Evolutionary analyses of the major variant surface antigen-encoding genes reveal population structure of Plasmodium falciparum within and between continents.

Malaria remains a major public health problem in many countries. Unlike influenza and HIV, where diversity in immunodominant surface antigens is understood geographically to inform disease surveillance, relatively little is known about the global population structure of PfEMP1, the major variant surface antigen of the malaria parasite Plasmodium falciparum. The complexity of the var multigene family that encodes PfEMP1 and that diversifies by recombination, has so far precluded its use in malaria surveillance.

Multiple Novel Mutations in Chloroquine Resistance Transporter Gene during Implementation of Artemisinin Combination Therapy in Thailand.

Mutations in the chloroquine resistance transporter gene of () are associated with drug susceptibility status of chloroquine and other antimalarials that interfere with heme detoxification process including artemisinin. We aim to investigate whether an increase in duration of artemisinin combination therapy (ACT) in Thailand could affect mutations in . The complete coding sequences of and dihydrofolate reductase (), and size polymorphisms of the merozoite surface proteins-1 and 2 ( and ) of 189 isolates collected during 1991 and 2016 were analyzed.

Unraveling Haplotype Diversity of the Apical Membrane Antigen-1 Gene in Populations in Thailand.

Development of an effective vaccine is critically needed for the prevention of malaria. One of the key antigens for malaria vaccines is the apical membrane antigen 1 (-1) of the human malaria parasite , the surface protein for erythrocyte invasion of the parasite. The gene encoding -1 has been sequenced from populations of worldwide, but the haplotype diversity of the gene in populations in the Greater Mekong Subregion (GMS), including Thailand, remains to be characterized.

Size and sequence polymorphisms in the glutamate-rich protein gene of the human malaria parasite Plasmodium falciparum in Thailand.

Background: The glutamate-rich protein (GLURP) of the malaria parasite Plasmodium falciparum is a key surface antigen that serves as a component of a clinical vaccine. Moreover, the GLURP gene is also employed routinely as a genetic marker for malarial genotyping in epidemiological studies. While extensive size polymorphisms in GLURP are well recorded, the extent of the sequence diversity of this gene is rarely investigated.

Global sequence diversity of the lactate dehydrogenase gene in Plasmodium falciparum.

Background: Antigen-detecting rapid diagnostic tests (RDTs) have been recommended by the World Health Organization for use in remote areas to improve malaria case management. Lactate dehydrogenase (LDH) of Plasmodium falciparum is one of the main parasite antigens employed by various commercial RDTs. It has been hypothesized that the poor detection of LDH-based RDTs is attributed in part to the sequence diversity of the gene.

Genetic diversity of the merozoite surface protein-3 gene in Plasmodium falciparum populations in Thailand.

Background: An effective malaria vaccine is an urgently needed tool to fight against human malaria, the most deadly parasitic disease of humans. One promising candidate is the merozoite surface protein-3 (MSP-3) of Plasmodium falciparum. This antigenic protein, encoded by the merozoite surface protein (msp-3) gene, is polymorphic and classified according to size into the two allelic types of K1 and 3D7.

Allelic Diversity and Geographical Distribution of the Gene Encoding Plasmodium falciparum Merozoite Surface Protein-3 in Thailand.

Merozoite surface proteins (MSPs) of malaria parasites play critical roles during the erythrocyte invasion and so are potential candidates for malaria vaccine development. However, because MSPs are often under strong immune selection, they can exhibit extensive genetic diversity. The gene encoding the merozoite surface protein-3 (MSP-3) of Plasmodium falciparum displays 2 allelic types, K1 and 3D7.

Molecular detection of the avian malaria parasite Plasmodium gallinaceum in Thailand.

Avian malaria is one of the most common veterinary problems in Southeast Asia. The standard molecular method for detection of the avian malaria parasite involves the phenol-chloroform extraction of parasite genomic (g)DNA followed by the amplification of parasite gDNA using polymerase chain reaction (PCR). However, the phenol-chloroform extraction method is time-consuming and requires large amounts of samples and toxic organic solvents, thereby limiting its applications for parasite detection in the field.

Effects of artesunate treatment on Plasmodium gallinaceum transmission in the vectors Aedes aegypti and Culex quinquefasciatus.

In the absence of vaccines, chemotherapy is an effective and economical way for controlling malaria. Development of anti-malarial drugs that target pathogenic blood stage parasites and gametocytes is preferable for the treatment as it can alleviate the host's morbidity and mortality and block transmission of the Plasmodium parasite. Recently, our laboratory has developed an in vivo transmission blocking assay that involves administration of 7 consecutive daily doses of a test compound into domestic chickens (Gallus gallus domesticus) infected with the avian malaria parasite Plasmodium gallinaceum with 10% parasitaemia and 1% gametocytaemia.

Diversity and population structure of Plasmodium falciparum in Thailand based on the spatial and temporal haplotype patterns of the C-terminal 19-kDa domain of merozoite surface protein-1.

Background: The 19-kDa C-terminal region of the merozoite surface protein-1 of the human malaria parasite Plasmodium falciparum (PfMSP-119) constitutes the major component on the surface of merozoites and is considered as one of the leading candidates for asexual blood stage vaccines. Because the protein exhibits a level of sequence variation that may compromise the effectiveness of a vaccine, the global sequence diversity of PfMSP-119 has been subjected to extensive research, especially in malaria endemic areas. In Thailand, PfMSP-119 sequences have been derived from a single parasite population in Tak province, located along the Thailand-Myanmar border, since 1995.

In vivo transmission blocking activities of artesunate on the avian malaria parasite Plasmodium gallinaceum.

Infection and transmission of the avian malaria parasite Plasmodium gallinaceum in domestic chickens is associated with high economic burden and presents a major challenge to poultry industry in South East Asia. Development of drugs targeting both asexual blood stage parasites and sexual stages of the avian malarias will be beneficial for malaria treatment and eradication. However, current drugs recommended for treatment of the avian malaria parasites target specifically the asexual blood stage parasites, but have little or no impact to the gametocytes, the major target for development of transmission-blocking strategies.

Green tea extract supplement inhibition of HMGB1 release in rats exposed to cigarette smoke.

Tobacco-smoke exposure is linked to carcinogenic, oxidative and inflammatory cellular reactions. Green tea has been reported to have anti-release properties against various pro-inflammatory cytokines. To determine the effects of green tea extract (GTE) on serum high mobility group box-1 (HMGB1) levels in rats exposed to cigarette smoke (CS), we divided rats into 4 treatment groups: (1) CS only, (2) dietary supplement with GTE (3 mg/d) and CS (GCS1), (3) dietary supplement with GTE (4.

The patterns of mutation and amplification of Plasmodium falciparum pfcrt and pfmdr1 genes in Thailand during the year 1988 to 2003.

The study investigated the patterns of pfmdr1 and pfcrt genetic polymorphisms in Plasmodium falciaprum isolates collected from Thailand during the periods 1988-1993 (35 isolates), and 2003 (21 isolates). Pfcrt polymorphisms were almost universal for the mutations at codons K76T, A220S, Q271E, N326S, and R371I. All parasites displayed the chloroquine (CQ)-resistant phenotypes.

Genetic diversity and population structure of Plasmodium falciparum in Thailand, a low transmission country.

Background: The population structure of the causative agents of human malaria, Plasmodium sp., including the most serious agent Plasmodium falciparum, depends on the local epidemiological and demographic situations, such as the incidence of infected people, the vector transmission intensity and migration of inhabitants (i.e.

Drug resistance and in vitro susceptibility of Plasmodium falciparum in Thailand during 1988-2003.

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.

Genetic homogeneity among colonies of the white-nest swiftlet (Aerodramus fuciphagus) in Thailand.

The white-nest swiftlet, Aerodramus fuciphagus, originally lived in large colonies in natural caves, but now it also occurs in man-made buildings. We investigated the patterns of genetic differentiation in two mitochondrial DNA genes (cyt-b and ND2) and eight microsatellite loci among and within colonies of A. fuciphagus from across recently established man-made colonies in Thailand.

Plasmodium falciparum: gene mutations and amplification of dihydrofolate reductase genes in parasites grown in vitro in presence of pyrimethamine.

Samples of three pyrimethamine-sensitive clones of Plasmodium falciparum were grown for periods of 22-46 weeks in media containing stepwise increases in pyrimethamine concentrations and were seen to develop up to 1000-fold increases in resistance to the drug. With clone T9/94RC17, the dihydrofolate reductase (DHFR) gene was sequenced from 10 uncloned populations and 29 pure clones, all having increased resistance to pyrimethamine, and these sequences were compared with the sequence of the original pyrimethamine-sensitive clone. No changes in amino acid sequence were found to have occurred.

Synthesis and properties of chiral peptide nucleic acids with a N-aminoethyl-D-proline backbone.

A synthon of D-proline substituted at the 4-position by thymine and at N by a flexible aminoethyl linker, has been used to prepare a novel chiral peptide nucleic acid (cPNA) with (2R,4R) stereochemistry using solid phase methodology. The homothymine decamer cPNA binds to complementary polyadenylic acid to form a 2:1 hybrid with high affinity and specificity according to UV and CD studies, whereas no binding to the corresponding polydeoxyadenylic acid was observed.

Stress, anxiety and peripheral benzodiazepine receptor mRNA levels in human lymphocytes.

Peripheral benzodiazepine receptor (PBR) mRNA levels were measured in lymphocytes obtained from a cohort of university students and clinically diagnosed anxious patients. The average level of PBR mRNA was decreased in anxious patients compared to a control group. This data confirms previously published results, but it also indicates that PBR mRNA levels cannot be used as a sole diagnostic measure of anxiety because the range of the individual PBR mRNA levels of the anxious group overlapped the range of the PBR mRNA levels of the control group.

Pseudoephedrine, a sympathomimetic agent, induces Fos-like immunoreactivity in rat nucleus accumbens and striatum.

The pharmacological properties of the ephedrine derivative pseudoephedrine were investigated at the nuclear level. Following intraperitoneal injection of Sprague Dawley rats with pseudoephedrine, Fos induction was measured in various brain areas by Western blots and immunocytochemistry. Pseudoephedrine induced Fos-like immunoreactivity in the nucleus accumbens and striatum in a time and concentration-dependent manner with maximal effect at 60 mg/kg 2 h after injection.

Dexamethasone, but not stress, induce measurable changes of mitochondrial benzodiazepine receptor mRNA levels in rats.

The expression of the mitochondrial benzodiazepine receptor gene was assayed by a semi-quantitative non-radioactive reverse transcriptase polymerase chain reaction (RT-PCR) assay. The level of amplified mitochondrial benzodiazepine receptor mRNA was expressed as a ratio of either glyceraldehyde-3-phosphate dehydrogenase (GAPDH) or beta-actin mRNA co-amplified in the same RT-PCR assay. The relative amounts of mitochondrial benzodiazepine receptor RNA in several rat tissues were found to be similar to the previously reported relative amount of mitochondrial benzodiazepine receptor binding sites.

Inhibitory monoclonal antibodies recognise epitopes adjacent to a proteolytic cleavage site on the RAP-1 protein of Plasmodium falciparum.

The low-molecular-weight rhoptry-associated protein (RAP) complex of Plasmodium falciparum consists of at least two gene products, RAP-1 and RAP-2, and has the ability to immunise Saimiri monkeys against experimental P. falciparum infection. Several monoclonal antibodies specifically recognise this complex and in this study we show that purified immunoglobulin derived from these monoclonals is capable of inhibiting parasite growth in vitro.