• Parasites, Hosts and Diseases
• /
• v.47 no.2
• /
• pp.139-144
• /
• 2009

The aim of the present study was to investigate antimalarial drug pressure resulting from the clinical use of different antimalarials in Thailand. The phenotypic diversity of the susceptibility profiles of antimalarials, i.e., chloroquine (CQ), quinine (QN), mefloquine (MQ), and artesunate (ARS) in Plasmodium falciparum isolates collected during the period from 1988 to 2003 were studied. P. falciparum isolates from infected patients were collected from the Thai-Cambodian border area at different time periods (1988-1989, 1991-1992, and 2003), during which 3 different patterns of drug use had been implemented: MQ+sulphadoxine (S)+pyrimethamine (P), MQ alone and MQ+ARS, respectively. The in vitro drug susceptibilities were investigated using a method based on the incorporation of $[^3H]$ hypoxanthine. A total of 50 isolates were tested for susceptibilities to CQ, QN, MQ, and ARS. Of these isolates, 19, 16, and 15 were adapted during the periods 1988-1989, 1991-1993, and 2003, respectively. P. falciparum isolates collected during the 3 periods were resistant to CQ. Sensitivities to MQ declined from 1988 to 2003. In contrast, the parasite was sensitive to QN, and similar sensitivity profile patterns were observed during the 3 time periods. There was a significantly positive but weak correlation between the $IC_{50}$ values of CQ and QN, as well as between the $IC_{50}$, values of QN and MQ. Drug pressure has impact on sensitivity of P. falciparum to MQ. A combination therapy of MQ and ARS is being applied to reduce the parasite resistance, and also increasing the efficacy of the drug.

• Parasites, Hosts and Diseases
• /
• v.52 no.4
• /
• pp.377-381
• /
• 2014

Microscopy is considered as the gold standard for malaria diagnosis although its wide application is limited by the requirement of highly experienced microscopists. PCR and serological tests provide efficient diagnostic performance and have been applied for malaria diagnosis and research. The aim of this study was to investigate the diagnostic performance of nested PCR and a recently developed an ELISA-based new rapid diagnosis test (RDT), NovaLisa test kit, for diagnosis of malaria infection, using microscopic method as the gold standard. The performance of nested-PCR as a malaria diagnostic tool is excellent with respect to its high accuracy, sensitivity, specificity, and ability to discriminate Plasmodium species. The sensitivity and specificity of nested-PCR compared with the microscopic method for detection of Plasmodium falciparum, Plasmodium vivax, and P. falciparum/P. vivax mixed infection were 71.4 vs 100%, 100 vs 98.7%, and 100 vs 95.0%, respectively. The sensitivity and specificity of the ELISA-based NovaLisa test kit compared with the microscopic method for detection of Plasmodium genus were 89.0 vs 91.6%, respectively. NovaLisa test kit provided comparable diagnostic performance. Its relatively low cost, simplicity, and rapidity enables large scale field application.

• Proceedings of the Korea Contents Association Conference
• /
• 2016.05a
• /
• pp.187-188
• /
• 2016

열대열 말라리아(Plasmodium falciparum, P. falciparum, P. f) 신속진단키트의 경우, P. falciparum에 특이적인 단백질로써 Histidine Rich Protein 2 (PfHRP2)가 사용되고 있다. 그러나 최근 연구에서 남아메리카와 중앙아메리카를 중심으로 pfhrp2/pfhrp3 유전자가 결여된 P. falciparum 열원충이 나타나는 것으로 보고된 바 있다. 본 연구에서는 생물정보학을 기반으로 PfHRP2 항원 단백질을 대체할 수 있는 새로운 P. falciparum 특이 항원 단백질을 선정하고자, PlasmoDB에서 5,777개의 P. falciparum 관련 단백질 리스트를 얻었다. 이후 NCBI BLAST를 통해 단백질 아미노산 서열을 분석하고 정상인에게 존재하지 않으며, 동시에 다른 말라리아 열원충(P. vivax, P. ovale, P. malariae, P. knowlesi)에도 존재하지 않는 P. falciparum 특이 아미노산 서열을 가진 단백질 15개를 추출하였다. IEDB analysis를 이용하여 에피토프, 수용성, 베타-턴, 접근성, 유연성, 면역원성을 분석하여 높은 평균값을 갖는 상위 3개 단백질을 선별하였다. KEGG pathway와 EMBL-EBI를 통해 선별된 3개 단백질의 혈액내 검출 가능성 및 아미노산 서열의 보존성을 분석하여 최종적으로 Glutamate-Rich Protein (GLURP)을 선정하였다. AIDA를 통해 단백질 아미노산 서열을 이용한 3차 구조 예측으로 GLURP의 구조 및 항체와의 결합을 도식화하였다. 최종적으로 선정한 GLURP는 pfhrp2/pfhrp3 유전자 결여 P. falciparum까지 특이적으로 진단이 가능하여 차세대 P. falciparum 특이 신속진단키트 개발에 도움이 될 수 있을 것으로 기대한다.

• Parasites, Hosts and Diseases
• /
• v.62 no.1
• /
• pp.42-52
• /
• 2024

Antimalarial drugs are an urgently need and crucial tool in the campaign against malaria, which can threaten public health. In this study, we examined the cytotoxicity of the 9 antimalarial compounds chemically synthesized using SKM13-2HCl. Except for SKM13-2HCl, the 5 newly synthesized compounds had a 50% cytotoxic concentration (CC₅₀) >100 μM, indicating that they would be less cytotoxic than SKM13-2HCl. Among the 5 compounds, only SAM13-2HCl outperformed SKM13-2HCl for antimalarial activity, showing a 3- and 1.3-fold greater selective index (SI) (CC₅₀/IC₅₀) than SKM13-2HCl in vitro against both chloroquine-sensitive (3D7) and chloroquine -resistant (K1) Plasmodium falciparum strains, respectively. Thus, the presence of morpholine amide may help to effectively suppress human-infectious P. falciparum parasites. However, the antimalarial activity of SAM13-2HCl was inferior to that of the SKM13-2HCl template compound in the P. berghei NK65-infected mouse model, possibly because SAM13-2HCl had a lower polarity and less efficient pharmacokinetics than SKM13-2HCl. SAM13-2HCl was more toxic in the rodent model. Consequently, SAM13-2HCl containing morpholine was selected from screening a combination of pharmacologically significant structures as being the most effective in vitro against human-infectious P. falciparum but was less efficient in vivo in a P. berghei-infected animal model when compared with SKM13-2HCl. Therefore, SAM13-2HCl containing morpholine could be considered a promising compound to treat chloroquine-resistant P. falciparum infections, although further optimization is crucial to maintain antimalarial activity while reducing toxicity in animals.

• Korean Journal of Pharmacognosy
• /
• v.43 no.3
• /
• pp.239-242
• /
• 2012

This study was carried out to investigate the anti-malarial activity of Juniperus chinensis by in vitro and in vivo system using Plasmodium falciparum chloroquine-sensitive(3D7) and P. falciparum chloroquine-resistant(S20) strains. According to cytotoxicty test on NIH 3T3 cell, the ethanol extract(EtOH), ethylacetate(EtOAc) fraction and aqueous fraction possessed significant anti-malarial activity against both 3D7 and S20 strains at non-toxic concentrations(<100 /). In vitro assay, EtOAc fraction showed notable activity against 3D7 and S20 strains of P. falciparum with $IC_{50}$ values of $37{\pm}2{\mu}g/ml$ and $36{\pm}6{\mu}g/ml$. In animal test using P. falciparum infected human erythrocytes, the treatment of EtOAc fraction significantly inhibited parasitaemia in mice in a dose-dependent manner that is parasitaemia of 42%, 34% and 31% in doses of 10 mg/kg, 20 mg/kg and 40 mg/kg, respectively. The study provides data to support the medicinal importance of the J. chinensis.

• Parasites, Hosts and Diseases
• /
• v.46 no.2
• /
• pp.65-70
• /
• 2008

Artemisinin-based combination therapy (ACT) is currently promoted as a strategy for treating both uncomplicated and severe falciparum malaria, targeting asexual blood-stage Plasmodium falciparum parasites. However, the effect of ACT on sexual-stage parasites remains controversial. To determine the clearance of sexual-stage P. falciparum parasites from 342 uncomplicated, and 217 severe, adult malaria cases, we reviewed and followed peripheral blood sexualstage parasites for 4 wk after starting ACT. All patients presented with both asexual and sexual stage parasites on admission, and were treated with artesunate-mefloquine as the standard regimen. The results showed that all patients were asymptomatic and negative for asexual forms before discharge from hospital. The percentages of uncomplicated malaria patients positive for gametocytes on days 3, 7, 14, 21, and 28 were 41.5, 13.1, 3.8, 2.0, and 2.0%, while the percentages of gametocyte positive severe malaria patients on days 3, 7, 14, 21, and 28 were 33.6, 8.2, 2.7, 0.9, and 0.9%, respectively. Although all patients were negative for asexual parasites by day 7 after completion of the artesunate-mefloquine course, gametocytemia persisted in some patients. Thus, a gametocytocidal drug, e.g., primaquine, may be useful in combination with an artesunate-mefloquine regimen to clear gametocytes, so blocking transmission more effectively than artesunate alone, in malaria transmission areas.

• Journal of Integrative Natural Science
• /
• v.10 no.1
• /
• pp.1-6
• /
• 2017

Demand for a new anti-malarial drug has been dramatically increasing in the recent years. Plasmodium falciparum enoyl-acyl carrier protein reductase (PfENR) plays a vital role in fatty acid elongation process, which now emerged as a new important target for the development of anti-microbial and anti-parasitic molecules. In the present study, 19 compounds namely alginic acid, atropine, chlorogenic acid, chrotacumine A & B, coenzyme $Q_1$, 4-coumaric acid, curcumin, ellagic acid, embelin, 5-O-methyl embelin, eugenyl glucoside, glabridin, hyoscyamine, nordihydroguaiaretic acid, rohitukine, scopolamine, tlatlancuayin and ursolic acid were evaluated on their docking behaviour on P. falciparum enoyl-acyl carrier protein reductase (PfENR) using Auto dock 4.2. The docking studies and binding free energy calculations exhibited that glabridin gave the highest binding energy (-8.07 kcal/mol) and 4-coumaric acid in contrast showed the least binding energy (-4.83 kcal/mol). All ligands except alginic acid, ellagic acid, hyoscyamine and glabridin interacted with Gln409 amino acid residue. Interestingly four ligands namely coenzyme $Q_1$, 4-coumaric acid, embelin and 5-O-methyl embelin interacted with Gln409 amino acid residue present in both chains (A & B) of PfENR protein. Thus, the results of this present study exhibited the potential of these 19 ligands as P. falciparum enoyl-acyl carrier protein reductase (PfENR) inhibitory agents and also as anti-malarial agents.

• Parasites, Hosts and Diseases
• /
• v.61 no.1
• /
• pp.24-32
• /
• 2023

Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1), encoded by the polymorphic var multigene family, is a highly polymorphic antigen that plays a crucial role in the pathology of malaria. The contribution of the genetic diversity of var toward the immune escape of P. falciparum has not yet been fully elucidated. This study aimed to characterize the diversity of var repertoires by screening P. falciparum Duffy-binding-like α domain (PfDBLα) among field isolates from central Myanmar. Genetic analysis revealed that the D-H segments of var in Myanmar populations have an extensive polymorphic repertoire, with high numbers of unique sequence types in each individual. However, var genes from the global population, including Myanmar, shared close genetic lineages regardless of their geographic origins, indicating that they have not undergone rapid evolutionary changes.

• Journal of Physiology & Pathology in Korean Medicine
• /
• v.17 no.3
• /
• pp.777-779
• /
• 2003

Among extracts prepared from Alstonia scholaris, Phyllostachys pubescens and Bambusa veitchii, methanol fraction of Alstonia scholaris was found to have antiplasmodial effect by inhibiting growth of the chloroquine-resistant Plasmodium falciparum strain FCR-3 with less than 14 μg/ml of EC50 values. Methanol fraction 2 of Alstonia scholaris revealed the strongest anti plasmodial effect with 40 μg/ml of EC50 value. Especially, this fraction showed higher than 3-folds selective toxicity on a Plasmodium as the EC value was 116 μg/ml on the host FM3A cell. This is the first report on which an extract compound from Alstonia scholaris showed antimalarial effect.

• Parasites, Hosts and Diseases
• /
• v.58 no.2
• /
• pp.147-152
• /
• 2020

Malaria is a potent burden on public healthcare worldwide due to requiring rapid diagnosis and treatment. Nowadays, prompt diagnosis with rapid diagnostic tests (RDTs) has been widely accepted as an effective diagnostic technique in malaria-endemic countries, primarily due to their easy operation, fast output, and straightforward interpretation. The global availability and use of RDTs have gradually grown over recent decades as field-applicable diagnostic tests for the reliable confirmation of malaria infection and proper case management. This study was conducted to evaluate diagnostic performance of 3 commercially available malaria RDT kits : BIOCREDIT^TM Malaria Ag Pf(pLDH), Malaria Ag Pf(pLDH/pHRPII), and Malaria Ag Pf/Pv(pLDH/pLDH) (where pLDH and pHRPII stand for plasmodium lactate dehydrogenase and histidine-rich protein 2, respectively) for the specific detection of Plasmodium falciparum. A total of 1,129 blood samples including 95 blood samples, confirmed as vivax malaria infection by microscopic examinations and a nested-PCR method, were tested for falciparum malaria infection. The overall sensitivity and specificity of Malaria Ag Pf(pLDH/pHRPII), Malaria Ag Pf/Pv(pLDH/pLDH), and Pf(pLDH) for P. falciparum were 99.0% and 100%, 95.8% and 100%, and 100% and 100%, respectively. It is proposed that the 3 RDT kits perform reliable level of diagnostic accuracy of detection for P. falciparum parasites.