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Fulltext Evaluation of WarmStart Colorimetric Loop-Mediated Isothermal Amplification Assay for Diagnosis of Malaria

Lai MY, Ooi CH, Jaimin JJ, Lau YL

Am J Trop Med Hyg, 2020 06;102(6):1370-1372.
PMID: 32228783 DOI: 10.4269/ajtmh.20-0001

The incidence of zoonotic malaria, Plasmodium knowlesi, infection is increasing and now is the major cause of malaria in Malaysia. Here, we describe a WarmStart colorimetric loop-mediated isothermal amplification (LAMP) assay for the detection of Plasmodium spp. The detection limit for this assay was 10 copies/µL for P knowlesi and Plasmodium ovale and 1 copy/µL for Plasmodium falciparum, Plasmodium vivax, and Plasmodium malariae. To test clinical sensitivity and specificity, 100 microscopy-positive and 20 malaria-negative samples were used. The WarmStart colorimetric LAMP was 98% sensitive and 100% specific. Amplification products were visible for direct observation, thereby eliminating the need for post-amplification processing steps. Therefore, WarmStart colorimetric LAMP is suitable for use in resource-limited settings.
Genetic polymorphism of circumsporozoite protein (CSP) in Plasmodium malariae isolates from Malaysia

Phang WK, Bukhari FDM, Zen LPY, Jaimin JJ, Dony JJF, Lau YL

Parasitol Int, 2022 Apr;87:102519.
PMID: 34800724 DOI: 10.1016/j.parint.2021.102519

Information about Plasmodium malariae is scanty worldwide due to its "benign" nature and low infection rates. Consequently, studies on the genetic polymorphisms of P. malariae are lacking. Here, we report genetic polymorphisms of 28 P. malariae circumsporozoite protein (Pmcsp) isolates from Malaysia which were compared with those in other regions in Asia as well as those from Africa. Phylogenetic analysis revealed that most Malaysian P. malariae isolates clustered together but independently from other Asian isolates. Low nucleotide diversity was observed in Pmcsp non-repeat regions in contrast to high nucleotide diversity observed in non-repeat regions of Plasmodium knowlesi CSP gene, the current major cause of malaria in Malaysia. This study contributes to the characterisation of naturally occurring polymorphisms in the P. malariae CSP gene.
Corrigendum to "Genetic polymorphism of circumsporozoite protein (CSP) in Plasmodium malariae isolates from Malaysia" [Parasitology International Volume 87, April 2022, 102519]

Phang WK, Bukhari FDM, Zen LPY, Jaimin JJ, Dony JJF, Lau YL

Parasitol Int, 2024 Feb;98:102811.
PMID: 37827924 DOI: 10.1016/j.parint.2023.102811
Fulltext The east coast districts are the possible epicenter of severe dengue in Sabah

Kaur N, Rahim SSSA, Jaimin JJ, Dony JJF, Khoon KT, Ahmed K

J Physiol Anthropol, 2020 Aug 14;39(1):19.
PMID: 32795350 DOI: 10.1186/s40101-020-00230-0

BACKGROUND: Malaysia recorded the highest number of dengue cases between 2014 and 2017. There are 13 states and three federal territories in Malaysia, and each area varies in their prevalence of dengue. Sabah is one of the states situated in Borneo, Malaysia. Although dengue has been increasing for the last several years, no study was being done to understand the burden and serotype distribution of the dengue virus (DENV) in Sabah. Therefore, the present study was carried out to understand the epidemiology of the dengue infection and the factors responsible for severe dengue in Sabah.
METHODS: Data on dengue infection were extracted from the dengue database of the state of Sabah from 2013 through 2018. DENV NS-1-positive serum samples from multiple sites throughout Sabah were sent to the state public health laboratory, Kota Kinabalu Public Health Laboratory, for serotype determination. The analysis of factors associated with severe dengue was determined from the data of 2018 only.
RESULTS: In 2013, there were 724 dengue cases; however, from 2014, dengue cases increased exponentially and resulted in 3423 cases in 2018. Increasing dengue cases also led to increased dengue mortality. The number of dengue deaths in 2013 was only five which then gradually increased, and in 2018, 29 patients died. This is an increase of 580% from 2013 to 2018. Deaths were considerably more in the districts of the east coast of Sabah compared with districts in the west coast. During the study period, all DENV serotypes could be identified as serotypes circulating in Sabah. In 2018, the predominant serotype was DENV-3. The monthly peak of dengue infection varied in different years. In the logistic regression analysis, it was identified that children were 6.5 times, patients infected with mixed serotype of DENV were 13 times, and cases from the districts of the east coast were 5.2 times more likely to develop severe dengue.
CONCLUSIONS: An increasing trend of dengue infection has been observed in Sabah. The burden of dengue, severe dengue, and mortality was noted especially in the districts of the east coast of Sabah. Severe dengue was most likely developed in children, cases from the east coast, and patients infected with mixed serotype of DENV.
Fulltext Genetic polymorphism of the thrombospondin-related apical merozoite protein (TRAMP) of Plasmodium knowlesi in Malaysia

Ng YL, Lau YL, Hamid MHA, Jelip J, Ooi CH, Mudin RN, et al.

Parasitol Res, 2023 Jan;122(1):195-200.
PMID: 36378331 DOI: 10.1007/s00436-022-07716-z

Plasmodium knowlesi is a simian malaria parasite that causes significant zoonotic infections in Southeast Asia, particularly in Malaysia. The Plasmodium thrombospondin-related apical merozoite protein (TRAMP) plays an essential role in the invasion of the parasite into its host erythrocyte. The present study investigated the genetic polymorphism and natural selection of the full length PkTRAMP from P. knowlesi clinical isolates from Malaysia. Blood samples (n = 40) were collected from P. knowlesi malaria patients from Peninsular Malaysia and Malaysian Borneo. The PkTRAMP gene was amplified using PCR, followed by cloning into a plasmid vector and sequenced. Results showed that the nucleotide diversity of PkTRAMP was low (π: 0.009). Z-test results indicated negative (purifying) selection of PkTRAMP. The alignment of the deduced amino acid sequences of PkTRAMP of Peninsular Malaysia and Malaysian Borneo revealed 38 dimorphic sites. A total of 27 haplotypes were identified from the amino acid sequence alignment. Haplotype analysis revealed that there was no clustering of PkTRAMP from Peninsular Malaysia and Malaysian Borneo.
Genetic diversity of secreted protein with an altered thrombospondin repeat (SPATR) of Plasmodium knowlesi clinical isolates from Malaysia

Azlan UW, Lau YL, Hamid MHA, Jelip J, Ooi CH, Mudin RN, et al.

Trop Biomed, 2022 Dec 01;39(4):504-510.
PMID: 36602208 DOI: 10.47665/tb.39.4.006

The Plasmodium knowlesi secreted protein with an altered thrombospondin repeat (PkSPATR) is an important protein that helps in the parasite's invasion into the host cell. This protein has been regarded as one of the potential vaccine candidates against P. knowlesi infection. This study investigates the genetic diversity and natural selection of PkSPATR gene of P. knowlesi clinical isolates from Malaysia. PCR amplification of the full length PkSPATR gene was performed on 60 blood samples of infected P. knowlesi patients from Peninsular Malaysia and Malaysian Borneo. The amplified PCR products were cloned and sequenced. Sequence analysis of PkSPATR from Malaysia showed higher nucleotide diversity (CDS p: 0.01462) than previously reported Plasmodium vivax PvSPATR (p = 0.0003). PkSPATR from Peninsular Malaysia was observed to have slightly higher diversity (CDS p: 0.01307) than those from Malaysian Borneo (CDS p: 0.01212). Natural selection analysis on PkSPATR indicated significant purifying selection. Multiple amino acid sequence alignment revealed 69 polymorphic sites. The phylogenetic tree and haplotype network did not show any distinct clustering of PkSPATR. The low genetic diversity level, natural selection and absence of clustering implied functional constrains of the PkSPATR protein.