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2. High end‐of‐treatment hepatitis B core‐related antigen levels predict hepatitis flare after stopping nucleot(s)ide analogue therapy.

Author

Hume, Simon J., Wong, Danny K., Yuen, Man‐Fung, Jackson, Kathy, Bonanzinga, Sara, Vogrin, Sara, Hall, Samuel A. L., Burns, Gareth S., Desmond, Paul V., Sundararajan, Vijaya, Ratnam, Dilip, Levy, Miriam T., Lubel, John S., Nicoll, Amanda J., Strasser, Simone I., Sievert, William, Ngu, Meng C., Sinclair, Marie, Meredith, Christopher, and Matthews, Gail

Subjects
*HEPATITIS associated antigen, *CHRONIC hepatitis B, *HEPATITIS B, *END of treatment, *CLINICAL trials
Abstract

Background and Aims: Accurate biomarkers to predict outcomes following discontinuation of nucleos(t)ide analogue (NA) therapy are needed. We evaluated serum hepatitis B core‐related antigen (HBcrAg) level as a biomarker for predicting outcomes after NA discontinuation. Methods: Patients with HBeAg‐negative chronic hepatitis B (CHB) without cirrhosis were enrolled in a prospective trial evaluating clinical outcomes until 96 weeks after NA discontinuation. End of treatment (EOT) and off‐treatment levels of serum HBcrAg, HBsAg, HBV RNA and HBV DNA were used to predict key clinical outcomes including hepatitis flare (ALT ≥5 × ULN and HBV DNA > 2000 IU/mL). The SCALE‐B score was calculated for the purposes of model validation. Results: HBcrAg was tested amongst 65 participants. The median age was 54 years, 54% were male and 83% were Asian. HBcrAg was detectable in 86% patients. HBcrAg level ≥4 log U/mL at EOT was predictive of hepatitis flare [8/10 (80%) vs. 17/55 (31%), p =.001]. The presence of either HBcrAg ≥4 log U/mL or detectable HBV RNA at EOT predicted for both biochemical relapse and hepatitis flare. The SCALE‐B model at EOT predicted for virological relapse, biochemical relapse, hepatitis flare and HBsAg loss in this cohort. An increase in the serum HBcrAg level off‐treatment was also associated with hepatitis flare. No participant with EOT HBcrAg level ≥4 log U/mL achieved HBsAg loss. Conclusions: High levels of serum HBcrAg predict for hepatitis flare after stopping NA therapy and low likelihood of HBsAg loss at week 96. People with high levels of serum HBcrAg are not suitable candidates for NA discontinuation. [ABSTRACT FROM AUTHOR]

Published
2024
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6. Fragmentomics of urinary cell-free DNA in nuclease knockout mouse models

Author

Chen, Meihui, primary, Chan, Rebecca W. Y., additional, Cheung, Peter P. H., additional, Ni, Meng, additional, Wong, Danny K. L., additional, Zhou, Ze, additional, Ma, Mary-Jane L., additional, Huang, Liangbo, additional, Xu, Xinzhou, additional, Lee, Wing-Shan, additional, Wang, Guangya, additional, Lui, Kathy O., additional, Lam, W. K. Jacky, additional, Teoh, Jeremy Y. C., additional, Ng, Chi-Fai, additional, Jiang, Peiyong, additional, Chan, K. C. Allen, additional, Chiu, Rossa W. K., additional, and Lo, Y. M. Dennis, additional

Published
2022
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12. Identification of O-antigen polymerase transcription and translation start signals and visualization of the protein in Salmonella enterica serovar Typhinurium

Author

Wong, Danny K.-H., Morris, Christina, Lam, Tin L., Wong, Wan K.R., and Hackett, Jim

Subjects
Cytochemistry -- Research, Salmonella typhimurium -- Physiological aspects, Endotoxins -- Research, Biological sciences
Abstract

O-antigen polymerase transcription and translation start signals and discussed with attention to the protein in Salmonella enterica serovar Typhinurium. The wzy (ital) transitional startpoint was at first identified by primer extension. Then the wzy (ital) promoter strength in Escherichia coli K-12 was measured and found to exceed that of the induced lac (ital) promoter.

Published
1999

37. Anodic Stripping Voltametry at Mercury Film Deposited on Ultrasmall Carbon Ring Electrodes

Author

PENNSYLVANIA STATE UNIV UNIVERSITY PARK DEPT OF CHEMISTRY, Wong, Danny K., Ewing, Andrew G., PENNSYLVANIA STATE UNIV UNIVERSITY PARK DEPT OF CHEMISTRY, Wong, Danny K., and Ewing, Andrew G.

Abstract

Anodic stripping voltammetry of lead and cadmium without deliberately added electrolytes has been studied at ultrasmall carbon ring electrodes following in situ deposition of mercury. The stripping of lead has been studied in detail to investigate the dependence of stripping peak current on experimental parameters such as potential scan rate, preconcentration duration, deposition potential, concentration of Hg + during deposition and concentration of Pb 2+. Anodic stripping voltammetry in solutions without deliberately added supporting electrolyte avoids problems associated with impurities introducing when electrolyte is added. These impurities appear to be highly important when Pb 2+ analysis is carried out in dilute solutions. In addition, a unique effects is observed when relatively low concentrations of Hg+ are used for the in situ deposition step. When low Hg+ concentrations are used, the stripping current does not decrease as rapidly as expected as the concentration of Pb 2+ is reduced. Keywords: Stripping voltammetry, Ultrasmall carbon ring electrodes.

Published
1990

38. Characterization of the Voltammetric Response at Intracellular Carbon Ring Electrodes

Author

PENNSYLVANIA STATE UNIV UNIVERSITY PARK DEPT OF CHEMISTRY, Lau, Yau Yi, Chien, Jennifer B., Wong, Danny K., Ewing, Andrew G., PENNSYLVANIA STATE UNIV UNIVERSITY PARK DEPT OF CHEMISTRY, Lau, Yau Yi, Chien, Jennifer B., Wong, Danny K., and Ewing, Andrew G.

Abstract

The Intracellular response of ultrasmall carbon ring electrodes has been investigated. Adsorption of high molecular weight species (e.g. proteins, lipids, sugars, etc.) on the electrode surface appears to result in deterioration of the amperometric signal, making in vivo voltammetric measurements difficult. Assuming a linear dependence between the degree of electrode fouling and the number of scans taken in the neuronal microenvironment an analytical method based on both pre- and post-calibration data is presented to evaluate the response obtained at deteriorating ultrasmall carbon ring electrodes during intracellular voltammetry. Additionally, poly(ester sulfonic acid)-coated carbon ring electrodes have been used in an attempt to increase selectivity in intracellular voltammetry, and to reduce the effects of electrode fouling. In vitro results results obtained in solutions of dopamine, dihy- droxyphenylacetic acid and asorbic acid indicate some exclusion of anionic species from the electrode by the negative charged polymer film. Moreover, use of polymer-coated electrodes in vivo results in a decrease in the percentage of electrode fouling to where the degredation of the response is only 45%. This leads to a more reproducible response and better detection limits compared to that of naked electrodes. Keywords: In vivo analysis, Voltammetric measurements, Ultrasmall carbon ring electrode.

Published
1990

48. The Shufflon of Salmonella entericaSerovar Typhi Regulates Type IVB Pilus-Mediated Bacterial Self-Association

Author

Morris, Christina, Yip, Cecilia M. C., Tsui, Inez S. M., Wong, Danny K.-H., and Hackett, Jim

Abstract

ABSTRACTPreviously, it was shown that type IVB pili encoded by the Salmonella entericaserovar Typhi piloperon are used to facilitate bacterial entry into human intestinal epithelial cells in vitro and that such entry is inhibited by purified prepilin (pre-PilS) protein (X.-L. Zhang, I. S. M. Tsui, C. M. C. Yip, A. W. Y. Fung, D. K.-H. Wong, X. Dai, Y. Yang, J. Hackett, and C. Morris, Infect. Immun. 68:3067-3073, 2000). The piloperon concludes with a simple shufflon, and a recombinase gene product (Rci) inverts DNA in the C-terminal region of the pilVgene to allow synthesis of two distinct PilV proteins, PilV1 and PilV2, which are presumptive minor pilus proteins. We show here that the type IVB pili mediate bacterial self-association, but only when the PilV1 and PilV2 proteins are not expressed. This may be achieved in wild-type serovar Typhi by rapid DNA inversion activity of the shufflon. We show that the inversion activity inhibits the expression of genes inserted between the 19-bp inverted repeats used for Rci-mediated recombination and that the activity of Rci increases when DNA is supercoiled. The data suggest that serovar Typhi self-associates under conditions (such as low oxygen tension in the gut) that favor DNA supercoiling. These results explain (i) the function of the serovar Typhi shufflon and (ii) why there are only two possible shufflon states, in contrast to the many possible states of other shufflon systems. The data further indicate that a very early step in serovar Typhi pathogenesis may be type IVB pilus-mediated self-association of bacteria in the anaerobic human small intestine prior to invasion of the human gut epithelium. The suggested type IVB pilus-dependent step in typhoid fever pathogenesis may partially explain the enhanced invasiveness of serovar Typhi for humans.

Published
2003
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49. Salmonella entericaSerovar Typhi Uses Type IVB Pili To Enter Human Intestinal Epithelial Cells

Author

Zhang, Xiao-Lian, Tsui, Inez S. M., Yip, Cecilia M. C., Fung, Ada W. Y., Wong, Danny K.-H., Dai, Xiaoyun, Yang, Yanhua, Hackett, Jim, and Morris, Christina

Abstract

ABSTRACTDNA sequencing upstream of the Salmonella entericaserovar Typhi pilVand rcigenes previously identified in the ca. 118-kb major pathogenicity island (X.-L. Zhang, C. Morris, and J. Hackett, Gene 202:139–146, 1997) identified a further 10 pilgenes apparently forming a piloperon. The product of the pilSgene, prePilS protein (a putative type IVB structural prepilin) was purified, and an anti-prePilS antiserum was raised in mice. Mutants of serovar Typhi either lacking the whole piloperon or with an insertion mutation in the pilSgene were constructed, as was a strain in which the pilNto pilVgenes were driven by the tacpromoter. The pil+strains synthesized type IVB pili, as judged by (i) visualization in the electron microscope of thin pili in culture supernatants of one such strain and (ii) the presence of PilS protein (smaller than the prePilS protein by removal of the leader peptide) on immunoblotting of material pelleted by high-speed centrifugation of either the culture supernatant or sonicates of pil+strains. Controlpilmutants did not express the PilS protein. ApilSmutant of serovar Typhi entered human intestinal INT407 cells in culture to levels only 5 to 25% of those of the wild-type strain, and serovar Typhi entry was strongly inhibited by soluble prePilS protein (50% inhibition of entry at 1.4 μM prePilS).

Published
2000
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50. Self-Assembled Layer of Thiolated Protein G as an Immunosensor Scaffold.

Author

Fowler, Jeremy M., Stuart, Margaret C., and Wong, Danny K. V.

Subjects
*MOLECULAR self-assembly, *ELECTRODES, *GOLD, *THIOLS, *PROTEINS, *ORGANOSULFUR compounds, *ANTIGENS, *IMMUNOGLOBULINS, *ANALYTICAL chemistry
Abstract

In this study, our goal was to produce a self-assembled layer on a gold electrode that would enable the capture of antibodies orientated for maximum binding to their specific antigen in an immunosensor. To achieve this, the amine groups from lysine residues in protein G were initially converted to thiol groups with 2-iminothiolane. The high affinity of thiols for a gold surface facilitates the direct formation of a self-assembled protein G layer. Following this, the coated gold electrode was exposed to a solution of capture antibody (mAb1) so that these antibodies could attach to the protein G layer through their nonantigenic regions, leaving antigen binding sites available with minimal steric hindrance for binding of target analyte. A comparative study between this method and the more conventional strategy of covalently attaching a layer of nonthiolated protein G on an alkanethiol self-assembled monolayer-coated gold electrode has been performed. Based on a reduced preparation time, and an enhanced capacity for immobilized capture antibody to bind its target analyte due to a more favorable orientation, the layer of thiolated protein G was found to be a more suitable backbone for an electrochemical immunosensor. [ABSTRACT FROM AUTHOR]

Published
2007
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