Displaying publications 1 - 20 of 101 in total

  1. Chan YF
    Med J Malaysia, 1972 Sep;27(1):48-51.
    PMID: 35158536
    No abstract available.
  2. Chan YF
    Med J Malaysia, 1972 Mar;26(3):211-214.
    PMID: 35158524
    No abstract available.
  3. Chan YF, Abubakar S
    Malays J Pathol, 2003 Jun;25(1):29-35.
    PMID: 16196375
    The effects of Enterovirus 71 (HEV71) infection on African green monkey kidney cells (Vero) were investigated. It was found that the infected cells showed progressive cellular morphological changes characteristic in apoptotic cells within 10 hours post-infection. The number of apoptotic cells correlated significantly with the number of HEV71 antigen positive cells when cells were labeled using terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL) and stained for HEV71 antigen. Approximately 11, 26, 45 and 50% of the infected cells were apoptotic at 12, 24, 48 and 72 hours post-infection, respectively. Internucleosomal DNA fragmentation, characteristic in the late stage of apoptosis was noted beginning on day 2 post-infection. The DNA fragmentation, however, was absent in cells treated with the heat- and ultraviolet light-inactivated virus inocula. These results demonstrate the capacity of HEV71 to induce apoptosis in the infected cells. The induction, however, requires high level of HEV71 infectivity and the presence of live virus particles, suggesting the need for the presence of specific viral proteins for apoptosis to occur.
  4. Chan YF, AbuBakar S
    Virol J, 2005;2:74.
    PMID: 16122396
    At least three different EV-71 subgenotypes were identified from an outbreak in Malaysia in 1998. The subgenotypes C2 and B4 were associated with the severe and fatal infections, whereas the B3 virus was associated with mild to subclinical infections. The B3 virus genome sequences had >= 85% similarity at the 3' end to CV-A16. This offers opportunities to examine if there are characteristic similarities and differences in virulence between CV-A16, EV-71 B3 and EV-71 B4 and to determine if the presence of the CV-A16-liked genes in EV-71 B3 would also confer the virus with a CV-A16-liked neurovirulence in mice model infection.
  5. Chan YF, Abu Bakar S
    Med J Malaysia, 2005 Jun;60(2):246-8.
    PMID: 16114171
    The efficacy of Virkon S, a commercial disinfectant as a virucidal spray against human enterovirus 71 (HEV71), the causative agent of the fatal form of hand, foot and mouth disease was examined. At least one log10 reduction of HEV71 titer was achieved when one spray of Virkon (1% or 2%) with ten minutes of contact time was applied. The infectivity was completely lost when four sprays of 1% or 2% Virkon were applied, suggesting that at least four sprays of 1% Virkon to the surface bound HEV71 was necessary to completely inactivate the virus. These findings suggest that Virkon S at the proper concentration is suitable to be used as an effective and easy to use disinfectant against HEV71.
  6. Chan YF, AbuBaker S
    Emerg Infect Dis, 2004 Aug;10(8):1468-70.
    PMID: 15496251
    Hand, foot and mouth disease (HFMD) is a common illness of infants and young children <10 years of age. It is characterized by fever, ulcers in the oral cavity, and rashes with blisters that appear on the palm and sole. The most common causal agents of HFMD are coxsackievirus A16 (CV-A16) and human enterovirus 71 (HEV71), but other enteroviruses, including CV-A5 and CV-A10, can also cause it. When caused by CV-A16 infection, it is usually a mild disease, and patients normally recover without requiring any special medical attention.
  7. Chan YF, Sam IC, AbuBakar S
    Infect Genet Evol, 2010 Apr;10(3):404-12.
    PMID: 19465162 DOI: 10.1016/j.meegid.2009.05.010
    Human enterovirus 71 (EV-71) is genotyped for molecular epidemiological investigation mainly using the two structural genes, VP1 and VP4. Based on these, EV-71 is divided into three genotypes, A, B and C, and within the genotypes B and C, there are further subgenotypes, B1-B5 and C1-C5. Classification using these genes is useful but gives incomplete phylogenetic information. In the present study, the phylogenetic relationships amongst all the known EV-71 and human enterovirus A (HEV-A) isolates with complete genome sequences were examined. A different tree topology involving EV-71 isolates of subgenotypes, C4 and B5 was obtained in comparison to that drawn using VP1. The nucleotide sequence divergence of the C4 isolates was 18.11% (17-20%) when compared to other isolates of subgenotype C. However, this positions the C4 isolates within the cut-off divergence value of 17-22% used to designate the virus genotypes. Hence, it is proposed here that C4 should be designated as a new genotype D. In addition, the subgenotype B5 isolates had an average nucleotide divergence of only 6.14% (4-8%) when compared to other subgenotype B4 isolates. This places the B5 isolates within the subgenotype B4. It is proposed here that the B5 isolates to be redesignated as B4. With the newly proposed genotype D and inclusion of subgenotype B5 within B4, the average nucleotide divergence between genotypes was 18.99% (17-22%). Inter- and intra-subgenotype average divergences were 12.02% (10-14%) and 3.92% (1-10%), respectively. A phylogenetic tree built using the full genome sequences is robust as it takes into consideration changes in the sequences of both the structural and non-structural genes. Similar nucleotide similarities, however, were obtained if only VP1 and 3D RNA polymerase genes were used. Furthermore, addition of 3D RNA polymerase sequences will also show recombination events. Hence, in the absence of full genome sequences, it is proposed here that a combination of VP1 and 3D RNA polymerase gene sequences be used for initial genotyping of EV-71 isolates.
  8. Chua CL, Sam IC, Chan YF
    Methods Mol Biol, 2016;1426:51-61.
    PMID: 27233260 DOI: 10.1007/978-1-4939-3618-2_5
    Chikungunya virus (CHIKV) is a mosquito-borne arbovirus which poses a major threat to global public health. Definitive CHIKV diagnosis is crucial, especially in distinguishing the disease from dengue virus, which co-circulates in endemic areas and shares the same mosquito vectors. Laboratory diagnosis is mainly based on serological or molecular approaches. The E2 glycoprotein is a good candidate for serological diagnosis since it is the immunodominant antigen during the course of infection, and reacts with seropositive CHIKV sera. In this chapter, we describe the generation of stable clone Sf9 (Spodoptera frugiperda) cells expressing secreted, soluble, and native recombinant CHIKV E2 glycoprotein. We use direct plasmid expression in insect cells, rather than the traditional technique of generating recombinant baculovirus. This recombinant protein is useful for serological diagnosis of CHIKV infection.
  9. AbuBakar S, Wong PF, Chan YF
    J Gen Virol, 2002 Oct;83(Pt 10):2437-2442.
    PMID: 12237425 DOI: 10.1099/0022-1317-83-10-2437
    Phylogenetic analyses of the envelope (E) gene sequence of five recently isolated dengue virus type 4 (DENV-4) suggested the emergence of a distinct geographical and temporal DENV-4 subgenotype IIA in Malaysia. Four of the isolates had direct ancestral lineage with DENV-4 Indonesia 1973 and showed evidence of intra-serotypic recombination with the other recently isolated DENV-4, MY01-22713. The E gene of isolate MY01-22713 had strong evidence of an earlier recombination involving DENV-4 genotype II Indonesia 1976 and genotype I Malaysia 1969. These results suggest that intra-serotypic recombination amongst DENV-4 from independent ancestral lineages may have contributed to the emergence of DENV-4 subgenotype IIA in Malaysia.
  10. Chua CL, Chan YF, Sam IC
    J Virol Methods, 2014 Jan;195:126-33.
    PMID: 24134938 DOI: 10.1016/j.jviromet.2013.10.015
    Chikungunya virus (CHIKV) is a mosquito-borne arbovirus which has recently re-emerged globally and poses a major threat to public health. Infection leads to severe arthralgia, and disease management remains supportive in the absence of vaccines and anti-viral interventions. The high specificities of monoclonal antibodies (mAbs) have been exploited in immunodiagnostics and immunotherapy in recent decades. In this study, eight different clones of mAbs were generated and characterised. These mAbs targeted the linear epitopes on the CHIKV E2 envelope glycoprotein, which is the major target antigen during infection. All the mAbs showed binding activity against the purified CHIKV virion or recombinant E2 when analysed by immunofluorescence, ELISA and Western blot. The epitopes of each mAb were mapped by overlapping synthetic peptide-based ELISA. The epitopes are distributed at different functional domains of E2 glycoprotein, namely at domain A, junctions of β-ribbons with domains A and B, and domain C. Alignment of mAb epitope sequences revealed that some are well-conserved within different genotypes of CHIKV, while some are identical to and likely to cross-react with the closely-related alphavirus O'nyong-nyong virus. These mAbs with their mapped epitopes are useful for the development of diagnostic or research tools, including immunofluorescence, ELISA and Western blot.
  11. Sam JI, Chan YF, Vythilingam I, Wan Sulaiman WY
    Med J Malaysia, 2016 04;71(2):66-8.
    PMID: 27326944 MyJurnal
    Zika virus (ZIKV) has re-emerged to cause explosive epidemics in the Pacific and Latin America, and appears to be associated with severe neurological complications including microcephaly in babies. ZIKV is transmitted to humans by Aedes mosquitoes, principally Ae. aegypti, and there is historical evidence of ZIKV circulation in Southeast Asia. It is therefore clear that Malaysia is at risk of similar outbreaks. Local and international guidelines are available for surveillance, diagnostics, and management of exposed and infected individuals. ZIKV is the latest arbovirus to have spread globally beyond its initial restricted niche, and is unlikely to be the last. Innovative new methods for surveillance and control of vectors are needed to target mosquito-borne diseases as a whole.
  12. Tan CW, Lai JK, Sam IC, Chan YF
    J Biomed Sci, 2014;21:14.
    PMID: 24521134 DOI: 10.1186/1423-0127-21-14
    Enterovirus 71 (EV-71) is the main etiological agent of hand, foot and mouth disease (HFMD). Recent EV-71 outbreaks in Asia-Pacific were not limited to mild HFMD, but were associated with severe neurological complications such as aseptic meningitis and brainstem encephalitis, which may lead to cardiopulmonary failure and death. The absence of licensed therapeutics for clinical use has intensified research into anti-EV-71 development. This review highlights the potential antiviral agents targeting EV-71 attachment, entry, uncoating, translation, polyprotein processing, virus-induced formation of membranous RNA replication complexes, and RNA-dependent RNA polymerase. The strategies for antiviral development include target-based synthetic compounds, anti-rhinovirus and poliovirus libraries screening, and natural compound libraries screening. Growing knowledge of the EV-71 life cycle will lead to successful development of antivirals. The continued effort to develop antiviral agents for treatment is crucial in the absence of a vaccine. The coupling of antivirals with an effective vaccine will accelerate eradication of the disease.
  13. Tan CW, Poh CL, Sam IC, Chan YF
    J Virol, 2013 Jan;87(1):611-20.
    PMID: 23097443 DOI: 10.1128/JVI.02226-12
    Enterovirus 71 (EV-71) infections are usually associated with mild hand, foot, and mouth disease in young children but have been reported to cause severe neurological complications with high mortality rates. To date, four EV-71 receptors have been identified, but inhibition of these receptors by antagonists did not completely abolish EV-71 infection, implying that there is an as yet undiscovered receptor(s). Since EV-71 has a wide range of tissue tropisms, we hypothesize that EV-71 infections may be facilitated by using receptors that are widely expressed in all cell types, such as heparan sulfate. In this study, heparin, polysulfated dextran sulfate, and suramin were found to significantly prevent EV-71 infection. Heparin inhibited infection by all the EV-71 strains tested, including those with a single-passage history. Neutralization of the cell surface anionic charge by polycationic poly-d-lysine and blockage of heparan sulfate by an anti-heparan sulfate peptide also inhibited EV-71 infection. Interference with heparan sulfate biosynthesis either by sodium chlorate treatment or through transient knockdown of N-deacetylase/N-sulfotransferase-1 and exostosin-1 expression reduced EV-71 infection in RD cells. Enzymatic removal of cell surface heparan sulfate by heparinase I/II/III inhibited EV-71 infection. Furthermore, the level of EV-71 attachment to CHO cell lines that are variably deficient in cell surface glycosaminoglycans was significantly lower than that to wild-type CHO cells. Direct binding of EV-71 particles to heparin-Sepharose columns under physiological salt conditions was demonstrated. We conclude that EV-71 infection requires initial binding to heparan sulfate as an attachment receptor.
  14. Khor CS, Sam IC, Hooi PS, Chan YF
    Infect Genet Evol, 2013 Mar;14:357-60.
    PMID: 23305888 DOI: 10.1016/j.meegid.2012.12.017
    From 1989 to 2011 in Kuala Lumpur, Malaysia, multiple genotypes from both respiratory syncytial virus (RSV) subgroups were found co-circulating each year. RSV-A subgroup predominated in 12 out of 17years with the remaining years predominated by RSV-B subgroup. Local RSV strains exhibited temporal clustering with RSV strains reported in previous epidemiological studies. Every few years, the existing predominant genotype was replaced by a new genotype. The RSV-A genotypes GA2, GA5 and GA7 were replaced by NA1 and NA2, while BA became the predominant RSV-B genotype. A unique local cluster, BA12, was seen in 2009, and the recently-described ON1 genotype with 72-nt duplication emerged in 2011. Our findings will have important implications for future vaccine intervention.
  15. Lai JK, Sam IC, Chan YF
    Viruses, 2016 Feb;8(2).
    PMID: 26828514 DOI: 10.3390/v8020032
    The Enterovirus genus of the Picornaviridae family comprises many important human pathogens, including polioviruses, rhinovirus, enterovirus A71, and enterovirus D68. They cause a wide variety of diseases, ranging from mild to severe life-threatening diseases. Currently, no effective vaccine is available against enteroviruses except for poliovirus. Enteroviruses subvert the autophagic machinery to benefit their assembly, maturation, and exit from host. Some enteroviruses spread between cells via a process described as autophagosome-mediated exit without lysis (AWOL). The early and late phases of autophagy are regulated through various lipids and their metabolizing enzymes. Some of these lipids and enzymes are specifically regulated by enteroviruses. In the present review, we summarize the current understanding of the regulation of autophagic machinery by enteroviruses, and provide updates on recent developments in this field.
Contact Us

Please provide feedback to Administrator (afdal@afpm.org.my)

External Links