Parasite Plasmodium Falciparum Research Articles

Cerebral Malaria Model Applying Human Brain Organoids.

Neural injuries in cerebral malaria patients are a significant cause of morbidity and mortality. Nevertheless, a comprehensive research approach to study this issue is lacking, so herein we propose an in vitro system to study human cerebral malaria using cellular approaches. Our first goal was to establish a cellular system to identify the molecular alterations in human brain vasculature cells that resemble the blood-brain barrier (BBB) in cerebral malaria (CM). Through transcriptomic analysis, we characterized specific gene expression profiles in human brain microvascular endothelial cells (HBMEC) activated by the Plasmodium falciparum parasites. We also suggest potential new genes related to parasitic activation. Then, we studied its impact at brain level after Plasmodium falciparum endothelial activation to gain a deeper understanding of the physiological mechanisms underlying CM. For that, the impact of HBMEC-P. falciparum-activated secretomes was evaluated in human brain organoids. Our results support the reliability of in vitro cellular models developed to mimic CM in several aspects. These systems can be of extreme importance to investigate the factors (parasitological and host) influencing CM, contributing to a molecular understanding of pathogenesis, brain injury, and dysfunction.

Low Prevalence of Plasmodium falciparum Histidine-Rich Protein 2 and 3 Gene Deletions-A Multiregional Study in Central and West Africa.

Plasmodium falciparum parasites carrying deletions of histidine-rich protein 2 and 3 genes, pfhrp2 and pfhrp3, respectively, are likely to escape detection via HRP2-based rapid diagnostic tests (RDTs) and, consequently, treatment, posing a major risk to both the health of the infected individual and malaria control efforts. This study assessed the frequency of pfhrp2- and pfhrp3-deleted strains at four different study sites in Central Africa (number of samples analyzed: Gabon N = 534 and the Republic of Congo N = 917) and West Africa (number of samples analyzed: Nigeria N = 466 and Benin N = 120) using a highly sensitive multiplex qPCR. We found low prevalences for pfhrp2 (1%, 0%, 0.03% and 0) and pfhrp3 single deletions (0%, 0%, 0.03% and 0%) at all study sites (Gabon, the Republic of Congo, Nigeria and Benin, respectively). Double-deleted P. falciparum were only found in Nigeria in 1.6% of all internally controlled samples. The results of this pilot investigation do not point towards a high risk for false-negative RDT results due to pfhrp2/pfhrp3 deletions in Central and West African regions. However, as this scenario can change rapidly, continuous monitoring is essential to ensure that RDTs remain a suitable tool for the malaria diagnostic strategy.

Limited genetic variations of the Rh5-CyRPA-Ripr invasion complex in Plasmodium falciparum parasite population in selected malaria-endemic regions, Kenya.

The invasion of human erythrocytes by Plasmodium falciparum merozoites requires interaction between parasite ligands and host receptors. Interaction of PfRh5-CyRPA-Ripr protein complex with basigin, an erythrocyte surface receptor, via PfRh5 is essential for erythrocyte invasion. Antibodies raised against each antigen component of the complex have demonstrated erythrocyte invasion inhibition, making these proteins potential blood-stage vaccine candidates. Genetic polymorphisms present a significant challenge in developing efficacious vaccines, leading to variant-specific immune responses. This study investigated the genetic variations of the PfRh5 complex proteins in P. falciparum isolates from Lake Victoria islands, Western Kenya. Here, twenty-nine microscopically confirmed P. falciparum field samples collected from islands in Lake Victoria between July 2014 and July 2016 were genotyped by whole genome sequencing, and results compared to sequences mined from the GenBank database, from a study conducted in Kilifi, as well as other sequences from the MalariaGEN repository. We analyzed the frequency of polymorphisms in the PfRh5 protein complex proteins, PfRh5, PfCyRPA, PfRipr, and PfP113, and their location mapped on the 3D protein complex structure. We identified a total of 58 variants in the PfRh5 protein complex. PfRh5 protein was the most polymorphic with 30 SNPs, while PfCyRPA was relatively conserved with 3 SNPs. The minor allele frequency of the SNPs ranged between 1.9% and 21.2%. Ten high-frequency alleles (>5%) were observed in PfRh5 at codons 147, 148, 277, 410, and 429 and in PfRipr at codons 190, 255, 259, and 1003. A SNP was located in protein-protein interaction region C203Y and F292V of PfRh5 and PfCyRPA, respectively. Put together, this study revealed low polymorphisms in the PfRh5 invasion complex in the Lake Victoria parasite population. However, the two mutations identified on the protein interaction regions prompts for investigation on their impacts on parasite invasion process to support the consideration of PfRh5 components as potential malaria vaccine candidates.

Phytofabrication and characterization of Alchornea cordifolia silver nanoparticles and evaluation of antiplasmodial, hemocompatibility and larvicidal potential.

Purpose: The recent emergence of Plasmodium falciparum (Pf) parasites resistant to current artemisinin-based combination therapies in Africa justifies the need to develop new strategies for successful malaria control. We synthesized, characterized and evaluated medical applications of optimized silver nanoparticles using Alchornea cordifolia (AC-AgNPs), a plant largely used in African and Asian traditional medicine. Methods: Fresh leaves of A. cordifolia were used to prepare aqueous crude extract, which was mixed with silver nitrate for AC-AgNPs synthesis and optimization. The optimized AC-AgNPs were characterized using several techniques including ultraviolet-visible spectrophotometry (UV-Vis), scanning/transmission electron microscopy (SEM/TEM), powder X-ray diffraction (PXRD), selected area electron diffraction (SAED), energy dispersive X-ray spectroscopy (EDX), Fourier transformed infrared spectroscopy (FTIR), dynamic light scattering (DLS) and Zeta potential. Thereafter, AC-AgNPs were evaluated for their hemocompatibility and antiplasmodial activity against Pf malaria strains 3D7 and RKL9. Finally, lethal activity of AC-AgNPs was assessed against mosquito larvae of Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti which are vectors of neglected diseases such as dengue, filariasis and chikungunya. Results: The AC-AgNPs were mostly spheroidal, polycrystalline (84.13%), stable and polydispersed with size of 11.77 ± 5.57nm. FTIR revealed the presence of several peaks corresponding to functional chemical groups characteristics of alkanoids, terpenoids, flavonoids, phenols, steroids, anthraquonones and saponins. The AC-AgNPs had a high antiplasmodial activity, with IC50 of 8.05μg/mL and 10.31μg/mL against 3D7 and RKL9 Plasmodium falciparum strains. Likewise, high larvicidal activity of AC-AgNPs was found after 24h- and 48h-exposure: LC50 = 18.41μg/mL and 8.97μg/mL (Culex quinquefasciatus), LC50 = 16.71μg/mL and 7.52μg/mL (Aedes aegypti) and LC50 = 10.67μg/mL and 5.85μg/mL (Anopheles stephensi). The AC-AgNPs were highly hemocompatible (HC50 > 500μg/mL). Conclusion: In worrying context of resistance of parasite and mosquitoes, green nanotechnologies using plants could be a cutting-edge alternative for drug/insecticide discovery and development.

Establishment of tetra-primer ARMS-PCR technique for detecting exo-E415G SNP in Plasmodium falciparum isolatesfrom Central Highlands of Vietnam

Drug resistance in Plasmodium falciparum parasites is associated with the single nucleotide polymorphism (SNP) exo-E415G, which is considered as a marker to reduce the susceptibility to artimisinin and leads to treatment failure. This study aims to establish a procedure based on tetra-primer ARMS PCR technique to detect the SNP exo-E415G in malaria patients who experienced treatment failure with artemisinin. DNA sample from P. falciparum 3D7 isolate was used to optimise the procedure based on tetra-primer ARMS PCR technique to detect exo-E415G SNP. The method was then applied to screen for exo-E415G SNP on 123 blood samples from patients who experienced treatment failure with artemisinin in 3 provinces (Gia Lai, Dak Nong, Dak Lak) from Central Highlands of Vietnam. A DNA fragment (749 bp) containing the exo-E415GSNP was amplified using primer pairs E415G-Fc and E415G-Rc. Specific primers for the wildtype alen (A alen) and the mutant alen (G alen) amplified fragments with the length of 316 and 474 bp, respectively. The genotyping results were consistent with Sanger sequencing. The tetra-primer ARMS PCR technique was used for genotyping exo-E415G SNP on 123 patients who failed with artemisinin treatment, the frequency of exo-E415G alen was observed at 78% (96/123). In conclusion, the simple tetra-primer ARMS PCR technique was established to detect the SNP Exo-E415G. The prevalence of the mutant alenExo-E415G was 78% in the Central Highlands of Vietnam.

Identifying inhibitors of β-haematin formation with activity against chloroquine-resistant Plasmodium falciparum malaria parasites via virtual screening approaches

The biomineral haemozoin, or its synthetic analogue β-haematin (βH), has been the focus of several target-based screens for activity against Plasmodium falciparum parasites. Together with the known βH crystal structure, the availability of this screening data makes the target amenable to both structure-based and ligand-based virtual screening. In this study, molecular docking and machine learning techniques, including Bayesian and support vector machine classifiers, were used in sequence to screen the in silico ChemDiv 300k Representative Compounds library for inhibitors of βH with retained activity against P. falciparum. We commercially obtained and tested a prioritised set of inhibitors and identified the coumarin and iminodipyridinopyrimidine chemotypes as potent in vitro inhibitors of βH and whole cell parasite growth.

Laboratory-based efficacy evaluation of Bacillus thuringiensis var. israelensis and temephos larvicides against larvae of Anopheles stephensi in ethiopia

BackgroundMalaria, transmitted by the bite of infective female Anopheles mosquitoes, remains a global public health problem. The presence of an invasive Anopheles stephensi, capable of transmitting Plasmodium vivax and Plasmodium falciparum parasites was first reported in Ethiopia in 2016. The ecology of An. stephensi is different from that of Anopheles arabiensis, the primary Ethiopian malaria vector, and this suggests that alternative control strategies may be necessary. Larviciding may be an effective alternative strategy, but there is limited information on the susceptibility of Ethiopian An. stephensi to common larvicides. This study aimed to evaluate the efficacy of temephos and Bacillus thuringiensis var. israelensis (Bti) larvicides against larvae of invasive An. stephensi.MethodsThe diagnostic doses of two larvicides, temephos (0.25 ml/l) and Bti (0.05 mg/l) were tested in the laboratory against the immature stages (late third to early fourth stages larvae) of An. stephensi collected from the field and reared in a bio-secure insectary. Larvae were collected from two sites (Haro Adi and Awash Subuh Kilo). For each site, three hundred larvae were tested against each insecticide (as well as an untreated control), in batches of 25. The data from all replicates were pooled and descriptive statistics prepared.ResultsThe mortality of larvae exposed to temephos was 100% for both sites. Mortality to Bti was 99.7% at Awash and 100% at Haro Adi site.ConclusionsLarvae of An. stephensi are susceptible to temephos and Bti larvicides suggesting that larviciding with these insecticides through vector control programmes may be effective against An. stephensi in these localities.

Evidence for exposure dependent carriage of malaria parasites across the dry season: modelling analysis of longitudinal data

BackgroundIn malaria endemic regions, transmission of Plasmodium falciparum parasites is often seasonal with very low transmission during the dry season and high transmission in the wet season. Parasites survive the dry season within some individuals who experience prolonged carriage of parasites and are thought to ‘seed’ infection in the next transmission season.MethodsDry season carriers and their role in the subsequent transmission season are characterized using a combination of mathematical simulations and data analysis of previously described data from a longitudinal study in Mali of individuals aged 3 months–12 years (n = 579).ResultsSimulating the life-history of individuals experiencing repeated exposure to infection predicts that dry season carriage is more likely in the oldest, most exposed and most immune individuals. This hypothesis is supported by the data from Mali, which shows that carriers are significantly older, experience a higher biting rate at the beginning of the transmission season and develop clinical malaria later than non-carriers. Further, since the most exposed individuals in a community are most likely to be dry season carriers, this is predicted to enable a more than twofold faster spread of parasites into the mosquito population at the start of the subsequent wet season.ConclusionsCarriage of malaria parasites over the months-long dry season in Mali is most likely in the older, more exposed and more immune children. These children may act as super-spreaders facilitating the fast spread of parasites at the beginning of the next transmission season.

Prevalence of histidine-rich protein 2 deletion among the Plasmodium falciparum isolates from Kolkata.

Histidine-rich protein 2 (HRP2) detecting rapid diagnostic tests (RDTs) have played an important role in enabling prompt malaria diagnosis in remote locations. HRP2 has advantages over other biomarkers because of its abundance in the bloodstream, repetitive binding epitopes, and falciparum-specificity. Most HRP2-based RDTs also exhibit some cross-reactivity to a closely related protein (HRP3). Plasmodium falciparum parasites lacking HRP2 (pfhrp2) and 3 (pfhrp3) genes escape detection by these RDTs. The objective of the study was to study the sensitivity and specificity of hrp2-based RDT for diagnosis of falciparum, to compare the RDT results with microscopy and polymerase chain reaction (PCR), and to determine the prevalence of HRP2 gene deletion among the RDT-negative, microscopy-positive falciparum strains. Blood samples were collected and diagnosis was done by microscopic examination, RDTs, and PCR. Out of 1000 patients examined, 138 were positive for P. falciparum. Fever was the most common symptom followed by chills with rigor and headache were recorded among more than >95% of the study patients. Three microscopy-confirmed P. falciparum cases were negative by HRP2-based RDT and were found to have deletion of HRP2 and HRP3 exon 2. Rapid and accurate diagnosis and prompt deployment of effective antimalarial medication are essential components of appropriate case management. P. falciparum strains that evade diagnosis by RDTs represent a major threat to malaria control and elimination efforts.

The Parasite Reduction Ratio (PRR) Assay Version 2: Standardized Assessment of Plasmodium falciparum Viability after Antimalarial Treatment In Vitro

With artemisinin-resistant Plasmodium falciparum parasites emerging in Africa, the need for new antimalarial chemotypes is persistently high. The ideal pharmacodynamic parameters of a candidate drug are a rapid onset of action and a fast rate of parasite killing or clearance. To determine these parameters, it is essential to discriminate viable from nonviable parasites, which is complicated by the fact that viable parasites can be metabolically inactive, whilst dying parasites can still be metabolically active and morphologically unaffected. Standard growth inhibition assays, read out via microscopy or [3H] hypoxanthine incorporation, cannot reliably discriminate between viable and nonviable parasites. Conversely, the in vitro parasite reduction ratio (PRR) assay is able to measure viable parasites with high sensitivity. It provides valuable pharmacodynamic parameters, such as PRR, 99.9% parasite clearance time (PCT99.9%) and lag phase. Here we report the development of the PRR assay version 2 (V2), which comes with a shorter assay duration, optimized quality controls and an objective, automated analysis pipeline that systematically estimates PRR, PCT99.9% and lag time and returns meaningful secondary parameters such as the maximal killing rate of a drug (Emax) at the assayed concentration. These parameters can be fed directly into pharmacokinetic/pharmacodynamic models, hence aiding and standardizing lead selection, optimization, and dose prediction.

In vitro evaluation of alkaline lignins as antiparasitic agents and their use as an excipient in the release of benznidazole

The Amazon rainforest is considered the largest tropical timber reserve in the world. The management of native forests in the Amazon is one of the most sensitive geopolitical issues today, given its national and international dimension. In this work, we obtained and characterized physicochemical lignins extracted from branches and leaves of Protium puncticulatum and Scleronema micranthum. In addition, we evaluated in vitro its potential as an antioxidant, cytotoxic agent against animal cells and antiparasitic against promastigotes of Leishmania amazonensis, trypomastigotes of T. cruzi and against Plasmodium falciparum parasites sensitive and resistant to chloroquine. The results showed that the lignins obtained are of the GSH type and have higher levels of guaiacyl units. However, they show structural differences as shown by spectroscopic analysis and radar charts. As for biological activities, they showed antioxidant potential and low cytotoxicity against animal cells. Antileishmanial/trypanocidal assays have shown that lignins can inhibit the growth of promastigotes and trypomastigotes in vitro. The lignins in this study showed low anti-Plasmodium falciparum activity against susceptible strains of Plasmodium falciparum and were able to inhibit the growth of the chloroquine-resistant strain. And were not able to inhibit the growth of Schistosoma mansoni parasites. Finally, lignins proved to be promising excipients in the release of benznidazole. These findings show the potential of these lignins not yet studied to promote different biological activities.

National-scale simulation of human movement in a spatially coupled individual-based model of malaria in Burkina Faso

Malaria due to the Plasmodium falciparum parasite remains a threat to human health despite eradication efforts and the development of anti-malarial treatments, such as artemisinin combination therapies. Human movement and migration have been linked to the propagation of malaria on national scales, highlighting the need for the incorporation of human movement in modeling efforts. Spatially couped individual-based models have been used to study how anti-malarial resistance evolves and spreads in response to drug policy changes; however, as the spatial scale of the model increases, the challenges associated with modeling of movement also increase. In this paper we discuss the development, calibration, and validation of a movement model in the context of a national-scale, spatial, individual-based model used to study the evolution of drug resistance in the malaria parasite.

Clinical profile and characteristics of cerebral malaria: An observational study in a tertiary care hospital in Western Maharashtra

Background: Cerebral malaria is a serious and potentially fatal complication of malaria caused by Plasmodium falciparum parasites. Symptoms may include an unarousable coma lasting for at least 30 min, seizures, altered sensorium, and fever. Diagnosis is made through a combination of clinical and laboratory findings, including the identification of parasites in blood smears or rapid diagnostic tests. Treatment involves prompt use of antimalarial drugs and supportive care. Severe cases of malaria can lead to complications such as cerebral malaria, severe anemia, and organ failure. Aim and Objective: The aim of thje study was to understand clinical profile and characteristics of cerebral malaria. Materials and Methods: This observational study conducted at a tertiary care center from September 2016 to June 2018. The study included patients aged 18 years and above who were admitted to the center and exhibited symptoms of altered sensorium, coma, convulsion, and fever with altered sensorium. Patients who tested positive for malarial parasites on peripheral smear or rapid malaria antigen were also included in the study. The study was ethically approved by the institutional committee and all participants provided informed consent before enrollment. The sample size included 30 patients. Results: The study involved 30 hospitalized patients with severe falciparum malaria. Of the patients, 60% were male and 40% were female, with a male to female ratio of 3:2. The average age was 42.3 years, with the highest number of patients belonging to the age group of 18–30 years. All patients had fever, with the majority reporting altered sensorium, chills and rigors, headache, and nausea. Multiorgan dysfunction was more common than extracranial single system involvement. CSF analysis showed normal cytology, with normal or slightly elevated protein and sugar levels. Most patients had a Glasgow coma scale score between 11 and 15, with brain edema and retinal changes observed in some patients. Conclusion: The study concludes that hospitalized patients with severe falciparum malaria, predominantly affecting young adults. Symptoms included fever, altered sensorium, chills, and rigors, with multiorgan dysfunction being more common than single-system involvement.

Multimodality strategy for cardiac damage assessment in falciparum malaria: A preliminary study

Malaria caused by the Plasmodium falciparum (P.f) parasite can result in life-threatening complications. Traditionally, cardiac involvement has not been included as a frequent cause of morbidity and mortality. Cardiac damage in P.f infection is probably underdiagnosed. To analyze the hypothesis of cardiac damage in apparently uncomplicated P.f infection with a multimodality strategy unavailable in most endemic countries. Cardiac biomarkers, ECG and 24 h ECG recording, transthoracic echocardiography with global strain analysis, and complete CMR analysis, including T2 (Fig. 1) and T1 mapping and extracellular volume quantification (ECV), were performed in patients hospitalized for malaria in a French tertiary center. Ten cases (sex ratio: 1 – mean age: 45 ± 13 years) imported from sub-Saharan Africa were prospectively included. Mean P.f parasitemia was 1.6 ± 1.7%. Hs-c Troponin T and NT pro BNP were mildly increased respectively in 1 and 2 patients. 24-h ECG recording revealed > 500 ventricular premature beats in 2 patients. Imaging revealed normal left and right ventricular systolic function, diastolic function and longitudinal global strain in all but one patient. CMR revealed 2 cases of focal late gadolinium enhancement consistent with the diagnosis of acute myocarditis in 1 case. ECV value was increased in 1 case (dilated cardiomyopathy). All patients were treated with piperaquine + dihydroartemisine and had a favorable outcome. Multimodality strategy reveals some cardiac abnormalities (ventricular ectopy, myocarditis) in patients hospitalized for falciparum malaria. Specificity of such findings remains questionable in this preliminary study. Further investigation is required to conclude about the hypothesis of a significant malaria-induced cardiac.

Naturally occurring phenylethanoids and phenylpropanoids: antimalarial potential.

Malaria as an infectious disease is one of the world's most dangerous parasitic diseases. There is an urgent need for the development of new antimalarial drugs. Natural products are a very rich source of new bioactive compounds. Our research aims to shed light on the recent studies which demonstrated the antimalarial potential of phenylpropanoids as a major natural-products class. This study involves an in silico analysis of naturally-occurring phenylpropanoids and phenylethanoids which showed 25 compounds with moderate to strong binding affinity to various amino acid residues lining the active site; P. falciparum kinase (PfPK5), P. falciparum cytochrome bc1 complex (cyt bc1), and P. falciparum lysyl-tRNA synthetase (PfKRS1); of Plasmodium falciparum parasite, a unicellular protozoan which causes the most severe and life-threatening malaria. Furthermore, the study was augmented by the assessment of antiplasmodial activity of glandularin, a naturally occurring dibenzylbutyrolactolic lignan, against chloroquine-sensitive 3D7 strain of P. falciparum using SYBR green I-based fluorescence assay, which showed high antimalarial activity with IC50 value of 11.2 μM after 24 hours of incubation. Our results highlight phenylpropanoids and glandularin in particular as a promising chemical lead for development of antimalarial drugs.

Association between Placenta Malaria Parasites and Preeclampsia/Eclampsia among Parturient Mothers in Alex Ekwueme Federal University Teaching Hospital Abakaliki

In tropical countries, malaria and preeclampsia/eclampsia are common diseases of pregnancy; and placenta have been implicated in the pathophysiology of both disease processes. The two diseases have pathophysiologic similarities in the placenta such as placenta ischaemia, endothelial dysfunction and production of pro-inflammatory cytokine. Yet, there is paucity of studies on the association of these two disease processes. Determining the association between the two disease processes may help to unravel the pathogenesis of preeclampsia and also help in its prevention and patient management. Objective: Determined the association between placenta malaria parasitemia and preeclampsia/eclampsia among parturients at Alex Ekwueme Federal University Teaching Hospital Abakaliki. Materials and Methods: This was a case control study that was conducted in the Labour wards of department of Obstetrics and Gynaecology, Alex Ekwueme Federal University Teaching Hospital Abakaliki (AEFUTHA) and Mile 4 Missionary Hospital Abakaliki, a comprehensive health care centre in Abakaliki, Ebonyi state. It was conducted over a period of 6 months between 1st October 2021 and 31st March, 2022. The cases in this study were parturients that developed preeclampsia/eclampsia in the course of pregnancy, while the controls were parturient without preeclampsia/eclampsia. Interviewer-administered questionnaires were used to collect data on socio-demographic characteristics, obstetrics and medical histories. Histological examinations were conducted to isolate plasmodium falciparum parasites from placenta samples obtained from the maternal surface of the placenta. The data was processed using Epi Info software. Categorical variables were analyzed using Mc Nemar X2 test, with a p-value of 0.05 considered statistically significant. Logistic regression models were used to estimate the odds ratios (OR) and 95% CI of the association between placenta malaria parasites and preeclampsia/eclampsia was conducted. Relative risk with 95% CI was used to determine both fetal and maternal outcomes. Results: The prevalence of preeclampsia during the study period was 2.9%. Placenta malaria was positive in twenty one (21) of the 67 cases of preeclampsia/eclampsia analyzed, giving a prevalence of 31.3% and in eleven (11) out of 68 controls (normotensive) patients analyzed, giving a prevalence of 16.2%. The presence of placenta malaria significantly increased the odds of developing preeclampsia/eclampsia among parturients (OR = 2.4, 95% CI = 1.0 - 5.4, P value = 0.04). Presence of placenta malaria in mothers with preeclampsia/eclampsia was associated with adverse pregnancy outcomes such as cerebrovascular accident (RR = 19.2, 95% CI = 1.1 - 341.7, P value = 0.04), DIC (RR = 10.9, 95% CI = 1.4 - 88.0, P value = 0.02), abruptio placenta (RR = 2.4, 95% CI = 1.2 - 4.8, P value = 0.01), pulmonary edema (RR = 2.7, 95% CI = 1.1 - 25.9, P value = 0.03), IUGR (RR = 2.1, 95% CI = 1.1 - 4.5, P value = 0.03) and IUFD (RR = 3.8, 95% CI = 1.3 - 11.7, P value = 0.02). Presence of placenta malaria also increased the risk of NICU admission (RR = 2.6, 95% CI = 1.1 - 6.0, P value = 0.03), Low 1st minute APGAR score (RR = 2.7, 95% CI = 1.2 - 6.1, P value = 0.02) and Low 5th minute APGAR score (RR = 3.0, 95% CI = 1.0 - 8.6, P value = 0.04) among neonates delivered by mothers with preeclampsia/eclampsia. However, presence of placenta malaria did not significantly increase maternal and perinatal mortalities. Conclusion: There is a higher prevalence of placenta malaria among mothers with preeclampsia/eclampsia when compared with normotensive controls and this was associated with increased risk of certain maternal and perinatal morbidities. Placental malaria was not associated with increased risk of either maternal or perinatal mortality.

Altitude, not potential larval habitat availability, explains pronounced variation in Plasmodium falciparum infection prevalence in the western Kenya highlands

Progress in malaria control has stalled over the recent years. Knowledge on main drivers of transmission explaining small-scale variation in prevalence can inform targeted control measures. We collected finger-prick blood samples from 3061 individuals irrespective of clinical symptoms in 20 clusters in Busia in western Kenya and screened for Plasmodium falciparum parasites using qPCR and microscopy. Clusters spanned an altitude range of 207 meters (1077-1284 m). We mapped potential mosquito larval habitats and determined their number within 250 m of a household and distances to households using ArcMap. Across all clusters, P. falciparum parasites were detected in 49.8% (1524/3061) of individuals by qPCR and 19.5% (596/3061) by microscopy. Across the clusters, prevalence ranged from 26% to 70% by qPCR. Three to 34 larval habitats per cluster and 0-17 habitats within a 250m radius around households were observed. Using a generalized linear mixed effect model (GLMM), a 5% decrease in the odds of getting infected per each 10m increase in altitude was observed, while the number of larval habitats and their proximity to households were not statistically significant predictors for prevalence. Kitchen located indoors, open eaves, a lower level of education of the household head, older age, and being male were significantly associated with higher prevalence. Pronounced variation in prevalence at small scales was observed and needs to be taken into account for malaria surveillance and control. Potential larval habitat frequency had no direct impact on prevalence.

The direct binding of Plasmodium vivax AMA1 to erythrocytes defines a RON2-independent invasion pathway

We used a transgenic parasite in which Plasmodium falciparum parasites were genetically modified to express Plasmodium vivax apical membrane antigen 1 (PvAMA1) protein in place of PfAMA1 to study PvAMA1-mediated invasion. In P. falciparum, AMA1 interaction with rhoptry neck protein 2 (RON2) is known to be crucial for invasion, and PfRON2 peptides (PfRON2p) blocked the invasion of PfAMA1 wild-type parasites. However, PfRON2p has no effect on the invasion of transgenic parasites expressing PvAMA1 indicating that PfRON2 had no role in the invasion of PvAMA1 transgenic parasites. Interestingly, PvRON2p blocked the invasion of PvAMA1 transgenic parasites in a dose-dependent manner. We found that recombinant PvAMA1 domains 1 and 2 (rPvAMA1) bound to reticulocytes and normocytes indicating that PvAMA1 directly interacts with erythrocytes during the invasion, and invasion blocking of PvRON2p may result from it interfering with PvAMA1 binding to erythrocytes. It was previously shown that the peptide containing Loop1a of PvAMA1 (PvAMA1 Loop1a) is also bound to reticulocytes. We found that the Loop1a peptide blocked the binding of PvAMA1 to erythrocytes. PvAMA1 Loop1a has no polymorphisms in contrast to other PvAMA1 loops and may be an attractive vaccine target. We thus present the evidence that PvAMA1 binds to erythrocytes in addition to interacting with PvRON2 suggesting that the P. vivax merozoites may exploit complex pathways during the invasion process.

The stochastic approximation method for semi-recursive multivariate kernel-type regression estimation

In this research paper, we elaborate an extension of the semi-recursive kernel-type regression function estimator. We investigate the asymptotic properties of this estimator and compare them with non-recursive Nadaraya Watson regression estimator. From this perspective, we first calculate the bias and the variance of the proposed estimator which strongly depend on the choice of three parameters, namely the stepsizes (βn) and (γn) as well as the bandwidth (hn) chosen using one of the best methods of bandwidth selection, the bootstrap approach compared to the plug-in method. An appropriate choice of those parameters yields that, under some conditions, the MSE (Mean Squared Error) of the proposed estimator can be smaller than that of Nadaraya Watson's estimator. We corroborate our theoretical results through simulations studies and by considering two real dataset applications, the French Hospital Data of COVID-19 epidemic as well as the Plasmodium Falciparum Parasite Load (PL).

MiR-451a and let-7i-5p loaded extracellular vesicles attenuate heme-induced inflammation in hiPSC-derived endothelial cells.

Hemolysis is associated with many pathologies, including trauma, sepsis, hemorrhagic stroke, malaria, and genetic disorders such as sickle cell disease (SCD). When hemolysis occurs, free-heme drives vascular inflammation, resulting in oxidative tissue damage and cardiometabolic complications. A better understanding of heme clearance and detoxification is essential to preventing sustained tissue damage. Human induced pluripotent stem cell (hiPSC)-derived endothelial cells (hiPSC-ECs) provide a novel source of patient-specific cells and tissues for disease modeling, drug discovery, and regenerative therapeutics. Here we report the use of hiPSC-ECs to elucidate the role of miR-451a and let-7i-5p-loaded extracellular vesicles (EVs, such as exosomes) in the inflammatory response to free-heme as a model for heme-induced inflammation. We provide evidence of a significant correlation between miR-451a and let-7i-5p-loaded circulating exosomes in plasmodium-infected patients with reported clinical benchmarks of malaria-severity (e.g., Hemoglobin (Hb) levels, white blood cell counts). Additionally, we determined that exposure of Plasmodium falciparum (Pf) parasites to EVs, loaded with either miRNA, significantly reduces their counts in vitro. Using hiPSCs derived from individuals with wild-type Hb (HbAA) or homozygous sickle cell mutated Hb (HbSS) genotypes, we demonstrate that heme-treated hiPSC-ECs secreted inflammatory products (cytokines, chemokines and growth factors) into supporting media at concentrations that were similar to that reported in HbAA and HbSS serum. This inflammatory response was attenuated by exposure with miR-451a or let-7i-5p-loaded EVs. We also found a decrease in transcription of ICAM1 and P-Selectin, as well as the secretion of key inflammatory cytokines (e.g., CXCL10, TNF-α, and IFN-γ). Based on these findings, we propose a model in which increased levels of exosomal miR-451a and let-7i-5p in Plasmodium-infected individuals will attenuate inflammatory responses to free-heme and parasite-derived products. As a result, infected erythrocytes will less likely adhere to the endothelium, sequester in brain micro vessels, and reduce vaso-occlusive crises that exacerbate cerebral malaria.