Molecular determinants of sulfadoxine-pyrimethamine resistance in Plasmodium falciparum in Nigeria and the regional emergence of dhps 431V.
ABSTRACT: There are few published reports of mutations in dihydropteroate synthetase (dhps) and dihydrofolate reductase (dhfr) genes in P. falciparum populations in Nigeria, but one previous study has recorded a novel dhps mutation at codon 431 among infections imported to the United Kingdom from Nigeria. To assess how widespread this mutation is among parasites in different parts of the country and consequently fill the gap in sulfadoxine-pyrimethamine (SP) resistance data in Nigeria, we retrospectively analysed 1000 filter paper blood spots collected in surveys of pregnant women and children with uncomplicated falciparum malaria between 2003 and 2015 from four sites in the south and north. Genomic DNA was extracted from filter paper blood spots and placental impressions. Point mutations at codons 16, 50, 51, 59, 108, 140 and 164 of the dhfr gene and codons 431, 436, 437, 540, 581 and 613 of the dhps gene were evaluated by nested PCR amplification followed by direct sequencing. The distribution of the dhps-431V mutation was widespread throughout Nigeria with the highest prevalence in Enugu (46%). In Ibadan where we had sequential sampling, its prevalence increased from 0% to 6.5% between 2003 and 2008. Although there were various combinations of dhps mutations with 431V, the combination 431V + 436A + 437G+581G+613S was the most common. All these observations support the view that dhps-431V is on the increase. In addition, P. falciparum DHPS crystal structure modelling shows that the change from Isoleucine to Valine (dhps-431V) could alter the effects of both S436A/F and A437G, which closely follow the 2nd ?-strand. Consequently, it is now a research priority to assess the implications of dhps-VAGKGS mutant haplotype on continuing use of SP in seasonal malaria chemoprevention (SMC) and intermittent preventive treatment in pregnancy (IPTp). Our data also provides surveillance data for SP resistance markers in Nigeria between 2003 and 2015.
Project description:BACKGROUND:Plasmodium falciparum-resistance to sulphadoxine-pyrimethamine (SP) has been largely reported among pregnant women. However, the profile of resistance markers to SP dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) in the general population are varied and not frequently monitored. Currently, SP is used as partner drug for artemisinin combination therapy (SP-artesunate) in some sub-Saharan African countries or as a prophylactic drug in intermittent preventive treatment of malaria during pregnancy and infants and in seasonal malaria chemoprevention (SMC). Profiling of P. falciparum-resistant genotypes to SP is dynamic and critical in providing data that would be useful for malaria control programmes. This study assessed the profile of dhfr and dhps genes genotypes among individuals with malaria in Lagos, Nigeria. METHODS:Molecular markers of SP resistance were identified by nested PCR and sequenced among malaria positive dried blood spots (DBS) that were collected from individuals attending health facilities from January 2013 to February 2014 and during community surveys from October 2010 to September 2011 across different Local Government Areas of Lagos State, Nigeria. RESULTS:A total of 242 and 167 samples were sequenced for dhfr and dhps, respectively. Sequence analysis of dhfr showed that 95.5% (231/242), 96.3% (233/242) and 96.7% (234/242) of the samples had N51I, C59R and S108N mutant alleles, respectively. The prevalence of dhps mutation at codons A437G, A613S, S436A, A581G, I431V and K540E were 95.8% (160/167), 41.9% (70/167), 41.3% (69/167), 31.1% (52/167), 25.1% (42/167), and 1.2% (2/167) respectively. The prevalence of triple mutations (CIRNI) in dhfr was 93.8% and 44.3% for the single dhps haplotype mutation (SGKAA). Partial SP-resistance due to quadruple dhfr-dhps haplotype mutations (CIRNI-SGKAA) and octuple haplotype mutations (CIRNI-VAGKGS) with rate of 42.6% and 22.0%, respectively has been reported. CONCLUSIONS:There was increased prevalence in dhfr triple haplotype mutations when compared with previous reports in the same environment but aligned with high prevalence in other locations in Nigeria and other countries in Africa. Also, high prevalence of dhfr and dhps mutant alleles occurred in the study areas in Lagos, Nigeria five to eight years after the introduction of artemisinin combination therapy underscores the need for continuous monitoring.
Project description:In 2005, the Nigerian Federal Ministry of Health revised the treatment policy for uncomplicated malaria with the introduction of artemisinin-based combination therapies (ACTs). This policy change discouraged the use of Sulphadoxine-pyrimethamine (SP) as the second-line treatment of uncomplicated falciparum malaria. However, SP is used as an intermittent preventive treatment of malaria in pregnancy (IPTp) and seasonal malaria chemoprevention (SMC) in children aged 3-59 months. There have been increasing reports of SP resistance especially in the non-pregnant population in Nigeria, thus, the need to continually monitor the efficacy of SP as IPTp and SMC by estimating polymorphisms in dihydropteroate synthetase (dhps) and dihydrofolate reductase (dhfr) genes associated with SP resistance. The high resolution-melting (HRM) assay was used to investigate polymorphisms in codons 51, 59, 108 and 164 of the dhfr gene and codons 437, 540, 581 and 613 of the dhps gene. DNA was extracted from 271 dried bloodspot filter paper samples obtained from children (<?5 years old) with uncomplicated malaria. The dhfr triple mutant I<sub>51</sub>R<sub>59</sub>N<sub>108</sub>, dhps double mutant G<sub>437</sub>G<sub>581</sub> and quadruple dhfr I<sub>51</sub>R<sub>59</sub>N<sub>108</sub>?+?dhps G<sub>437</sub> mutant haplotypes were observed in 80.8%, 13.7% and 52.8% parasites, respectively. Although the quintuple dhfr I<sub>51</sub>R<sub>59</sub>N<sub>108</sub>?+?dhps G<sub>437</sub>E<sub>540</sub> and sextuple dhfr I<sub>51</sub>R<sub>59</sub>N<sub>108</sub>?+?dhps G<sub>437</sub>E<sub>540</sub>G<sub>581</sub> mutant haplotypes linked with in-vivo and in-vitro SP resistance were not detected, constant surveillance of these haplotypes should be done in the country to detect any change in prevalence.
Project description:Pregnant women are a high-risk group for Plasmodium falciparum infections, which may result in maternal anaemia and low birth weight newborns, among other adverse birth outcomes. Intermittent preventive treatment with sulfadoxine-pyrimethamine during pregnancy (IPTp-SP) is widely implemented to prevent these negative effects of malaria. However, resistance against SP by P. falciparum may decrease efficacy of IPTp-SP. Combinations of point mutations in the dhps (codons A437, K540) and dhfr genes (codons N51, C59, S108) of P. falciparum are associated with SP resistance. In this study the prevalence of SP resistance mutations was determined among P. falciparum found in pregnant women and the general population (GP) from Nanoro, Burkina Faso and the association of IPTp-SP dosing and other variables with mutations was studied.Blood spots on filter papers were collected from pregnant women at their first antenatal care visit (ANC booking) and at delivery, from an ongoing trial and from the GP in a cross-sectional survey. The dhps and dhfr genes were amplified by nested PCR and products were sequenced to identify mutations conferring resistance (ANC booking, n = 400; delivery, n = 223; GP, n = 400). Prevalence was estimated with generalized estimating equations and for multivariate analyses mixed effects logistic regression was used.The prevalence of the triple dhfr mutation was high, and significantly higher in the GP and at delivery than at ANC booking, but it did not affect birth weight. Furthermore, quintuple mutations (triple dhfr and double dhps mutations) were found for the first time in Burkina Faso. IPTp-SP did not significantly affect the occurrence of any of the mutations, but high transmission season was associated with increased mutation prevalence in delivery samples. It is unclear why the prevalence of mutations was higher in the GP than in pregnant women at ANC booking.The high number of mutants and the presence of quintuple mutants in Burkina Faso confirm concerns about the efficacy of IPTp-SP in the near future. Other drug combinations to tackle malaria in pregnancy should, therefore, be explored. An increase in mutation prevalence due to IPTp-SP dosing could not be confirmed.
Project description:Malaria caused by Plasmodium falciparum infects roughly 30,000 individuals in Haiti each year. Haiti has used chloroquine (CQ) as a first-line treatment for malaria for many years and as a result there are concerns that malaria parasites may develop resistance to CQ over time. Therefore it is important to prepare for alternative malaria treatment options should CQ resistance develop. In many other malaria-endemic regions, antifolates, particularly pyrimethamine (PYR) and sulphadoxine (SDX) treatment combination (SP), have been used as an alternative when CQ resistance has developed. This study evaluated mutations in the dihydrofolate reductase (dhfr) and dihydropteroate synthetase (dhps) genes that confer PYR and SDX resistance, respectively, in P. falciparum to provide baseline data in Haiti. This study is the first comprehensive study to examine PYR and SDX resistance genotypes in P. falciparum in Haiti.DNA was extracted from dried blood spots and genotyped for PYR and SDX resistance mutations in P. falciparum using PCR and DNA sequencing methods. Sixty-one samples were genotyped for PYR resistance in codons 51, 59, 108 and 164 of the dhfr gene and 58 samples were genotyped for SDX resistance codons 436, 437, 540 of the dhps gene in P. falciparum.Thirty-three percent (20/61) of the samples carried a mutation at codon 108 (S108N) of the dhfr gene. No mutations in dhfr at codons 51, 59, 164 were observed in any of the samples. In addition, no mutations were observed in dhps at the three codons (436, 437, 540) examined. No significant difference was observed between samples collected in urban vs rural sites (Welch's T-test p-value = 0.53 and permutations p-value = 0.59).This study has shown the presence of the S108N mutation in P. falciparum that confers low-level PYR resistance in Haiti. However, the absence of SDX resistance mutations suggests that SP resistance may not be present in Haiti. These results have important implications for ongoing discussions on alternative malaria treatment options in Haiti.
Project description:The resistance of Plasmodium falciparum to sulfadoxine-pyrimethamine (SP) is an emerging public health threat. Resistance to these drugs is associated with point mutations in the genes encoding dihydropteroate synthase (DHPS) and dihydrofolate reductase (DHFR). We describe here an assay using real-time PCR and sequence-specific probes that detects these mutations. Using DNA from plasmids, cultured strains, and clinical samples, real-time PCR could distinguish four DHPS polymorphisms (codons 437, 540, 581, and 613) and three DHFR polymorphisms (codons 51, 59, and 108). This assay is rapid and sensitive, with a detection limit of 10 copies in most cases. This assay is amenable to large-scale studies of drug resistance.
Project description:In 2007, Malawi replaced sulfadoxine-pyrimethamine (SP) with an artemisinin-based combination therapy as the first-line treatment for uncomplicated Plasmodium falciparum malaria in response to failing SP efficacy. Here we estimate the effect of reduced SP pressure on the prevalence of SP-resistant parasites and the characteristics of the associated selective sweeps flanking the resistance loci.Samples obtained from individuals with clinical malaria during a period of high SP use (1999-2001), a transitional period (2007-2008), and a period of low SP use (2012) were genotyped for resistance markers at pfdhfr-ts codons 51, 59, and 108 and pfdhps codons 437, 540, and 581. Expected heterozygosity was estimated to evaluate the genetic diversity flanking pfdhfr-ts and pfdhps.An increase in the prevalence of the resistance haplotypes DHFR 51I/59R/108N and DHPS 437G/540E occurred under sustained drug pressure, with no change in haplotype prevalence 5 years after reduction in SP pressure. The DHPS 437G/540E/581G haplotype was observed in 2007 and increased in prevalence during a period of reduced SP pressure. Changes to the sweep characteristics flanking pfdhfr-ts and pfdhps were minimal.In contrast to the rapid and complete return of chloroquine-susceptible falciparum malaria after chloroquine was withdrawn from Malawi, a reemergence of SP efficacy is unlikely in the near future.
Project description:BACKGROUND:Artesunate plus sulphadoxine-pyrimethamine (AS+SP) is now first-line treatment for Plasmodium falciparum infection in several south Asian countries, including Afghanistan. Molecular studies provide a sensitive means to investigate the current state of drug susceptibility to the SP component, and can also provide information on the likely efficacy of other potential forms of artemisinin-combination therapy. METHODS:During the years 2007 to 2010, 120 blood spots from patients with P. falciparum malaria were obtained in four provinces of Afghanistan. PCR-based methods were used to detect drug-resistance mutations in dhfr, dhps, pfcrt and pfmdr1, as well as to determine copy number of pfmdr1. RESULTS:The majority (95.5%) of infections had a double mutation in the dhfr gene (C59R, S108N); no mutations at dhfr positions 16, 51 or 164 were seen. Most isolates were wild type across the dhps gene, but five isolates from the provinces of Kunar and Nangarhar in eastern Afghanistan had the triple mutation A437G / K540E / A581G; all five cases were successfully treated with three receiving AS+SP and two receiving dihydroartemisinin-piperaquine. All isolates showed the pfcrt SVNMT chloroquine resistance haplotype. Five of 79 isolates had the pfmdr1 N86Y mutation, while 52 had pfmdr1 Y184F; positions 1034, 1042 and 1246 were wild type in all isolates. The pfmdr1 gene was not amplified in any sample. CONCLUSIONS:This study indicates that shortly after the adoption of AS+SP as first-line treatment in Afghanistan, most parasites had a double mutation haplotype in dhfr, and a small number of isolates from eastern Afghanistan harboured a triple mutation haplotype in dhps. The impact of these mutations on the efficacy of AS+SP remains to be assessed in significant numbers of patients, but these results are clearly concerning since they suggest a higher degree of SP resistance than previously detected. Further focused molecular and clinical studies in this region are urgently required.
Project description:The frequency of alleles with triple mutations conferring sulfadoxine-pyrimethamine (SP) resistance in the Peruvian Amazon Basin has declined (16.9% for dhfr and 0% for dhps compared to 47% for both alleles in 1997) 5 years after SP was replaced as the first-line treatment for Plasmodium falciparum malaria. Microsatellite analysis showed that the dhfr and dhps alleles are of common origin.
Project description:BACKGROUND:Genes encoding dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) are the targets of sulfadoxine-pyrimethamine (SP) present in artemisinin based combination therapy (ACT; artesunate?+?sulfadoxine pyrimethamine) for Plasmodium falciparum. Although SP is generally not used to treat vivax infection, mutations in dhfr and dhps that confer antifolate resistance in Plasmodium vivax are common; which may be attributed to its sympatric existence with P. falciparum. Current study was aimed to determine the pattern of mutations in dhfr and dhps in P. vivax isolates from Mangaluru region. METHODS:A total of 140 blood samples were collected from P. vivax-infected people attending Wenlock Hospital Mangaluru during July 2014 to January 2016. Out of 140 isolates, 25 (18%) and 50 (36%) isolates were selected randomly for sequence analysis of pvdhfr and pvdhps genes respectively. Fragment of pvdhps and full length pvdhfr were amplified, sequenced and analysed for single nucleotide polymorphisms. dhps was analysed by PCR-RFLP also, to detect the two specific mutations (A383G and A553G). RESULTS:Analysis of pvdhps sequences from 50 isolates revealed single and double mutants at 38 and 46% respectively. Three non-synonymous mutations (K55R, S58R and S117N) were identified for pvdhfr. Among these, K55R was detected for the first time. CONCLUSIONS:The current study indicates that P. vivax dhps and dhfr mutant alleles are prevalent in this area, suggesting significant SP pressure.
Project description:Combination therapy with artesunate plus sulfadoxine-pyrimethamine (SP) was adopted as recommended treatment for Plasmodium falciparum infection in Afghanistan in 2003.A series of prospective clinical studies examining the efficacy of artesunate plus sulfadoxine-pyrimethamine (AS + SP) against P. falciparum were undertaken in sentinel sites in Afghanistan from 2007 to 2014, accompanied by relevant molecular studies. The first study was a randomized trial of AS + SP versus dihydroartemisinin-piperaquine, while two subsequent studies were standard therapeutic efficacy studies of AS + SP.Three hundred and three patients were enrolled across four provinces in the north and east of the country. Curative efficacy was high in all the trials, with an adequate clinical and parasitological response (ACPR) of more than 95 % in all groups and trial stages. Genotyping for drug-resistance alleles at dhfr indicated fixation of the S108 N mutation and a prevalence of the C59R mutation of approximately 95 % across all sites. Other mutations in dhfr and dhps remained rare or absent entirely, although five isolates from the first trial carried the dhps triple mutant SGEGA haplotype. In the last study undertaken in 2012-2014 the K13 artemisinin resistance marker was examined; only two of 60 successfully sequenced samples carried a K13-propeller mutation.These data confirm maintained efficacy 10 years after introduction of artesunate plus SP as combination treatment of P. falciparum in Afghanistan. The molecular data indicate that despite a substantial fall in incidence, resistance has not developed to artemisinins, or intensified to the ACT partner drug components. Trial Registration http://www.clinicaltrials.gov/ct NCT00682578, NCT01115439 and NCT01707199.