Genetic diversity and natural selection of Plasmodium vivax reticulocyte invasion genes in Ecuador.

BACKGROUND: Knowledge of the diversity of invasion ligands in malaria parasites in endemic regions is essential to understand how natural selection influences genetic diversity of these ligands and their feasibility as possible targets for future vaccine development. In this study the diversity of four genes for merozoite invasion ligands was studied in Ecuadorian isolates of Plasmodium vivax. METHODS: Eighty-eight samples from P. vivax infected individuals from the Coast and Amazon region of Ecuador were obtained between 2012 and 2015. The merozoite invasion genes pvmsp-1-19, pvdbpII, pvrbp1a-2 and pvama1 were amplified, sequenced, and compared to the Sal-1 strain. Polymorphisms were mapped and genetic relationships between haplotypes were determined. RESULTS: Only one nonsynonymous polymorphism was detected in pvmsp-1-19, while 44 nonsynonymous polymorphisms were detected in pvdbpII, 56 in pvrbp1a-2 and 33 in pvama1. While haplotypes appeared to be more related within each area of study and there was less relationship between parasites of the coastal and Amazon regions of the country, diversification processes were observed in the two Amazon regions. The highest haplotypic diversity for most genes occurred in the East Amazon of the country. The high diversity observed in Ecuadorian samples is closer to Brazilian and Venezuelan isolates, but lower than reported in other endemic regions. In addition, departure from neutrality was observed in Ecuadorian pvama1. Polymorphisms for pvdbpII and pvama1 were associated to B-cell epitopes. CONCLUSIONS: pvdbpII and pvama1 genetic diversity found in Ecuadorian P. vivax was very similar to that encountered in other malaria endemic countries with varying transmission levels and segregated by geographic region. The highest diversity of P. vivax invasion genes in Ecuador was found in the Amazonian region. Although selection appeared to have small effect on pvdbpII and pvrbp1a-2, pvama1 was influenced by significant balancing selection.

Resolving drug selection and migration in an inbred South American Plasmodium falciparum population with identity-by-descent analysis.

The human malaria parasite Plasmodium falciparum is globally widespread, but its prevalence varies significantly between and even within countries. Most population genetic studies in P. falciparum focus on regions of high transmission where parasite populations are large and genetically diverse, such as sub-Saharan Africa. Understanding population dynamics in low transmission settings, however, is of particular importance as these are often where drug resistance first evolves. Here, we use the Pacific Coast of Colombia and Ecuador as a model for understanding the population structure and evolution of Plasmodium parasites in small populations harboring less genetic diversity. The combination of low transmission and a high proportion of monoclonal infections means there are few outcrossing events and clonal lineages persist for long periods of time. Yet despite this, the population is evolutionarily labile and has successfully adapted to changes in drug regime. Using newly sequenced whole genomes, we measure relatedness between 166 parasites, calculated as identity by descent (IBD), and find 17 distinct but highly related clonal lineages, six of which have persisted in the region for at least a decade. This inbred population structure is captured in more detail with IBD than with other common population structure analyses like PCA, ADMIXTURE, and distance-based trees. We additionally use patterns of intra-chromosomal IBD and an analysis of haplotypic variation to explore past selection events in the region. Two genes associated with chloroquine resistance, crt and aat1, show evidence of hard selective sweeps, while selection appears soft and/or incomplete at three other key resistance loci (dhps, mdr1, and dhfr). Overall, this work highlights the strength of IBD analyses for studying parasite population structure and resistance evolution in regions of low transmission, and emphasizes that drug resistance can evolve and spread in small populations, as will occur in any region nearing malaria elimination.

High-throughput Plasmodium falciparum hrp2 and hrp3 gene deletion typing by digital PCR to monitor malaria rapid diagnostic test efficacy.

Most rapid diagnostic tests for Plasmodium falciparum malaria target the Histidine-Rich Proteins 2 and 3 (HRP2 and HRP3). Deletions of the hrp2 and hrp3 genes result in false-negative tests and are a threat for malaria control. A novel assay for molecular surveillance of hrp2/hrp3 deletions was developed based on droplet digital PCR (ddPCR). The assay quantifies hrp2, hrp3, and a control gene with very high accuracy. The theoretical limit of detection was 0.33 parasites/µl. The deletion was reliably detected in mixed infections with wild-type and hrp2-deleted parasites at a density of >100 parasites/reaction. For a side-by-side comparison with the conventional nested PCR (nPCR) assay, 248 samples were screened in triplicate by ddPCR and nPCR. No deletions were observed by ddPCR, while by nPCR hrp2 deletion was observed in 8% of samples. The ddPCR assay was applied to screen 830 samples from Kenya, Zanzibar/Tanzania, Ghana, Ethiopia, Brazil, and Ecuador. Pronounced differences in the prevalence of deletions were observed among sites, with more hrp3 than hrp2 deletions. In conclusion, the novel ddPCR assay minimizes the risk of false-negative results (i.e., hrp2 deletion observed when the sample is wild type), increases sensitivity, and greatly reduces the number of reactions that need to be run.

Anopheline and human drivers of malaria risk in northern coastal, Ecuador: a pilot study.

BACKGROUND: Understanding local anopheline vector species and their bionomic traits, as well as related human factors, can help combat gaps in protection. METHODS: In San José de Chamanga, Esmeraldas, at the Ecuadorian Pacific coast, anopheline mosquitoes were sampled by both human landing collections (HLCs) and indoor-resting aspirations (IAs) and identified using both morphological and molecular methods. Human behaviour observations (HBOs) (including temporal location and bed net use) were documented during HLCs as well as through community surveys to determine exposure to mosquito bites. A cross-sectional evaluation of Plasmodium falciparum and Plasmodium vivax infections was conducted alongside a malaria questionnaire. RESULTS: Among 222 anopheline specimens captured, based on molecular analysis, 218 were Nyssorhynchus albimanus, 3 Anopheles calderoni (n = 3), and one remains unidentified. Anopheline mean human-biting rate (HBR) outdoors was (13.69), and indoors (3.38) (p = 0.006). No anophelines were documented resting on walls during IAs. HBO-adjusted human landing rates suggested that the highest risk of being bitten was outdoors between 18.00 and 20.00 h. Human behaviour-adjusted biting rates suggest that overall, long-lasting insecticidal bed nets (LLINs) only protected against 13.2% of exposure to bites, with 86.8% of exposure during the night spent outside of bed net protection. The malaria survey found 2/398 individuals positive for asymptomatic P. falciparum infections. The questionnaire reported high (73.4%) bed net use, with low knowledge of malaria. CONCLUSION: The exophagic feeding of anopheline vectors in San Jose de Chamanga, when analysed in conjunction with human behaviour, indicates a clear gap in protection even with high LLIN coverage. The lack of indoor-resting anophelines suggests that indoor residual spraying (IRS) may have limited effect. The presence of asymptomatic infections implies the presence of a human reservoir that may maintain transmission.

Número dedicado a la Educación Universitaria / Number dedicated to University Education

El volumen 5 número 1 de nuestra Revista Methodo Investigación Aplicada a las ciencias biológicas, la iniciamos proponiendo a la comunidad científica y educativa un análisis de diferentes factores que hacen a la Educación Universitaria, en especial de las carreras en ciencias de la salud. (AU)

Perspectivas Ignacianas para ser un buen docente en la Universidad / Ignatian perspectives to be a good teacher at the University

INTRODUCCIÓN: Existe el concepto social que "saber" transforma al experto en un buen docente, pero probablemente "saber" es la condición básica para ejercer la docencia. El objetivo de este trabajo es analizar las características que superan al conocimiento para transformarse en un buen docente enriquecido por la Visión Ignaciana de esta actividad. MATERIAL Y MÉTODO: Para elaborar este informe se trabajó sobre tres documentos de alto impacto en nuestro hacer: 1) el paradigma Paradigma Ledesma ­ Kolvenbach; 2) Constitución apostólica sobre las Universidades Católicas de SS Juan Pablo II y 3) La pedagogía Ignaciana. DISCUSIÓN Y CONCLUSIÓN: Ser buen docente, parte del saber especifico, pero es mucho más que simplemente saber, implica compromiso con la realidad y la capacidad de crear espacios, que favorecen la apropiación crítica del conocimiento y la actitud de búsqueda permanente por parte de la comunidad estudiantil.

INTRODUCTION: There is the social concept that "knowing" transforms the expert into a good teacher, but probably "knowing" is the basic condition for teaching. The objective of this work is to analyze the characteristics that surpass knowledge to become a good teacher enriched by the Ignatian Vision of this activity. MATERIAL AND METHOD: To prepare this report, we worked on three documents of high impact in our work: 1) the Paradigm Ledesma - Kolvenbach paradigm; 2) Apostolic Constitution on the Catholic Universities of SS John Paul II and 3) Ignatian pedagogy. DISCUSSION AND CONCLUSSON: The conclusions are that being a good teacher part of the specific knowledge, but it is much more than just knowing, implies commitment to reality and the ability to create spaces that favor the critical appropriation of knowledge and the attitude of permanent search by the student community.

Genotypes and phenotypes of resistance in Ecuadorian Plasmodium falciparum.

BACKGROUND: Malaria continues to be endemic in the coast and Amazon regions of Ecuador. Clarifying current Plasmodium falciparum resistance in the country will support malaria elimination efforts. In this study, Ecuadorian P. falciparum parasites were analysed to determine their drug resistance genotypes and phenotypes. METHODS: Molecular analyses were performed to search for mutations in known resistance markers (Pfcrt, Pfdhfr, Pfdhps, Pfmdr1, k13). Pfmdr1 copy number was determined by qPCR. PFMDR1 transporter activity was characterized in live parasites using live cell imaging in combination with the Fluo-4 transport assay. Chloroquine, quinine, lumefantrine, mefloquine, dihydroartemisinin, and artemether sensitivities were measured by in vitro assays. RESULTS: The majority of samples from this study presented the CVMNT genotype for Pfcrt (72-26), NEDF SDFD mutations in Pfmdr1 and wild type genotypes for Pfdhfr, Pfdhps and k13. The Ecuadorian P. falciparum strain ESM-2013 showed in vitro resistance to chloroquine, but sensitivity to quinine, lumefantrine, mefloquine, dihydroartemisinin and artemether. In addition, transport of the fluorochrome Fluo-4 from the cytosol into the digestive vacuole (DV) of the ESM-2013 strain was minimally detected in the DV. All analysed samples revealed one copy of Pfmdr1. CONCLUSION: This study indicates that Ecuadorian parasites presented the genotype and phenotype for chloroquine resistance and were found to be sensitive to SP, artemether-lumefantrine, quinine, mefloquine, and dihydroartemisinin. The results suggest that the current malaria treatment employed in the country remains effective. This study clarifies the status of anti-malarial resistance in Ecuador and informs the P. falciparum elimination campaigns in the country.

Diverse origin of Plasmodium falciparum in northwest Ecuador.

BACKGROUND: Ecuador plans to eliminate malaria by 2020, and the country has already seen a decrease in the number of cases from more than 100,000 in 2000 to only 618 in 2015. Around 30% of malaria infections in Ecuador are caused by Plasmodium falciparum. Most malaria population genetics studies performed in Latin America, especially in the Pacific Coast, indicate a high clonality and a clear structure of P. falciparum populations. It was shown that an outbreak of P. falciparum in northwest Ecuador was the result of a clonal expansion of parasites circulating at low levels in the country or re-invading Ecuador from neighbouring territories. However, general characteristics of P. falciparum circulating in the northwest coast of Ecuador have not been determined. The main goal of this study was to genetically characterize the population structure of P. falciparum in coastal Ecuadorian localities bordering with Colombia. METHODS: Molecular investigation of 41 samples collected from 2013 to 2016 in San Lorenzo County, northwest Ecuador was performed using seven neutral microsatellite markers. RESULTS: The genetic population structure of P. falciparum in northwest Ecuador is clearly defined as three different genetic groups previously reported in Ecuador, Peru and Colombia. CONCLUSIONS: The limited number of P. falciparum clonal types that are circulating in northwest Ecuador, are related to ancestral parasite clonal lineages reported in the Pacific Coast. These parasites could be a product of migration from neighbouring regions or residual clonal types circulating in the country in low proportions. Studies of the genetic characterization of P. falciparum in eliminating areas help determine the possible origin of parasites in order to create strategies to prevent the entrance of new lineages and achieve local elimination of malaria.

Malaria epidemiology in low-endemicity areas of the northern coast of Ecuador: high prevalence of asymptomatic infections.

BACKGROUND: The recent scale-up in malaria control measures in Latin America has resulted in a significant decrease in the number of reported cases in several countries including Ecuador, where it presented a low malaria incidence in recent years (558 reported cases in 2015) with occasional outbreaks of both Plasmodium falciparum and Plasmodium vivax in the coastal and Amazonian regions. This success in malaria control in recent years has led Ecuador to transition its malaria policy from control to elimination. RESULTS: This study evaluated the general knowledge, attitude and practices (KAP) about malaria, as well as its prevalence in four communities of an endemic area in northwest Ecuador. A total of 258 interviews to assess KAP in the community indicated that most people in the study area have a basic knowledge about the disease but did not use to contribute to its control. Six hundred and forty-eight blood samples were collected and analysed by thick blood smear and real-time PCR. In addition, the distribution of the infections was mapped in the study communities. Although, no parasites were found by microscopy, by PCR the total malaria prevalence was 7.5% (6.9% P. vivax and 0.6% P. falciparum), much higher than expected and comparable to that reported in endemic areas of neighbouring countries with higher malaria transmission. Serology using ELISA and immunofluorescence indicated 27% respondents for P. vivax and 22% respondents for P. falciparum. CONCLUSIONS: Results suggest that despite a great malaria reduction in Ecuador, transition from control to elimination would demand further improvement in malaria diagnostics, including active case detection to identify and treat parasite asymptomatic carriers, as well as community participation in its elimination.

Clonal population expansion in an outbreak of Plasmodium falciparum on the northwest coast of Ecuador.

BACKGROUND: Determining the source of malaria outbreaks in Ecuador and identifying remaining transmission foci will help in malaria elimination efforts. In this study, the genetic signatures of Plasmodium falciparum isolates, obtained from an outbreak that occurred in northwest Ecuador from 2012 to 2013, were characterized. METHODS: Molecular investigation of the outbreak was performed using neutral microsatellites, drug resistance markers and pfhrp2 and pfhrp3 genotyping. RESULTS: A majority of parasite isolates (31/32) from this outbreak were of a single clonal type that matched a clonal lineage previously described on the northern coast of Peru and a historical isolate from Ecuador. All but one isolate carried a chloroquine-resistant pfcrt genotype and sulfadoxine- and pyrimethamine-sensitive pfdhps and pfdhfr genotypes. Pfmdr1 mutations were identified in codons 184 and 1042. In addition, most samples (97 %) showed presence of pfhrp2 gene. CONCLUSIONS: This study indicates that parasites from a single clonal lineage largely contributed to this outbreak and this lineage was found to be genetically related to a lineage previously reported in the Peruvian coast and historical Ecuadorian parasites.

[Comparison of FRAX Score without bone mineral density determination and the criteria proposed by the Argentine Osteoporosis Society for the use of antiresorptive therapy in postmenopausal women]. / Comparación entre score de frax sin densidad mineral ósea y los criterios propuestos por la Sociedad Argentina de Osteoporosis para el uso de tratamiento antirresortivo en mujeres postmenopáusicas.

To identify patients at high risk of fracture using clinical risk factors could reduce health costs arising from the realization of a bone densitometry. The aim of this study was to compare the FRAX score without bone mineral density (BMD) with the criteria proposed by the Argentine Society of Osteoporosis (SAO) to consider starting antiresorptive treatment. We conducted an observational, cross-sectional study where 330 postmenopausal women between 40 and 90 years of age were included. The number of treatments given if the FRAX tool without BMD had been followed was compared with the number of treatments indicated using the SAO criteria. Using the SAO criteria, 85 (25.8%) patients would initiate antiresorptive treatment compared with 15 (4.5%) using the FRAX without BMD (p = 0.0019). Among the 67 patients with a diagnosis of osteoporosis by BMD determination, all of them (100%) would have received treatment by using the SAO criteria compared with 10 (15%) using the FRAX score (p = 0.011). The use of FRAX without BMD significantly underestimates the number of patients who should receive antiresorptive treatment. In patients diagnosed with osteoporosis by BMD, the FRAX score underestimates the number of patients to be treated.

Comparación entre score de frax sin densidad mineral ósea y los criterios propuestos por la sociedad Argentina de osteoporosis para el uso de tratamiento antirresortivo en mujeres postmenopáusicas

Identificar pacientes con alto riesgo de fractura utilizando factores de riesgo clínicos podría reducir los gastos en salud derivados de la realización de una densitometría ósea. El objetivo de este estudio fue comparar el score de FRAX sin determinación de densidad mineral ósea (DMO) con los criterios propuestos por la Sociedad Argentina de Osteoporosis (SAO), para considerar el inicio de tratamiento antirresortivo. Realizamos un estudio observacional, transversal. Se incluyeron 330 mujeres postmenopáusicas entre 40 y 90 años de edad. Se determinó la cantidad de tratamientos indicados según se utilice la herramienta FRAX sin DMO, o los criterios de la SAO. Utilizando los criterios de la SAO, 85 (25.8%) pacientes recibirían tratamiento, mientras que si se utilizara la herramienta FRAX sin DMO, lo harían 15 (4.5%) pacientes (p = 0.0019). De los 67 pacientes con diagnóstico de osteoporosis por densitometría ósea, todas recibirían tratamiento utilizando los criterios de la SAO y solo 10 (15%) lo harían si utilizáramos el score de FRAX sin DMO (p = 0.011). La utilización del score de FRAX sin DMO reduce en forma significativa la cantidad de pacientes tratables en comparación con los criterios actuales de la SAO. En pacientes con diagnóstico de osteoporosis por DMO, el score de FRAX subestima los pacientes a tratar.

To identify patients at high risk of fracture using clinical risk factors could reduce health costs arising from the realization of a bone densitometry. The aim of this study was to compare the FRAX score without bone mineral density (BMD) with the criteria proposed by the Argentine Society of Osteoporosis (SAO) to consider starting antiresorptive treatment. We conducted an observational, cross-sectional study where 330 postmenopausal women between 40 and 90 years of age were included. The number of treatments given if the FRAX tool without BMD had been followed was compared with the number of treatments indicated using the SAO criteria. Using the SAO criteria, 85 (25.8%) patients would initiate antiresorptive treatment compared with 15 (4.5%) using the FRAX without BMD (p = 0.0019). Among the 67 patients with a diagnosis of osteoporosis by BMD determination, all of them (100%) would have received treatment by using the SAO criteria compared with 10 (15%) using the FRAX score (p = 0.011). The use of FRAX without BMD significantly underestimates the number of patients who should receive antiresorptive treatment. In patients diagnosed with osteoporosis by BMD, the FRAX score underestimates the number of patients to be treated.

Comparación entre score de frax sin densidad mineral ósea y los criterios propuestos por la sociedad Argentina de osteoporosis para el uso de tratamiento antirresortivo en mujeres postmenopáusicas

Identificar pacientes con alto riesgo de fractura utilizando factores de riesgo clínicos podría reducir los gastos en salud derivados de la realización de una densitometría ósea. El objetivo de este estudio fue comparar el score de FRAX sin determinación de densidad mineral ósea (DMO) con los criterios propuestos por la Sociedad Argentina de Osteoporosis (SAO), para considerar el inicio de tratamiento antirresortivo. Realizamos un estudio observacional, transversal. Se incluyeron 330 mujeres postmenopáusicas entre 40 y 90 años de edad. Se determinó la cantidad de tratamientos indicados según se utilice la herramienta FRAX sin DMO, o los criterios de la SAO. Utilizando los criterios de la SAO, 85 (25.8%) pacientes recibirían tratamiento, mientras que si se utilizara la herramienta FRAX sin DMO, lo harían 15 (4.5%) pacientes (p = 0.0019). De los 67 pacientes con diagnóstico de osteoporosis por densitometría ósea, todas recibirían tratamiento utilizando los criterios de la SAO y solo 10 (15%) lo harían si utilizáramos el score de FRAX sin DMO (p = 0.011). La utilización del score de FRAX sin DMO reduce en forma significativa la cantidad de pacientes tratables en comparación con los criterios actuales de la SAO. En pacientes con diagnóstico de osteoporosis por DMO, el score de FRAX subestima los pacientes a tratar.(AU)

To identify patients at high risk of fracture using clinical risk factors could reduce health costs arising from the realization of a bone densitometry. The aim of this study was to compare the FRAX score without bone mineral density (BMD) with the criteria proposed by the Argentine Society of Osteoporosis (SAO) to consider starting antiresorptive treatment. We conducted an observational, cross-sectional study where 330 postmenopausal women between 40 and 90 years of age were included. The number of treatments given if the FRAX tool without BMD had been followed was compared with the number of treatments indicated using the SAO criteria. Using the SAO criteria, 85 (25.8%) patients would initiate antiresorptive treatment compared with 15 (4.5%) using the FRAX without BMD (p = 0.0019). Among the 67 patients with a diagnosis of osteoporosis by BMD determination, all of them (100%) would have received treatment by using the SAO criteria compared with 10 (15%) using the FRAX score (p = 0.011). The use of FRAX without BMD significantly underestimates the number of patients who should receive antiresorptive treatment. In patients diagnosed with osteoporosis by BMD, the FRAX score underestimates the number of patients to be treated.(AU)

Orally bioavailable 6-chloro-7-methoxy-4(1H)-quinolones efficacious against multiple stages of Plasmodium.

The continued proliferation of malaria throughout temperate and tropical regions of the world has promoted a push for more efficacious treatments to combat the disease. Unfortunately, more recent remedies such as artemisinin combination therapies have been rendered less effective due to developing parasite resistance, and new drugs are required that target the parasite in the liver to support the disease elimination efforts. Research was initiated to revisit antimalarials developed in the 1940s and 1960s that were deemed unsuitable for use as therapeutic agents as a result of poor understanding of both physicochemical properties and parasitology. Structure-activity and structure-property relationship studies were conducted to generate a set of compounds with the general 6-chloro-7-methoxy-2-methyl-4(1H)-quinolone scaffold which were substituted at the 3-position with a variety of phenyl moieties possessing various properties. Extensive physicochemical evaluation of the quinolone series was carried out to downselect the most promising 4(1H)-quinolones, 7, 62, 66, and 67, which possessed low-nanomolar EC50 values against W2 and TM90-C2B as well as improved microsomal stability. Additionally, in vivo Thompson test results using Plasmodium berghei in mice showed that these 4(1H)-quinolones were efficacious for the reduction of parasitemia at >99% after 6 days.

Evidence for pyronaridine as a highly effective partner drug for treatment of artemisinin-resistant malaria in a rodent model.

The increasing prevalence in Southeast Asia of Plasmodium falciparum infections with delayed parasite clearance rates, following treatment of malaria patients with the artemisinin derivative artesunate, highlights an urgent need to identify which of the currently available artemisinin-based combination therapies (ACTs) are most suitable to treat populations with emerging artemisinin resistance. Here, we demonstrate that the rodent Plasmodium berghei SANA strain has acquired artemisinin resistance following drug pressure, as defined by reduced parasite clearance and early recrudescence following daily exposure to high doses of artesunate or the active metabolite dihydroartemisinin. Using the SANA strain and the parental drug-sensitive N strain, we have interrogated the antimalarial activity of five ACTs, namely, artemether-lumefantrine, artesunate-amodiaquine, artesunate-mefloquine, dihydroartemisinin-piperaquine, and the newest combination artesunate-pyronaridine. By monitoring parasitemia and outcome for 30 days following initiation of treatment, we found that infections with artemisinin-resistant P. berghei SANA parasites can be successfully treated with artesunate-pyronaridine used at doses that are curative for the parental drug-sensitive N strain. No other partner drug combination was as effective in resolving SANA infections. Of the five partner drugs tested, pyronaridine was also the most effective at suppressing the recrudescence of SANA parasites. These data support the potential benefit of implementing ACTs with pyronaridine in regions affected by artemisinin-resistant malaria.

4-(1H)-Quinolones and 1,2,3,4-Tetrahydroacridin-9(10H)-ones prevent the transmission of Plasmodium falciparum to Anopheles freeborni.

Malaria kills approximately 1 million people a year, mainly in sub-Saharan Africa. Essential steps in the life cycle of the parasite are the development of gametocytes, as well as the formation of oocysts and sporozoites, in the Anopheles mosquito vector. Preventing transmission of malaria through the mosquito is necessary for the control of the disease; nevertheless, the vast majority of drugs in use act primarily against the blood stages. The study described herein focuses on the assessment of the transmission-blocking activities of potent antierythrocytic stage agents derived from the 4(1H)-quinolone scaffold. In particular, three 3-alkyl- or 3-phenyl-4(1H)-quinolones (P4Qs), one 7-(2-phenoxyethoxy)-4(1H)-quinolone (PEQ), and one 1,2,3,4-tetrahydroacridin-9(10H)-one (THA) were assessed for their transmission-blocking activity against the mosquito stages of the human malaria parasite (Plasmodium falciparum) and the rodent parasite (P. berghei). Results showed that all of the experimental compounds reduced or prevented the exflagellation of male gametocytes and, more importantly, prevented parasite transmission to the mosquito vector. Additionally, treatment with ICI 56,780 reduced the number of sporozoites that reached the Anopheles salivary glands. These findings suggest that 4(1H)-quinolones, which have activity against the blood stages, can also prevent the transmission of Plasmodium to the mosquito and, hence, are potentially important drug candidates to eradicate malaria.

Quinolone-3-diarylethers: a new class of antimalarial drug.

The goal for developing new antimalarial drugs is to find a molecule that can target multiple stages of the parasite's life cycle, thus impacting prevention, treatment, and transmission of the disease. The 4(1H)-quinolone-3-diarylethers are selective potent inhibitors of the parasite's mitochondrial cytochrome bc1 complex. These compounds are highly active against the human malaria parasites Plasmodium falciparum and Plasmodium vivax. They target both the liver and blood stages of the parasite as well as the forms that are crucial for disease transmission, that is, the gametocytes, the zygote, the ookinete, and the oocyst. Selected as a preclinical candidate, ELQ-300 has good oral bioavailability at efficacious doses in mice, is metabolically stable, and is highly active in blocking transmission in rodent models of malaria. Given its predicted low dose in patients and its predicted long half-life, ELQ-300 has potential as a new drug for the treatment, prevention, and, ultimately, eradication of human malaria.