Displaying publications 1 - 20 of 69 in total

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  1. Tan WS, Tan GH, Yusoff K, Seow HF
    J. Clin. Virol., 2005 Sep;34(1):35-41.
    PMID: 16087122
    The surface antigen (HBsAg) of hepatitis B virus (HBV) is highly conformational and generally evokes protective humoral immune response in human. A disulfide constrained random heptapeptide library displayed on the coat protein III of filamentous bacteriophage M13 was employed to select specific ligands that interact with HBsAg subtype ad. Fusion phages carrying the amino acid sequence ETGAKPH and other related sequences were isolated. The binding site of peptide ETGAKPH was located on the immunodominant region of HBsAg. An equilibrium binding assay in solution showed that the phage binds tightly to HBsAg with a relative dissociation constant (KDrel) of 2.9+/-0.9 nM. The phage bearing this peptide has the potential to be used as a diagnostic reagent and two assays for detecting HBsAg in blood samples are described.
    Matched MeSH terms: Hepatitis B Surface Antigens/blood; Hepatitis B Surface Antigens/isolation & purification; Hepatitis B Surface Antigens/metabolism*; Hepatitis B Surface Antigens/chemistry
  2. Tan GH, Yusoff K, Seow HF, Tan WS
    J. Med. Virol., 2005 Dec;77(4):475-80.
    PMID: 16254965
    The immunodominant region of hepatitis B virus (HBV) located in the viral small surface antigen (S-HBsAg) elicits virus-neutralizing and protective antibodies. In order to develop an easy and inexpensive method to produce this region without the need for extensive purification, amino acid residues 111-156 of S-HBsAg were fused to the C-terminal end of the 10B capsid protein of T7 phage. Western blotting and ELISA confirmed the expression of the recombinant protein on the surface of the phage particles. The recombinant phage exhibited the antigenic and immunogenic characteristics of HBsAg, illustrating its potential as an immunological reagent and vaccine.
    Matched MeSH terms: Hepatitis B Surface Antigens/analysis; Hepatitis B Surface Antigens/genetics; Hepatitis B Surface Antigens/immunology*; Hepatitis B Surface Antigens/chemistry
  3. Tan SS, Chua A
    Med. J. Malaysia, 2013 Apr;68(2):103-4.
    PMID: 23629552
    Matched MeSH terms: Hepatitis B Surface Antigens*
  4. Tam YJ, Allaudin ZN, Lila MA, Bahaman AR, Tan JS, Rezaei MA
    BMC Biotechnol., 2012;12:70.
    PMID: 23039947 DOI: 10.1186/1472-6750-12-70
    Cell disruption strategies by high pressure homogenizer for the release of recombinant Hepatitis B surface antigen (HBsAg) from Pichia pastoris expression cells were optimized using response surface methodology (RSM) based on the central composite design (CCD). The factors studied include number of passes, biomass concentration and pulse pressure. Polynomial models were used to correlate the above mentioned factors to project the cell disruption capability and specific protein release of HBsAg from P. pastoris cells.
    Matched MeSH terms: Hepatitis B Surface Antigens/genetics*; Hepatitis B Surface Antigens/isolation & purification; Hepatitis B Surface Antigens/metabolism
  5. Ooi A, Tan S, Mohamed R, Rahman NA, Othman RY
    J. Biotechnol., 2006 Feb 24;121(4):471-81.
    PMID: 16271415
    A cucumber green mosaic mottle virus (CGMMV) full-length clone was developed for the expression of Hepatitis B surface antigen (HBsAg). The expression of the surface displayed HBsAg by the chimeric virus was confirmed through a double antibody sandwich ELISA. Assessment of the coat protein composition of the chimeric virus particles by SDS-PAGE analysis showed that 50% of the coat proteins were fused to the HBsAg. Biological activity of the expressed HBsAg was assessed through the stimulation of in vitro antibody production by cultured peripheral blood mononuclear cells (PBMC). PBMC that were cultured in the presence of the chimeric virus showed up to an approximately three-fold increase in the level of anti HBsAg immunoglobulin thus suggesting the possible use of this new chimeric virus as an effective Hepatitis B vaccine.
    Matched MeSH terms: Hepatitis B Surface Antigens/biosynthesis*; Hepatitis B Surface Antigens/genetics; Hepatitis B Surface Antigens/immunology
  6. Kok WL, Yusoff K, Nathan S, Tan WS
    J. Biochem. Mol. Biol. Biophys., 2002 Feb;6(1):55-8.
    PMID: 12186783
    The PreS domain of hepatitis B virus (HBV) is believed to be involved in virion assembly and attachment to a hepatocyte receptor during infection. In order to study the functions of this region, we fused it to the g3p protein of bacteriophage M13 that allows the fusion protein to be displayed at the tip of the filament. The fusion protein was detected by the anti-E tag antibody on a Western blot. The polypeptide in a soluble form was produced by transfecting a non-suppressor E. coli host cell with the recombinant phagemid. The soluble protein was detected in cytoplasm, in the periplasmic space and also in the medium. The functional display of the PreS domain would provide an alternative means to study its interactions with the nuleocapsid and hepatocytes.
    Matched MeSH terms: Hepatitis B Surface Antigens/genetics*; Hepatitis B Surface Antigens/metabolism; Hepatitis B Surface Antigens/chemistry*
  7. Yousuf R, Rapiaah M, Ahmed SA, Rosline H, Salam A, Selamah S, et al.
    PMID: 18613548
    The objective of this study was to determine the prevalence and trends in hepatitis B infection among blood donors attending the Transfusion Medicine Unit at the Hospital Universiti Sains Malaysia, Kelantan, Malaysia. A retrospective study was carried out by reviewing the results of HBsAg among blood donors for the years 2000 to 2004. During this period, 44,658 blood donors were studied. We noted that there was a significant difference in the prevalence of hepatitis B infection between regular and first time donors. There was also a decreasing trend noticed in both study groups. The mean prevalence was significantly different between first time (1.83%) and regular donors (0.45%) (p < 0.005). There is a need to improve public awareness programs to lower the incidence of hepatitis B infection in the general population and consequently first time blood donors. Future studies are also required to determine the trends and outcomes of these programs.
    Matched MeSH terms: Hepatitis B Surface Antigens/blood; Hepatitis B Surface Antigens/isolation & purification
  8. Tan TC, Vadivale M, Ong CN
    Asia Pac J Public Health, 1992;6(3):134-9.
    PMID: 1342800 DOI: 10.1177/101053959200600303
    This study was based on a hepatitis B screening program conducted in one of the states in Malaysia in 1989. The majority (84.6%) of the 2986 health employees were screened. One quarter (25%) was found to have serological markers for the Hepatitis B Virus (HBV); 2.1% had Hepatitis B surface Antigen (HBsAg) and 22.8% had antibody to the Hepatitis B surface Antigen (anti-HBs). The occurrence of HBsAg was higher in ethnic Chinese (6.3%) compared to Malays (1.8%) and Indians (0.9%), even when analyzed by sex, but not with age, type of institution and geographical locality. The distribution of anti-HBs was higher with ethnic Chinese (41.6%), male sex (27.2%) and age. There was a wide variation of the prevalence of serological markers among occupations and increased relative risks of HBsAg were found among medical assistants (RR3.7; 95% CI 1.4-9.1) and laboratory staff (RR 3.2; 95% CI 1-8.8), and that of anti-HBs among medical assistants (RR 2.8; 95% CI 1.8-3.7). The variations of HBsAg among occupations by type of institutions was marginal while that of anti-HBs was higher among attendants and midwives in hospitals, medical assistants in health departments, and assistant nurses and dentists in dental centers. The patterns of distribution of serological markers of HBV among health staff reflect the situation in the community with high endemicity and resemble specific occupational factors noted in previous studies in the West.
    Publication year is 1992-1993
    Matched MeSH terms: Hepatitis B Surface Antigens/blood*; Hepatitis B Surface Antigens/immunology
  9. Muhamad A, Ho KL, Rahman MB, Uhrín D, Tan WS
    Chem Biol Drug Des, 2013 Jun;81(6):784-94.
    PMID: 23405984 DOI: 10.1111/cbdd.12120
    A specific ligand targeting the immunodominant region of hepatitis B virus is desired in neutralizing the infectivity of the virus. In a previous study, a disulfide constrained cyclic peptide cyclo S(1) ,S(9) Cys-Glu-Thr-Gly-Ala-Lys-Pro-His-Cys (S(1) , S(9) -cyclo-CETGAKPHC) was isolated from a phage displayed cyclic peptide library using an affinity selection method against hepatitis B surface antigen. The cyclic peptide binds tightly to hepatitis B surface antigen with a relative dissociation constant (KD (rel) ) of 2.9 nm. The binding site of the peptide was located at the immunodominant region on hepatitis B surface antigen. Consequently, this study was aimed to elucidate the structure of the cyclic peptide and its interaction with hepatitis B surface antigen in silico. The solution structure of this cyclic peptide was solved using (1) H, (13) C, and (15) N NMR spectroscopy and molecular dynamics simulations with NMR-derived distance and torsion angle restraints. The cyclic peptide adopted two distinct conformations due to the isomerization of the Pro residue with one structured region in the ETGA sequence. Docking studies of the peptide ensemble with a model structure of hepatitis B surface antigen revealed that the cyclic peptide can potentially be developed as a therapeutic drug that inhibits the virus-host interactions.
    Matched MeSH terms: Hepatitis B Surface Antigens/metabolism*; Hepatitis B Surface Antigens/chemistry
  10. Tang KH, Yusoff K, Tan WS
    J. Virol. Methods, 2009 Aug;159(2):194-9.
    PMID: 19490973 DOI: 10.1016/j.jviromet.2009.03.015
    Hepatitis B is a major public health problem worldwide which may lead to chronic liver diseases, cirrhosis and hepatocellular carcinoma. An interaction between hepatitis B virus (HBV) envelope protein, particularly the PreS1 region, and a specific cell surface receptor is believed to be the initial step of HBV infection through attachment to hepatocytes. In order to develop a gene delivery system, bacteriophage T7 was modified genetically to display polypeptides of the PreS1 region. A recombinant T7 phage displaying amino acids 60-108 of the PreS1 region (PreS1(60-108)) was demonstrated to be most effective in transfecting HepG2 cells in a dose- and time-dependant manner. The phage genome was recovered from the cell lysate and confirmed by PCR whereas the infectious form of the internalized phage was measured by a plaque-forming assay. The internalized phage exhibited the appearance of green fluorescent dots when examined by immunofluorescence microscopy. Surface modification, particularly by displaying the PreS1(60-108) enhanced phage uptake, resulting in more efficient in vitro gene transfer. The ability of the recombinant phage to transfect HepG2 cells demonstrates the potential of the phage display system as a gene therapy for liver cancer.
    Matched MeSH terms: Hepatitis B Surface Antigens/genetics; Hepatitis B Surface Antigens/metabolism*
  11. Ong HT, Duraisamy G, Kee Peng N, Wen Siang T, Seow HF
    Microbes Infect., 2005 Mar;7(3):494-500.
    PMID: 15792534
    Hepatitis B virus (HBV) has been classified into eight genotypes, designated A-H. These genotypes are known to have distinct geographic distributions. The clinical importance of genotype-related differences in the pathogenicity of HBV has been revealed recently. In Malaysia, the current distribution of HBV remains unclear. The aim of this study was to determine the genotypes and subtypes of HBV by using PCR, followed by DNA sequencing, as well as to analyse the mutations in the immunodominant region of preS and S proteins. The S gene sequence was determined from HBV DNA of four apparently healthy blood donors' sera and three sera from asymptomatic chronic hepatitis B carriers. Of this batch of sera, the preS gene sequence was obtained from HBV DNA from three out of the four blood donors and two out of the three chronic carriers. Due to insufficient sera, we had to resort to using sera from another blood donor to make up for the sixth DNA sequence of the preS gene. Based on the comparative analysis of the preS sequences with the reported sequences in the GenBank database, HBV DNA from two normal carriers was classified as genotype C. Genotype B was assigned to HBV from one blood donor and two hepatitis B chronic carriers, whereas HBV of one chronic carrier was of genotype D. Based on the S gene sequences, HBV from three blood donors was of genotype C, that of one blood donor and one chronic carrier was of genotype B, and the remaining, of genotype D. In the five cases where both preS and S gene sequences were determined, the genotypes assigned based on either the preS or S gene sequences were in concordance. The nature of the deduced amino acid (aa) sequences at positions 125, 127, 134, 143, 159, 161 and 168 of the S gene enabled the classification of these sequences into subtypes, namely, adrq+, adw2 and ayw2. The clustering of our DNA sequences into genotype groups corresponded to their respective subtype, that is, adw2 in genotype B, adrq in genotype C and ayw in genotype D. Analysis of the point mutations revealed that five of the sequences contained aa substitutions at immunodominant epitopes involved in B or/and T cell recognition. In conclusion, despite the low numbers of samples studied, due to budget constraints, these data are still worthwhile reporting, as it is important for the control of HBV infections. In addition, the genotype and mutational data obtained in this study may be useful for designing new treatment regimes for HBV patients.
    Matched MeSH terms: Hepatitis B Surface Antigens/genetics*; Hepatitis B Surface Antigens/chemistry
  12. Hudu SA, Harmal NS, Saeed MI, Alshrari AS, Malik YA, Niazlin MT, et al.
    Afr Health Sci, 2016 Sep;16(3):677-683.
    PMID: 27917199
    BACKGROUND: Occult hepatitis B infections are becoming a major global threat, but the available data on its prevalence in various parts of the world are often divergent.

    OBJECTIVE: This study aimed to detect occult hepatitis B virus in hepatitis B surface antigen-negative serum using anti-HBc as a marker of previous infection.

    PATIENT AND METHODS: A total of 1000 randomly selected hepatitis B surface antigen-negative sera from blood donors were tested for hepatitis B core antibody and hepatitis B surface antibody using an ELISA and nested polymerase chain reaction was done using primers specific to the surface gene (S-gene).

    RESULTS: Of the 1000 samples 55 (5.5%) were found to be reactive, of which 87.3% (48/55) were positive for hepatitis B surface antibody, indicating immunity as a result of previous infection however, that does not exclude active infection with escaped mutant HBV. Nested PCR results showed the presence of hepatitis B viral DNA in all the 55 samples that were positive for core protein, which is in agreement with the hepatitis B surface antibody result.

    CONCLUSION: This study reveals the 5.5% prevalence of occult hepatitis B among Malaysian blood donors as well as the reliability of using hepatitis B core antibody in screening for occult hepatitis B infection in low endemic, low socioeconomic settings.

    Matched MeSH terms: Hepatitis B Surface Antigens/blood*; Hepatitis B Surface Antigens/genetics
  13. Lee MF, Chan ES, Tan WS, Tam KC, Tey BT
    J Chromatogr A, 2016 May 6;1445:1-9.
    PMID: 27059397 DOI: 10.1016/j.chroma.2016.03.066
    Purification of virus-like particles (VLPs) in bind-and-elute mode has reached a bottleneck. Negative chromatography has emerged as the alternative solution; however, benchmark of negative chromatography media and their respective optimized conditions are absent. Hence, this study was carried out to compare the performance of different negative chromatography media for the purification of hepatitis B VLPs (HB-VLPs) from clarified Escherichia coli feedstock. The modified anion exchange media, core-shell adsorbents (InertShell and InertLayer 1000) and polymer grafted adsorbents (SQ) were compared. The results of chromatography from packed bed column of core-shell adsorbents showed that there is a trade-off between the purity and recovery of HB-VLPs in the flowthrough fraction due to the shell thickness. Atomic force microscopic analysis revealed funnel-shaped pore channels in the shell layer which may contribute to the entrapment of HB-VLPs. A longer residence time at a lower feed flow rate (0.5ml/min) improved slightly the HB-VLPs purity in all modified adsorbents, but the recovery in InertShell reduced substantially. The preheat-treatment is not recommended for the negative chromatography as the thermal-induced co-aggregation of HCPs and HB-VLPs would flow along with HB-VLPs and thus reduced the HB-VLPs purity in the flowthrough. Further reduction in the feedstock concentration enhanced the purity of HB-VLPs especially in InertLayer 1000 but reduced substantially the recovery of HB-VLPs. In general, the polymer grafted adsorbent, SQ, performed better than the core-shell adsorbents in handling a higher feedstock concentration.
    Matched MeSH terms: Hepatitis B Surface Antigens/metabolism
  14. Looi LM, Prathap K
    Histopathology, 1982 Mar;6(2):141-7.
    PMID: 7042512
    In view of a high prevalence of hepatitis B virus infection in the Malaysian population, indirect immunofluorescence examination for hepatitis B surface antigen (HBsAg) was routinely performed on renal biopsy specimen at the University Hospital, Kuala Lumpur, over a 3-year period. Examination of renal tissue from 259 patients, including 47 with systemic lupus erythematosus (SLE), revealed 43 cases with HBsAg in glomerular immune complexes. A significantly high proportion (30/43) of these were SLE patients. The deposits were granular in nature, situated in both the capillary walls and mesangium and associated with immunoglobulin deposition. Morphological patterns of lupus nephritis involved were focal proliferative (one case), diffuse proliferative (23 cases) and membranous (six cases). None of these patients showed clinical evidence of liver disease. The significance of these findings remains uncertain, but the possibility exists that the hepatitis B virus may have a role in the pathogenesis of SLE in the tropics where both SLE and HBs antigenaemia are common.
    Matched MeSH terms: Hepatitis B Surface Antigens/analysis*
  15. Ng KP, Saw TL
    Med. J. Malaysia, 1999 Sep;54(3):352-7.
    PMID: 11045062
    Hepatitis B surface antigen can be serologically defined as ayw1, ayw2, ayw3, ayw4, ayr, adw2, adw4 and adrq+ or adrq-. A study of common HBsAg subtypes in 44 HBsAg reactive sera in University Hospital was conducted using a solid-phase sandwich EIA. Eleven samples were found not typable and among the 33 typable HBsAg reactive sera, 3 HBsAg subtypes: adw, adr and ayw were identified. Subtype adw was found in 66.7% (22/33) of the typable HBsAg reactive sera; 24.2% (8/33) was of subtype adr and 6.0% (2/33) of subtype ayw. One sample was found to be reactive to both adw and adr. HBsAg subtype adw was found more commonly in Chinese but among the Malays, HBsAg subtype adr appeared to predominate. However, the small sample size precludes firm conclusions on the predominant subtype among the Malays.
    Matched MeSH terms: Hepatitis B Surface Antigens/analysis*
  16. Menon BS, Aiyar S
    Med. J. Malaysia, 1997 Dec;52(4):331-4.
    PMID: 10968109
    This study examined the prevalence of hepatitis B and C markers in 55 paediatric oncology patients who had completed treatment at the Hospital Universiti Sains Malaysia in Kota Baru. All these children had received blood products and had been treated between 1985-1996. Forty seven per cent of patients were positive for hepatitis B or C. Twenty nine per cent were positive for hepatitis C and twenty two per cent were HBsAg positive. Two children were positive for both and none were HIV positive. Four children had an elevated ALT level and one child had jaundice and hepatomegaly. Some children were marker-positive despite immunization and screening of blood.
    Matched MeSH terms: Hepatitis B Surface Antigens/analysis*
  17. Ott JJ, Horn J, Krause G, Mikolajczyk RT
    J. Hepatol., 2017 Jan;66(1):48-54.
    PMID: 27592304 DOI: 10.1016/j.jhep.2016.08.013
    BACKGROUND & AIMS: Information on trends in chronic hepatitis B virus (HBV) prevalence across countries is lacking. We studied changes in chronic HBV infection over previous decades by country, and assessed patterns of change between and within WHO-defined regions.

    METHODS: Based on data from a published systematic review on chronic HBV, we applied a linear model on the logit scale to assess time trends in country-specific prevalence. Estimated HBsAg prevalence in 2000 and relative changes in prevalence over time were evaluated by country and region.

    RESULTS: Sufficient data were available for 50 countries, mostly showing reductions in prevalence over time. Various degrees of heterogeneity were observed within regions, with a relatively homogenous pattern in the Eastern Mediterranean region with strong decreases in HBsAg prevalence. Europe showed a mixed pattern: higher and stable chronic HBsAg prevalence in Eastern, and constantly low prevalence in Western Europe. In Africa, some countries demonstrated no change in prevalence; increases were seen in Uganda (odds ratio 1.05 per year; 95% confidence interval 1.04-1.06), Nigeria (1.02; 1.02-1.02), Senegal (1.01; 1.01-1.02), and South Africa (1.02; 1.01-1.02). With some exceptions, country-patterns overlapped among countries of South East Asian and Western Pacific regions, characterized by low-medium HBsAg decreases, most prominent in China and Malaysia.

    CONCLUSIONS: Most countries experienced decreases in HBsAg prevalence. Dynamics varied, even within regions; decreases occurred mostly before the direct effects of childhood vaccination may have manifested. These findings together with stable and increasing HBsAg prevalence in some countries of Africa and Eastern Europe indicate the need for further tailored country-specific prevention.

    LAY SUMMARY: This study investigated time trends in prevalence of chronic HBV infection in 50 countries worldwide over the last decade, by estimating relative changes in prevalence. Results show decreases in chronic HBV infection in most countries; no changes or increases in prevalence are noted in some African countries. Reasons for time changes need to be investigated further; based on the results, various prevention measures have contributed to reductions, and further tailored HBV prevention is required to combat the disease on a global level.

    Matched MeSH terms: Hepatitis B Surface Antigens/analysis
  18. Alexander MJ, Sinnatamby AS, Rohaimah MJ, Harun AH, Ng JS
    Ann. Acad. Med. Singap., 1990 May;19(3):344-6.
    PMID: 2393233
    Brunei Darussalam has a mixed population with entirely different cultures and religions. The overall incidence of Hepatitis B virus (HBV) infection is 6%. A racial analysis of the incidence of HBV infection in Brunei shows a significantly higher incidence in Chinese compared to the other races. This is consistent with the incidence in the neighbouring countries.
    Matched MeSH terms: Hepatitis B Surface Antigens/analysis
  19. Cheah PL, Looi LM, Lin HP, Yap SF
    Cancer, 1990 Jan 1;65(1):174-6.
    PMID: 2152851
    In the 7-year period between 1980 and 1987, six cases of childhood primary hepatocellular carcinoma (PHC) were confirmed histologically in our institution. Hepatitis B surface antigen (HBsAg) seropositivity was confirmed in five of the cases, and tissue HBsAg was shown in four of these using the Shikata's orcein stain. An associated maternal HBsAg seropositivity was shown in two of the seropositive children. The youngest seropositive patient who developed PHC was 7 years old. The mother of this patient was also seropositive. These observations support a causal relation between childhood Hepatitis B virus infection and PHC. The importance of vertical or perinatal transmission of HBV in the causation of childhood PHC and the prophylactic role of childhood vaccination is emphasized. Attention is also drawn to the relative short malignant transformation time seen in some of these patients.
    Matched MeSH terms: Hepatitis B Surface Antigens/analysis
  20. Vadivale M, Tan TC, Ong CN
    Singapore Med J, 1992 Aug;33(4):367-9.
    PMID: 1411666
    Dental employees in government institutions in a State in Peninsular Malaysia were screened for exposure to hepatitis B virus (HBV) in 1989. Almost all (96.8%) of the 217 employees responded. One quarter (24.8%) was positive for at least one serological markers to HBV; 2.4% had hepatitis B surface antigen (HBsAg) and 22.4% had anti-body to HBsAg (anti-HBs). The presence of HBsAg was unrelated to age, sex, ethnicity, geographical locality and occupations of the subjects. The prevalence of anti-HBs increased with age and was highest for ethnic Chinese (53.6%), followed by Indians (25%), compared to Malays (14.9%) (p less than 0.001) and were increased among dentists (53.1%) and assistant nurses (33.3%). The overall prevalence of HBsAg and anti-HBs were similar to the situation in the community. However, dentists and their chairside assistant nurses, with a higher proportion of Chinese, had higher anti-HBs prevalences compared with that of the general population.
    Matched MeSH terms: Hepatitis B Surface Antigens/analysis*
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