Malaria Research Articles

Reduced red blood cell deformability in vivax malaria.

Reduced deformability of both infected and uninfected red blood cells (RBC) contributes to pathogenesis in falciparum malaria. Whole blood RBC-deformability is not well-characterised in vivax malaria. We used a laser-assisted optical rotational cell analyzer to measure the RBC deformability in fresh whole blood from Malaysian patients with vivax malaria (n=25). Deformability of whole blood RBC, the vast majority of which were uninfected, was reduced in vivax malaria compared to controls (n=15), though not to the same degree as in falciparum malaria (n=90). Reduced RBC-deformability may contribute to the pathogenesis of vivax malaria, including splenic retention of uninfected RBC.

Low prevalence of soil transmitted helminth infection in Ugandan children hospitalized with severe malaria.

Co-infection by intestinal helminths and Plasmodium spp. may be common in endemic communities. Several studies have identified a relationship between helminth infection, Plasmodium spp. infection and malaria severity. However, the relationship is not well defined, and results are inconclusive. We analyzed 202 stool samples from a cohort of children with severe malaria enrolled in two hospitals in Uganda from 2014-2017 and asymptomatic community children from the same household or neighborhood and enrolled at the same time, all 6 months to 48 months of age. We investigated if intestinal helminth infection modified risk of severe malaria. We extracted nucleic acids from stool and tested them for six helminth species ( Anyclostoma duodenale, Ascaris lumbricoides, Necator americanus, Strongyloides stercolaris, Trichuris trichiura, Shistosoma mansoni ) using highly sensitive quantitative PCR. We found a low prevalence of infection by ≥1 intestinal helminth species in children with severe malaria (5.1%, n=9/177) and community control children (4.0%, n=1/25). Infection by ≥1 of the helminths assessed was not associated with severe malaria (aRR = 1.0, 95% Confidence Interval = 0.82, 1.3, p = 0.78). In 2003 Uganda instituted a national deworming program, with anti-helminth medication provided twice annually to children 6 months to 5 years of age. In these areas of Uganda, the national deworming campaign has been highly successful, as stool-based helminth infection was rare even when using highly sensitive methods of detection and was not a major contributor to risk of severe malaria.

Quality of care and post-discharge morbidity among children diagnosed with severe malaria in rural Uganda: A prospective cohort study.

Pediatric severe malaria is a significant contributor of morbidity and mortality in Uganda. Most information is derived from tertiary referral centers and urban centers. Little is known about routine care or post-discharge outcomes in rural areas. We conducted a longitudinal cohort study of pediatric severe malaria at St. Paul's Level IV Health Center (SPHC) in Kasese, Uganda. We collected demographic, clinical, and laboratory results, and conducted follow-up 14 days post-discharge to assess patient outcomes in the immediate post-discharge period. The initial cohort included 187 children aged 0 to 17 years enrolled between July 9th, 2023 and January 9th, 2024. Almost all (94.7%) participants had a parasitological confirmed malaria diagnosis by rapid diagnostic tests or blood smear. While at SPHC, 95.7% of patients received 3+ doses of intravenous Artesunate, and 92.0% also received oral antimalarials. 62.0% had at least one symptom of severe malaria, with altered consciousness (40.6%) and convulsions (29.9%) the most frequently reported. 26.1% had evidence of severe malarial anemia (Hb <5 g/dl), of whom 93.5% received a blood transfusion. Most (82.2%) patients received care that we assessed as consistent with key elements of WHO management guidelines. We were able to contact 183 of the 187 patient caregivers post-discharge. Caregivers reported that 25.6% of patients were experiencing symptoms related to their hospitalization, with fever (18.5%) and nausea/ not feeding well (10.3%) reported most frequently. Children who experienced altered consciousness during their acute illness had 1.69 times the adjusted risk of reporting symptoms 14-days post-discharge compared to those who did not have altered consciousness (aRR: 1.69, 95% CI: 1.01-2.82). Six deaths were recorded, including three at SPHC and three post-transfer or discharge. Findings suggest that at private health facilities in rural areas, treatment appears to be consistent with guidelines. Future research should investigate high morbidity in the immediate post-discharge period.

Factors associated with acute kidney injury and outcomes in patients with malaria in a district hospital in Rwanda

Introduction: Acute kidney injury (AKI) remains one of the complications of severe malaria. Evidence on associated factors and outcomes for patients with complicated malaria and AKI is limited in Rwanda. Aim: To assess the factors associated with acute kidney injury and outcomes in patients with malaria in a district hospital in Rwanda. Method: A retrospective study design was applied. A census sampling strategy was used to select 122 files of patients admitted as severe malaria patients in 2016- 2017. A developed clinical audit form was used to collect data from patients’ files. Both descriptive and inferential statistics were used to analyze data. Results: Among the confirmed severe malaria files, 44% of participants were over 50 years and 52.5% were males. The majority, (91.5%) had community-based health insurance and 16.3% had acute kidney injury. The significant associated clinical factors were dehydration (p=.01), high-grade fever (p=.002), profuse sweating (p=.034), vomiting (p=.043), and diarrhea (p=.025). Of the 20 patients who developed AKI, 55% completely recovered, 15% died and 30% of cases were transferred to the highest facilities for hemodialysis. Conclusion: The existence of AKI among severe malaria patients was evident with some recovering and others dying. There is a need for educating healthcare professionals, mostly at district hospitals about the diagnosis and management of AKI as a result of complicated malaria. Keywords: Acute kidney injury; severe malaria; complications of malaria.

From eradication to reemergence: the growing threat of malaria in Turkey.

According to WHO, between 2000 and 2021, there were approximately 247 million malaria cases and 627,000 deaths globally, with the majority of cases occurring in sub-Saharan Africa. In Turkey, indigenous P. vivax malaria was a major public health problem until its eradication was achieved in 2010. Although indigenous malaria transmission has been significantly reduced since 2010, the country is challenged with imported malaria due to increasing global travel and migration from endemic regions. In this study, all imported malaria cases admitted to Dr. Sadi Konuk Research and Training Hospital, Istanbul, between 2018 and 2023 were included. DNA extraction was performed using archived slides and EDTA blood samples. Real-time PCR was performed to identify samples at the species level using previously reported primers and probes. In addition, all available patient demographics are presented. During the six years between 2018 and 2023, 157 patients were diagnosed with imported malaria. According to the real-time PCR results, 149 cases were P. falciparum (94.9%), five cases were P. vivax (3.2%), two cases were P. ovale (1.3%), and one case was P. malariae (0.6%). The male/female ratio among diagnosed patients was 2.34 (110♂/47♀) among diagnosed patients. Plasmodium falciparum was detected in patients from all African regions, whereas P. vivax was detected only in patients from Liberia and Djibouti. Although malaria cases in Turkey have significantly decreased due to elimination efforts and effective public health interventions, the recent increase in both imported and indigenous cases, as well as the presence of suitable vector species in the country, indicates that malaria still remains a serious public health problem for Turkey.

Determining the Association Between MSP1/2 Variant and Multiplicity of Infection on Incidence of Severe Malaria in Sudanese Children in Gezira State, Sudan

The Almanagil province located in Gezira scheme, Gezira state, Sudan, represents a suitable environment for the breeding of malaria-carrying mosquitoes. An estimated 5.9% of Sudanese people suffer from malaria, with 87.6% of cases caused by Plasmodium falciparum and 12.4% by Plasmodium vivax. Clinical manifestation of malaria cases range from mild uncomplicated to severe and fatal complications and the genetic variants and multiplicity of falciparum infection can worsen the manifestations of malaria. The objective of this work is to determine the degree of genetic variation in P. falciparum infection in a high-transmission region of central Sudan by analyzing merozoite surface protein-1 (msp1) and merozoite surface protein-2 (msp2) variations. During the rainy season of 2022, Eighty-nine children with confirmed severe falciparum malaria whom admitted to Almanagil Pediatric Hospital were included in this study. Dry blood spots were used to extract the DNA and amplification of three msp1 and two of msp2 allelic subfamilies, namely K1, RO33 and MAD20 and FC27 and IC/3D7, respectively. The data was analyzed by using SPSS computer program (v 23.0). The three genetic subfamilies of msp1 (K1, RO33 and MAD20) and the two alleles of msp2 (FC27 and IC/3D7) were identified. Msp1 variants represent K1 (64/89, 71.9%), RO33 (56/89, 62.9%) and MAD20 (72/89, 80.9%), while msp2 diversity represents ICI/3D7 (52/89, 58.4%), FC27 (62/89, 69.6%) and ICI/3D7/FC27(33/89, 37.1%). The MAD20 and FC27 showed high genetic diversity among both genes respectively. RO33 allele shows a strong association with severity of falciparum malaria (OR 2.572, P 0.045 ), while the K1 was the lowest risk factor for malaria severity. The allele subfamily K1 and MAD20 of msp1 were associated with hypoglycemia (OR 4.21 and 2.91) respectively. Our study revealed high genetic polymorphisms of msp1 and msp2. Among Central Sudanese children with high MOI of P. falciparum isolates, there was a significant frequency of msp1, a strong association between the K1 allele and hypoglycemia, and a substantial association between the RO33 and MAD20 alleles with the severity of the infection. These findings could help develop malaria control strategies.

Enriching Clinical Trials Enrolling Children With Cerebral Malaria Using Admission Demographics, Physical Examination and Point-of-care Testing Results.

Multiple clinical trials evaluating therapies for cerebral malaria (CM) have failed to demonstrate improved outcomes. This may derive from inclusion of children at all risk levels, including those at low risk of mortality or neurologic morbidity, limiting power to detect significant differences between intervention arms. One solution is enrichment, enrolling clinical trial participants at higher risk of adverse outcomes. We assessed if demographic, physical examination and point-of-care laboratory testing results in combination could identify children with CM at higher risk of death or neurologic disability. Retrospective case-control study of 1674 children hospitalized with CM in Blantyre, Malawi. We used univariate and multivariate analyses of admission factors to find the most parsimonious model associated with death or neurologic disability. To assess the clinical utility of the models, we evaluated derived probability density curve separation. Blantyre Coma Score (BCS), deep breathing and high blood lactate were independently associated with mortality. The derived receiver operating curve yielded an area under the curve of 0.7118. There was poor separation of derived probability density curves predicting death or survival, indicating limited clinical utility of this model. On multivariate modeling of neurologic sequelae in CM survivors, only BCS was associated with adverse outcomes (area-under-the-curve = 0.6151). Probability density curves again largely overlapped, demonstrating limited utility of BCS alone in outcome prediction. Combinations of admission demographic, clinical and point-of-care laboratory factors are inadequate to predict prognosis in children with CM. Higher technology assessment methods are necessary for clinical trial enrichment.

Safety and pharmacokinetic properties of a new formulation of parenteral artesunate in healthy Thai volunteers

BackgroundParenteral artesunate is the first-line therapy for severe malaria. Artesunate, in its current formulation, must be prepared immediately before administration by first dissolving in sodium bicarbonate solution and then diluting in saline. A novel solvent for rapid and stable single step reconstitution of artesunate was recently developed showing improved solubility and stability. This study aimed to compare the safety and pharmacokinetic properties of the currently available and newly developed parenteral formulation of artesunate in healthy Thai volunteers.MethodsThis was an open-label, randomized, 4 periods, 4-treatments, 24-sequence, single-dose, cross-over study in 72 male and female healthy Thai volunteers. Frequent pharmacokinetic samples were collected in all volunteers at each dose occasion. Observed concentration–time profiles were analysed with a non-compartmental approach followed by a bioequivalence evaluation.ResultsBoth intramuscular and intravenous administrations of the new parenteral formulation of artesunate were safe and well-tolerated, with no additional safety signals compared to the currently used formulation. The pharmacokinetic properties of artesunate and its active metabolite, dihydroartemisinin, were well-characterized, and showed rapid conversion of artesunate into dihydroartemisinin. Intramuscular administration of the newly formulated artesunate resulted in almost complete bioavailability of dihydroartemisinin. The pharmacokinetic properties were similar between the old and new formulation.ConclusionsThe new and more easily prepared formulation of artesunate was safe and well-tolerated, with similar pharmacokinetic properties compared to the currently used formulation. Dihydroartemisinin, the active metabolite responsible for the majority of the anti-malarial effect, showed equivalent exposure after both intravenous and intramuscular administration of artesunate, suggesting that both routes of administration should generate comparable therapeutic effects.Trial registration: The study was registered to clinicaltrials.gov (#TCTR20170907002).

Revising the Interpretation of Transcranial Doppler Ultrasound Examinations in Pediatric Cerebral Malaria.

Cerebral malaria (CM) is a devastating disease globally. Transcranial Doppler ultrasound (TCD) has identified five different phenotypes of deranged cerebrovascular hemodynamics in children with CM, each associated with different outcomes. For TCD to be used as a point of care neurodiagnostic and neuromonitoring tool in CM patients, proper interpretation of examinations is paramount. Comparison of measured cerebral blood flow velocities (CBFVs) to age-matched normative values is needed to interpret any pediatric TCD study. Until recently, normative values in African children did not exist, so previous work reported the frequency of CM phenotypes by classifying studies compared with normative values of European children. Now that normative TCD values in healthy African children have been established, we performed this retrospective analysis of prospectively collected data to determine phenotype frequency and associated outcomes in children with CM by comparing CBFV values to these contemporary controls.

Antibodies to specific domains of Plasmodium falciparum erythrocyte membrane protein-1 and its relationship with protection from severe malarial anemia: A prospective study among Ghanaian children.

Plasmodium falciparum erythrocyte membrane protein-1 (PfEMP-1) is important in malaria pathogenicity as it mediates Pf-infected erythrocytes cytoadherence to host endothelial microvasculature receptors. Naturally acquired antibodies against specific PfEMP-1 antigens may be beneficial in clinical malaria protection. This study determined antibodies to DBLα2, CIDRα1, DBLβ12, and DBLγ6 domains of PfEMP-1 in children with P. falciparum malaria in Tamale, Ghana. Sixty P. falciparum-infected children, and 30 controls, aged 1-12 years were recruited for this case-control study from April to July 2023 in Northern Ghana. Participants with uncomplicated malaria had asexual P. falciparum in peripheral blood and Hb ≥ 5.0 g/dL, and severe malaria was diagnosed when participants had Hb < 5.0 g/dL in addition to asexual P. falciparum in peripheral blood. Blood cell indices were measured using hematology analyzer, and IgG antibodies to DBLα2, CIDRα1, DBLβ12, and DBLγ6 domains of PfEMP-1 and pro-inflammatory cytokines were detected using enzyme-linked immunosorbent assay. Data were analyzed using SPSS version 26.0. The prevalence of PfEMP-1 IgG antibodies among P. falciparum-infected children and the uninfected group was 65.0% and 6.7%, respectively. PfEMP-1 IgG antibodies were present in 83.3% of uncomplicated malaria cases, and 46.7% in severe malaria subjects. Plasma levels of PfEMP-1 IgG antibodies were elevated in participants with uncomplicated malaria compared to those with severe malaria (p < 0.001). Hemoglobin, RBC, HCT, and platelet were significantly lower among P. falciparum-infected children without PfEMP-1 IgG antibodies than among those with the antibodies. Prevalence of anemia among children with PfEMP-1 IgG antibodies and those without the antibodies were 74.4% and 100%, respectively. The high prevalence of PfEMP-1 IgG antibodies to DBLα2, CIDRα1, DBLβ12, and DBLγ6 domains observed in participants with uncomplicated malaria, and the relationship between PfEMP-1 IgG antibodies and blood cell parameters could indicate that the antibodies may be related to effective erythropoietic response in P. falciparum malaria. Immune antibodies against DBLα2, CIDRα1, DBLβ12, and DBLγ6 domains of PfEMP-1 may suppress the deteriorating effects of PfEMP-1 antigens and provide immune protection against severe malarial anemia in children.

Development and longevity of naturally acquired antibody and memory B cell responses against Plasmodium vivax infection.

Plasmodium vivax malaria causes significant public health problems in endemic regions. Considering the rapid spread of drug-resistant parasite strains and the development of hypnozoites in the liver with potential for relapse, development of a safe and effective vaccine for preventing, controlling, and eliminating the infection is critical. Immunity to malaria is mediated by antibodies that inhibit sporozoite or merozoite invasion into host cells and protect against clinical disease. Epidemiologic data from malaria endemic regions show the presence of naturally acquired antibodies to P. vivax antigens during and following infection. But data on the persistence of these antibodies, development of P. vivax-specific memory B cells (MBCs), and their relation to reduction of malaria severity and risk is limited. This review provides an overview of the acquisition and persistence of naturally acquired humoral immunity to P. vivax infection. Also, we summarize and discuss current progress in assessment of immune responses to candidate vaccine antigens in P. vivax patients from different transmission settings. Longitudinal studies of MBC and antibody responses to these antigens will open new avenues for developing vaccines against malaria infection and its transmission.

Identification of the drug/metabolite transporter 1 as a marker of quinine resistance in a NF54×Cam3.II P. falciparum genetic cross.

The genetic basis of Plasmodium falciparum resistance to quinine (QN), a drug used to treat severe malaria, has long been enigmatic. To gain further insight, we used FRG-NOD human liver-chimeric mice to conduct a P. falciparum genetic cross between QN-sensitive and QN-resistant parasites, which also differ in their susceptibility to chloroquine (CQ). By applying different selective conditions to progeny pools prior to cloning, we recovered 120 unique recombinant progeny. These progeny were subjected to drug profiling and QTL analyses with QN, CQ, and monodesethyl-CQ (md-CQ, the active metabolite of CQ), which revealed predominant peaks on chromosomes 7 and 12, consistent with a multifactorial mechanism of resistance. A shared chromosome 12 region mapped to resistance to all three antimalarials and was preferentially co-inherited with pfcrt. We identified an ATP-dependent zinc metalloprotease (FtsH1) as one of the top candidates and observed using CRISPR/Cas9 SNP-edited lines that ftsh1 is a potential mediator of QN resistance and a modulator of md-CQ resistance. As expected, CQ and md-CQ resistance mapped to a chromosome 7 region harboring pfcrt. However, for QN, high-grade resistance mapped to a chromosome 7 peak centered 295kb downstream of pfcrt. We identified the drug/metabolite transporter 1 (DMT1) as the top candidate due to its structural similarity to PfCRT and proximity to the peak. Deleting DMT1 in QN-resistant Cam3.II parasites significantly sensitized the parasite to QN but not to the other drugs tested, suggesting that DMT1 mediates QN response specifically. We localized DMT1 to structures associated with vesicular trafficking, as well as the parasitophorous vacuolar membrane, lipid bodies, and the digestive vacuole. We also observed that mutant DMT1 transports more QN than the wild-type isoform in vitro. Our study demonstrates that DMT1 is a novel marker of QN resistance and a new chromosome 12 locus associates with CQ and QN response, with ftsh1 is a potential candidate, suggesting these genes should be genotyped in surveillance and clinical settings.

The New Spectrum of Plasmodium Vivax Malaria Severity: A Single-Center Experience

Plasmodium vivax malaria, once considered a benign and self-limiting disease, has emerged as a significant public health concern, with increasing reports of severe and even fatal cases. Objective: To evaluate the clinical severity and complications associated with Plasmodium vivax malaria in patients in Peshawar. Methods: A descriptive cross-sectional study was conducted at Lady Reading Hospital, Peshawar, for about two months. A total of 160 patients diagnosed with Plasmodium vivax malaria were enrolled. Participants were divided into two groups based on platelet count. Laboratory tests, including complete blood count, liver function tests, and Renal Function Tests were performed. Data were analyzed using SPSS version 20.0 , An Independent sample t-test was used to assess the significant difference between the two groups with statistical significance set at p&lt;0.05. Results: A total of 165 patients were included in the study. In the severe thrombocytopenia group (&lt;100,000/µL), there were 23 cases of anemia, jaundice (n=25), acute renal failure (n=7), cerebral malaria (n=2), seizures (n=1) and hypoglycemia (n=1). In the less severe thrombocytopenia group (&gt;100,000/µL), there were 14 cases of anemia, jaundice (n=17), and acute renal failure (n=2). The blood glucose level (p=0.37), systolic blood pressure (p=0.18) and pulse rate (p=0.21) revealed no significant differences between the two groups. Conclusions: It was concluded that severe thrombocytopenia in P. vivax malaria was associated with more severe clinical manifestations, with a few cases requiring transfusions. Patients with less severe thrombocytopenia had fewer complications

Genetic polymorphism of Duffy binding protein in Pakistan Plasmodium vivax isolates

Plasmodium vivax Duffy binding protein (PvDBP) is crucial for erythrocyte invasion, interacting with the Duffy Antigen Receptor for Chemokines (DARC) on the erythrocyte surface. The amino-terminal cysteine-rich region II of PvDBP (PvDBPII) is a promising blood stage vaccine candidate, yet the genetic polymorphisms of this protein in global P. vivax isolates complicate the design of effective vaccines against vivax malaria. This study analyzed the genetic polymorphism of PvDBPII in Pakistan P. vivax isolates. A total of 29 single nucleotide polymorphisms (SNPs), including 22 nonsynonymous SNPs, were identified in 118 Pakistan PvDBPII. Most amino acid substitutions occurred in subdomains II and III, with six commonly observed in the global PvDBPII population. The amino acid change patterns in Pakistan PvDBPII generally mirrored those in global PvDBPII, although the frequencies of amino acid changes varied by country. Nucleotide diversity in Pakistan PvDBPII was comparable to that found in global PvDBPII. Evidence of natural selection and recombination in Pakistan PvDBPII aligned with observations in global PvDBPII. Analysis of the haplotype network of global PvDBPII revealed a complexed network of 167 haplotypes, but no geographical clustering was observed. The findings are crucial for understanding the genetic characteristics of Pakistan PvDBPII. A comprehensive analysis of nucleotide diversity and evolutionary trends in the global PvDBPII population offers valuable insights for the development of vivax malaria vaccines based on this antigen.

Risk factors for death among children with severe malaria, Ivukula sub-county, Namutumba district, Eastern Uganda, september 2021–february 2022

BackgroundIn February 2022, the Ministry of Health received reports of more than 100 child deaths from a ‘strange disease’ in Namutumba District over a period of 6 months from politicians through the media. Preliminary investigations by the district rapid response team confirmed the strange disease to be severe malaria. The scope of severe malaria deaths was investigated, associated factors identified, and recommendations made for control measures to inform early malaria treatment strategies in Namutumba District.MethodsA retrospective study was conducted in March 2022 in the most affected subcounty (Ivukula Subcounty) involving cases and controls. A case was defined as a death with a positive malaria test, fever and any of the following: convulsions, difficulty breathing, yellowing of eyes or palms, tea-coloured urine, anaemia (evidenced by pale eyes or palms, or clinically-identified in medical records), loss of consciousness, or reduced urine output (very little or no urine in a day) in a child ≤ 12 years from September 2021 to February 2022 in Ivukula Subcounty, Namutumba District. Controls were survivors with the same signs and symptoms, recruited in a 2:1 ratio with cases. Cases and controls were actively searched using a door-to-door approach with the help of community health workers. Caretakers were interviewed to obtain data on signs and symptoms, socio-demographic information, health-seeking behaviours and health system risk factors. Drugs and bloodstock status information was obtained from health workers using an interview guide. Factors associated with death were identified using multivariate logistic regression and thematic analysis for qualitative data.ResultsAmong 46 cases, 29 (63%) were < 5 years, and 23 (50%) were female. Death among children with severe malaria was significantly associated with treatment non-completion (aOR = 9.7, 95%CI 1.8–53) and inability to receive blood transfusion for anaemic patients (aOR = 7.1, (95%CI 1.4–36). Healthcare workers reported that inability to reach referral sites due to transport costs, stockouts of anti-malarials and blood products at health facilities, and absence of integrated community case management of childhood illnesses (iCCM) contributed to deaths among children with severe malaria.ConclusionLack of access to anti-malarial treatment and to blood transfusions among anaemic patients due to stockouts were associated with severe malaria deaths among children ≤ 12 years in Ivukula Subcounty. Recommendations made were: accurate quantification of anti-malarials for health facilities, offering transport support to severe patients referred to higher-level facilities, and increasing access to blood products. Activation of iCCM could facilitate public health efforts against severe malaria in the district.

Methaemoglobin as a surrogate marker of primaquine antihypnozoite activity in Plasmodium vivax malaria: A systematic review and individual patient data meta-analysis.

The 8-aminoquinolines, primaquine and tafenoquine, are the only available drugs for the radical cure of Plasmodium vivax hypnozoites. Previous evidence suggests that there is dose-dependent 8-aminoquinoline induced methaemoglobinaemia and that higher methaemoglobin concentrations are associated with a lower risk of P. vivax recurrence. We undertook a systematic review and individual patient data meta-analysis to examine the utility of methaemoglobin as a population-level surrogate endpoint for 8-aminoquinoline antihypnozoite activity to prevent P. vivax recurrence. We conducted a systematic search of Medline, Embase, Web of Science, and the Cochrane Library, from 1 January 2000 to 29 September 2022, inclusive, of prospective clinical efficacy studies of acute, uncomplicated P. vivax malaria mono-infections treated with radical curative doses of primaquine. The day 7 methaemoglobin concentration was the primary surrogate outcome of interest. The primary clinical outcome was the time to first P. vivax recurrence between day 7 and day 120 after enrolment. We used multivariable Cox proportional-hazards regression with site random-effects to characterise the time to first recurrence as a function of the day 7 methaemoglobin percentage (log base 2 transformed), adjusted for the partner schizonticidal drug, the primaquine regimen duration as a proxy for the total primaquine dose (mg base/kg), the daily primaquine dose (mg/kg), and other factors. The systematic review protocol was registered with PROSPERO (CRD42023345956). We identified 219 P. vivax efficacy studies, of which 8 provided relevant individual-level data from patients treated with primaquine; all were randomised, parallel arm clinical trials assessed as having low or moderate risk of bias. In the primary analysis data set, there were 1,747 patients with normal glucose-6-phosphate dehydrogenase (G6PD) activity enrolled from 24 study sites across 8 different countries (Indonesia, Brazil, Vietnam, Thailand, Peru, Colombia, Ethiopia, and India). We observed an increasing dose-response relationship between the daily weight-adjusted primaquine dose and day 7 methaemoglobin level. For a given primaquine dose regimen, an observed doubling in day 7 methaemoglobin percentage was associated with an estimated 30% reduction in the risk of P. vivax recurrence (adjusted hazard ratio = 0.70; 95% confidence interval [CI] [0.57, 0.86]; p = 0.0005). These pooled estimates were largely consistent across the study sites. Using day 7 methaemoglobin as a surrogate endpoint for recurrence would reduce required sample sizes by approximately 40%. Study limitations include the inability to distinguish between recrudescence, reinfection, and relapse in P. vivax recurrences. For a given primaquine regimen, higher methaemoglobin on day 7 was associated with a reduced risk of P. vivax recurrence. Under our proposed causal model, this justifies the use of methaemoglobin as a population-level surrogate endpoint for primaquine antihypnozoite activity in patients with P. vivax malaria who have normal G6PD activity.

Peripheral Perfusion Index in Ugandan Children With Plasmodium falciparum Severe Malaria: Secondary Analysis of Outcomes in a 2014-2017 Cohort Study.

Continuous, noninvasive tools to monitor peripheral perfusion, such as perfusion index (PI), can detect hemodynamic abnormalities and assist in the management of critically ill children hospitalized with severe malaria. In this study of hospitalized children with severe malaria, we aimed to assess whether PI correlates with clinical markers of perfusion and to determine whether combining PI with these clinical measures improves identification of children with greater odds of mortality. Post hoc analysis of a prospective, multicenter, cohort study conducted between 2014 and 2017. Two referral hospitals in Central and Eastern Uganda. Six hundred children younger than 5 years old with severe malaria and 120 asymptomatic community children. None. PI was measured at 6-hour intervals for the first 24 hours of hospitalization. We compared PI to standard clinical perfusion measures such as capillary refill time, presence of cold peripheral limbs, or temperature gradient. Admission PI was highly correlated with clinical measures of perfusion. Admission PI was lower in children with severe malaria compared with asymptomatic community children; and, among the children with severe malaria, PI was lower in those with clinical features of poor perfusion or complications of severe malaria, such as shock and hyperlactatemia (all p < 0.02). Among children with severe malaria, lower admission PI was associated with greater odds of mortality after adjustment for age, sex, and severe malaria criteria (adjusted odds ratio, 2.4 for each log decrease in PI [95% CI, 1.0-5.9]; p = 0.045). Diagnostically, the presence of two consecutive low PI measures (< 1%) predicted mortality, with a sensitivity of 50% and a specificity of 76%. In severe malaria, PI correlates with clinical complications (including shock and elevated serum lactate) and may be useful as an objective, continuous explanatory variable associated with greater odds of later in-hospital mortality.

Comparative genomics of two protozoans Dictyostelium discoideum and Plasmodium falciparum reveals conserved as well as distinct regulatory pathways crucial for exploring novel therapeutic targets for Malaria

Plasmodium falciparum, which causes life-threatening cerebral malaria has rapidly gained resistance against most frontline anti-malarial drugs, thereby generating an urgent need to develop novel therapeutic approaches. Conducting in-depth investigations on Plasmodium in its native form is challenging, thereby necessitating the requirement of an efficient model system. In line, mounting evidence suggests that Dictyostelium discoideum retains both conformational and functional properties of Plasmodium proteins, however, the true potential of Dictyostelium as a host system is not fully explored. In the present study, we have exploited comparative genomics as a tool to extract, compare, and curate the extensive data available on the organism-specific databases to evaluate if D. discoideum can be established as a prime model system for functional characterization of P. falciparum genes. Through comprehensive in silico analysis, we report that despite the presence of adaptation-specific genes, the two display noteworthy conservation in the housekeeping genes, signaling pathway components, transcription regulators, and post-translational modulators. Furthermore, through orthologue analysis, the known, potential, and novel drug target genes of P. falciparum were found to be significantly conserved in D. discoideum. Our findings advocate that D. discoideum can be employed to express and functionally characterize difficult-to-express P. falciparum genes.

Acetylsalicylic acid and dihydroartemisinin combined therapy on experimental malaria-associated acute lung injury: analysis of lung function and the inflammatory process

BackgroundSevere malaria can cause respiratory symptoms, which may lead to malaria-acute lung injury (MA-ALI) due to inflammation and damage to the blood-gas barrier. Patients with severe malaria also often present thrombocytopenia, and the use of acetylsalicylic acid (ASA), a commonly used non-steroidal anti-inflammatory drug with immunomodulatory and antiplatelet effects, may pose a risk in regions where malaria is endemic. Thus, this study aimed to investigate the systemic impact of ASA and dihydroartemisinin (DHA) on ALI induced in mice by Plasmodium berghei NK65 (PbNK65).MethodsC57BL/6 mice were randomly divided into control (C) and PbNK65 infected groups and were inoculated with uninfected or 104 infected erythrocytes, respectively. Then, the animals were treated with DHA (3 mg/kg) or vehicle (DMSO) at the 8-day post-infection (dpi) for 7 days and with ASA (100 mg/kg, single dose), and analyses were performed at 9 or 15 dpi. Lung mechanics were performed, and lungs were collected for oedema evaluation and histological analyses.ResultsPbNK65 infection led to lung oedema, as well as increased lung static elastance (Est, L), resistive (ΔP1, L) and viscoelastic (ΔP2, L) pressures, percentage of mononuclear cells, inflammatory infiltrate, hemorrhage, alveolar oedema, and alveolar thickening septum at 9 dpi. Mice that received DHA or DHA + ASA had an increase in Est, L, and CD36 expression on inflammatory monocytes and higher protein content on bronchoalveolar fluid (BALF). However, only the DHA-treated group presented a percentage of inflammatory monocytes similar to the control group and a decrease in ΔP1, L and ΔP2, L compared to Pb + DMSO. Also, combined treatment with DHA + ASA led to an impairment in diffuse alveolar damage score and lung function at 9 dpi.ConclusionsTherapy with ASA maintained lung morpho-functional impairment triggered by PbNK65 infection, leading to a large influx of inflammatory monocytes to the lung tissue. Based on its deleterious effects in experimental MA-ALI, ASA administration or its treatment maintenance might be carefully reconsidered and further investigated in human malaria cases.

Ternary structure of Plasmodium vivaxN-myristoyltransferase with myristoyl-CoA and inhibitor IMP-0001173.

Plasmodium vivax is a major cause of malaria, which poses an increased health burden on approximately one third of the world's population due to climate change. Primaquine, the preferred treatment for P. vivax malaria, is contraindicated in individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency, a common genetic cause of hemolytic anemia, that affects ∼2.5% of the world's population and ∼8% of the population in areas of the world where P. vivax malaria is endemic. The Seattle Structural Genomics Center for Infectious Disease (SSGCID) conducted a structure-function analysis of P.vivax N-myristoyltransferase (PvNMT) as part of efforts to develop alternative malaria drugs. PvNMT catalyzes the attachment of myristate to the N-terminal glycine of many proteins, and this critical post-translational modification is required for the survival of P. vivax. The first step is the formation of aPvNMT-myristoyl-CoA binary complex that can bind to peptides. Understanding how inhibitors prevent protein binding will facilitate the development of PvNMT as a viable drug target. NMTs are secreted in all life stages of malarial parasites, making them attractive targets, unlike current antimalarials that are only effective during the plasmodial erythrocytic stages. The 2.3 Å resolution crystal structure of the ternary complex of PvNMT with myristoyl-CoA and a novel inhibitor is reported. One asymmetric unit contains two monomers. The structure reveals notable differences between the PvNMT and human enzymes and similarities to other plasmodial NMTs that can be exploited to develop new antimalarials.