Srivicha Krudsood

Ascaris lumbricoides infection is associated with protection from cerebral malaria

Following reports of increased IgE in severe malaria and hypothesizing that helminth coinfections could modify its outcome, we conducted a retrospective case–control study to establish whether helminths affect the evolution of Plasmodium falciparum malaria. Some 182 severe cases, 315 mild controls and 40 controls with circulating schizonts were examined for intestinal helminths. Comparing cerebral malaria with mild controls, Ascaris lumbricoides was associated with a protective adjusted odds ratio (OR) of 0.58 (0.32–1.03) P = 0.06, for coinfection with Ascaris and Necator americanus, OR = 0.39 (0.17–0.88) P = 0.02. Protection followed a dose–effect trend (P = 0.008). When comparing cerebral malaria cases and controls with circulating schizonts the OR was 0.25 (0.009–0.67) P = 0.006. We hypothesized that Ascaris infected patients may have had decreased cyto‐adherence, possibly through endothelial cell receptor downregulation and/or decreased splenic clearance leading to the absence of selection of virulent P. falciparum strains. IgE‐anti‐IgE immune complexes resulting from helminth preinfection may have an important role in influencing clinical presentation of severe malaria, and in establishing malaria tolerance, through the CD23/NO pathway.

Malaria Diagnosis: A Brief Review

Malaria is a major cause of death in tropical and sub-tropical countries, killing each year over 1 million people globally; 90% of fatalities occur in African children. Although effective ways to manage malaria now exist, the number of malaria cases is still increasing, due to several factors. In this emergency situation, prompt and effective diagnostic methods are essential for the management and control of malaria. Traditional methods for diagnosing malaria remain problematic; therefore, new technologies have been developed and introduced to overcome the limitations. This review details the currently available diagnostic methods for malaria.

Plasmodium falciparum genome-wide scans for positive selection, recombination hot spots and resistance to antimalarial drugs

Antimalarial drugs impose strong selective pressure on Plasmodium falciparum parasites and leave signatures of selection in the parasite genome; screening for genes under selection may suggest potential drug or immune targets. Genome-wide association studies (GWAS) of parasite traits have been hampered by the lack of high-throughput genotyping methods, inadequate knowledge of parasite population history and time-consuming adaptations of parasites to in vitro culture. Here we report the first Plasmodium GWAS, which included 189 culture-adapted P. falciparum parasites genotyped using a custom-built Affymetrix molecular inversion probe 3K malaria panel array with a coverage of ∼1 SNP per 7 kb. Population structure, variation in recombination rate and loci under recent positive selection were detected. Parasite half-maximum inhibitory concentrations for seven antimalarial drugs were obtained and used in GWAS to identify genes associated with drug responses. This study provides valuable tools and insight into the P. falciparum genome.

Tafenoquine plus chloroquine for the treatment and relapse prevention of Plasmodium vivax malaria (DETECTIVE): a multicentre, double-blind, randomised, phase 2b dose-selection study

BACKGROUND Clinical effectiveness of previous regimens to treat Plasmodium vivax infection have been hampered by compliance. We aimed to assess the dose-response, safety, and tolerability of single-dose tafenoquine plus 3-day chloroquine for P vivax malaria radical cure. METHODS In this double-blind, randomised, dose-ranging phase 2b study, men and women (aged ≥16 years) with microscopically confirmed P vivax monoinfection (parasite density >100 to <100,000 per μL blood) were enrolled from community health centres and hospitals across seven sites in Brazil, Peru, India, and Thailand. Patients with glucose-6-phosphate dehydrogenase enzyme activity of less than 70% were excluded. Eligible patients received chloroquine (days 1-3) and were randomly assigned (1:1:1:1:1:1) by a computer-generated randomisation schedule to receive single-dose tafenoquine 50 mg, 100 mg, 300 mg, or 600 mg, primaquine 15 mg for 14 days, or chloroquine alone. Randomisation was stratified by baseline parasite count (≤7500 and >7500 per μL blood). The primary efficacy endpoint was relapse-free efficacy at 6 months from initial dose (ie, clearance of initial infection without subsequent microscopically confirmed infection), analysed by intention to treat. This study is registered with ClinicalTrials.gov, number NCT01376167. FINDINGS Between Sept 19, 2011, and March 25, 2013, 329 patients were randomly assigned to a treatment group (chloroquine plus tafenoquine 50 mg [n=55], 100 mg [n=57], 300 mg [n=57], 600 mg [n=56]; or to chloroquine plus primaquine [n=50]; or chloroquine alone [n=54]). Relapse-free efficacy at 6 months was 57·7% (95% CI 43-70) with tafenoquine 50 mg, 54·1% (40-66) with tafenoquine 100 mg, 89·2% (77-95) with tafenoquine 300 mg, 91·9% (80-97) with tafenoquine 600 mg, 77·3% (63-87) with primaquine, and 37·5% (23-52) with chloroquine alone. Tafenoquine 300 mg and 600 mg had better efficacy than chloroquine alone (treatment differences 51·7% [95% CI 35-69], p<0·0001, with tafenoquine 300 mg and 54·5% [38-71], p<0·0001, with tafenoquine 600 mg), as did primaquine (treatment difference 39·9% [21-59], p=0·0004). Adverse events were similar between treatments. 29 serious adverse events occurred in 26 (8%) of 329 patients; QT prolongation was the most common serious adverse event (11 [3%] of 329), occurring in five (2%) of 225 patients receiving tafenoquine, four (8%) of 50 patients receiving primaquine, and two (4%) of 54 patients receiving chloroquine alone, with no evidence of an additional effect on QT of chloroquine plus tafenoquine coadministration. INTERPRETATION Single-dose tafenoquine 300 mg coadministered with chloroquine for P vivax malaria relapse prevention was more efficacious than chloroquine alone, with a similar safety profile. As a result, it has been selected for further clinical assessment in phase 3. FUNDING GlaxoSmithKline, Medicines for Malaria Venture.

Randomized, Controlled Dose-Optimization Studies of Dihydroartemisinin-Piperaquine for the Treatment of Uncomplicated Multidrug-Resistant Falciparum Malaria in Thailand

BACKGROUND Dihydroartemisinin-piperaquine (DP) is a new and relatively inexpensive artemisinin-containing fixed-combination antimalarial treatment. An adult treatment course contained 6.4 mg/kg dihydroartemisinin (DHA), which is >40% lower than the level in most artemisinin-containing combinations. This raised the possibility that the efficacy of the current coformulation may not be optimal in the treatment of multidrug-resistant falciparum malaria. METHODS In 2 large randomized, controlled studies in Thailand, the recommended dose of DP was compared with a regimen with additional artemisinin derivative (12 mg/kg; DP+) and with mefloquine plus artesunate (MAS3). RESULTS A total of 731 patients were included: 201 in a hospital-based study and 530 in a community study. Day-28 cure rates in the hospital-based study were 100% (95% confidence interval [CI], 93.9%-100%) in the MAS3 and DP+ groups and 98.3% (95% CI, 91%-99.7%) in the DP group, with a single recrudescence on day 21. In the community study, polymerase chain reaction genotyping-adjusted cure rates on day 63 were 96.1% (95% CI, 92.6%-99.7%) in the DP group, 98.3% (95% CI, 96.1%-100%) in the DP+ group, and 94.9% (95% CI, 91.2%-98.6%) in the MAS3 group (P=.2). Adverse events were few, with an excess of mild abdominal pain in the DP group. CONCLUSIONS The current dosage of DP (6.4 mg/kg DHA and 51.2 mg/kg piperaquine phosphate) given over the course of 48 h is highly effective, safe, and well tolerated for the treatment of multidrug-resistant falciparum malaria, and its efficacy is not improved by the addition of more DHA.

Deployment of Early Diagnosis and Mefloquine- Artesunate Treatment of Falciparum Malaria in Thailand: The Tak Malaria Initiative

Background Early diagnosis and treatment with artesunate-mefloquine combination therapy (MAS) have reduced the transmission of falciparum malaria dramatically and halted the progression of mefloquine resistance in camps for displaced persons along the Thai-Burmese border, an area of low and seasonal transmission of multidrug-resistant Plasmodium falciparum. We extended the same combination drug strategy to all other communities (estimated population 450,000) living in five border districts of Tak province in northwestern Thailand. Methods and Findings Existing health structures were reinforced. Village volunteers were trained to use rapid diagnostic tests and to treat positive cases with MAS. Cases of malaria, hospitalizations, and malaria-related deaths were recorded in the 6 y before, during, and after the Tak Malaria Initiative (TMI) intervention. Cross-sectional surveys were conducted before and during the TMI period. P. falciparum malaria cases fell by 34% (95% confidence interval [CI], 33.5–34.4) and hospitalisations for falciparum malaria fell by 39% (95% CI, 37.0–39.9) during the TMI period, while hospitalisations for P. vivax malaria remained constant. There were 32 deaths attributed to malaria during, and 22 after the TMI, a 51.5% (95% CI, 39.0–63.9) reduction compared to the average of the previous 3 y. Cross-sectional surveys indicated that P. vivax had become the predominant species in Thai villages, but not in populations living on the Myanmar side of the border. In the displaced persons population, where the original deployment took place 7 y before the TMI, the transmission of P. falciparum continued to be suppressed, the incidence of falciparum malaria remained low, and the in vivo efficacy of the 3-d MAS remained high. Conclusions In the remote malarious north western border area of Thailand, the early detection of malaria by trained village volunteers, using rapid diagnostic tests and treatment with mefloquine-artesunate was feasible and reduced the morbidity and mortality of multidrug-resistant P. falciparum.

Randomized Trial of 3-Dose Regimens of Tafenoquine (WR238605) versus Low-Dose Primaquine for Preventing Plasmodium vivax Malaria Relapse

BACKGROUND Tafenoquine is an 8-aminoquinoline developed as a more effective replacement for primaquine. In a previous dose-ranging study in Thailand, 3 tafenoquine regimens with total doses ranging from 500 mg to 3000 mg prevented relapse of Plasmodium vivax malaria in most patients when administered 2 days after receipt of a blood schizonticidal dose of chloroquine. METHODS To improve convenience and to begin comparison of tafenoquine with primaquine, 80 patients with P. vivax infection were randomized to receive 1 of the following 5 treatments 1 day after receiving a blood schizonticidal dose of chloroquine: (A) tafenoquine, 300 mg per day for 7 days (n=18); (B) tafenoquine, 600 mg per day for 3 days (n=19); (C) tafenoquine, 600 mg as a single dose (n=18); (D) no further treatment (n=13); or (E) primaquine base, 15 mg per day for 14 days (n=12). The minimum duration of protocol follow-up was 8 weeks, with additional follow-up to 24 weeks. RESULTS Forty-six of 55 tafenoquine recipients, 10 of 13 recipients of chloroquine only, and 12 of 12 recipients of chloroquine plus primaquine completed at least 8 weeks of follow-up (or had relapse). There was 1 relapse among recipients of chloroquine plus tafenoquine, 8 among recipients of chloroquine only, and 3 among recipients of chloroquine plus primaquine. The rate of protective efficacy (determined on the basis of reduction in incidence density) for all recipients of chloroquine plus tafenoquine, compared with recipients of chloroquine plus primaquine, was 92.6% (95% confidence interval, 7.3%-99.9%; P=.042, by Fishers exact test). CONCLUSIONS Tafenoquine doses as low as a single 600-mg dose may be useful for prevention of relapse of P. vivax malaria in Thailand.

Circulating Red Cell–derived Microparticles in Human Malaria

In patients with falciparum malaria, plasma concentrations of cell-derived microparticles correlate with disease severity. Using flow cytometry, we quantified red blood cell-derived microparticles (RMPs) in patients with malaria and identified the source and the factors associated with production. RMP concentrations were increased in patients with Plasmodium falciparum (n = 29; median, 457 RMPs/μL [range, 13-4,342 RMPs/μL]), Plasmodium vivax (n = 5; median, 409 RMPs/μL [range, 281-503/μL]), and Plasmodium malariae (n = 2; median, 163 RMPs/μL [range, 127-200 RMPs/μL]) compared with those in healthy subjects (n = 11; median, 8 RMPs/μL [range, 3-166 RMPs/μL]; P = .01). RMP concentrations were highest in patients with severe falciparum malaria (P = .01). Parasitized red cells produced >10 times more RMPs than did unparasitized cells, but the overall majority of RMPs still derived from uninfected red blood cells (URBCs). In cultures, RMP production increased as the parasites matured. Hemin and parasite products induced RMP production in URBCs, which was inhibited by N-acetylcysteine, suggesting heme-mediated oxidative stress as a pathway for the generation of RMPs.

Whole blood angiopoietin-1 and -2 levels discriminate cerebral and severe (non-cerebral) malaria from uncomplicated malaria

BackgroundSevere and cerebral malaria are associated with endothelial activation. Angiopoietin-1 (ANG-1) and angiopoietin-2 (ANG-2) are major regulators of endothelial activation and integrity. The aim of this study was to investigate the clinical utility of whole blood angiopoietin (ANG) levels as biomarkers of disease severity in Plasmodium falciparum malaria.MethodsThe utility of whole blood ANG levels was examined in Thai patients to distinguish cerebral (CM; n = 87) and severe (non-cerebral) malaria (SM; n = 36) from uncomplicated malaria (UM; n = 70). Comparative statistics are reported using a non-parametric univariate analysis (Kruskal-Wallis test or Chi-squared test, as appropriate). Multivariate binary logistic regression was used to examine differences in whole blood protein levels between groups (UM, SM, CM), adjusting for differences due to ethnicity, age, parasitaemia and sex. Receiver operating characteristic curve analysis was used to assess the diagnostic accuracy of the ANGs in their ability to distinguish between UM, SM and CM. Cumulative organ injury scores were obtained for patients with severe disease based on the presence of acute renal failure, jaundice, severe anaemia, circulatory collapse or coma.ResultsANG-1 and ANG-2 were readily detectable in whole blood. Compared to UM there were significant decreases in ANG-1 (p < 0.001) and significant increases in ANG-2 (p < 0.001) levels and the ratio of ANG-2: ANG-1 (p < 0.001) observed in patients with SM and CM. This effect was independent of covariates (ethnicity, age, parasitaemia, sex). Further, there was a significant decrease in ANG-1 levels in patients with SM (non-cerebral) versus CM (p < 0.001). In participants with severe disease, ANG-2, but not ANG-1, levels correlated with cumulative organ injury scores; however, ANG-1 correlated with the presence of renal dysfunction and coma. Receiver operating characteristic curve analysis demonstrated that the level of ANG-1, the level of ANG-2 or the ratio of ANG-2: ANG-1 discriminated between individuals with UM and SM (area under the curve, p-value: ANG-2, 0.763, p < 0.001; ANG-1, 0.884, p < 0.001; Ratio, 0.857, p < 0.001) or UM and CM (area under the curve, p-value: ANG-2, 0.772, p < 0.001; ANG-1, 0.778, p < 0.001; Ratio, 0.820, p < 0.001).ConclusionsThese results suggest that whole blood ANG-1/2 levels are promising clinically informative biomarkers of disease severity in malarial syndromes.

The clinical efficacy of artemether/lumefantrine (Coartem®).

Current World Health Organization (WHO) guidelines for the treatment of uncomplicated falciparum malaria recommend the use of artemisinin-based combination therapy (ACT). Artemether/lumefantrine is an ACT prequalified by the WHO for efficacy, safety and quality, approved by Swissmedic in December 2008 and recently approved by the USA FDA. Coartem® is a fixed-dose combination of artemether and lumefantrine. Its two components have different modes of action that provide synergistic anti-malarial activity. It is indicated for the treatment of infants, children and adults with acute, uncomplicated infection due to Plasmodium falciparum or mixed infections including P. falciparum. A formulation with improved palatability has been developed especially for children (Coartem® Dispersible), which rapidly disperses in a small amount of water for ease of administration.The efficacy of the six-dose regimen of artemether/lumefantrine has been confirmed in many different patient populations around the world, consistently achieving 28-day PCR (polymerase chain reaction)-corrected cure rates of >95% in the evaluable population, rapidly clearing parasitaemia and fever, and demonstrating a significant gametocidal effect, even in areas of widespread parasite resistance to other antimalarials.