MyMedR

Fulltext Avoid haste in defining human muscular sarcocystosis

Italiano CM, Wong KT, AbuBakar S, Lau YL, Ramli N, Syed Omar SF, et al.

Clin Infect Dis, 2015 Apr 1;60(7):1134.

Detection of human malaria using recombinant Plasmodium knowlesi merozoire surface protein-1 (MSP-1₁₉) expressed in Escherichia coli

Sonaimuthu P, Cheong FW, Chin LC, Mahmud R, Fong MY, Lau YL

Exp Parasitol, 2015 Jun;153:118-22.

PMID: 25812552 DOI: 10.1016/j.exppara.2015.03.010

Malaria remains one of the world's most important infectious diseases and is responsible for enormous mortality and morbidity. Human infection with Plasmodium knowlesi is widely distributed in Southeast Asia. Merozoite surface protein-1₁₉ (MSP-1₁₉), which plays an important role in protective immunity against asexual blood stage malaria parasites, appears as a leading immunogenic antigen of Plasmodium sp. We evaluated the sensitivity and specificity of recombinant P. knowlesi MSP-1₁₉ (rMSP-1₁₉) for detection of malarial infection. rMSP-1₁₉ was expressed in Escherichia coli expression system and the purified rMSP-1₁₉ was evaluated with malaria, non-malaria and healthy human serum samples (n = 215) in immunoblots. The sensitivity of rMSP-1₁₉ for detection of P. knowlesi, Plasmodium falciparum, Plasmodium vivax and Plasmodium ovale infection was 95.5%, 75.0%, 85.7% and 100%, respectively. rMSP-1₁₉ did not react with all the non-malaria and healthy donor sera, which represents 100% specificity. The rMSP-1₁₉ could be used as a potential antigen in serodiagnosis of malarial infection in humans.

Autoantibody profile of patients infected with knowlesi malaria

Liew J, Amir A, Chen Y, Fong MY, Razali R, Lau YL

Clin Chim Acta, 2015 Aug 25;448:33-8.

PMID: 26086445 DOI: 10.1016/j.cca.2015.06.006

Autoantibodies or antibodies against self-antigens are produced either during physiological processes to maintain homeostasis or pathological process such as trauma and infection. Infection with parasites including Plasmodium has been shown to generally induce elevated self-antibody (autoantibody) levels. Plasmodium knowlesi is increasingly recognized as one of the most important emerging human malaria in Southeast Asia that can cause severe infection leading to mortality. Autoimmune-like phenomena have been hypothesized to play a role in the protective immune responses in malaria infection.

Modified use of methylene blue in the tissue compression technique to detect sarcocysts in meat-producing animals

Ng YH, Subramaniam V, Lau YL

Vet Parasitol, 2015 Nov 30;214(1-2):200-3.

PMID: 26455572 DOI: 10.1016/j.vetpar.2015.09.032

Sarcocystosis in meat-producing animals is a major cause of reduced productivity in many countries, especially those that rely on agriculture. Although several diagnostic methods are available to detect sarcocystosis, many are too time-consuming for routine use in abattoirs and meat inspection centers, where large numbers of samples need to be tested. This study aimed to compare the sensitivity of the methylene blue tissue preparation, unstained tissue preparation and nested PCR in the detection of sarcocysts in tissue samples. Approximately three-fold more sarcocysts were detected in methylene blue-stained tissue compared to unstained controls (McNemar's test: P<0.01). Test sensitivity was comparable to that of the gold standard for sarcocyst detection, nested polymerase chain reaction. These results suggest that methylene blue can be used in tissue compression as a rapid, safe, and inexpensive technique for the detection of ruminant sarcocystosis in abattoirs.

Genetic polymorphism in domain I of the apical membrane antigen-1 among Plasmodium knowlesi clinical isolates from Peninsular Malaysia

Fong MY, Wong SS, Silva JR, Lau YL

Acta Trop, 2015 Dec;152:145-150.

PMID: 26384455 DOI: 10.1016/j.actatropica.2015.09.009

The simian malaria parasite Plasmodium knowlesi is now recognized as a species that can cause human malaria. The first report of large scale human knowlesi malaria was in 2004 in Malaysia Borneo. Since then, hundreds of human knowlesi malaria cases have been reported in Southeast Asia. The present study investigates the genetic polymorphism of P. knowlesi DI domain of the apical membrane antigen-1 (AMA-1), a protein considered as a promising vaccine candidate for malaria. The DI domain of AMA-1 gene of P. knowlesi clinical isolates from Peninsular Malaysia was amplified by PCR, cloned into Escherichia coli, then sequenced and analysed. Ninety-seven DI domain sequences were obtained. Comparison at the nucleotide level against P. knowlesi strain H as reference sequence showed 21 synonymous and 25 nonsynonymous mutations. Nonetheless, nucleotide sequence analysis revealed low genetic diversity of the DI domain, and it was under purifying (negative) selection. At the amino acid level, 26 different haplotypes were identified and 2 were predominant haplotypes (H1, H2) with high frequencies. Phylogenetic analysis revealed that the 26 haplotypes could be clustered into 2 distinct groups (I and II). Members of the groups were basically derived from haplotypes H1 and H2, respectively.

Compound heterozygous mutations in TTC7A cause familial multiple intestinal atresias and severe combined immunodeficiency

Yang W, Lee PP, Thong MK, Ramanujam TM, Shanmugam A, Koh MT, et al.

Clin Genet, 2015 Dec;88(6):542-9.

PMID: 25534311 DOI: 10.1111/cge.12553

Familial multiple intestinal atresias is an autosomal recessive disease with or without combined immunodeficiency. In the last year, several reports have described mutations in the gene TTC7A as causal to the disease in different populations. However, exact correlation between different genotypes and various phenotypes are not clear. In this study, we report identification of novel compound heterozygous mutations in TTC7A gene in a Malay girl with familial multiple intestinal atresias and severe combined immunodeficiency (MIA-SCID) by whole exome sequencing. We found two mutations in TTC7A: one that destroyed a putative splicing acceptor at the junction of intron 17/exon 18 and one that introduced a stop codon that would truncate the last two amino acids of the encoded protein. Reviewing the recent reports on TTC7A mutations reveals correlation between the position and nature of the mutations with patient survival and clinical manifestations. Examination of public databases also suggests carrier status for healthy individuals, making a case for population screening on this gene, especially in populations with suspected frequent founder mutations.

Short communication: Genetic variants of Sarcocystis cruzi in infected Malaysian cattle based on 18S rDNA

Ng YH, Fong MY, Subramaniam V, Shahari S, Lau YL

Res Vet Sci, 2015 Dec;103:201-4.

PMID: 26679818 DOI: 10.1016/j.rvsc.2015.10.009

Sarcocystis species are pathogenic parasites that infect a wide range of animals, including cattle. A high prevalence of cattle sarcocystosis has been reported worldwide, but its status is unknown in Malaysia. This study focused on utilizing 18S rDNA to identify Sarcocystis species in Malaysian cattle and to determine their genetic variants. In this study, only Sarcocystis cruzi was detected in Malaysian cattle. The intra-species S. cruzi phylogenetic tree analysis and principal coordinate analysis (PCoA), respectively displayed two minor groups among the parasite isolates. This finding was supported by high Wright FST value (FST=0.647). The definitive hosts (dogs) may play a fundamental role in the development of S. cruzi genetic variants. Additionally, the existence of microheterogeneity within the S. cruzi merozoites and/or distinct genetic variants arisen from independent merozoites in mature sarcocysts, possibly contributed to the existence of intra-species variations within the population.

Fulltext Identification of circulating biomarkers in sera of Plasmodium knowlesi-infected malaria patients--comparison against Plasmodium vivax infection

Chen Y, Chan CK, Kerishnan JP, Lau YL, Wong YL, Gopinath SC

BMC Infect Dis, 2015;15:49.

PMID: 25656928 DOI: 10.1186/s12879-015-0786-2

Plasmodium knowlesi was identified as the fifth major malaria parasite in humans. It presents severe clinical symptoms and leads to mortality as a result of hyperparasitemia in a short period of time. This study aimed to improve the current understanding of P. knowlesi and identify potential biomarkers for knowlesi malaria.

Fulltext Genetic Diversity and Natural Selection of the Plasmodium knowlesi Circumsporozoite Protein Nonrepeat Regions

Fong MY, Ahmed MA, Wong SS, Lau YL, Sitam F

PLoS One, 2015;10(9):e0137734.

PMID: 26379157 DOI: 10.1371/journal.pone.0137734

Plasmodium knowlesi is a simian malaria parasite that has been identified to cause malaria in humans. To date, several thousand cases of human knowlesi malaria have been reported around Southeast Asia. Thus far, there is no detailed study on genetic diversity and natural selection of P. knowlesi circumsporozoite protein (CSP), a prominent surface antigen on the sporozoite of the parasite. In the present study, the genetic diversity and natural selection acting on the nonrepeat regions of the gene encoding P. knowlesi CSP were investigated, focusing on the T-cell epitope regions at the C-terminal of the protein.

Fulltext Draft genome of Brugia pahangi: high similarity between B. pahangi and B. malayi

Lau YL, Lee WC, Xia J, Zhang G, Razali R, Anwar A, et al.

Parasit Vectors, 2015;8:451.

PMID: 26350613 DOI: 10.1186/s13071-015-1064-2

Efforts to completely eradicate lymphatic filariasis from human population may be challenged by the emergence of Brugia pahangi as another zoonotic lymphatic filarial nematode. In this report, a genomic study was conducted to understand this species at molecular level.

Fulltext Colorimetric Detection of Dengue by Single Tube Reverse-Transcription-Loop-Mediated Isothermal Amplification

Lau YL, Lai MY, Teoh BT, Abd-Jamil J, Johari J, Sam SS, et al.

PLoS One, 2015;10(9):e0138694.

PMID: 26384248 DOI: 10.1371/journal.pone.0138694

Dengue is usually diagnosed by isolation of the virus, serology or molecular diagnostic methods. Several commercial kits for the diagnosis of dengue are existing, but concerns have arisen regarding to the affordability and performance characteristics of these kits. Hence, the loop-mediated isothermal amplification (LAMP) is potentially ideal to be used especially in resource limited environments. Serum was collected from healthy donors and patients diagnosed with dengue infection. RNA extracted from the serum samples were tested by reverse-transcription-LAMP assay developed based on 3'-NCR gene sequences for DENV 1-4. Results were interpreted by a turbidity meter in real time or visually at the end of the assay. Sensitivity and specificity of RT-LAMP results were calculated and compared to qRT-PCR and ELISA. RT-LAMP is highly sensitive with the detection limit of 10 RNA copies for all serotypes. Dengue virus RNA was detected in all positive samples using RT-LAMP and none of the negative samples within 30-45 minutes. With continuing efforts in the optimization of this assay, RT-LAMP may provide a simple and reliable test for detecting DENV in areas where dengue is prevalent.

Fulltext First report of brown widow spider sightings in Peninsular Malaysia and notes on its global distribution

Muslimin M, Wilson JJ, Ghazali AR, Braima KA, Jeffery J, Wan-Nor F, et al.

J Venom Anim Toxins Incl Trop Dis, 2015;21:11.

PMID: 25995738 DOI: 10.1186/s40409-015-0010-2

The brown widow spider (Latrodectus geometricus Koch, 1841) has colonised many parts of the world from its continent of origin, Africa. By at least 1841, the species had successfully established populations in South America and has more recently expanded its range to the southern states of North America. This highly adaptable spider has been far more successful in finding its niche around the world than its famous cousins, the black widow, Latrodectus mactans, found in the south-eastern states of North America, and the red-back, Latrodectus hasselti, found mostly in Australia, New Zealand and Japan.

Fulltext Genetic variation of pfhrp2 in Plasmodium falciparum isolates from Yemen and the performance of HRP2-based malaria rapid diagnostic test

Atroosh WM, Al-Mekhlafi HM, Al-Jasari A, Sady H, Al-Delaimy AK, Nasr NA, et al.

Parasit Vectors, 2015;8:388.

PMID: 26198252 DOI: 10.1186/s13071-015-1008-x

The genetic variation in the Plasmodium falciparum histidine-rich protein 2 (pfhrp2) gene that may compromise the use of pfhrp2-based rapid diagnostic tests (RDTs) for the diagnosis of malaria was assessed in P. falciparum isolates from Yemen.

Fulltext Distinct genetic difference between the Duffy binding protein (PkDBPαII) of Plasmodium knowlesi clinical isolates from North Borneo and Peninsular Malaysia

Fong MY, Rashdi SA, Yusof R, Lau YL

Malar J, 2015;14:91.

PMID: 25890095 DOI: 10.1186/s12936-015-0610-x

Plasmodium knowlesi is one of the monkey malaria parasites that can cause human malaria. The Duffy binding protein of P. knowlesi (PkDBPαII) is essential for the parasite's invasion into human and monkey erythrocytes. A previous study on P. knowlesi clinical isolates from Peninsular Malaysia reported high level of genetic diversity in the PkDBPαII. Furthermore, 36 amino acid haplotypes were identified and these haplotypes could be separated into allele group I and allele group II. In the present study, the PkDBPαII of clinical isolates from the Malaysian states of Sarawak and Sabah in North Borneo was investigated, and compared with the PkDBPαII of Peninsular Malaysia isolates.

Fulltext A Basis for Rapid Clearance of Circulating Ring-Stage Malaria Parasites by the Spiroindolone KAE609

Zhang R, Suwanarusk R, Malleret B, Cooke BM, Nosten F, Lau YL, et al.

J Infect Dis, 2016 Jan 1;213(1):100-4.

PMID: 26136472 DOI: 10.1093/infdis/jiv358

Recent clinical trials revealed a surprisingly rapid clearance of red blood cells (RBCs) infected with malaria parasites by the spiroindolone KAE609. Here, we show that ring-stage parasite-infected RBCs exposed to KAE609 become spherical and rigid, probably through osmotic dysregulation consequent to the disruption of the parasite's sodium efflux pump (adenosine triphosphate 4). We also show that this peculiar drug effect is likely to cause accelerated splenic clearance of the rheologically impaired Plasmodium vivax- and Plasmodium falciparum-infected RBCs.

Evaluation of new multiplex PCR primers for the identification ofPlasmodium species found in Sabah, Malaysia

Stanis CS, Song BK, Chua TH, Lau YL, Jelip J

Turk J Med Sci, 2016 Jan 05;46(1):207-18.

PMID: 27511356 DOI: 10.3906/sag-1411-114

BACKGROUND/AIM: Malaria is a major public health problem, especially in the Southeast Asia region, caused by 5 species of Plasmodium (P. falciparum, P. vivax, P. malariae, P. ovale, and P. knowlesi). The aim of this study was to compare parasite species identification methods using the new multiplex polymerase chain reaction (PCR) against nested PCR and microscopy.

MATERIALS AND METHODS: Blood samples on filter papers were subject to conventional PCR methods using primers designed by us in multiplex PCR and previously designed primers of nested PCR. Both sets of results were compared with microscopic identification.

RESULTS: Of the 129 samples identified as malaria-positive by microscopy, 15 samples were positive for P. falciparum, 14 for P. vivax, 6 for P. knowlesi, 72 for P. malariae, and 2 for mixed infection of P. falciparum/P. malariae. Both multiplex and nested PCR identified 12 P. falciparum single infections. For P. vivax, 9 were identified by multiplex and 12 by nested PCR. For 72 P. malariae cases, multiplex PCR identified 58 as P. knowlesi and 10 as P. malariae compared to nested PCR, which identified 59 as P. knowlesi and 7 as P. malariae.

CONCLUSION: Multiplex PCR could be used as alternative molecular diagnosis for the identification of all Plasmodium species as it requires a shorter time to screen a large number of samples.

Fulltext Field evaluation of a PfHRP-2/pLDH rapid diagnostic test and light microscopy for diagnosis and screening of falciparum malaria during the peak seasonal transmission in an endemic area in Yemen

Alareqi LM, Mahdy MA, Lau YL, Fong MY, Abdul-Ghani R, Ali AA, et al.

Malar J, 2016 Jan 28;15:49.

PMID: 26821911 DOI: 10.1186/s12936-016-1103-2

Malaria is a public health threat in Yemen, with 149,451 cases being reported in 2013. Of these, Plasmodium falciparum represents 99%. Prompt diagnosis by light microscopy (LM) and rapid diagnostic tests (RTDs) is a key element in the national strategy of malaria control. The heterogeneous epidemiology of malaria in the country necessitates the field evaluation of the current diagnostic strategies, especially RDTs. Thus, the present study aimed to evaluate LM and an RDT, combining both P. falciparum histidine-rich protein-2 (PfHRP-2) and Plasmodium lactate dehydrogenase (pLDH), for falciparum malaria diagnosis and survey in a malaria-endemic area during the transmission season against nested polymerase chain reaction (PCR) as the reference method.

Fulltext Loop-Mediated Isothermal Amplification Assay for Identification of Five Human Plasmodium Species in Malaysia

Lau YL, Lai MY, Fong MY, Jelip J, Mahmud R

Am J Trop Med Hyg, 2016 Feb;94(2):336-339.

PMID: 26598573 DOI: 10.4269/ajtmh.15-0569

The lack of rapid, affordable, and accurate diagnostic tests represents the primary hurdle affecting malaria surveillance in resource- and expertise-limited areas. Loop-mediated isothermal amplification (LAMP) is a sensitive, rapid, and cheap diagnostic method. Five species-specific LAMP assays were developed based on 18S rRNA gene. Sensitivity and specificity of LAMP results were calculated as compared with microscopic examination and nested polymerase chain reaction. LAMP reactions were highly sensitive with the detection limit of one copy for Plasmodium vivax, Plasmodium falciparum, and Plasmodium malariae and 10 copies for Plasmodium knowlesi and Plasmodium ovale. LAMP positively detected all human malaria species in all positive samples (N = 134; sensitivity = 100%) within 35 minutes. All negative samples were not amplified by LAMP (N = 67; specificity = 100%). LAMP successfully detected two samples with very low parasitemia. LAMP may offer a rapid, simple, and reliable test for the diagnosis of malaria in areas where malaria is prevalent.

Identification and characterization of epitopes on Plasmodium knowlesi merozoite surface protein-142 (MSP-142) using synthetic peptide library and phage display library

Cheong FW, Fong MY, Lau YL

Acta Trop, 2016 Feb;154:89-94.

PMID: 26624919 DOI: 10.1016/j.actatropica.2015.11.005

Plasmodium knowlesi can cause potentially life threatening human malaria. The Plasmodium merozoite surface protein-142 (MSP-142) is a potential target for malaria blood stage vaccine, and for diagnosis of malaria. Two epitope mapping techniques were used to identify the potential epitopes within P. knowlesi MSP-142. Nine and 14 potential epitopes were identified using overlapping synthetic peptide library and phage display library, respectively. Two regions on P. knowlesi MSP-142 (amino acid residues 37-95 and residues 240-289) were identified to be the potential dominant epitope regions. Two of the prominent epitopes, P10 (TAKDGMEYYNKMGELYKQ) and P31 (RCLLGFKEVGGKCVPASI), were evaluated using mouse model. P10- and P31-immunized mouse sera reacted with recombinant P. knowlesi MSP-142, with the IgG isotype distribution of IgG2b>IgG1>IgG2a>IgG3. Significant higher level of cytokines interferon-gamma and interleukin-2 was detected in P31-immunized mice. Both P10 and P31 could be the suitable epitope candidates to be used in malaria vaccine designs and immunodiagnostic assays, provided further evaluation is needed to validate the potential uses of these epitopes.

Fulltext Invasion characteristics of a Plasmodium knowlesi line newly isolated from a human

Amir A, Russell B, Liew JW, Moon RW, Fong MY, Vythilingam I, et al.

Sci Rep, 2016 Apr 21;6:24623.

PMID: 27097521 DOI: 10.1038/srep24623

Plasmodium knowlesi is extensively used as an important malaria model and is now recognized as an important cause of human malaria in Malaysia. The strains of P. knowlesi currently used for research were isolated many decades ago, raising concerns that they might no longer be representative of contemporary parasite populations. We derived a new P. knowlesi line (University Malaya line, UM01), from a patient admitted in Kuala Lumpur, Malaysia, and compared it with a human-adapted laboratory line (A1-H.1) derived from the P. knowlesi H strain. The UM01 and A1-H.1 lines readily invade human and macaque (Macaca fascicularis) normocytes with a preference for reticulocytes. Whereas invasion of human red blood cells was dependent on the presence of the Duffy antigen/receptor for chemokines (DARC) for both parasite lines, this was not the case for macaque red blood cells. Nonetheless, differences in invasion efficiency, gametocyte production and the length of the asexual cycle were noted between the two lines. It would be judicious to isolate and characterise numerous P. knowlesi lines for use in future experimental investigations of this zoonotic species.

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