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Scientific Reports Jun 2024Pyrethroid bednets treated with the synergist piperonyl butoxide (PBO) offer the possibility of improved vector control in mosquito populations with metabolic...
LLIN Evaluation in Uganda Project (LLINEUP)-effects of a vector control trial on Plasmodium infection prevalence and genotypic markers of insecticide resistance in Anopheles vectors from 48 districts of Uganda.
Pyrethroid bednets treated with the synergist piperonyl butoxide (PBO) offer the possibility of improved vector control in mosquito populations with metabolic resistance. In 2017-2019, we conducted a large-scale, cluster-randomised trial (LLINEUP) to evaluate long-lasting insecticidal nets (LLINs) treated with a pyrethroid insecticide plus PBO (PBO LLINs), as compared to conventional, pyrethroid-only LLINs across 104 health sub-districts (HSDs) in Uganda. In LLINEUP, and similar trials in Tanzania, PBO LLINs were found to provide greater protection against malaria than conventional LLINs, reducing parasitaemia and vector density. In the LLINEUP trial, we conducted cross-sectional household entomological surveys at baseline and then every 6 months for two years, which we use here to investigate longitudinal changes in mosquito infection rate and genetic markers of resistance. Overall, 5395 female Anopheles mosquitoes were collected from 5046 households. The proportion of mosquitoes infected (PCR-positive) with Plasmodium falciparum did not change significantly over time, while infection with non-falciparum malaria decreased in An. gambiae s.s., but not An. funestus. The frequency of genetic markers associated with pyrethroid resistance increased significantly over time, but the rate of change was not different between the two LLIN types. The knock-down resistance (kdr) mutation Vgsc-995S declined over time as Vgsc-995F, the alternative resistance mutation at this codon, increased. Vgsc-995F appears to be spreading into Uganda. Distribution of LLINs in Uganda was previously found to be associated with reductions in parasite prevalence and vector density, but here we show that the proportion of infective mosquitoes remained stable across both PBO and non-PBO LLINs, suggesting that the potential for transmission persisted. The increased frequency of markers of pyrethroid resistance indicates that LLIN distribution favoured the evolution of resistance within local vectors and highlights the potential benefits of resistance management strategies.Trial registration: This study is registered with ISRCTN, ISRCTN17516395. Registered 14 February 2017, http://www.isrctn.com/ISRCTN17516395 .
Topics: Animals; Anopheles; Insecticide Resistance; Uganda; Mosquito Vectors; Insecticide-Treated Bednets; Mosquito Control; Humans; Pyrethrins; Insecticides; Malaria; Female; Plasmodium falciparum; Prevalence; Genetic Markers; Cross-Sectional Studies; Malaria, Falciparum; Piperonyl Butoxide; Genotype
PubMed: 38914669
DOI: 10.1038/s41598-024-65050-z -
MBio Jun 2024Piperaquine (PPQ) is widely used in combination with dihydroartemisinin as a first-line treatment against malaria. Multiple genetic drivers of PPQ resistance have been...
Piperaquine (PPQ) is widely used in combination with dihydroartemisinin as a first-line treatment against malaria. Multiple genetic drivers of PPQ resistance have been reported, including mutations in the () and increased copies of (). We generated a cross between a Cambodia-derived multidrug-resistant KEL1/PLA1 lineage isolate (KH004) and a drug-susceptible Malawian parasite (Mal31). Mal31 harbors a wild-type (3D7-like) allele and a single copy of , while KH004 has a chloroquine-resistant (Dd2-like) allele with an additional G367C substitution and multiple copies of . We recovered 104 unique recombinant parasites and examined a targeted set of progeny representing all possible combinations of variants at and . We performed a detailed analysis of competitive fitness and a range of PPQ susceptibility phenotypes with these progenies, including PPQ survival assay, area under the dose response curve, and a limited point IC. We find that inheritance of the KH004 allele is required for reduced PPQ sensitivity, whereas copy number variation in further decreases susceptibility but does not confer resistance in the absence of additional mutations in . A deep investigation of genotype-phenotype relationships demonstrates that progeny clones from experimental crosses can be used to understand the relative contributions , , and parasite genetic background to a range of PPQ-related traits. Additionally, we find that the resistance phenotype associated with parasites inheriting the G367C substitution in pfcrt is consistent with previously validated PPQ resistance mutations in this transporter.IMPORTANCEResistance to piperaquine, used in combination with dihydroartemisinin, has emerged in Cambodia and threatens to spread to other malaria-endemic regions. Understanding the causal mutations of drug resistance and their impact on parasite fitness is critical for surveillance and intervention and can also reveal new avenues to limiting the evolution and spread of drug resistance. An experimental genetic cross is a powerful tool for pinpointing the genetic determinants of key drug resistance and fitness phenotypes and has the distinct advantage of quantifying the effects of naturally evolved genetic variation. Our study was strengthened since the full range of copies of KH004 was inherited among the progeny clones, allowing us to directly test the role of the copy number on resistance-related phenotypes in the context of a unique allele. Our multigene model suggests an important role for both loci in the evolution of this multidrug-resistant parasite lineage.
PubMed: 38912775
DOI: 10.1128/mbio.00805-24 -
Protein and Peptide Letters Jun 2024Malaria caused by Plasmodium falciparum (Pf) is an illness that contributes significantly to the global health burden. Pf makes significant alterations to the host cell...
Malaria caused by Plasmodium falciparum (Pf) is an illness that contributes significantly to the global health burden. Pf makes significant alterations to the host cell to meet its metabolic demands and escape the immune response of the host. These include the export of a large number of parasite proteins to the infected Red Blood Cells (iRBC). Variable Surface Antigens (VSAs), which are highly polymorphic protein families with important roles in immune evasion, form an important component of the exported proteins. A total of five protein families constitute the VSAs, viz. PfEMP1 (Pf erythrocyte membrane protein 1), RIFIN (repetitive interspersed family), STEVOR (sub-telomeric open reading frame), SURFIN (surface-associated interspersed gene family), and PfMC-2TM (Pf Maurer's cleft two transmembrane). With orthologues present in various simian-infecting species, VSAs take up a variety of domain topologies and organizational structures while exhibiting differential expressions throughout the parasite life cycle. Their expression varies across clinical isolates and laboratory strains, which suggests their crucial role in host cell survival and defense. Members of VSAs are reported to contribute significantly to disease pathogenesis through immune evasion processes like cytoadherence, iRBC sequestration in the host vasculature, rosetting, reduced erythrocyte deformability, and direct immunosuppression. In this study, we have gathered information on various aspects of VSAs, like their orthologues, domain architecture, surface topology, functions and interactions, and three-dimensional structures, while emphasizing discoveries in the field. Considering the vast repertoire of Plasmodial VSAs with new emergent functions, a lot remains unknown about these families and, hence, malaria biology.
PubMed: 38910420
DOI: 10.2174/0109298665298567240530170924 -
Trends in Parasitology Jun 2024Small-Saunders et al. uncovered a new facet of artemisinin resistance in Plasmodium in which parasites use a previously underexplored arm of stress response mechanisms....
Small-Saunders et al. uncovered a new facet of artemisinin resistance in Plasmodium in which parasites use a previously underexplored arm of stress response mechanisms. Through altered epitranscriptomic modifications on tRNA, changed translation patterns adapt resistant cells to facilitate entry into a quiescent-like state which provides the parasite an escape from many drugs.
PubMed: 38910099
DOI: 10.1016/j.pt.2024.06.004 -
Trends in Parasitology Jun 2024The protozoan parasite Plasmodium falciparum, responsible for the deadliest form of human malaria, employs antigenic variation via monoallelic expression as a key... (Review)
Review
The protozoan parasite Plasmodium falciparum, responsible for the deadliest form of human malaria, employs antigenic variation via monoallelic expression as a key survival strategy. The selective activation of one out of the 60-member var gene family is key to understanding the parasite's ability to cause severe disease and evade the host immune response. var gene activation is initiated by its relocation to a specialized expression site. While the perinuclear expression site (PES) plays a crucial role in enabling the expression of a single allele, the characteristics of this PES remain largely obscure. Recent breakthroughs in genome editing tools and the discovery of regulatory noncoding RNAs have shed light on this intriguing biological feature, offering significant insights into the mechanisms of pathogen virulence.
PubMed: 38910098
DOI: 10.1016/j.pt.2024.06.002 -
European Journal of Medicinal Chemistry Jun 2024The increase in research funding for the development of antimalarials since 2000 has led to a surge of new chemotypes with potent antimalarial activity. High-throughput...
The increase in research funding for the development of antimalarials since 2000 has led to a surge of new chemotypes with potent antimalarial activity. High-throughput screens have delivered several thousand new active compounds in several hundred series, including the 4,7-diphenyl-1,4,5,6,7,8-hexahydroquinolines, hereafter termed dihydropyridines (DHPs). We optimized the DHPs for antimalarial activity. Structure-activity relationship studies focusing on the 2-, 3-, 4-, 6-, and 7-positions of the DHP core led to the identification of compounds potent (EC < 10 nM) against all strains of P. falciparum tested, including the drug-resistant parasite strains K1, W2, and TM90-C2B. Evaluation of efficacy of several compounds in vivo identified two compounds that reduced parasitemia by >75 % in mice 6 days post-exposure following a single 50 mg/kg oral dose. Resistance acquisition experiments with a selected dihydropyridine led to the identification of a single mutation conveying resistance in the gene encoding for Plasmodium falciparum multi-drug resistance protein 1 (PfMDR1). The same dihydropyridine possessed transmission blocking activity. The DHPs have the potential for the development of novel antimalarial drug candidates.
PubMed: 38909569
DOI: 10.1016/j.ejmech.2024.116599 -
Diagnostic Microbiology and Infectious... Jun 2024Drug resistance surveillance is a major integral part of malaria control programs. Molecular methods play a pivotal role in drug resistance detection and related...
Drug resistance surveillance is a major integral part of malaria control programs. Molecular methods play a pivotal role in drug resistance detection and related molecular research. This study aimed to develop a rapid and accurate detection method for drug resistance of Plasmodium falciparum (P. falciparum). A quantitative real-time PCR (qPCR) assay has been developed that identifies the mutation at locus A256T in the P.falciparum multi-drug resistance(pfmdr1) gene producing amino acid change at position 86. The results of 198 samples detected by qPCR were consistent with nested PCR and sequencing, giving an accuracy of 94.3%. The sensitivity, specificity, positive and negative predictive value of qPCR were 85.7%, 97.6%, 90.0% and 96.4%, respectively. The results of qPCR are basically consistent with the nested PCR, which is expected to replace the nested PCR as a new molecular biological method for drug resistance detection, providing reliable technical support for global malaria prevention and control.
PubMed: 38909426
DOI: 10.1016/j.diagmicrobio.2024.116400 -
The National Medical Journal of India 2023Background Malaria in pregnancy (MIP) is a major public health problem due to the vulnerability of pregnant women to infections, resulting in adverse maternal/foetal...
Burden of malaria during pregnancy in perennial transmission settings of two densely forested and remote blocks (Baihar and Birsa) of district Balaghat, Madhya Pradesh, central India.
Background Malaria in pregnancy (MIP) is a major public health problem due to the vulnerability of pregnant women to infections, resulting in adverse maternal/foetal outcomes in endemic areas. Methods We did a field-based study to assess the burden of MIP (prevalence at the time of enrolment and follow-up) and to identify risk factors for MIP in the Birsa and Baihar blocks of district Balaghat in Madhya Pradesh, which have perennial malaria transmission. Malaria screening (during 2015-2017) was done by microscopy and bivalent rapid diagnostic test (SD Bioline RDT, malaria antigen Plasmodium falciparum/Plasmodium vivax Pf/Pv). Dried blood spots were used for haemoglobin estimation. Sociodemographic details with past and present pregnancy status were obtained. A subset of pregnant women were followed up for malaria during pregnancy. Women were also screened for malaria post delivery. Malaria treatment was given as per the National Guidelines of 2013. Multivariate analysis was done to assess independent risk factors for malaria. Results A total of 1728 pregnant women were screened, of which 1651 were included in the final analysis. Malaria prevalence at first screening was 23.4% (Pf 88%). Prevalence and Pf parasitaemia both were significantly higher among primigravid (G1) compared to multigravid (G>2; p value 0.012 and 0.019, respectively). Pregnant women of the Baiga ethnic group were more likely to have malaria compared to those belonging to the Gond group (OR [95% CI]; 2.4 [1.7-3.4]; p<0.00001) and non-indigenous group (OR [95% CI]; 8.3 [3.9-19.7]; p<0.00001). Primigravid status of women, first and second trimester of pregnancy, women belonging to indigenous ethnic tribal group and cash crop insufficiency for whole year (a socioeconomic indicator) in the family were the independent risk factors for malaria. Conclusion MIP is a major public health problem in forested tribal settlements of Birsa and Baihar blocks of Balaghat district in Madhya Pradesh and requires immediate intervention.
Topics: Humans; Female; Pregnancy; India; Adult; Pregnancy Complications, Parasitic; Prevalence; Risk Factors; Malaria, Falciparum; Young Adult; Malaria, Vivax; Forests; Adolescent; Antimalarials; Plasmodium falciparum
PubMed: 38909309
DOI: 10.25259/NMJI_535_21 -
Malaria Journal Jun 2024Imported malaria continues to be reported in Sri Lanka after it was eliminated in 2012, and a few progress to life-threatening severe malaria.
BACKGROUND
Imported malaria continues to be reported in Sri Lanka after it was eliminated in 2012, and a few progress to life-threatening severe malaria.
METHODS
Data on imported malaria cases reported in Sri Lanka from 2013 to 2023 were extracted from the national malaria database maintained by the Anti Malaria Campaign (AMC) of Sri Lanka. Case data of severe malaria as defined by the World Health Organization were analysed with regard to patients' general characteristics and their health-seeking behaviour, and the latter compared with that of uncomplicated malaria patients. Details of the last three cases of severe malaria in 2023 are presented.
RESULTS
532 imported malaria cases were diagnosed over 11 years (2013-2023); 46 (8.6%) were severe malaria, of which 45 were Plasmodium falciparum and one Plasmodium vivax. Most severe malaria infections were acquired in Africa. All but one were males, and a majority (87%) were 26-60 years of age. They were mainly Sri Lankan nationals (82.6%). Just over half (56.5%) were treated at government hospitals. The average time between arrival of the person in Sri Lanka and onset of illness was 4 days. 29 cases of severe malaria were compared with 165 uncomplicated malaria cases reported from 2015 to 2023. On average both severe and uncomplicated malaria patients consulted a physician equally early (mean = 1 day) with 93.3% of severe malaria doing so within 3 days. However, the time from the point of consulting a physician to diagnosis of malaria was significantly longer (median 4 days) in severe malaria patients compared to uncomplicated patients (median 1 day) (p = 0.012) as was the time from onset of illness to diagnosis (p = 0.042). All severe patients recovered without sequelae except for one who died.
CONCLUSIONS
The risk of severe malaria among imported cases increases significantly beyond 5 days from the onset of symptoms. Although patients consult a physician early, malaria diagnosis tends to be delayed by physicians because it is now a rare disease. Good access to expert clinical care has maintained case fatality rates of severe malaria at par with those reported elsewhere.
Topics: Sri Lanka; Humans; Male; Adult; Middle Aged; Female; Young Adult; Communicable Diseases, Imported; Malaria, Falciparum; Malaria, Vivax; Aged; Adolescent; Malaria; Disease Eradication
PubMed: 38909255
DOI: 10.1186/s12936-024-05014-w -
Scientific Reports Jun 2024Hemozoin is a natural biomarker formed during the hemoglobin metabolism of Plasmodium parasites, the causative agents of malaria. The rotating-crystal magneto-optical...
Hemozoin is a natural biomarker formed during the hemoglobin metabolism of Plasmodium parasites, the causative agents of malaria. The rotating-crystal magneto-optical detection (RMOD) has been developed for its rapid and sensitive detection both in cell cultures and patient samples. In the current article we demonstrate that, besides quantifying the overall concentration of hemozoin produced by the parasites, RMOD can also track the size distribution of the hemozoin crystals. We establish the relations between the magneto-optical signal, the mean parasite age and the median crystal size throughout one erythrocytic cycle of Plasmodium falciparum parasites, where the latter two are determined by optical and scanning electron microscopy, respectively. The significant correlation between the magneto-optical signal and the stage distribution of the parasites indicates that the RMOD method can be utilized for species-specific malaria diagnosis and for the quick assessment of drug efficacy.
Topics: Hemeproteins; Plasmodium falciparum; Humans; Erythrocytes; Malaria, Falciparum; Microscopy, Electron, Scanning
PubMed: 38906910
DOI: 10.1038/s41598-024-60988-6