed polarized effector memory phenotypes. Consistent with effector phenotypes, Tim-3+CD4+ and Tim-3+CD8+ T-cell subsets showed greater effector functions for producing Th1/Th22 cytokines and CTL effector molecules than Tim-3- counterparts, and Tim-3-expressing T cells more apparently limited intracellular Mtb replication in macrophages. The increased effector functions for Tim-3-expressing T cells consisted with cellular activation signaling as Tim-3+CD4+ and Tim-3+CD8+ T-cell subsets expressed much higher levels of phosphorylated signaling molecules p38, stat3, stat5, and Erk1/2 than Tim-3- controls. Mechanistic experiments showed that siRNA silencing of Tim-3 or soluble Tim-3 treatment interfering with membrane Tim-3-ligand interaction reduced de novo production of IFN-γ and TNF-α by Tim-3-expressing T cells. Furthermore, stimulation of Tim-3 signaling pathways by antibody cross-linking of membrane Tim-3 augmented effector function of IFN-γ production by CD4+ and CD8+ T cells, suggesting that Tim-3 signaling helped to drive stronger effector functions in active TB patients. This study therefore uncovered a previously unknown mechanism for T-cell immune responses regulated by Tim-3, and findings may have implications for potential immune intervention in TB. © 2012 Qiu et al. Source


Liu Y.,Shenzhen Institute of Hepatology | Dong C.feng.,Shenzhen Institute of Hepatology | Yang G.,Shenzhen Institute of Hepatology | Liu J.,Shenzhen Institute of Hepatology | And 10 more authors.
Liver International | Year: 2015

Background and Aims: Accurate assessment of liver fibrosis in patients with chronic hepatitis B (CHB) is necessary not only to predict the long-term clinical course but also to determine an appropriate antiviral therapy scheme. Several noninvasive approaches - serum markers and elastography - have been proposed as alternatives for the histopathological analysis of liver biopsies. The aim of this study was to evaluate two ultrasound elastography methods (ARFI and TE) and one biochemical test (APRI), as well as their optimal linear combination, in the assessment of liver fibrosis in CHB. Methods: Ninety five patients with CHB and 16 volunteers underwent ARFI, TE and APRI; and liver fibrosis was staged in the patients by a liver biopsy. An optimal linear combination of the three methods was developed, and its diagnostic performance was evaluated by a 10-fold cross-validation. Results: The accuracy of the linear combination was 83.86% and 91.88% for significant fibrosis (≥F2) and cirrhosis (F4), respectively, higher than those obtained for ARFI (83.50%, 88.76%), TE (75.27%, 87.61%) and APRI (73.29% and 81.67%). The combination also increased the sensitivity and the negative predictive values for the diagnosis of significant fibrosis and cirrhosis. Conclusions: The optimal linear combination algorithm is effective for noninvasive staging of liver fibrosis in CHB. However, linear combination has its own limitations; nonlinear methods may eventually reveal even clearer diagnostic results. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd. Source

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