Kok Keng Tee

University of Malaya, Kuala Lumpor, Kuala Lumpur, Malaysia

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Publications (37)111.85 Total impact

  • Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. 06/2014;
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    ABSTRACT: The HIV epidemic is primarily characterised by the circulation of HIV-1 group M (main) comprising of 11 subtypes and sub-subtypes (A1, A2, B-D, F1, F2, G, H, J, and K) and to date 55 circulating recombinant forms (CRFs). In Southeast Asia, active inter-subtype recombination involving three main circulating genotypes-subtype B (including subtype B', the Thai variant of subtype B), CRF01_AE, and CRF33_01B-have contributed to the emergence of novel unique recombinant forms. In the present study, we conducted the molecular epidemiological surveillance of HIV-1 gag-RT genes among 258 people who inject drugs (PWIDs) in Kuala Lumpur, Malaysia, between 2009 and 2011 whereby a novel CRF candidate was recently identified. The near full-length genome sequences obtained from six epidemiologically unlinked individuals showed identical mosaic structures consisting of subtype B' and CRF01_AE, with six unique recombination breakpoints in the gag-RT, pol, and env regions. Among the high-risk population of PWIDs in Malaysia, which was predominantly infected by CRF33_01B (>70%), CRF58_01B circulated at a low but significant prevalence (2.3%, 6/258). Interestingly, the CRF58_01B shared two unique recombination breakpoints with other established CRFs in the region: CRF33_01B, CRF48_01B, and CRF53_01B in the gag gene, and CRF15_01B (from Thailand) in the env gene. Extended Bayesian Markov chain Monte Carlo sampling analysis showed that CRF58_01B and other recently discovered CRFs were most likely to have originated in Malaysia, and that the recent spread of recombinant lineages in the country had little influence from neighbouring countries. The isolation, genetic characterization, and evolutionary features of CRF58_01B among PWIDs in Malaysia signify the increasingly complex HIV-1 diversity in Southeast Asia that may hold an implication on disease treatment, control, and prevention.
    PLoS ONE 01/2014; 9(1):e85250. · 3.53 Impact Factor
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    ABSTRACT: A novel HIV-1 recombinant clade (CRF51_01B) was recently identified among men who have sex with men (MSM) in Singapore. As cases of sexually transmitted HIV-1 infection increase concurrently in two socioeconomically intimate countries such as Malaysia and Singapore, cross transmission of HIV-1 between said countries is highly probable. In order to investigate the timeline for the emergence of HIV-1 CRF51_01B in Singapore and its possible introduction into Malaysia, 595 HIV-positive subjects recruited in Kuala Lumpur from 2008 to 2012 were screened. Phylogenetic relationship of 485 amplified polymerase gene sequences was determined through neighbour-joining method. Next, near-full length sequences were amplified for genomic sequences inferred to be CRF51_01B and subjected to further analysis implemented through Bayesian Markov chain Monte Carlo (MCMC) sampling and maximum likelihood methods. Based on the near full length genomes, two isolates formed a phylogenetic cluster with CRF51_01B sequences of Singapore origin, sharing identical recombination structure. Spatial and temporal information from Bayesian MCMC coalescent and maximum likelihood analysis of the protease, gp120 and gp41 genes suggest that Singapore is probably the country of origin of CRF51_01B (as early as in the mid-1990s) and featured a Malaysian who acquired the infection through heterosexual contact as host for its ancestral lineages. CRF51_01B then spread rapidly among the MSM in Singapore and Malaysia. Although the importation of CRF51_01B from Singapore to Malaysia is supported by coalescence analysis, the narrow timeframe of the transmission event indicates a closely linked epidemic. Discrepancies in the estimated divergence times suggest that CRF51_01B may have arisen through multiple recombination events from more than one parental lineage. We report the cross transmission of a novel CRF51_01B lineage between countries that involved different sexual risk groups. Understanding the cross-border transmission of HIV-1 involving sexual networks is crucial for effective intervention strategies in the region.
    PLoS ONE 01/2014; 9(10):e111236. · 3.53 Impact Factor
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    ABSTRACT: A complex HIV-1 unique recombinant form involving subtypes CRF01_AE, B, and B' was recently identified from an injecting drug user in Malaysia. A total of 13 recombination breakpoints were mapped across the near-full-length genome of isolate 10MYPR226, indicating the increasingly diverse molecular epidemiology and frequent linkage among various high-risk groups.
    Genome announcements. 01/2014; 2(2).
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    ABSTRACT: Serratia marcescens is an opportunistic bacterial pathogen with broad range of host ranging from vertebrates, invertebrates and plants. S. marcescens strain W2.3 was isolated from a diseased tilapia fish and it was suspected to be the causal agent for the fish disease as virulence genes were found within its genome. In this study, for the first time, the genome sequences of S. marcescens strain W2.3 were sequenced using the Illumina MiSeq platform.Result: Several virulent factors of S. marcescens such as serrawettin, a biosurfactant, has been reported to be regulated by N-acyl homoserine lactone (AHL)-based quorum sensing (QS). In our previous studies, an unusual AHL with long acyl side chain was detected from this isolate suggesting the possibility of novel virulence factors regulation. This evokes our interest in the genome of this bacterial strain and hereby we present the draft genome of S. marcescens W2.3, which carries the serrawettin production gene, swrA and the AHL-based QS transcriptional regulator gene, luxR which is an orphan luxR. With the availability of the whole genome sequences of S. marcescens W2.3, this will pave the way for the study of the QS-mediated genes expression in this bacterium.
    Gut Pathogens 10/2013; 5(1):29. · 2.74 Impact Factor
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    ABSTRACT: Expansion of antiretroviral treatment programs have led to the growing concern for the development of antiretroviral drug resistance. The aims were to assess the prevalence of drug resistant HIV-1 variants and to identify circulating subtypes among HAART-naïve patients. Plasma specimens from N = 100 HIV+ HAART-naïve adult were collected between March 2008 and August 2010 and viral RNA were extracted for nested PCR and sequenced. PR-RT sequences were protein aligned and checked for transmitted drug resistance mutations. Phylogenetic reconstruction and recombination analysis were performed to determine the genotypes. Based on the WHO consensus guidelines, none of the recruited patients had any transmitted drug resistance mutations. When analyzed against the Stanford guidelines, 35% of patients had at least one reported mutation that may reduce drug susceptibility to PI (24%), NRTI (5%), and NNRTI (14%). The commonly detected mutation that may affect current first line therapy was V179D (3%), which may lead to reduced susceptibility to NNRTI. The predominant circulating HIV-1 genotypes were CRF01_AE (51%) and CRF33_01B (17%). The prevalence of unique recombinant forms (URF) was 7%; five distinct recombinant structures involving CRF01_AE and subtype B' were observed, among them a cluster of three isolates that could form a novel circulating recombinant form (CRF) candidate. Transmitted drug resistance prevalence among HAART-naïve patients was low in this cohort of patients in Kuala Lumpur despite introduction of HAART 5 years ago. Owing to the high genetic diversity, continued molecular surveillance can identify the persistent emergence of HIV-1 URF and novel CRF with significant epidemiological impact. J. Med. Virol. © 2013 Wiley Periodicals, Inc.
    Journal of Medical Virology 10/2013; · 2.37 Impact Factor
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    ABSTRACT: In this study, we investigated the HCV molecular epidemiology and evolutionary dynamics. Both E1 and NS5B sequences were characterized in 379 of 433 patients in southern China, classifying five major subtypes: 1b in 259 patients, 6a in 67, 2a in 29, 3a in 14, and 3b in 13. Using the obtained E1 sequences with those from other studies that were sampled in China, we inferred the HCV epidemic history by means of coalescence strategies. Five Bayesian skyline plots (BSPs) were estimated for the five subtypes. They concurrently highlighted the rapid growth in the HCV-infected population size in 1993-2000, followed by an abrupt slowing. Although flanked on both sides by variable population sizes, the plots showed distinct patterns of the rapid HCV growth. Coincidently, 1993-2000 was a period when contaminated blood transfusions were common in China due to a procedural error in an officially encouraged plasma campaign. An abrupt slowing in 1998-2000 corresponded to the central government outlawing paid blood donations in 1998. Using a parametric model, the HCV population growth rates were estimated during 1993-2000. It was revealed that the 6a rate was the highest, followed by that of 1b, 2a, 3b, and 3a. Because these rates differed significantly (p<1E-9) from each other, they may help explain why 6a is increasingly prevalent in southern China and 1b is predominant nationwide. These rates are approximately ten-fold higher than those reported elsewhere. These findings suggested that during the plasma campaign, certain barriers to efficient viral transmission were removed, allowing wide HCV dissemination.
    Journal of Virology 08/2013; · 5.08 Impact Factor
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    ABSTRACT: Bacterial cell-to-cell communication (quorum sensing) refers to the regulation of bacterial gene expression in response to changes in microbial population density. Quorum sensing bacteria produce, release and respond to chemical signal molecules called autoinducers. Bacteria use two types of autoinducers, namely autoinducer-1 (AI-1) and autoinducer-2 (AI-2) where the former are N-acylhomoserine lactones and the latter is a product of the luxS gene. Most of the reported literatures show that the majority of oral bacteria use AI-2 for quorum sensing but rarely the AI-1 system. Here we report the isolation of Pseudomonas putida strain T2-2 from the oral cavity. Using high resolution mass spectrometry, it is shown that this isolate produced N-octanoylhomoserine lactone (C8-HSL) and N-dodecanoylhomoserine lactone (C12-HSL) molecules. This is the first report of the finding of quorum sensing of P. putida strain T2-2 isolated from the human tongue surface and their quorum sensing molecules were identified.
    Sensors 01/2013; 13(10):13192-13203. · 2.05 Impact Factor
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    ABSTRACT: HIV-1 epidemics among men who have sex with men (MSM) continue to expand in developed and developing countries. Although HIV infection in MSM is amongst the highest of the key affected populations in many countries in Southeast Asia, comprehensive molecular epidemiological study of HIV-1 among MSM remains inadequate in the region including in Malaysia. Here, we reported the phylodynamic profiles of HIV-1 genotypes circulating among MSM population in Kuala Lumpur, Malaysia. A total of n = 459 newly-diagnosed treatment-naïve consenting subjects were recruited between March 2006 and August 2012, of whom 87 (18.9%) were self-reported MSM. Transmitted drug resistance mutations were absent in these isolates. Cumulatively, phylogenetic reconstructions of the pro-rt gene (HXB2∶2253-3275) showed that HIV-1 subtype B and CRF01_AE were predominant and contributed to approximately 80% of the total HIV-1 infection among MSM. In addition to numerous unique transmission lineages within these genotypes, twelve monophyletic transmission clusters of different sizes (2-7 MSM sequences, supported by posterior probability value of 1) were identified in Malaysia. Bayesian coalescent analysis estimated that the divergence times for these clusters were mainly dated between 1995 and 2005 with four major transmission clusters radiating at least 12 years ago suggesting that active spread of multiple sub-epidemic clusters occurred during this period. The changes in effective population size of subtype B showed an exponential growth within 5 years between 1988 and 1993, while CRF01_AE lineage exhibited similar expansion between 1993 and 2003. Our study provides the first insight of the phylodynamic profile of HIV-1 subtype B and CRF01_AE circulating among MSM population in Kuala Lumpur, Malaysia, unravelling the importance of understanding transmission behaviours as well as evolutionary history of HIV-1 in assessing the risk of outbreak or epidemic expansion.
    PLoS ONE 01/2013; 8(6):e67286. · 3.53 Impact Factor
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    ABSTRACT: We report the full genome sequence of hepatitis C virus (HCV) subtype 6n from Kuala Lumpur, Malaysia. Phylogenetic analysis of the isolate 10MYKJ032 suggests that Southeast Asia might be the origin for the HCV subtype 6n and highlights the possible spread of this lineage from Southeast Asia to other regions.
    Genome announcements. 01/2013; 1(1).
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    ABSTRACT: Since the discovery of HIV-1 circulating recombinant form (CRF) 33_01B in Malaysia in the early 2000 s, continuous genetic diversification and active recombination involving CRF33_01B and other circulating genotypes in the region including CRF01_AE and subtype B' of Thai origin, have led to the emergence of novel CRFs and unique recombinant forms. The history and magnitude of CRF33_01B transmission among various risk groups including people who inject drugs (PWID) however have not been investigated despite the high epidemiological impact of CRF33_01B in the region. We update the most recent molecular epidemiology of HIV-1 among PWIDs recruited in Malaysia between 2010 and 2011 by population sequencing and phylogenetic analysis of 128 gag-pol sequences. HIV-1 CRF33_01B was circulating among 71% of PWIDs whilst a lower prevalence of other previously dominant HIV-1 genotypes [subtype B' (11%) and CRF01_AE (5%)] and CRF01_AE/B' unique recombinants (13%) were detected, indicating a significant shift in genotype replacement in this population. Three clusters of CRF01_AE/B' recombinants displaying divergent yet phylogenetically-related mosaic genomes to CRF33_01B were identified and characterized, suggestive of an abrupt emergence of multiple novel CRF clades. Using rigorous maximum likelihood approach and the Bayesian Markov chain Monte Carlo (MCMC) sampling of CRF33_01Bpol sequences to elucidate the past population dynamics, we found that the founder lineages of CRF33_01B were likely to have first emerged among PWIDs in the early 1990 s before spreading exponentially to various high and low-risk populations (including children who acquired infections from their mothers) and later on became endemic around the early 2000 s. Taken together, our findings provide notable genetic evidence indicating the widespread expansion of CRF33_01B among PWIDs and into the general population. The emergence of numerous previously unknown recombinant clades highlights the escalating genetic complexity of HIV-1 in the Southeast Asian region.
    PLoS ONE 01/2013; 8(5):e62560. · 3.53 Impact Factor
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    ABSTRACT: HIV-1 subtype B and CRF01_AE are the predominant infecting subtypes among men who have sex with men (MSM) in Singapore. The genetic history, population dynamics and pattern of transmission networks of these genotypes remain largely unknown. We delineated the phylodynamic profiles of HIV-1 subtype B, CRF01_AE and the recently characterized CRF51_01B strains circulating among the MSM population in Singapore. A total of 105 (49.5%) newly-diagnosed treatment-naïve MSM were recruited between February 2008 and August 2009. Phylogenetic reconstructions of the protease gene (HXB2: 2239 - 2629), gp120 (HXB2: 6942 - 7577) and gp41 (HXB2: 7803 - 8276) of the env gene uncovered five monophyletic transmission networks (two each within subtype B and CRF01_AE and one within CRF51_01B lineages) of different sizes (involving 3 - 23 MSM subjects, supported by posterior probability measure of 1.0). Bayesian coalescent analysis estimated that the emergence and dissemination of multiple sub-epidemic networks occurred between 1995 and 2005, driven largely by subtype B and later followed by CRF01_AE. Exponential increase in effective population size for both subtype B and CRF01_AE occurred between 2002 to 2007 and 2005 to 2007, respectively. Genealogical estimates suggested that the novel CRF51_01B lineages were probably generated through series of recombination events involving CRF01_AE and multiple subtype B ancestors. Our study provides the first insight on the phylodynamic profiles of HIV-1 subtype B, CRF01_AE and CRF51_01B viral strains circulating among MSM in Singapore.
    PLoS ONE 01/2013; 8(12):e80884. · 3.53 Impact Factor
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    ABSTRACT: BACKGROUND: HIV-1 group M viruses diverge 25%-35% in envelope, important for viral attachment during infection, and 10-15% in the pol region, under selection pressure from common antiretrovirals. In Asia, subtypes B and CRF01_AE are common genotypes. Our objectives were to determine whether clinical, immunologic or virologic treatment responses differed by genotype in treatment-naïve patients initiating first-line therapy. METHODS: Prospectively collected, longitudinal data from patients in Thailand, Hong Kong, Malaysia, Japan, Taiwan and South Korea were provided for analysis. Covariates included demographics, hepatitis B and C coinfections, baseline CD4 T lymphocyte count and plasma HIV-1 RNA levels. Clinical deterioration (a new diagnosis of CDC category B/AIDS-defining illness or death) was assessed by proportional hazards models. Surrogate endpoints were 12-month change in CD4 cell count and virologic suppression post-therapy, evaluated by linear and logistic regression, respectively. RESULTS: Of 1105 patients, 1036 (93.8%) infected with CRF01_AE or subtype B were eligible for inclusion in clinical deterioration analyses and contributed 1546.7 person-years of follow-up (median:413 days, IQR:169-672 days). Patients >40 years demonstrated smaller immunological increases (p=0.002) and higher risk of clinical deterioration (HR=2.17; p=0.008). Patients with baseline CD4 cell counts >200 cells/μL had lower risk of clinical deterioration (HR=0.373; p=0.003). A total of 532 patients (48.1% of eligible) had CD4 counts available at baseline and 12 months post-therapy for inclusion in immunolgic analyses. Patients infected with subtype B had larger increases in CD4 counts at 12 months (p=0.024). A total of 530 patients (48.0% of eligible) were included in virologic analyses with no differences in response found between genotypes. CONCLUSIONS: Results suggest that patients infected with CRF01_AE have reduced immunologic response to therapy at 12 months, compared to subtype-B-infected counterparts. Clinical deterioration was associated with low baseline CD4 counts and older age. The lack of differences in virologic outcomes suggests that all patients have opportunities for virologic suppression. OPEN ACCESS full text is available from Publisher. http://journals.lww.com/jaids/Fulltext/2013/03010/Evaluating_Immunologic_Response_and_Clinical.6.aspx
    JAIDS Journal of Acquired Immune Deficiency Syndromes 11/2012; · 4.65 Impact Factor
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    ABSTRACT: A novel HIV-1 genotype designated CRF53_01B was recently characterized from three epidemiologically unrelated persons in Malaysia. Here we announced three recently isolated full-length genomes of CRF53_01B, which is likely to be phylogenetically linked to CRF33_01B, circulating widely in Southeast Asia. The genome sequences may contribute to HIV-1 molecular surveillance and future vaccine development in the region.
    Journal of Virology 10/2012; 86(20):11398-9. · 5.08 Impact Factor
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    ABSTRACT: We report here the first novel HIV-1 circulating recombinant form (CRF) 54_01B (CRF54_01B) isolated from three epidemiologically unlinked subjects of different risk groups in Malaysia. These recently sampled recombinants showed a complex genome organization composed of parental subtype B' and CRF01_AE, with identical recombination breakpoints observed in the gag, pol, and vif genes. Such a discovery highlights the ongoing active generation and spread of intersubtype recombinants involving the subtype B' and CRF01_AE lineages and indicates the potential of the new CRF in bridging HIV-1 transmission among different risk groups in Southeast Asia.
    Journal of Virology 10/2012; 86(20):11405-6. · 5.08 Impact Factor
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    ABSTRACT: Phylogenetic analyses can give new insights into the evolutionary history of viruses, especially of viruses with segmented genomes. However, sequence information for many viral families or genera is still limited and phylogenies based on single or short genome fragments can be misleading. We report the first genetic analysis of all three genome segments of Wyeomyia group viruses Wyeomyia, Taiassui, Macaua, Sororoca, Anhembi and Cachoeira Porteira (BeAr328208) in the genus Orthobunyavirus of the family Bunyaviridae. In addition, Tucunduba and Iaco viruses were identified as members of the Wyeomyia group. Features of Wyeomyia group members that distinguish them from other viruses in the Bunyamwera serogroup and from other orthobunyaviruses, including truncated NSs sequences that may not counteract the host's interferon response, were characterized. Our findings also suggest genome reassortment within the Wyeomyia group, identifying Macaua and Tucunduba viruses as M-segment reassortants that, in the case of Tucunduba virus, may have altered pathogenicity, stressing the need for whole-genome sequence information to facilitate characterization of orthobunyaviruses and their phylogenetic relationships.
    Journal of General Virology 02/2012; 93(Pt 5):1023-34. · 3.13 Impact Factor
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    Virology 09/2010; 405(1):267-268. · 3.37 Impact Factor
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    ABSTRACT: The effects of oil palm phenolics (OPP) on cell lines were demonstrated in this study. OPP dose-dependent studies in selected cell cultures showed that OPP inhibited the proliferation of mouse IgA-secreting myeloma (J558), estrogen-receptor-positive human breast adenocarcinoma (MCF7) and human lung carcinoma (A549) cells at all doses. However, OPP enhanced the proliferation of Madin Darby Canine Kidney (MDCK) and Aedes albopictus larvae (C6/36) cells at all concentrations, whereas, growth of Syrian Baby Hamster Kidney (BHK) cells was only enhanced with low doses of OPP. 5% OPP in combination with 5% fetal calf serum (FCS) was shown to be as effective as 10% FCS on the growth of BHK and A549 cells. In vivo studies using J558 myeloma cells showed that OPP caused tumor regression. These findings imply that OPP has anti-proliferative effects on tumor cells in vitro and in vivo, but conversely enhances the growth of normal cells.
    African Journal of Food Science. 09/2010; 4:495-502.

Publication Stats

434 Citations
111.85 Total Impact Points

Institutions

  • 2005–2014
    • University of Malaya
      • • Institute of Biological Sciences
      • • Department of Medicine
      • • Department of Medical Microbiology
      Kuala Lumpor, Kuala Lumpur, Malaysia
  • 2007–2013
    • National Institute of Infectious Diseases, Tokyo
      Edo, Tōkyō, Japan
  • 2008
    • Kunming University of Science and Technology
      Yün-nan, Yunnan, China