Displaying publications 1 - 20 of 146 in total

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  1. Tan le V, Tuyen NT, Thanh TT, Ngan TT, Van HM, Sabanathan S, et al.
    J Virol Methods, 2015 Apr;215-216:30-6.
    PMID: 25704598 DOI: 10.1016/j.jviromet.2015.02.011
    Enterovirus A71 (EV-A71) has emerged as the most important cause of large outbreaks of severe and sometimes fatal hand, foot and mouth disease (HFMD) across the Asia-Pacific region. EV-A71 outbreaks have been associated with (sub)genogroup switches, sometimes accompanied by recombination events. Understanding EV-A71 population dynamics is therefore essential for understanding this emerging infection, and may provide pivotal information for vaccine development. Despite the public health burden of EV-A71, relatively few EV-A71 complete-genome sequences are available for analysis and from limited geographical localities. The availability of an efficient procedure for whole-genome sequencing would stimulate effort to generate more viral sequence data. Herein, we report for the first time the development of a next-generation sequencing based protocol for whole-genome sequencing of EV-A71 directly from clinical specimens. We were able to sequence viruses of subgenogroup C4 and B5, while RNA from culture materials of diverse EV-A71 subgenogroups belonging to both genogroup B and C was successfully amplified. The nature of intra-host genetic diversity was explored in 22 clinical samples, revealing 107 positions carrying minor variants (ranging from 0 to 15 variants per sample). Our analysis of EV-A71 strains sampled in 2013 showed that they all belonged to subgenogroup B5, representing the first report of this subgenogroup in Vietnam. In conclusion, we have successfully developed a high-throughput next-generation sequencing-based assay for whole-genome sequencing of EV-A71 from clinical samples.
  2. Goldsmith CS, Whistler T, Rollin PE, Ksiazek TG, Rota PA, Bellini WJ, et al.
    Virus Res, 2003 Mar;92(1):89-98.
    PMID: 12606080
    Nipah virus, which was first recognized during an outbreak of encephalitis with high mortality in Peninsular Malaysia during 1998-1999, is most closely related to Hendra virus, another emergent paramyxovirus first recognized in Australia in 1994. We have studied the morphologic features of Nipah virus in infected Vero E6 cells and human brain by using standard and immunogold electron microscopy and ultrastructural in situ hybridization. Nipah virions are enveloped particles composed of a tangle of filamentous nucleocapsids and measured as large as 1900 nm in diameter. The nucleocapsids measured up to 1.67 microm in length and had the herringbone structure characteristic for paramyxoviruses. Cellular infection was associated with multinucleation, intracytoplasmic nucleocapsid inclusions (NCIs), and long cytoplasmic tubules. Previously undescribed for other members of the family Paramyxoviridae, infected cells also contained an inclusion formed of reticular structures. Ultrastructural ISH studies suggest these inclusions play an important role in the transcription process.
  3. Rajahram GS, Hale G, Bhatnagar J, Hiu J, Thayan R, William T, et al.
    Int J Infect Dis, 2019 06;83:163-166.
    PMID: 30763620 DOI: 10.1016/j.ijid.2019.01.047
  4. Costa H, Xu X, Overbeek G, Vasaikar S, Patro CP, Kostopoulou ON, et al.
    Oncotarget, 2016 Jul 26;7(30):47221-47231.
    PMID: 27363017 DOI: 10.18632/oncotarget.9722
    BACKGROUND: Both arginase (ARG2) and human cytomegalovirus (HCMV) have been implicated in tumorigenesis. However, the role of ARG2 in the pathogenesis of glioblastoma (GBM) and the HCMV effects on ARG2 are unknown. We hypothesize that HCMV may contribute to tumorigenesis by increasing ARG2 expression.

    RESULTS: ARG2 promotes tumorigenesis by increasing cellular proliferation, migration, invasion and vasculogenic mimicry in GBM cells, at least in part due to overexpression of MMP2/9. The nor-NOHA significantly reduced migration and tube formation of ARG2-overexpressing cells. HCMV immediate-early proteins (IE1/2) or its downstream pathways upregulated the expression of ARG2 in U-251 MG cells. Immunostaining of GBM tissue sections confirmed the overexpression of ARG2, consistent with data from subsets of Gene Expression Omnibus. Moreover, higher levels of ARG2 expression tended to be associated with poorer survival in GBM patient by analyzing data from TCGA.

    METHODS: The role of ARG2 in tumorigenesis was examined by proliferation-, migration-, invasion-, wound healing- and tube formation assays using an ARG2-overexpressing cell line and ARG inhibitor, N (omega)-hydroxy-nor-L-arginine (nor-NOHA) and siRNA against ARG2 coupled with functional assays measuring MMP2/9 activity, VEGF levels and nitric oxide synthase activity. Association between HCMV and ARG2 were examined in vitro with 3 different GBM cell lines, and ex vivo with immunostaining on GBM tissue sections. The viral mechanism mediating ARG2 induction was examined by siRNA approach. Correlation between ARG2 expression and patient survival was extrapolated from bioinformatics analysis on data from The Cancer Genome Atlas (TCGA).

    CONCLUSIONS: ARG2 promotes tumorigenesis, and HCMV may contribute to GBM pathogenesis by upregulating ARG2.

  5. Penjor D, Khizuan AK, Chong AW, Wong KT
    J Laryngol Otol, 2014 Dec;128(12):1117-9.
    PMID: 25382114 DOI: 10.1017/S0022215114002655
    Chromoblastomycosis is a chronic fungal infection of the skin and subcutaneous tissue that most commonly affects the feet and lower limbs. It is rare for this infection to occur on the face, and it is exceptionally rare for it to involve the nose and sinuses. This paper reports a rare case of nasal chromoblastomycosis in a 50-year-old Malaysian male.
  6. Tan SH, Ong KC, Wong KT
    J. Neuropathol. Exp. Neurol., 2014 Nov;73(11):999-1008.
    PMID: 25289894 DOI: 10.1097/NEN.0000000000000122
    Enterovirus 71 (EV71)-associated hand, foot, and mouth disease may be complicated by encephalomyelitis. We investigated EV71 brainstem infection and whether this infection could be ameliorated by passive immunization in a mouse model. Enterovirus 71 was injected into unilateral jaw/facial muscles of 2-week-old mice, and hyperimmune sera were given before or after infection. Harvested tissues were studied by light microscopy, immunohistochemistry, in situ hybridization, and viral titration. In unimmunized mice, viral antigen and RNA were detected within 24 hours after infection only in ipsilateral cranial nerves, motor trigeminal nucleus, reticular formation, and facial nucleus; viral titers were significantly higher in the brainstem than in the spinal cord samples. Mice given preinfection hyperimmune serum showed a marked reduction of ipsilateral viral antigen/RNA and viral titers in the brainstem in a dose-dependent manner. With optimum hyperimmune serum given after infection, brainstem infection was significantly reduced in a time-dependent manner. A delay in disease onset and a reduction of disease severity and mortality were also observed. Thus, EV71 can directly infect the brainstem, including the medulla, via cranial nerves, most likely by retrograde axonal transport. This may explain the sudden cardiorespiratory collapse in human patients with fatal encephalomyelitis. Moreover, our results suggest that passive immunization may still benefit EV71-infected patients who have neurologic complications.
  7. Lau YL, Chang PY, Tan CT, Fong MY, Mahmud R, Wong KT
    Am J Trop Med Hyg, 2014 Feb;90(2):361-4.
    PMID: 24420776 DOI: 10.4269/ajtmh.12-0678
    Sarcocystis nesbitti is an intracellular protozoan parasite found as sarcocysts within muscle fibers of intermediate hosts (monkey and baboon). The definitive host is suspected to be the snake. We report two cases from a larger cohort of 89 patients who had fever, headache, and generalized myalgia after a trip to Pangkor Island, Malaysia. Sarcocysts were detected in skeletal muscle biopsy specimens by light and electron microscopy from these two patients. DNA sequencing based on the 18S ribosomal DNA region identified the Sarcocystis species as S. nesbitti. We also identified S. nesbitti sequences in the stools of a snake (Naja naja). Phylogenetic analysis showed that these sequences form a cluster with most of the other known Sarcocystis species for which the snake is a definitive host. We believe these two patients were likely to have symptomatic acute muscular sarcocystosis after S. nesbitti infection that may have originated from snakes.
  8. Wong KT
    Acta Neuropathol., 2010 Sep;120(3):317-25.
    PMID: 20652579 DOI: 10.1007/s00401-010-0720-z
    In the last few decades, there is an increasing emergence and re-emergence of viruses, such as West Nile virus, Enterovirus 71 and henipaviruses that cause epidemic viral encephalitis and other central nervous system (CNS) manifestations. The mortality and morbidity associated with these outbreaks are significant and frequently severe. While aspects of epidemiology, basic virology, etc., may be known, the pathology and pathogenesis are often less so, partly due to a lack of interest among pathologists or because many of these infections are considered "third world" diseases. In the study of epidemic viral encephalitis, the pathologist's role in unravelling the pathology and pathogenesis is critical. The novel henipavirus infection is a good example. The newly created genus Henipavirus within the family Paramyxoviridae consists of two viruses, viz., Hendra virus and Nipah virus. These two viruses emerged in Australia and Asia, respectively, to cause severe encephalitides in humans and animals. Studies show that the pathological features of the acute encephalitis caused by henipaviruses are similar and a unique dual pathogenetic mechanism of vasculitis-induced microinfarction and parenchymal cell infection in the CNS (mainly neurons) and other organs causes severe tissue damage. Both viruses can cause relapsing encephalitis months and years after the acute infection due to a true recurrent infection as evidenced by the presence of virus in infected cells. Future emerging viral encephalitides will no doubt continue to pose considerable challenges to the neuropathologist, and as the West Nile virus outbreak demonstrates, even economically advanced nations are not spared.
  9. Ong KC, Devi S, Cardosa MJ, Wong KT
    J Virol, 2010 Jan;84(1):661-5.
    PMID: 19864378 DOI: 10.1128/JVI.00999-09
    Enterovirus 71 (EV71) causes childhood hand, foot, and mouth disease and neurological complications, and no vaccines or therapeutic drugs are currently available. Formaldehyde-inactivated whole-virus vaccines derived from EV71 clinical isolates and a mouse-adapted virus (MAV) were tested in a mouse model of EV71 encephalomyelitis. After only two immunizations, given to mice at 1 and 7 days of age, the MAV vaccine protected mice at 14 days of age from disease. Tissues from immunized mice were negative for virus by viral culture, reverse transcriptase PCR, immunohistochemistry analysis, and in situ hybridization. Cross-neutralizing EV71 antibodies to strains with genotypes B3, B4, and C1 to C5 generated in immunized adult mice were able to passively protect 14-day-old mice from disease.
  10. Yaiw KC, Hyatt A, Vandriel R, Crameri SG, Eaton B, Wong MH, et al.
    Arch Virol, 2008;153(5):865-75.
    PMID: 18330496 DOI: 10.1007/s00705-008-0059-0
    Tioman virus (TioPV) and Menangle virus (MenPV) are two antigenically and genetically related paramyxoviruses (genus: Rubulavirus, family: Paramyxoviridae) isolated from Peninsular Malaysia (2001) and Australia (1997), respectively. Both viruses are potential zoonotic agents. In the present study, the infectivity, growth kinetics, morphology and morphogenesis of these two paramyxoviruses in a human neuronal cell (SK-N-SH) line were investigated. Sub-confluent SK-N-SH cells were infected with TioPV and MenPV at similar multiplicity of infection. These cells were examined by conventional and immunoelectron microscopy, and virus titres in the supernatants were assayed. Syncytia were observed for both infections in SK-N-SH cells and were more pronounced during the early stages of TioPV infection. The TioPV titre increased consistently (10(1)) every 12 h after infection. In MenPV-infected cells, cellular material was frequently observed within budding virions, and microfilaments and microtubules were abundant. Viral budding was common, and extracellular MenPVs tended to be more pleomorphic compared to TioPVs, which appeared to be more spherical in appearance. The MenPV cytoplasmic viral inclusion appeared to be comparatively smaller, loose and interspersed with randomly scattered circle-like particles, whereas huge tubule-like cytoplasmic inclusions were observed in TioPV-infected cells. Both viruses also displayed different cellular pathology in the SK-N-SH cells. The intracellular ultrastructural characteristics of these two viruses in infected neuronal cells may allow them to be differentiated by electron microscopy.
  11. Ong KC, Badmanathan M, Devi S, Leong KL, Cardosa MJ, Wong KT
    J. Neuropathol. Exp. Neurol., 2008 Jun;67(6):532-42.
    PMID: 18520772 DOI: 10.1097/NEN.0b013e31817713e7
    We describe a model of Enterovirus 71 encephalomyelitis in 2-week-old mice that shares many features with the human central nervous system (CNS) disease. Mice were infected via oral and parenteral routes with a murine-adapted virus strain originally from a fatal human case. The mice succumbed to infection after 2 to 5 days. Vacuolated and normal-appearing CNS neurons showed viral RNA and antigens and virions by in situ hybridization, immunohistochemistry, and electron microscopy; inflammation was minimal. The most numerous infected neurons were in anterior horns, motor trigeminal nuclei, and brainstem reticular formation; fewer neurons in the red nucleus, lateral cerebellar nucleus, other cranial nerve nuclei, motor cortex, hypothalamus, and thalamus were infected. Other CNS regions, dorsal root, and autonomic ganglia were spared. Intramuscular-inoculated mice killed 24 to 36 hours postinfection had viral RNA and antigens in ipsilateral lumbar anterior horn cells and adjacent axons. Upper cord motor neurons, brainstem, and contralateral motor cortex neurons were infected from 48-72 hours. Viral RNA and antigens were abundant in skeletal muscle and adjacent tissues but not in other organs. The distinct, stereotypic viral distribution in this model suggests that the virus enters the CNS via peripheral motor nerves after skeletal muscle infection, and spread within the CNS involves motor and other neural pathways. This model may be useful for further studies on pathogenesis and for testing therapies.
  12. Murty OP, Mun K, Gopinath N, Wong KT
    Am J Forensic Med Pathol, 2008 Dec;29(4):364-7.
    PMID: 19259028 DOI: 10.1097/PAF.0b013e3181859ff7
    Every body has to eat to survive but it becomes a matter of great concern, when the life provider food becomes an asphyxiating agent. In this case, a 60-year-old woman choked herself while swallowing biscuits. On autopsy examination, biscuits were found lodged in larygo-pharynx. Brain showed marked dystrophy and loosened lusterless white matter. On histopathologic examination, brain tissue had numerous eosinophilic globules representing astrocytic processes called "Rosenthal fibers"; hence, it was diagnosed as a case of Alexander dystrophy. It is a disease of white matter, where there is a progressive degeneration of the white matter of the brain because of imperfect growth or development of the myelin sheath. The histopathology of brain showed Rosenthal fibers in abundance. This is one of the rarest disease in which choking can occur because of lack of nervous and muscular coordination and weakness. Its specific relation to choking is documented in this report.
  13. Thong MK, Bazlin RI, Wong KT
    Dev Med Child Neurol, 2005 Jul;47(7):474-7.
    PMID: 15991868
    Clinical data on Duchenne muscular dystrophy (DMD) are lacking in developing countries. The objective of this study was to delineate the demographic characteristics, investigations, and outcome of 21 Malaysian males diagnosed with DMD over a period of 10 years. Mean age presentation was 3 years 8 months (SD 23mo; range 10 to 84mo), mean duration from first presentation to diagnosis was 3y 7mo (SD 26mo; range 5 to 84) and the mean age for loss of ambulation was 11 years (SD 25mo; range 102 to 168). There was family history of DMD in five of the 21 patients. Muscle biopsy showed confirmatory findings of DMD in the 16 patients tested. Molecular genetic analysis showed dystrophin gene deletions in 11 of these 16 patients. Four and seven of the students stopped schooling and had learning difficulties, respectively; only nine had satisfactory school performances. Eight out of 14 patients evaluated were classified as having severe to total dependency levels on the modified Barthel Index for activities of daily living assessment. DMD is associated with significant medical and social needs for a developing country such as Malaysia. Earlier referral, genetic counselling, and provision of support and rehabilitative services are the main priorities.
  14. Tan SH, Ong KC, Perera D, Wong KT
    Antiviral Res, 2016 Aug;132:196-203.
    PMID: 27340013 DOI: 10.1016/j.antiviral.2016.04.015
    BACKGROUND: Enterovirus A71 (EV-A71) encephalomyelitis is an often fatal disease for which there is no specific treatment available. Passive immunization with a specific monoclonal antibody to EV-A71 was used on a murine model of EV-A71 encephalomyelitis to evaluate its therapeutic effectiveness before and after established central nervous system (CNS) infection.

    METHODS: Mice were intraperitoneally-infected with a mouse-adapted EV-A71 strain and treated with a dose of monoclonal antibody (MAb) daily for 3 days on day 1, 2 and 3 post-infection or for 3 days on 3, 4 and 5 post-infection. Treatment effectiveness was evaluated by signs of infection and survival rate. Histopathology and qPCR analyses were performed on mice sacrificed a day after completing treatment.

    RESULTS: In mock-treated mice, CNS infection was established from day 3 post-infection. All mice treated before established CNS infection, survived and recovered completely without CNS infection. All mice treated after established CNS infection survived with mild paralysis, and viral load and antigens/RNA at day 6 post-infection were significantly reduced.

    CONCLUSIONS: Passive immunization with our MAb could prevent CNS infection in mice if given early before the establishment of CNS infection. It could also ameliorate established CNS infection if optimal and repeated doses were given.

  15. Phyu WK, Ong KC, Wong KT
    PLoS One, 2016;11(1):e0147463.
    PMID: 26815859 DOI: 10.1371/journal.pone.0147463
    Enterovirus A71 (EV-A71) causes self-limiting, hand-foot-and-mouth disease (HFMD) that may rarely be complicated by encephalomyelitis. Person-to-person transmission is usually by fecal-oral or oral-oral routes. To study viral replication sites in the oral cavity and other tissues, and to gain further insights into virus shedding and neuropathogenesis, we developed a consistent, orally-infected, 2-week-old hamster model of HFMD and EV-A71 encephalomyelitis. Tissues from orally-infected, 2-week-old hamsters were studied by light microscopy, immunohistochemistry and in situ hybridization to detect viral antigens and RNA, respectively, and by virus titration. Hamsters developed the disease and died after 4-8 days post infection; LD50 was 25 CCID50. Macroscopic cutaneous lesions around the oral cavity and paws were observed. Squamous epithelium in the lip, oral cavity, paw, skin, and esophagus, showed multiple small inflammatory foci around squamous cells that demonstrated viral antigens/RNA. Neurons (brainstem, spinal cord, sensory ganglia), acinar cells (salivary gland, lacrimal gland), lymphoid cells (lymph node, spleen), and muscle fibres (skeletal, cardiac and smooth muscles), liver and gastric epithelium also showed varying amounts of viral antigens/RNA. Intestinal epithelium, Peyer's patches, thymus, pancreas, lung and kidney were negative. Virus was isolated from oral washes, feces, brain, spinal cord, skeletal muscle, serum, and other tissues. Our animal model should be useful to study squamous epitheliotropism, neuropathogenesis, oral/fecal shedding in EV-A71 infection, person-to-person transmission, and to test anti-viral drugs and vaccines.
  16. Chow TK, Eu LC, Chin KF, Ong KC, Pailoor J, Vadivelu J, et al.
    Am J Trop Med Hyg, 2016 Mar 2;94(3):522-4.
    PMID: 26787155 DOI: 10.4269/ajtmh.15-0774
    We report a rare case of an asymptomatic latent melioidosis lesion in a posttraumatic splenectomy specimen from a diabetic patient. The 2-cm yellowish, lobulated lesion was found in the splenic parenchyma well away from the traumatized areas. Microscopically, it consisted of a central area of necrosis and exudate surrounded by macrophages, epithelioid cells, lymphocytes, and occasional multinucleated giant cells. Burkholderia bacilli were detected by a novel in situ hybridization (ISH) assay, and confirmed by polymerase chain reaction and sequencing to be Burkholderia pseudomallei. As melioidosis was not suspected initially, bacterial culture was not done but electron microscopy showed morphologically viable and dividing bacilli in the lesion. Moreover, the surgical wound became infected with B. pseudomallei several days post-surgery. After treatment with ceftazidime and trimethoprim/sulfamethoxazole, the wound infection cleared. We believe this could be a unique case of asymptomatic latent melioidosis in the spleen. In endemic countries, chronic granulomas should be investigated for B. pseudomallei infection, and if available, ISH may be helpful for diagnosis.
  17. Tan CT, Wong KT
    Ann Acad Med Singap, 2003 Jan;32(1):112-7.
    PMID: 12625108
    INTRODUCTION: Between September 1998 and June 1999, there was a severe outbreak of viral encephalitis among the pig farm workers in Malaysia.

    METHODS: This is a review of the published literature related to the outbreak with the focus on human diseases.

    RESULTS: The encephalitis was caused by a newly discovered paramyxovirus related to Hendra virus, later named Nipah virus. There were 265 patients with acute encephalitis. The disease is thought to spread from pig to man through close contact. The risk of human-to-human spread is thought to below. The disease affected mainly adult Chinese males, half of whom had affected family members. The disease presented mainly as acute encephalitis with a short incubation period of less than two weeks, with the main symptoms of fever, headache, and giddiness followed by coma. Distinctive clinical signs include segmental myoclonus, areflexia and hypotonia, hypertension, and tachycardia. Initial cerebrospinal fluid was abnormal in 75% of patients. Serology was helpful in confirming the diagnosis. Magnetic resonance imaging showed distinctive changes of multiple, discrete, and small high signal lesions, best seen with fluid-attenuated inversion recovery (FLAIR) sequences. Mortality was high at 40% and death was probably due to severe brainstem involvement. The main necropsy finding in acute encephalitis was that of disseminated microinfarction associated with vasculitis and direct neuronal involvement. Ribavirin was able to reduce the mortality by 36%. Relapse encephalitis was seen in 7.5% of those who recovered from acute encephalitis, and late-onset encephalitis in 3.4% of those with initial non-encephalitic or asymptomatic diseases. The mean interval between initial illness and the onset of the complication was 8.4 months. The relapse and late-onset encephalitis which manifested as focal encephalitis arose from recurrent infection.

    CONCLUSION: Nipah virus, a recently discovered paramyxovirus, causes a unique encephalitis with high mortality as well as relapse and late-onset encephalitis. The infection is mainly spread from pigs to man.

  18. Wong KT
    Neuropathol. Appl. Neurobiol., 2000 Aug;26(4):313-8.
    PMID: 10931364
    Two major epidemics of viral encephalitis occurred in Asia in 1997 and 1998. The first was a re-emergence of neurovirulent strains of enterovirus 71, which caused severe encephalomyelitis in children in Malaysia, Taiwan and Japan, on a background of hand, foot and mouth disease. Necropsy studies of patients who died of enterovirus 71 infection showed severe perivascular cuffing, parenchymal inflammation and neuronophagia in the spinal cord, brainstem and diencephalon, and in focal areas in the cerebellum and cerebrum. Although no viral inclusions were detected, immunohistochemistry showed viral antigen in the neuronal cytoplasm. Inflammation was often more extensive than neuronal infection, suggesting that other factors, in addition to direct viral cytolysis, may be involved in tissue damage. The second epidemic of viral encephalitis was the result of a novel paramyxovirus called Nipah, which mainly involved pig handlers in Malaysia and Singapore. Pathological evidence suggested that the endothelium of small blood vessels in the central nervous system was particularly susceptible to infection. This led to disseminated endothelial damage and syncytium formation, vasculitis, thrombosis, ischaemia and microinfarction. However, there was also evidence of neuronal infection by the virus and this may also have contributed to the neurological dysfunction in Nipah encephalitis. Some patients who seemed to recover from the acute symptoms have been re-admitted with clinical findings suggestive of relapsing encephalitis. As these two epidemics indicate, the emergence and re-emergence of viral encephalitides continue to pose considerable challenges to the neuropathologist, in establishing the diagnosis and unravelling the pathogenesis of the neurological disease.
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