76
|
Lim SA, Heng WJ, Lim TH, Leo YS, Wong SY. Ophthalmic manifestations in human immunodeficiency virus infection in Singapore. ANNALS OF THE ACADEMY OF MEDICINE, SINGAPORE 1997; 26:575-80. [PMID: 9494660] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The paper retrospectively reviews the spectrum of ophthalmic manifestations in human immunodeficiency virus (HIV) infection in Singapore between May 1995 and October 1996. One hundred and eighteen patients were examined for ocular abnormalities. Criteria for examination were 1) visual complaints, 2) absolute CD4 count of less than 50 cells/ul, 3) patients with acquired immunodeficiency syndrome-defining illness or 4) any relevant systemic illnesses which may have ocular involvement. Only 25 patients (21.2%) had visual symptoms. Eighteen patients (15.3%) had abnormalities associated with microvasculature. Forty-four patients (37.3%) had opportunistic infection involving the eye of which 37 were that of cytomegalovirus retinitis (CMVR). Seven patients (5.9%) had neuro-ophthalmic disorders. One patient presented with proptosis due to orbital lymphoma. Four patients (3.4%) had episcleritis and 3 patients (2.5%) had symptomatic dry eyes. It is still not known if episcleritis and dry eyes are associated with HIV infection or are coincidental. Fifty-one patients (43.2%) had no ocular pathology and remained so throughout the period of study. Nine patients (7.6%) had more than one pathology. The major cause of visual loss was due to ocular infections, with CMVR being most prevalent. Recognising the ophthalmic signs in HIV patients will facilitate early diagnosis. Prompt treatment of eye involvement can prevent or delay blindness, which is psychologically and functionally important to these patients.
Collapse
|
77
|
Tan BH, Lam MS, Wong SY. Three new cases of leishmaniasis: implications for the Singapore medical community. ANNALS OF THE ACADEMY OF MEDICINE, SINGAPORE 1997; 26:717-20. [PMID: 9494685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Although visceral and cutaneous leishmaniasis are important clinical and public health problems worldwide, these diseases are not endemic in Singapore and the medical profession here has little opportunity to diagnose and manage these conditions. We report our experience with two patients with culture-proven visceral leishmaniasis and one with histologically-proven cutaneous leishmaniasis. The patients with kala-azar were migrant workers from countries in which the disease is endemic. The patient with proven cutaneous leishmaniasis (and another who was diagnosed to have the condition clinically) had entered the jungles of an endemic area. With increasing travel on the part of Singaporeans along less well-trodden paths to exotic destinations as well as the burgeoning traffic of migrant workers from less developed countries, doctors in Singapore will continue to see diseases such as leishmaniasis.
Collapse
|
78
|
Lam MS, Wong SY. Travel medicine: a perspective on the emerging problem of travel-related infections. ANNALS OF THE ACADEMY OF MEDICINE, SINGAPORE 1997; 26:620-7. [PMID: 9494668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Travel Medicine has come a long way since it was started in the 1980s. Today, with the advances in electronic communications and efficient international travel, the demand for up-to-date information on international health situation is more urgent than before. Disease outbreaks can be updated and be available immediately across to the whole world in a matter of hours via the Internet. Travel medicine specialists no longer can give the excuse that they are unaware of such a situation because it is posted all over the net. Advances in vaccine development and the work of international agencies like the World Health Organization and the Centres for Disease Control have helped further the strategies and the knowledge we have in travel health risks. For the traveller, this means that they should no longer be travelling to a destination without knowing the health hazards and without taking the appropriate prophylaxis and precautions.
Collapse
|
79
|
Wong SY. Penoscrotal area resurfacing with the scrotal myofasciocutaneous flap. Chin Med J (Engl) 1997; 110:574-6. [PMID: 9594219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
|
80
|
Wu KC, Chan KC, Wu RS, Wong SY, Wong TK, Tan PP. Dislodgment of catheter during arterial cannulation: a case report. CHANGGENG YI XUE ZA ZHI 1997; 20:138-141. [PMID: 9260375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Invasive blood pressure monitoring is important in medical practice, especially for hemodynamic monitoring of the critically ill. Catheter dislodgment is a rarely reported complication. We herein report a catheter dislodgment complication during the procedure of arterial cannulation.
Collapse
|
81
|
Wong SY, Woo CY, Luk WK, Yuen KY. Nucleic acid technology and infectious diseases. Hong Kong Med J 1997; 3:179-185. [PMID: 11850569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023] Open
Abstract
The past decade has witnessed an explosion in the knowledge of microbial genetics, pathogenesis, and antimicrobial resistance as a result of advances in molecular technology. This has brought important breakthroughs in the management of patients with infectious diseases, as organisms that had previously been difficult to demonstrate in vitro can now be detected by molecular techniques such as the polymerase chain reaction. Not only is rapid diagnosis now possible, but old diseases of uncertain aetiology have been found to have an infective origin, for instance, Whipple's disease. Molecular technology has also contributed greatly to epidemiological studies of outbreaks, understanding antimicrobial resistance, developing new antimicrobial agents, the in vitro synthesis of immunomodulators, production of vaccines, and gene therapy. The limitations of these latest technologies, however, need to be remembered so that they yield meaningful information for patient care.
Collapse
|
82
|
Abstract
BACKGROUND Unbuffered rapid urease test (RUT) is an accurate and inexpensive method to detect Helicobacter pylori. However, the test is not always readily available because the reagents must be mixed freshly or stored at -20 degrees C after mixing. From our experience, storage at 4 degrees C for less than 6 days seemed to have no effect on the test's accuracy. This prospective study was undertaken to evaluate the shelf life of our unbuffered RUT. MATERIAL AND METHODS Forty-five patients were studied. From all patients, two sets of antral biopsy (X2) and body biopsy (X1) were taken. One set was subjected to histological examination; the other set was placed into a single capped Eppendorff tube for RUT. The tube was examined for any color change at 1 and 5 minutes. RESULTS Twenty-six patients (58%) were infected as defined by histological examination. The reagent was classified according to the storage time (group 1, < or = 5 days; group 2, > 5 days). The mean storage times of group 1 (n = 24) and group 2 (n = 21) were 3.1 (1.7 SD) days and 7.7 (1.2 SD) days, respectively. At 1 and 5 minutes, the sensitivity of group 1 was consistently higher than that of group 2 (1 minute, 61% versus 38%; 5 minutes, 92% versus 62%), and no false-positive result was observed in either group. CONCLUSION RUT remains highly sensitive and specific when it was stored at 4 degrees C for up to 5 days but should be discarded after that period.
Collapse
|
83
|
Abstract
A case of a 72 year old man is reported who developed a choledochoduodenal fistula due to distal biliary obstruction by a tumor of the papilla. A metal stent, introduced through this fistula into the common bile duct, dislodged and passed spontaneously with the feces. Plastic stents were then successfully inserted.
Collapse
|
84
|
Mok CK, Lau ST, Leung PM, Wong SY, Siu W, Au SY. A survey of the long term outcome of elderly stroke survivors and the needs of their carers. Hong Kong Med J 1997; 3:158-162. [PMID: 11850566] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023] Open
Abstract
A survey was conducted to assess the long term outcome of 60 elderly stroke survivors (mean age, 81.7 years). Of these patients, 48% died within one year of discharge and 79% of the mortality occurred in the first six months. Patients discharged to institutions after the initial stroke had a significantly higher risk of death in one year (relative risk=1.47) compared with those who were discharged home. For those who survived for a mean period of 18.6months, 72% (21/29) were institutionalised. This group had significantly worse functional status and mobility compared with those who were living at home. The caring of elderly stroke patients was considered a heavy burden for most carers at home or in institutions and the need for medical and social support was great.
Collapse
|
85
|
Ng FH, Wong SY, Lai ST, Lo HY. Reloading a variceal rubber band ligator with hemorrhoidal bands: an inexpensive and effective method. Endoscopy 1997; 29:233. [PMID: 9201489 DOI: 10.1055/s-2007-1004181] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
|
86
|
Speert DP, Wong SY, Macdonald M, Sargeant R. Modulation of macrophage function for defence of the lung against Pseudomonas aeruginosa. BEHRING INSTITUTE MITTEILUNGEN 1997:274-82. [PMID: 9382751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Pseudomonas aeruginosa is a common respiratory tract pathogen in certain groups of compromised hosts, most notably those with cystic fibrosis. The pathogenicity of P. aeruginosa may depend in part upon its capacity to resist normal phagocytic cell clearance. We have recently shown that phagocytosis of P. aeruginosa by macrophages is a unique two-step process; binding is glucose-independent but ingestion occurs only in the presence of D-glucose or D-mannose. P. aeruginosa is the only particle we have found which is ingested by macrophages in a glucose-dependent manner. Since glucose is present in only negligible quantities in the endobronchial space, P. aeruginosa may be pathogenic by virtue of its capacity to exploit the opportunity presented in the lower airway to resist normal nonspecific phagocytic defences. The purpose of the studies reported here is to better understand the glucose-dependent phagocytosis of P. aeruginosa and to design novel therapies to facilitate phagocytic cell clearance of it from the lower respiratory tract. We have shown that phagocytosis of unopsonized P. aeruginosa depends upon facilitated transport of glucose into macrophages via the GLUT1 isoform. After transport into the macrophage, the glucose must be metabolized to trigger phagocytosis of P. aeruginosa; pretreatment with 2-deoxyglucose or 5-thioglucose abrogates glucose-dependent ingestion. We have recently demonstrated that pulmonary alveolar macrophages (as opposed to all other macrophage phenotypes studied) lack the capacity to transport glucose and to phagocytose unopsonized P. aeruginosa; however, after the cells have been cultured in vitro for 48 hours, they are able to perform both functions. Whereas most macrophages (such as peritoneal cells) primarily depend upon glycolysis for metabolic energy, pulmonary alveolar macrophages reside in a high oxygen tension environment and appear to utilize oxidative phosphorylation. Treatment of freshly explanted pulmonary alveolar macrophages with sodium azide (to poison oxidative respiration) dramatically enhances both glucose transport and glucose-dependent phagocytosis of P. aeruginosa. We are currently investigating the compromised phagocytic function of pulmonary alveolar macrophages and the mechanism by which azide enhances glucose transport and phagocytosis of P. aeruginosa. Although physiological measurements have indicated that glucose is removed from the endobronchial space by an active transport process of the lung epithelium, the types of glucose transporters that are expressed in the lung are as yet unknown. Using RT-PCR, we have amplified a product from human and murine lung RNA which has a high degree of homology with members of the sodium-dependent glucose transporter (SGLT) family. The ultimate goal of these studies is to design novel agents for enhancing the phagocytic function of pulmonary alveolar macrophages. Delivery of simple glucose by aerosol would not be effective because (i) it would be exported by sodium-dependent active transport and (ii) pulmonary alveolar macrophages lack the capacity to transport glucose. Various approaches for targeting glucose to alveolar macrophages by receptor-mediated endocytosis are under investigation.
Collapse
|
87
|
|
88
|
Poon KF, Chan LK, Tan HK, Wong SY. Cervical ectopic pregnancy--a case report. Singapore Med J 1997; 38:27-8. [PMID: 9269351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Mdm LLG, a 28-year-old Chinese, a gravida 2 para I, presented at 9 weeks of pregnancy with painless vaginal bleeding. Ultrasound examination showed features of a cervical pregnancy. Hysterectomy was employed for treatment. Various recent conservative and surgical treatment modalities employed for this condition are discussed.
Collapse
|
89
|
Cheng G, Chui CH, Yeung KL, Kan EO, Wong SY, Yee KO, Yip SC, Leung MN, Fung HK, Fan TC. Provision of an out-of-hours blood banking service at a satellite hospital without blood bank staff. CLINICAL AND LABORATORY HAEMATOLOGY 1996; 18:201-5. [PMID: 8939391 DOI: 10.1046/j.1365-2257.1996.00176.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
With limited health care resources and financial constraints, many hospitals have to reduce their service. Computer crossmatching has been accepted as a safe crossmatching procedure for patients without clinically significant alloantibodies. We report here a novel way of providing an out-of-hours blood banking service at a satellite hospital. The system is easy to introduce and can provide a safe transfusion service to small hospitals without stationing blood banking staff at these hospitals after regular working hours.
Collapse
|
90
|
Balram C, Lim BL, Lee EJ, Wong SY, Ang B. Validity of Bayesian forecasting programme in therapeutic drug monitoring of vancomycin in a surgical intensive care unit: a prospective evaluation. ANNALS OF THE ACADEMY OF MEDICINE, SINGAPORE 1996; 25:492-5. [PMID: 8893916] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The objectives of this study were: (a) to assess the predictive performance of a 2-compartment Bayesian vancomycin forecasting programme in critically ill patients in the surgical intensive care unit, and (b) to show the applicability of the programme, which is based on parameters derived from Western population, in our local Asian population. Twenty critically ill patients were enrolled into the study programme. All patients received multiple-dose vancomycin for infections due to methicillin-resistant staphylococcus aureus (MRSA). The patients dosage regimen were optimised by entering a set of peak and trough vancomycin serum levels into a clinical computer program (MB; USC*PACK PC collection; University of Southern California, USA) by utilising a 2-compartment Bayesian population model. The correlation between observed and predicted serum peak and trough concentrations were evaluated for both the non-fitted and fitted models by linear regression analysis. There was a significant correlation between observed and predicted concentrations using the fitted model (r = 0.97, P < 0.05). There was no significant correlation of these concentrations in the non-fitted model (r = 0.8). This study shows that the Bayesian programme is able to accurately predict future vancomycin concentrations in our local Asian population. It is possible to optimise patients dosage regimens with the knowledge of two concentrations of vancomycin in order to achieve targeted therapeutic goals.
Collapse
|
91
|
|
92
|
Suzuki Y, Wong SY, Grumet FC, Fessel J, Montoya JG, Zolopa AR, Portmore A, Schumacher-Perdreau F, Schrappe M, Köppen S, Ruf B, Brown BW, Remington JS. Evidence for genetic regulation of susceptibility to toxoplasmic encephalitis in AIDS patients. J Infect Dis 1996; 173:265-8. [PMID: 8537674 DOI: 10.1093/infdis/173.1.265] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The frequency of HLA-DQ antigens in AIDS patients with toxoplasmic encephalitis (TE) were examined. HLA-DQ3 was significantly more frequent in white North American AIDS patients with TE (85.0%) than in the general white population (51.8%; P = .007, corrected P = .028) or randomly selected control AIDS patients who had not developed TE (40.0%; P = .016). In contrast, the frequency of HLA-DQ1 was lower in TE patients than in healthy controls (40.0% vs. 66.5%, P = .027), but this difference did not reach statistical significance when corrected for the number of variables tested (corrected P = .108 for the general white population). HLA-DQ3 thus appears to be a genetic marker of susceptibility to development of TE in AIDS patients, and DQ1 may be a resistance marker. These HLA associations with disease indicate that development of TE in AIDS patients is affected by a gene or genes in the HLA complex and that HLA-DQ typing may help in decisions regarding TE prophylaxis.
Collapse
|
93
|
Raghuram J, Ong YY, Wong SY. Tetanus in Singapore: report of three cases. ANNALS OF THE ACADEMY OF MEDICINE, SINGAPORE 1995; 24:869-73. [PMID: 8838999] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Three cases of tetanus in Singapore are presented. One local resident had cephalic tetanus most likely secondary to otitis media and the other two, residents from surrounding Asean countries, had generalised tetanus. The portal of entry was a puncture wound on the foot in one patient and the ear in another. No portal of entry was identified in one patient. All three patients required tracheostomy, ventilatory support and intensive care management for periods ranging from 11 to 22 days. One patient died from complications of nosocomial septicaemia and one patient required prolonged rehabilitation. There was a questionable history of tetanus immunization in the Singapore resident whereas the other two patients who were foreigners had never received any immunization. Tetanus is an uncommon but important disease in Singapore. In spite of the availability of intensive care management, it continues to be a disease with significant morbidity and mortality. Early recognition and treatment of the disease are critical factors in determining the prognosis. This is a disease that may be largely prevented by adequate immunization.
Collapse
|
94
|
Tan YK, Ling AE, Lin RV, Ong YY, Wong SY. Two cases of lower respiratory tract infection due to Chlamydia pneumonia in Singapore. ANNALS OF THE ACADEMY OF MEDICINE, SINGAPORE 1995; 24:863-6. [PMID: 8838997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Chlamydia pneumoniae, previously known as Chlamydia psittaci strain TWAR, causes both upper and lower respiratory tract infection. We report the first two cases of culture-positive Chlamydia pneumoniae lower respiratory infection in Singapore. Both patients had underlying fibrosing alveolitis and presented with a history of prolonged productive cough and fever. Chlamydia pneumoniae was isolated from the bronchoalveolar lavage fluid in the absence of other pathogens. The patients responded clinically to three weeks of oral doxycycline therapy. Infection due to Chlamydia pneumoniae should be considered when a patient with community-acquired pneumonia fails to respond to the usual standard antimicrobial therapy.
Collapse
|
95
|
Abstract
Within the past two years new developments in neoglycoconjugate formation have increased the accessibility and usefulness of these probes for the analyses of glycan structure and function. This article reviews several simple chemical and enzymatic methods for tagging oligosaccharides with chromophores, biotin, peptides, proteins and lipids, and describes some representative applications of these neoglycoconjugates.
Collapse
|
96
|
Lam MS, Wong SY. Use of prophylactic antibiotics in the prevention of infective endocarditis and prosthesis infection. Singapore Med J 1995; 36:424-7. [PMID: 8919161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
In the field of antimicrobial therapy, few areas have created more debate and controversy than the subject of antibiotic prophylaxis for infective endocarditis. Firstly, there still exists considerable controversy about the efficacy of prophylactic antibiotics for prevention of bacterial endocarditis. Secondly, dental surgeons, orthopaedic surgeons, cardiologists and endoscopists have differing opinions regarding indications for pre-procedural prophylactic antibiotics against infective endocarditis. The British have a different set of recommendations from the Americans although the basic tenets on which these recommendations are founded are similar. This article summarises the updated recommendations issued by the American Heart Association (AHA) as well as those from the British Society for Antimicrobial Chemotherapy. A short discussion of the use of prophylactic antibiotics prior to endoscopy and surgery for patients with non-valvular prosthetic devices has been included in this paper. Practitioners should also be reminded that these recommendations are issued as guidelines and clinical judgement must be exercised when dealing with individual patients.
Collapse
|
97
|
Wong SY, Lam MS. Pyrexia of unknown origin--approach to management. Singapore Med J 1995; 36:204-8. [PMID: 7676269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Pyrexia of unknown origin (PUO) remains one of the major diagnostic challenges for the clinician. Although infection, malignancy and collagen vascular disease remain the 3 most important causes of PUO, the relative importance of different disease entities within each of these major categories has changed because of improvements in serodiagnosis, culture techniques and radiologic imaging modalities. A detailed clinical history and meticulous physical examination remain the mainstay of the approach to management of patients with PUO. There is no set of "routine" investigations that patients with PUO should be subjected to. Instead, diagnostic testing should be individualised and guided by abnormalities found on clinical examination and simple laboratory testing. In patients in whom the diagnosis remains obscure in spite of extensive investigations and in whom the disease process is clearly progressive, judicious use of narrow spectrum anti-microbial therapy may be warranted. In the majority of the other patients who remain stable, careful clinical observation for new symptoms and signs are advised in the place of multiple courses of antimicrobials.
Collapse
|
98
|
Guile GR, Wong SY, Dwek RA. Analytical and preparative separation of anionic oligosaccharides by weak anion-exchange high-performance liquid chromatography on an inert polymer column. Anal Biochem 1994; 222:231-5. [PMID: 7856854 DOI: 10.1006/abio.1994.1478] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The use of ammonium formate buffers for analytical and preparative weak anion-exchange high-performance chromatography of anionic sugars is described. The method can be used for structures containing sulfate, phosphate, sialic acid, and uronic acid moieties. Excellent separation of the anionic sugars was achieved from pH 5.5 to 9. In contrast to silica matrix columns the polymer matrix column used can tolerate a wide range of pH values for the eluting buffer and it does not shed material into the eluent. The use of a single volatile buffer avoids additional purification steps to recover separated sugars suitable for further structural and functional analyses.
Collapse
|
99
|
Haurum JS, Arsequell G, Lellouch AC, Wong SY, Dwek RA, McMichael AJ, Elliott T. Recognition of carbohydrate by major histocompatibility complex class I-restricted, glycopeptide-specific cytotoxic T lymphocytes. J Exp Med 1994; 180:739-44. [PMID: 8046349 PMCID: PMC2191607 DOI: 10.1084/jem.180.2.739] [Citation(s) in RCA: 337] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Cytotoxic T cells (CTL) recognize short peptide epitopes presented by class I glycoproteins encoded by the major histocompatibility complex (MHC). It is not yet known whether peptides containing posttranslationally modified amino acids can also be recognized by CTL. To address this issue, we have studied the immunogenicity and recognition of a glycopeptide carrying an O-linked N-acetylglucosamine (GlcNAc) monosaccharide-substituted serine residue. This posttranslational modification is catalyzed by a recently described cytosolic glycosyltransferase. We show that glycosylation does not affect peptide binding to MHC class I and that glycopeptides can elicit a strong CTL response that is glycopeptide specific. Furthermore, glycopeptide recognition by cytotoxic T cells is dependent on the chemical structure of the glycan as well as its position within the peptide.
Collapse
|
100
|
Wong SY, Guile GR, Dwek RA, Arsequell G. Synthetic glycosylation of proteins using N-(beta-saccharide) iodoacetamides: applications in site-specific glycosylation and solid-phase enzymic oligosaccharide synthesis. Biochem J 1994; 300 ( Pt 3):843-50. [PMID: 8010968 PMCID: PMC1138242 DOI: 10.1042/bj3000843] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A simple and efficient synthetic glycosylation method suitable for use in solid-phase enzymic oligosaccharide synthesis and site-specific glycosylation of recombinant proteins to produce defined glycoforms is described. This strategy utilizes N-(beta-saccharide) haloacetamides for attaching oligosaccharides specifically to cysteine residues of proteins in solution to form neoglycoproteins. The alkylation reaction was tested using N-(beta-chitotriose) bromoacetamide and an unprotected synthetic hexapeptide containing a single cysteine residue. The glycosylated product was confirmed by amino acid and hexosamine analyses as well as laser desorption mass spectrometry. Similarly N-(beta-chitotriose) iodoacetamide was covalently linked to non-reduced BSA to produce a defined glycoform of this protein. The specific attachment of chitotriose at the single cysteine residue in non-reduced serum albumin was suggested by Ellman's assay for free thiols. This was verified by amino acid sequencing of tryptic glycopeptide derived from this neoglycoprotein. Multiple sugar attachment was accomplished using fully reduced serum albumin as demonstrated by the formation of two neoglycoproteins using iodoacetamide derivatives of galactose beta 1-3-N-acetylgalactosamine (Gal beta 1-3GalNAc) and the major xylose/fucose-class plant-type oligosaccharide of horseradish peroxidase. These two neoglycoproteins with an average of 18-21 sugar residues attached were assayed positively for binding to peanut agglutinin and a sugar-specific anti-(horseradish peroxidase) monoclonal antibody YZ1/2.23 respectively. Sialylation of the neoglycoprotein containing Gal beta 1-3GalNAc was accomplished using alpha-2,3-sialyltransferase and radiolabelled CMP-N-acetylneuraminic acid. Significantly, glycan attachment using this conjugation method is reversible as demonstrated by the release of oligosaccharides from these two neoglycoproteins using hydrazinolysis. Therefore this method could provide invaluable reagents for many glycobiological studies.
Collapse
|