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Liew OW, Ling SSM, Lilyanna S, Chong JPC, Ng JYX, Richards AM. One-Shot Generation of Epitope-Directed Monoclonal Antibodies to Multiple Nonoverlapping Targets: Peptide Selection, Antigen Preparation, and Epitope Mapping. Methods Mol Biol 2023; 2578:121-141. [PMID: 36152284 DOI: 10.1007/978-1-0716-2732-7_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
This chapter describes an epitope-directed approach to generate antipeptide monoclonal antibodies to multiple nonoverlapping protein sites using a cocktail of fusion peptides as immunogen. It provides a step-by-step protocol on how antigenic peptides on a target protein can be identified by in silico prediction and discusses considerations for final peptide selection. Each antigenic peptide (10-20 amino acids long) is displayed as three-copy inserts on the surface exposed loop of a thioredoxin scaffold protein. The corresponding DNA coding sequence specifying the tripeptide insert flanked by Gly-Ser-Gly-Ser-Gly linkers is cloned in-frame into the Rsr II site of the thioredoxin gene in the pET-32a vector. The presence of a C-terminal polyhistidine tag (His6-tag) allows the soluble fusion proteins to be purified by one-step native immobilized metal affinity chromatography (IMAC) to greater than 95% purity. Multiple thioredoxin fusion proteins are mixed in equimolar concentrations and used as an immunogen cocktail for animal immunization. The use of short antigenic peptides of known sequence facilitates direct epitope mapping requiring only small mutagenesis scan peptide libraries in the multipin peptide format.
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Affiliation(s)
- Oi Wah Liew
- Cardiovascular Research Institute, Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore, Singapore.
| | - Samantha Shi Min Ling
- Cardiovascular Research Institute, Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore, Singapore
| | - Shera Lilyanna
- Cardiovascular Research Institute, Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore, Singapore
| | - Jenny Pek Ching Chong
- Cardiovascular Research Institute, Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore, Singapore
| | - Jessica Yan Xia Ng
- Cardiovascular Research Institute, Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore, Singapore
| | - Arthur Mark Richards
- Cardiovascular Research Institute, Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore, Singapore
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Liew OW, Fanusi F, Ng JYX, Ahidjo BA, Ling SSM, Lilyanna S, Chong JPC, Lim AES, Lim WZ, Ravindran S, Chu JJH, Lim SL, Richards AM. Immunoassay-Compatible Inactivation of SARS-CoV-2 in Plasma Samples for Enhanced Handling Safety. ACS Omega 2022; 7:25510-25520. [PMID: 35903176 PMCID: PMC9301769 DOI: 10.1021/acsomega.2c02585] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) inactivation is an important step toward enhanced biosafety in testing facilities and affords a reduction in the biocontainment level necessary for handling virus-positive biological specimens. Virus inactivation methods commonly employ heat, detergents, or combinations thereof. In this work, we address the dearth of information on the efficacy of SARS-CoV-2 inactivation procedures in plasma and their downstream impact on immunoassays. We evaluated the effects of heat (56 °C for 30 min), detergent (1-5% Triton X-100), and solvent-detergent (SD) combinations [0.3-1% tri-n-butyl phosphate (TNBP) and 1-2% Triton X-100] on 19 immunoassays across different assay formats. Treatments are deemed immunoassay-compatible when the average and range of percentage recovery (treated concentration relative to untreated concentration) lie between 90-110 and 80-120%, respectively. We show that SD treatment (0.3% TNBP/1% Triton-X100) is compatible with more than half of the downstream immunoassays tested and is effective in reducing SARS-CoV-2 infectivity in plasma to below detectable levels in plaque assays. This facile method offers enhanced safety for laboratory workers handling biological specimens in clinical and research settings.
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Affiliation(s)
- Oi Wah Liew
- Cardiovascular
Research Institute, Department of Medicine, Yong Loo Lin School of
Medicine, National University of Singapore, National University Health System, 14 Medical Drive, Singapore 117599, Singapore
| | - Felic Fanusi
- NUS
Medicine BSL3 Core Facility, Yong Loo Lin School of Medicine, National
University of Singapore, National University
Health System, 14 Medical
Drive, Singapore 117599, Singapore
- Department
of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, 5 Science Drive 2, Singapore 117545, Singapore
| | - Jessica Yan Xia Ng
- Cardiovascular
Research Institute, Department of Medicine, Yong Loo Lin School of
Medicine, National University of Singapore, National University Health System, 14 Medical Drive, Singapore 117599, Singapore
| | - Bintou Ahmadou Ahidjo
- NUS
Medicine BSL3 Core Facility, Yong Loo Lin School of Medicine, National
University of Singapore, National University
Health System, 14 Medical
Drive, Singapore 117599, Singapore
- Department
of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, 5 Science Drive 2, Singapore 117545, Singapore
| | - Samantha Shi Min Ling
- Cardiovascular
Research Institute, Department of Medicine, Yong Loo Lin School of
Medicine, National University of Singapore, National University Health System, 14 Medical Drive, Singapore 117599, Singapore
| | - Shera Lilyanna
- Cardiovascular
Research Institute, Department of Medicine, Yong Loo Lin School of
Medicine, National University of Singapore, National University Health System, 14 Medical Drive, Singapore 117599, Singapore
| | - Jenny Pek Ching Chong
- Cardiovascular
Research Institute, Department of Medicine, Yong Loo Lin School of
Medicine, National University of Singapore, National University Health System, 14 Medical Drive, Singapore 117599, Singapore
| | - Angeline Eng Siew Lim
- Cardiovascular
Research Institute, Department of Medicine, Yong Loo Lin School of
Medicine, National University of Singapore, National University Health System, 14 Medical Drive, Singapore 117599, Singapore
| | - Wei Zheng Lim
- Cardiovascular
Research Institute, Department of Medicine, Yong Loo Lin School of
Medicine, National University of Singapore, National University Health System, 14 Medical Drive, Singapore 117599, Singapore
| | - Sindhu Ravindran
- NUS
Medicine BSL3 Core Facility, Yong Loo Lin School of Medicine, National
University of Singapore, National University
Health System, 14 Medical
Drive, Singapore 117599, Singapore
| | - Justin Jang Hann Chu
- NUS
Medicine BSL3 Core Facility, Yong Loo Lin School of Medicine, National
University of Singapore, National University
Health System, 14 Medical
Drive, Singapore 117599, Singapore
- Department
of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, 5 Science Drive 2, Singapore 117545, Singapore
- Infectious
Disease Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, Singapore
| | - Shir Lynn Lim
- Yong
Loo Lin School of Medicine, National University of Singapore, National University Health System, 1E Kent Ridge Road, Singapore 119228, Singapore
- Department
of Cardiology, National University Heart
Centre Singapore, 1E
Kent Ridge Road, Singapore 119228, Singapore
| | - Arthur Mark Richards
- Cardiovascular
Research Institute, Department of Medicine, Yong Loo Lin School of
Medicine, National University of Singapore, National University Health System, 14 Medical Drive, Singapore 117599, Singapore
- Christchurch
Heart Institute, University of Otago, Christchurch 8140, New Zealand
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Ling SSM, Khoo LHB, Hwang LA, Yeoh KG, Ho B. Instrumental Role of Helicobacter pylori γ-Glutamyl Transpeptidase in VacA-Dependent Vacuolation in Gastric Epithelial Cells. PLoS One 2015; 10:e0131460. [PMID: 26111186 PMCID: PMC4482420 DOI: 10.1371/journal.pone.0131460] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 06/02/2015] [Indexed: 01/27/2023] Open
Abstract
Helicobacter pylori causes cellular vacuolation in host cells, a cytotoxic event attributed to vacuolating cytotoxin (VacA) and the presence of permeant weak bases such as ammonia. We report here the role of γ-glutamyl transpeptidase (GGT), a constitutively expressed secretory enzyme of H. pylori, in potentiating VacA-dependent vacuolation formation in H. pylori-infected AGS and primary gastric cells. The enhancement is brought about by GGT hydrolysing glutamine present in the extracellular medium, thereby releasing ammonia which accentuates the VacA-induced vacuolation. The events of vacuolation in H. pylori wild type (WT)- and Δggt-infected AGS cells were first captured and visualized by real-time phase-contrast microscopy where WT was observed to induce more vacuoles than Δggt. By using semi-quantitative neutral red uptake assay, we next showed that Δggt induced significantly less vacuolation in AGS and primary gastric epithelial cells as compared to the parental strain (P<0.05) indicating that GGT potentiates the vacuolating effect of VacA. Notably, vacuolation induced by WT was significantly reduced in the absence of GGT substrate, glutamine (P<0.05) or in the presence of a competitive GGT inhibitor, serine-borate complex. Furthermore, the vacuolating ability of Δggt was markedly restored when co-incubated with purified recombinant GGT (rGGT), although rGGT itself did not induce vacuolation independently. Similarly, the addition of exogenous ammonium chloride as a source of ammonia also rescued the ability of Δggt to induce vacuolation. Additionally, we also show that monoclonal antibodies against GGT effectively inhibited GGT activity and successfully suppressed H. pylori-induced vacuolation. Collectively, our results clearly demonstrate that generation of ammonia by GGT through glutamine hydrolysis is responsible for enhancing VacA-dependent vacuolation. Our findings provide a new perspective on GGT as an important virulence factor and a promising target in the management of H. pylori-associated gastric diseases.
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Affiliation(s)
- Samantha Shi Min Ling
- Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | | | - Le-Ann Hwang
- Monoclonal Antibody Unit, Institute of Molecular and Cell Biology, Singapore, Singapore
| | - Khay Guan Yeoh
- Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Bow Ho
- Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
- * E-mail:
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Gong M, Ling SSM, Lui SY, Yeoh KG, Ho B. Helicobacter pylori gamma-glutamyl transpeptidase is a pathogenic factor in the development of peptic ulcer disease. Gastroenterology 2010; 139:564-73. [PMID: 20347814 DOI: 10.1053/j.gastro.2010.03.050] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2008] [Revised: 02/03/2010] [Accepted: 03/11/2010] [Indexed: 12/14/2022]
Abstract
BACKGROUND & AIMS gamma-Glutamyl transpeptidase (GGT) has been reported to be a virulence factor of Helicobacter pylori associated with bacterial colonization and cell apoptosis. But its mechanism of pathogenesis is not firmly established. This study aims to examine its role in H pylori-mediated infection. METHODS Various H pylori isogenic mutants were constructed by a polymerase chain reaction (PCR) approach. H pylori native GGT protein (HP-nGGT) was purified with ion-exchange and gel-filtration chromatography. Generation of H2O2 was measured with fluorimetric analysis, whereas nuclear factor-kappaB (NF-kappaB) activation was determined by luciferase assay and Western blot. Cytokine production was examined by enzyme-linked immunoabsorbent assay and real-time PCR. DNA damage was assessed with comet assay and flow cytometry. The GGT activity of 98 H pylori isolates was analyzed by an enzymatic assay. RESULTS Purified HP-nGGT generated H2O2 in primary gastric epithelial cells and AGS gastric cancer cells, resulting in the activation of NF-kappaB and up-regulation of interleukin-8 (IL-8) production. In addition, HP-nGGT caused an increase in the level of 8-OH-dG, indicative of oxidative DNA damage. In contrast, Deltaggt showed significantly reduced levels of H2O2 generation, IL-8 production, and DNA damage in cells compared with the wild type (P<.05). The clinical importance of GGT was indicated by significantly higher (P<.001) activity in H pylori isolates obtained from patients with peptic ulcer disease (n=54) than isolates from patients with nonulcer dyspepsia (n=44). CONCLUSION Our findings provide evidence that GGT is a pathogenic factor associated with H pylori-induced peptic ulcer disease.
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Affiliation(s)
- Min Gong
- Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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