Molecular cloning, polymorphism, and functional activity of the bovine and water buffalo Mx2 gene promoter region.

BACKGROUND: Bovine Mx2 gene sequences were already reported, but further information about the gene properties is not yet available. The objective of the current study was to elucidate the structural properties of the bovine Mx2 gene mainly the promoter region and its possible functional role. If available, such information would help in assessing the functional properties of the gene, which was reported to confer antiviral action against recombinant VSV. RESULTS: Examinations on the bovine genomic BAC clone-confirmed to contain the Mx2 gene-revealed 883-bp sequences. A computer scan unequivocally identified a 788-bp promoter region containing a typical TATA box, three ISREs and other promoter-specific motifs. Comparative analysis of nine bovine genomic DNA samples showed 19 nucleotide substitutions suggesting the existence of five different genotypes in the promoter region. The water buffalo Mx2 promoter region was determined by using primers based on the bovine Mx2 promoter region disclosing 893-bp, with 56 substitutions, two insertions, 9 and 1 nt at two different sites. A functional analysis of the putative ISRE indicated that ISRE played a synergetic role in the activation of bovine Mx2 gene transcription. CONCLUSION: Bovine and water buffalo Mx2 promoter region was identified disclosing, the conserved ISRE, located in the proximal end of the promoter region like other members of the antiviral family, suggesting functional activity under interferon stimulation.

Ellagic acid protects against cisplatin-induced nephrotoxicity in rats: a dose-dependent study.

BACKGROUND: The anticancerdrug cisplatin (CP) causes nephrotoxicity through different mechanisms, including generation of free radicals. Ellagic acid (EA) is a polyphenolic antioxidant found in fruits and nuts. AIM: This study aimed to investigate the ability of different doses of EA to ameliorate CP nephrotoxicity in rats. MATERIALS AND METHODS: Animals were randomly divided into six groups and treated with saline; CP alone (6 mg/kg); two doses of EA, both alone (10 and 30 mg/kg) or with CP. RESULTS: Treatment with CP alone reduced body weight, water intake, urine output, and renal total antioxidant and reduced glutathione (GSH) concentrations (p < 0.01). In addition, it increased relative kidney weight, plasma creatinine, and blood urea nitrogen (BUN) concentrations (p < 0.01). However, a dose of 30 mg/kg EA mitigated most of the CP-induced actions, but no effect was seen for the 10 mg/kg dose. Histopathologically, rats given CP+EA30 showed < 25% necrotic lesions in the renal cortical area compared with > 60% in rats treated with CP alone. Molecular analysis showed that clusterin (Clu) mRNA and protein were expressed in all treated groups, meanwhile kidney injury molecule-1 (Kim-1) mRNA and protein were only expressed in the CP and CP+EA treated rats. CONCLUSIONS: EA (30 mg/kg) ameliorated most of the physiological, histological, and biochemical markers of CP nephrotoxicity. The molecular findings in this work did not completely tally with the conventional method used. The overexpression of the molecular markers may be related to the EA induced repair mechanism.

Bovine and water buffalo Mx2 genes: polymorphism and antiviral activity.

Millennia-long selective pressure of single-strand RNA viruses on the bovine Mx locus has increased the advantages of using the bovine Mx protein to evaluate the ultimate significance of the antiviral role of Mx proteins. The conclusions of research based only on the bovine Mx1 protein showed the need for comprehensive studies that demonstrate the role of all isoforms, individually or together, especially in the presence of a second isoform, the bovine Mx2 gene. This study provides information about bovine and water buffalo Mx2 genes, as well as their allelic polymorphism and basic antiviral potential. Observation of an Mx2 cDNA sequence (2,381 bp) obtained from 15 animals from 11 breeds using primers based on a previous sequence (NCBI accession no. AF335147) revealed several nucleotide substitutions, with eight different alleles and two amino acid exchanges: Gly to Ser at position 302 and Ile to Val at position 354, though the latter was found only in the NCBI database. A water buffalo Mx2 cDNA sequence was identified for the first time, revealing 46 nucleotide substitutions with 12 amino acid variations, in addition to a 9-bp insertion in the 5' untranslated region UTR, compared with the bovine Mx2 cDNA. Transfected 3T3 cells expressing bovine Mx2 mRNAs coding Gly or Ser at position 302, water buffalo Mx2 mRNA, positive control bovine Mx1 mRNA-expressing cells, and negative control parental 3T3 were subjected to infection with recombinant vesicular stomatitis virus (VSVDeltaG*-G), as were empty pCI-neo vector-transfected cells. The positive control and all cells expressing Mx2 mRNAs displayed significantly higher levels of antiviral activity against VSVDeltaG*-G (P < 0.01) than did the negative controls.

Genetic complexity and gametocyte production of Plasmodium falciparum in Fulani and Mossi communities in Burkina Faso.

We have examined Plasmodium falciparum gametocyte prevalence, density and their genetic complexity among children of 2 sympatric ethnic groups (Mossi and Fulani) in villages in Burkina Faso. The 2 groups are known to have distinct differences in their susceptibility and immune responses to malaria. We used RT-PCR and sequence-specific probes to detect and type RNA of the gametocyte-specific protein Pfs48/45. There were no differences in detection rates of asexual forms and gametocytes among the 2 groups, using PCR and RT-PCR, respectively. However, there were significant differences in densities of asexual forms and gametocytes, which were both higher among Mossi than Fulani. Both asexual forms and gametocyte densities were influenced by age and ethnicity. Multiple-clone infections with more than 1 gametocyte genotype were equally prevalent among Fulani and Mossi. These differences can most probably be attributed to genetic differences in malaria susceptibility in the 2 ethnic groups.

Local differentiation in Plasmodium falciparum drug resistance genes in Sudan.

Studies of population genetic structure of parasites can be used to infer which parasite genes are under selection. Here, the population structure of 4 genes associated with drug resistance of Plasmodium falciparum (the chloroquine resistance transporter, pfcrt, dihydrofolate reductase, dhfr, dihydropteroate synthase, dhps, and multi-drug resistance, pfmdr-1) were examined in parasite populations in 3 villages in eastern Sudan and in an urban area of Khartoum, the capital. In order to differentiate the effects of drug selection from neutral influences on population structure, parasites were also genotyped for 3 putatively neutral microsatellite loci (polyalpha, TA81 and pfg377), and for 2 antigenic loci that are either under balancing selection or neutral, merozoite surface protein 1 and 2, (MSP-1 and MSP-2). Cross-sectional surveys were carried out during the peak transmission (wet) season and in the ensuing dry season. No significant variation in frequencies of MSP-1 and MSP-2 alleles was seen among villages in the eastern region and between the villages and Khartoum, nor between the wet and dry season. However, the drug resistance genes, pfmdr-1, pfcrt and dhfr and to a lesser extent the microsatellite loci showed high FST values when comparing villages with Khartoum, indicating strong geographical differentiation at these loci. Moreover, variation in frequencies of the drug resistance genes, pfmdr-1, pfcrt and dhfr, was observed between the wet and dry season. These differences most probably reflect the variation in drug pressure between each region, and in drug usage between the wet and dry season in a given region.

Critical comparison of molecular genotyping methods for detection of drug-resistant Plasmodium falciparum.

We have critically evaluated 3 techniques for the detection of mutations conferring drug resistance of Plasmodium falciparum, using samples containing known numbers of well-characterized parasites and artificial mixtures of these parasites at known proportions. We compared the sensitivity and specificity of mutation-specific polymerase chain reaction (MS-PCR), polymerase chain reaction followed by restriction enzyme digestion at polymorphic sites (PCR/RFLP), and a dot-blot/probe hybridization technique, for detection of point mutations at nucleotide 323 of the P. falciparum dihydrofolate reductase gene (dhfr) that confer resistance to the antimalarial drug pyrimethamine. We have also investigated the benefits in terms of sensitivity and reproducibility of the incorporation of radiolabelled nucleotides into the PCR/RFLP assay. We found that MS-PCR was very sensitive--at least 10 parasites could be detected in a sample--but non-specific amplification resulted in erroneous typing of some samples. PCR/RFLP was less sensitive; 10 parasites per sample could not always be detected, but the technique was specific. The addition of radiolabelled nucleotides to the assay did not markedly improve the sensitivity but the results were easier to read and there was less subjectivity in scoring the results. The dot-blot/probe hybridization technique was specific and sensitive, with similar levels of specificity and sensitivity to PCR/RFLP. On balance, the dot-blot/probe hybridization technique seems best suited to large-scale epidemiological surveys of genes associated with antimalarial drug resistance.

Diversity of Plasmodium falciparum clones infecting children living in a holoendemic area in north-eastern Tanzania.

The diversity of Plasmodium falciparum clones and their role in progression from asymptomatic to symptomatic condition in children have been investigated. Attempts to identify whether particular parasite genotypes were associated with the development of clinical symptoms have been made. A cohort of 34 initially asymptomatic parasitaemic children aged 1-5 years were followed daily for 31 days. Clinical examinations were made each day for signs and symptoms of clinical malaria, followed by parasitological investigation. Nineteen children developed symptoms suggestive of clinical malaria during this period. Daily blood parasite samples from 13 children who developed clinical malaria symptoms and 7 who remained asymptomatic were genotyped by PCR-amplification of the polymorphic regions of the merozoite surface proteins 1 and 2 (MSP1 and MSP2) and the glutamate rich protein (GLURP) genes. Infections were found to be highly complex in both groups of children. Every isolate examined from both groups had a mixture of parasite clones. Daily changes were observed in both parasite density and genotypic pattern. The mean number of genotypes per individual was estimated at 4.9 and 2.7 for asymptomatic and symptomatic groups of children, respectively. Analysis of allele frequency distributions showed that these differed significantly for the MSP1 locus only.

Efficacy of Sulphadoxine and Pyrimethamine, Doxycycline and their combination in the treatment of chloroquine resistant Falciparum Malaria.

OBJECTIVE: The present in vivo study evaluates the efficacy of sulphadoxine/pyrimethamine, doxycycline and their combination in the treatment of Sudanese patients infected by chloroquine resistant falciparum malaria. METHODS: Febrile patients with positive blood smears of Plasmodium falciparum were given chloroquine 25mg-base/kg body weight and followed up for 3 days. Patients with recrudescence due to chloroquine resistance were readmitted for test treatment. Using simple number randomization patients were divided into groups, A, B and C. These were treated with doxycycline, sulphadoxine/ pyrimethamine and a combination therapy of sulphadoxine/pyrimethamine plus doxycycline. Doxycycline was initially administered as a single dose of 200mg followed by 100mg daily for 6 days whereas sulphadoxine/pyrimethamine was given as a single dose of sulphadoxine 1500mg and pyrimethamine 75mg. Patients of group C received the combination therapy of sulphadoxine/pyrimethamine and doxycycline. Clinical observations and examination of blood films were carried out for each patient daily for 6 days and thereafter weekly for 4 weeks. RESULTS: A high level of chloroquine resistance (75%) was documented amongst 280 patients (age 15-53 years) visiting Omdurman Hospital of Endemic Diseases during 1996-1998. The study demonstrated that only 46% and 78% of the patients were cured after 4 days of treatment by doxycycline and sulphadoxine/pyrimethamine. Patients treated with sulphadoxine/pyrimethamine in combination with doxycycline had a cure rate of 90% and 100% after 3-4 days of treatment, a single recrudescent case was detected on day 6. No relapses occurred during the follow up period. All patients were successfully treated by all regimens with the exception of one case treated by doxycycline. All treatments were well tolerated but a few cases had complaints of nausea. CONCLUSION: The combination therapy of doxycycline/sulphadoxine/pyrimethamine appeared to be significantly effective in the treatment of patients with chloroquine resistant falciparum malaria without causing any serious side effects. Such a combination regimen has the advantages of being available at a reasonable cost and less prone to development of resistance.

Population genetic analysis of the Plasmodium falciparum erythrocyte binding antigen-175 (eba-175) gene.

The Plasmodium falciparum erythrocyte binding antigen-175 gene (eba-175) has highly divergent allelic segments (Cseg and Fseg) in one part of the gene (region III), but only a small number of single nucleotide polymorphisms (SNPs) in the rest of the sequence. Here, evidence for the possible importance of the Cseg/Fseg dimorphism was sought in a molecular population genetic analysis of the gene. First, allele frequency distributions were determined for the Cseg/Fseg dimorphism and five SNPs in a sample of five populations in Africa. The inter-population variance in frequencies was higher for Cseg/Fseg (F(ST)=0.18) than for the SNPs (F(ST) values from 0.03 to 0.10), but these values were entirely dependent on the inclusion of one particularly divergent population (Sudan). Second, linkage disequilibrium was measured among the intragenic loci. There was the expected trend of declining linkage disequilibrium with increasing molecular distance, but it is notable that the Cseg allele was in absolute linkage disequilibrium with the two flanking SNPs, whereas the Fseg allele was associated with a broader range of SNP haplotypes. Finally, there was no association between the Cseg/Fseg alleles of eba-175 in parasites and the M/N alleles of the glycophorin A erythrocyte receptor in the human subjects.

Chlorinated alkaloids in Menispermum dauricum DC: root culture.

Feeding experiments using (36)Cl showed that Menispermum dauricum root culture produces four alkaloids containing chlorine. They included the novel alkaloids dauricumine and dauricumidine as well as the known alkaloids acutumine and acutumidine. The structures of novel alkaloids were established by spectroscopic, crystallographic, and chemical methods. These four alkaloids were labeled with (36)Cl, isolated, and fed independently to root cultures. Mutual conversion between acutumine and acutumidine, and between dauricumine and dauricumidine by N-methylation and N-demethylation, was demonstrated. Moreover, dauricumine was converted to acutumine and acutumidine. Epimerization of acutumidine to dauricumidine or vice versa was not observed. These results suggest that dauricumine is the first chlorinated alkaloid formed in cultured M. dauricum roots. Skewed distribution of radioactivity derived from labeled dauricumine is proof that epimerization at C-1 proceeds at a lower rate than N-demethylation.

Genotyping of Plasmodium falciparum infections by PCR: a comparative multicentre study.

Genetic diversity of malaria parasites represents a major issue in understanding several aspects of malaria infection and disease. Genotyping of Plasmodium falciparum infections with polymerase chain reaction (PCR)-based methods has therefore been introduced in epidemiological studies. Polymorphic regions of the msp1, msp2 and glurp genes are the most frequently used markers for genotyping, but methods may differ. A multicentre study was therefore conducted to evaluate the comparability of results from different laboratories when the same samples were analysed. Analyses of laboratory-cloned lines revealed high specificity but varying sensitivity. Detection of low-density clones was hampered in multiclonal infections. Analyses of isolates from Tanzania and Papua New Guinea revealed similar positivity rates with the same allelic types identified. The number of alleles detected per isolate, however, varied systematically between the laboratories especially at high parasite densities. When the analyses were repeated within the laboratories, high agreement was found in getting positive or negative results but with a random variation in the number of alleles detected. The msp2 locus appeared to be the most informative single marker for analyses of multiplicity of infection. Genotyping by PCR is a powerful tool for studies on genetic diversity of P. falciparum but this study has revealed limitations in comparing results on multiplicity of infection derived from different laboratories and emphasizes the need for highly standardized laboratory protocols.

High-level chloroquine resistance in Sudanese isolates of Plasmodium falciparum is associated with mutations in the chloroquine resistance transporter gene pfcrt and the multidrug resistance Gene pfmdr1.

Polymorphisms were examined in 2 Plasmodium falciparum genes, as were chloroquine responses of clones and isolates from a village in eastern Sudan. There was a significant association between an allele of the P. falciparum chloroquine resistance transporter gene (pfcrt-T76) and both in vitro and in vivo resistance. There was a less significant association with the multidrug resistance gene pfmdr1-Y86 allele. A significant association between pfmdr1-Y86 and pfcrt-T76 was apparent among resistant isolates, which suggests a joint action of the 2 genes in high-level chloroquine resistance.

Population dynamics of Plasmodium falciparum in an unstable malaria area of eastern Sudan.

The Plasmodium falciparum population in Asar village, eastern Sudan, where malaria transmission is markedly seasonal, was monitored monthly over a period of 15 months. A cohort of infected patients was treated and then followed monthly throughout the dry season until the next transmission season. Parasitaemia detected by microscopy among the cohort reduced dramatically following treatment, but remained sporadic during the dry season, and reappeared following the onset of the next wet season. However between 40 and 50% of the cohort retained a persisting parasitaemia detectable by PCR throughout the dry season. These parasites were genetically complex, consisting of multiple clones with a large repertoire of alleles of the studied genes. While the number of clones per host dropped significantly following treatment of acute cases during the transmission season, drug treated people nevertheless maintained an average of one clone throughout the dry season. Allele frequencies of MSP-1, MSP-2 and GLURP showed slight, statistically insignificant, fluctuations between the dry and wet seasons. A higher frequency of inbreeding was estimated among the parasites that survived the dry season compared to the wet season.

Genetic structure and dynamics of Plasmodium falciparum infections in the Kilombero region of Tanzania.

Plasmodium falciparum parasites exist as genetically distinct haploid clones in infected people. In the Kilombero valley in south-east Tanzania, at least 85% of the inhabitants of Michenga village harbour more than one clone. Using 2 highly polymorphic unlinked markers, it has been estimated that each infected person harbours between one and 6 P. falciparum clones at any one time, with a mean of 3.5 clones. When mosquitoes acquire gametocytes of 2 different clones in a blood meal, crossing generates recombinant clones differing from their parental genotypes. The inbreeding coefficient of the parasite population has been estimated as 0.33.

Biosynthetic Relationship between Acutumine and Dechloroacutumine in Menispermum dauricum Root Cultures.

The biosynthetic relationship between acutumine 1 and dechloroacutumine 2 was studied using (13)C-labeled tyrosine and (3)H-labeled 2 as tracers. (13)C-NMR spectra of (13)C-labeled 1 and 2 showed that the alkaloids, each composed of two molecules of tyrosine, are derived from the same biosynthetic pathway. Feeding Menispermum dauricum (Menispermaceae) roots, cultured in a chloride-enriched medium, with (3)H-labeled 2 demonstrated that 1 is the only alkaloid metabolite of 2. Conversion (5%) of the exogenously applied 2, taken up by the roots, into 1 showed that 2 is the precursor of 1. Incomplete conversion of 2 into 1 suggests accumulation of the exogenously applied 2 in cell organelles and/or compartmentation of the enzymes involved in the biosynthesis of 1.

Characteristics of Plasmodium falciparum parasites that survive the lengthy dry season in eastern Sudan where malaria transmission is markedly seasonal.

We have examined 83 inhabitants of Asar village in eastern Sudan, where malaria transmission lasts approximately 2-3 months each year, for the presence of Plasmodium falciparum during the prolonged dry season. All patients were treated with a standard dose of chloroquine following the first diagnosis, then examined by microscopy and the polymerase chain reaction (PCR) every two weeks for the first two months and subsequently once each month for the next 15 months throughout the dry season until the following transmission season. The PCR primers used amplified polymorphic regions of the merozoite surface protein-1 (MSP-1), MSP-2, and glutamate-rich protein genes. Results show that subpatent and asymptomatic parasitemias persisted in some patients for several months throughout the dry season, often as genetically complex infections. Different genotypes could coexist together in a single infection and the proportions of each could fluctuate dramatically during this period. However, in some individuals, single genotypes appeared to persist for several months. Reappearance of clinical symptoms among patients with chronic infections was often associated with appearance of new alleles, indicating reinfections with parasites of novel genotypes.

Unstable malaria in Sudan: the influence of the dry season. Plasmodium falciparum population in the unstable malaria area of eastern Sudan is stable and genetically complex.

This paper reviews surveys carried out, over a period of 6 years between 1989 and 1995, to examine Plasmodium falciparum population structure in Asar village in eastern Sudan, an area of unstable malaria, the incidence of which is confined to a few weeks following the short rainy season (June-October). The first phase of the study involved regular cross sectional surveys, between 1989 and 1993 during the seasons of malaria incidence, while the second involved surveys during the malaria-free months of the dry seasons. The parasites were examined for 20 polymorphic loci, including enzyme electrophoretic variants, proteins detected by 2 dimensional polyacrylamide gel electrophoresis, antigens detected by monoclonal antibodies, and in vitro responses to antimalarial drugs. In addition, alleles of the polymorphic genes for merozoite surface proteins 1 and 2 (MSP-1, MSP-2) were examined using the polymerase chain reaction and oligonucleotide probes. Great genetic complexity was observed among the parasites which appeared during the short transmission seasons. A large proportion of the patients who were infected during the transmission season maintained asymptomatic, subpatent parasitaemias throughout the subsequent dry season, often as genetically complex infections.

Current views on the population structure of plasmodium falciparum: Implications for control.

In recent years there has been a considerable debate on the population genetic structure of malaria parasites. Work on this subject has been revolutionized by the advent of the polymerase chain reaction (PCR) technique, which has made it feasible to study the genetic diversity of parasites in small samples of infected blood, allowing extensive surveys of natural parasite populations to be made. In addition, the technique can be applied to the mosquito stages of the malaria parasite, allowing direct assessments to be trade of the frequency of crossing between parasite clones in Nature. Studies on Plasmodium falcjparum in a wide range of malaria-endemic regions are now revealing the relationship between parasite population structure and malaria epidemiology. In this article, Hamza Babiker and David Walliker review recent work in this field, and discuss how such knowledge might be used to advise on the future deployment of control measures such as antimalarial drugs and possible malaria vaccines.

Population structure of Plasmodium falciparum in villages with different malaria endemicity in east Africa.

We have compared allelic polymorphism of two merozoite surface protein genes, MSP-1 and MSP-2, of Plasmodium falciparum and the parasite load in infected individuals in two villages in east Africa. In Michenga village in Tanzania, malaria is holoendemic and transmission is perennial; in Asar village in Sudan, malaria is mesoendemic and transmission is markedly seasonal. The numbers of alleles of both genes were found to be much greater in Michenga than in Asar. More parasite clones exhibiting higher allelic polymorphisms of the genes studied were carried by infected inhabitants in Michenga than those in Asar. The high mean number of clones in Michenga is associated with a very high frequency of out-crossing compared with that estimated in Asar.