Recent increase of genetic diversity in Plasmodium vivax population in the Republic of Korea

<p>Abstract</p> <p>Background</p> <p>The reemergence of <it>Plasmodium vivax </it>in South Korea since 1993 represents a serious public health concern. Despite the importance in understanding genetic diversity for control strategies, however, studies remain inconclusive with the general premise that due to low rate of malaria transmission, there is generally low genetic diversity with very few strains involved. In this study, the genetic diversity and population structure of <it>P. vivax </it>in South Korea were explored by analysing microsatellite polymorphism.</p> <p>Methods</p> <p>Sequences for 13 microsatellite loci distributed across the twelve chromosomes of <it>P. vivax </it>were obtained from 58 South Korean isolates collected during two sampling periods, namely 1997-2000 and 2007. The sequences were used for the analysis of expected heterozygosity and multilocus genotype diversity. Population structure was evaluated using STRUCTURE version 2.3.2. Linkage disequilibrium was also analysed to investigate the extent of outbreeding in the <it>P. vivax </it>population.</p> <p>Results</p> <p>Mean expected heterozygosity significantly increased from 0.382 in 1997-2000 to 0.545 in 2007 (<it>P </it>< 0.05). The number of multilocus genotypes was 7 and 27; and genotype diversity was statistically significant (<it>P </it>< 0.01) at 0.661 and 0.995 in 1997-2000 and 2007, respectively. Analysis by STRUCTURE showed a more complex population structure in 2007 than in 1997-2000. Linkage disequilibrium between 13 microsatellites, although significant in both time points, was notably lower in 2007.</p> <p>Conclusions</p> <p>The present microsatellite analysis clearly showed recent increase of genetic diversity and recent relaxation of the strong population structure observed in 1997-2000. These results suggest that multiple genotypes not present previously recently migrated into South Korea, accompanied by substantial outbreeding between different genotypes.</p

Evidence of artemisinin-resistant malaria in Africa

From Balikagala B., Fukuda N., Ikeda M., et al, Evidence of artemisinin-resistant malaria in Africa, 385(13), 1163-1171. Copyright © 2021 Massachusetts Medical Society. Reprinted with permission. https://doi.org/10.1056/nejmoa2101746.BACKGROUND In the six Southeast Asian countries that make up the Greater Mekong Subregion, Plasmodium falciparum has developed resistance to derivatives of artemisinin, the main component of first-line treatments for malaria. Clinical resistance to artemisinin monotherapy in other global regions, including Africa, would be problematic. METHODS In this longitudinal study conducted in Northern Uganda, we treated patients who had P. falciparum infection with intravenous artesunate (a water-soluble artemisinin derivative) and estimated the parasite clearance half-life. We evaluated ex vivo susceptibility of the parasite using a ring-stage survival assay and genotyped resistancerelated genes. RESULTS From 2017 through 2019, a total of 14 of 240 patients who received intravenous artesunate had evidence of in vivo artemisinin resistance (parasite clearance halflife, >5 hours). Of these 14 patients, 13 were infected with P. falciparum parasites with mutations in the A675V or C469Y allele in the kelch13 gene. Such mutations were associated with prolonged parasite clearance half-lives (geometric mean, 3.95 hours for A675V and 3.30 hours for C469Y, vs. 1.78 hours for wild-type allele; P<0.001 and P = 0.05, respectively). The ring-stage survival assay showed a higher frequency of parasite survival among organisms with the A675V allele than among those with the wild-type allele. The prevalence of parasites with kelch13 mutations increased significantly, from 3.9% in 2015 to 19.8% in 2019, due primarily to the increased frequency of the A675V and C469Y alleles (P<0.001 and P = 0.004, respectively). Single-nucleotide polymorphisms flanking the A675V mutation in Uganda were substantially different from those in Southeast Asia. CONCLUSIONS The independent emergence and local spread of clinically artemisinin-resistant P. falciparum has been identified in Africa. The two kelch13 mutations may be markers for detection of these resistant parasites

Absence of in vivo selection for K13 mutations after artemether–lumefantrine treatment in Uganda

Additional file 1. Eligibility criteria for recruitment into the therapeutic efficacy study and the molecular study

The diversity of Plasmodium falciparum isolates from asymptomatic and symptomatic school-age children in Kinshasa Province, Democratic Republic of Congo

Background:Understanding Plasmodium falciparum population diversity and transmission dynamics provides information on the intensity of malaria transmission, which is needed for assessing malaria control interventions. This study aimed to determine P. falciparum allelic diversity and multiplicity of infection (MOI) among asymptomatic and symptomatic school-age children in Kinshasa Province, Democratic Republic of Congo (DRC).Methods:A total of 438 DNA samples (248 asymptomatic and 190 symptomatic) were characterized by nested PCR and genotyping the polymorphic regions of pfmsp1 block 2 and pfmsp2 block 3.Results:Nine allele types were observed in pfmsp1 block2. The K1-type allele was predominant with 78% (229/293) prevalence, followed by the MAD20-type allele (52%, 152/293) and RO33-type allele (44%, 129/293). Twelve alleles were detected in pfmsp2, and the 3D7-type allele was the most frequent with 84% (256/304) prevalence, followed by the FC27-type allele (66%, 201/304). Polyclonal infections were detected in 63% (95% CI 56, 69) of the samples, and the MOI (SD) was 1.99 (0.97) in P. falciparum single-species infections. MOIs significantly increased in P. falciparum isolates from symptomatic parasite carriers compared with asymptomatic carriers (2.24 versus 1.69, adjusted b: 0.36, (95% CI 0.01, 0.72), p = 0.046) and parasitaemia > 10,000 parasites/μL compared to parasitaemia < 5000 parasites/μL (2.68 versus 1.63, adjusted b: 0.89, (95% CI 0.46, 1.25), p < 0.001).Conclusion:This survey showed low allelic diversity and MOI of P. falciparum, which reflects a moderate intensity of malaria transmission in the study areas. MOIs were more likely to be common in symptomatic infections and increased with the parasitaemia level. Further studies in different transmission zones are needed to understand the epidemiology and parasite complexity in the DRC

Engineering-Model Results of X-Band Synthetic Aperture Radar for Small Satellite and its Application to Constellation Mission

This paper presents the engineering model results of this X band synthetic aperture radar for small satellites and its application to constellation missions.The specifications of SAR performance are single polarization SAR with 1m ground resolution at 350 km altitude and with 3m ground resolution at 600km altitude orbit. A satellite is supposed to be 130kg in mass and the size is 0.7m x 0.8m x 0.9m on a rocket. A size of the deployed antenna is 4.9m x 0.7m. A chirped transmitting signal is amplified in a six GaN HEMT 200W amplifier modules to be combined in a waveguide resonator. The type of antenna system is deployable plane antenna due to its compact stow volume. Novel parallel plate slotted array antennas have been developed. We have performed compact range test, near-field measurement of an antenna wing with 2.8m x 0.7m size. The peak aperture efficiency is measured to be higher than 50%. We will launch the first demonstration satellite in late 2019. We finally will build a constellation of several tens SAR satellites with 1-3m resolution to realize from every day to every few hours revisit

Differential remodelling of peroxisome function underpins the environmental and metabolic adaptability of diplonemids and kinetoplastids

The remodelling of organelle function is increasingly appreciated as a central driver of eukaryotic biodiversity and evolution. Kinetoplastids including Trypanosoma and Leishmania have evolved specialized peroxisomes, called glycosomes. Glycosomes uniquely contain a glycolytic pathway as well as other enzymes, which underpin the physiological flexibility of these major human pathogens. The sister group of kinetoplastids are the diplonemids, which are among the most abundant eukaryotes in marine plankton. Here we demonstrate the compartmentalization of gluconeogenesis, or glycolysis in reverse, in the peroxisomes of the free-living marine diplonemid, Diplonema papillatum. Our results suggest that peroxisome modification was already under way in the common ancestor of kinetoplastids and diplonemids, and raise the possibility that the central importance of gluconeogenesis to carbon metabolism in the heterotrophic free-living ancestor may have been an important selective driver. Our data indicate that peroxisome modification is not confined to the kinetoplastid lineage, but has also been a factor in the success of their free-living euglenozoan relatives

Identification of pyrimethamine- and chloroquine-resistant Plasmodium falciparum in Africa between 1984 and 1998: genotyping of archive blood samples

<p>Abstract</p> <p>Background</p> <p>Understanding the geographical distribution of drug resistance of <it>Plasmodium falciparum </it>is important for the effective treatment of malaria. Drug resistance has previously been inferred mainly from records of clinical resistance. However, clinical resistance is not always consistent with the parasite's genetic resistance. Thus, molecular identification of the parasite's drug resistance is required. In Africa, clinical resistance to pyrimethamine (Pyr) and chloroquine (CQ) was evident before 1980 but few studies investigating the genetic resistance to these drugs were conducted before the late 1990s. In this study, genotyping of genes involved in resistance to Pyr and CQ was performed using archive blood samples from Africa between 1984 and 1998.</p> <p>Methods</p> <p>Parasite DNA was extracted from <it>P. falciparum</it>-infected blood smears collected from travellers returning to Japan from Africa between 1984 and 1998. Genotypes of the dihydrofolate reductase gene (<it>dhfr</it>) and CQ-resistance transporter gene (<it>pfcrt) </it>were determined by polymerase chain reaction amplification and sequencing.</p> <p>Results</p> <p>Genotyping of <it>dhfr </it>and <it>pfcrt </it>was successful in 59 and 80 samples, respectively. One wild-type and seven mutant <it>dhfr </it>genotypes were identified. Three <it>dhfr </it>genotypes lacking the S108N mutation (NRSI, ICSI, IRSI; amino acids at positions 51, 59, 108, and 164 with mutations underlined) were highly prevalent before 1994 but reduced after 1995, accompanied by an increase in genotypes with the S108N mutation. The <it>dhfr </it>IRNI genotype was first identified in Nigeria in 1991 in the present samples, and its frequency gradually increased. However, two double mutants (ICNI and NRNI), the latter of which was exclusively found in West Africa, were more frequent than the IRNI genotype. Only two <it>pfcrt </it>genotypes were found, the wild-type and a Southeast Asian type (CVIET; amino acids at positions 72-76 with mutations underlined). The CVIET genotype was already present as early as 1984 in Tanzania and Nigeria, and appeared throughout Africa between 1984 and 1998.</p> <p>Conclusions</p> <p>This study is the first to report the molecular identification of Pyr- and CQ-resistant genotypes of <it>P. falciparum </it>in Africa before 1990. Genotyping of <it>dhfr </it>and <it>pfcrt </it>using archive samples has revealed new aspects of the evolutionary history of Pyr- and CQ-resistant parasites in Africa.</p

Low prevalence of Plasmodium falciparum parasites lacking pfhrp2/3 genes among asymptomatic and symptomatic school-age children in Kinshasa, Democratic Republic of Congo

Background: Loss of efcacy of diagnostic tests may lead to untreated or mistreated malaria cases, compromising case management and control. There is an increasing reliance on rapid diagnostic tests (RDTs) for malaria diagnosis, with the most widely used of these targeting the Plasmodium falciparum histidine-rich protein 2 (PfHRP2). There are numerous reports of the deletion of this gene in P. falciparum parasites in some populations, rendering them unde‑ tectable by PfHRP2 RDTs. The aim of this study was to identify P. falciparum parasites lacking the P. falciparum histidine rich protein 2 and 3 genes (pfhrp2/3) isolated from asymptomatic and symptomatic school-age children in Kinshasa, Democratic Republic of Congo.Methods: The performance of PfHRP2-based RDTs in comparison to microscopy and PCR was assessed using blood samples collected and spotted on Whatman 903™ flter papers between October and November 2019 from schoolage children aged 6–14 years. PCR was then used to identify parasite isolates lacking pfhrp2/3 genes.Results: Among asymptomatic malaria carriers (N=266), 49%, 65%, and 70% were microscopy, PfHRP2_RDT, and pfdh-qPCR positive, respectively. The sensitivity and specifcity of RDTs compared to PCR were 80% and 70% while the sensitivity and specifcity of RDTs compared to microscopy were 92% and 60%, respectively. Among sympto‑ matic malaria carriers (N=196), 62%, 67%, and 87% were microscopy, PfHRP2-based RDT, pfdh-qPCR and positive, respectively. The sensitivity and specifcity of RDTs compared to PCR were 75% and 88%, whereas the sensitivity and specifcity of RDTs compared to microscopy were 93% and 77%, respectively. Of 173 samples with sufcient DNA for PCR amplifcation of pfhrp2/3, deletions of pfhrp2 and pfhrp3 were identifed in 2% and 1%, respectively. Three (4%)of samples harboured deletions of the pfhrp2 gene in asymptomatic parasite carriers and one (1%) isolate lacked the pfhrp3 gene among symptomatic parasite carriers in the RDT positive subgroup. No parasites lacking the pfhrp2/3 genes were found in the RDT negative subgroup.Conclusion: Plasmodium falciparum histidine-rich protein 2/3 gene deletions are uncommon in the surveyed popu‑ lation, and do not result in diagnostic failure. The use of rigorous PCR methods to identify pfhrp2/3 gene deletions is encouraged in order to minimize the overestimation of their prevalence