Rolling Back a Malaria Epidemic in South Africa

The authors discuss the success in malaria control in KwaZulu-Natal (reported by Barnes and colleagues), and its implications for the rest of Africa

Maternal peripheral blood level of IL-10 as a marker for inflammatory placental malaria

Background: Placental malaria (PM) is an important cause of maternal and foetal mortality in tropical areas, and severe sequelae and mortality are related to inflammation in the placenta. Diagnosis is difficult because PM is often asymptomatic, peripheral blood smear examination detects parasitemia as few as half of PM cases, and no peripheral markers have been validated for placental inflammation. Methods: In a cohort of Tanzanian parturients, PM was determined by placental blood smears and placental inflammation was assessed by histology and TNF mRNA levels. Maternal peripheral blood levels of several immune mediators previously implicated in PM pathogenesis, as well as ferritin and leptin were measured. The relationship between the levels of these soluble factors to PM and placental inflammation was examined. Results: Peripheral levels of TNF, TNF-RI, TNF-RII, IL-1, IL-10, and ferritin were elevated during PM, whereas levels of IFN-[gamma], IL-4, IL-5 and IL-6 were unchanged and levels of leptin were decreased. In receiver operating characteristic curve analysis, IL-10 had the greatest area under the curve, and would provide a sensitivity of 60% with a false positive rate of 10%. At a cut off level of 15 pg/mL, IL-10 would detect PM with a sensitivity of 79.5% and a specificity of 84.3%. IL-10 levels correlated with placental inflammatory cells and placental TNF mRNA levels in first time mothers. Conclusion: These data suggest that IL-10 may have utility as a biomarker for inflammatory PM in research studies, but that additional biomarkers may be required to improve clinical diagnosis and management of malaria during pregnancy.This work was supported by grants from Bill and Melinda Gates Foundation (grant 29202), NIH (R01 AI52059 and TW05509) and Puget Sound Partners for Global Health to P.E.D

Cost-Effectiveness Study of Three Antimalarial Drug Combinations in Tanzania

BACKGROUND: As a result of rising levels of drug resistance to conventional monotherapy, the World Health Organization (WHO) and other international organisations have recommended that malaria endemic countries move to combination therapy, ideally with artemisinin-based combinations (ACTs). Cost is a major barrier to deployment. There is little evidence from field trials on the cost-effectiveness of these new combinations. METHODS AND FINDINGS: An economic evaluation of drug combinations was designed around a randomised effectiveness trial of combinations recommended by the WHO, used to treat Tanzanian children with non-severe slide-proven malaria. Drug combinations were: amodiaquine (AQ), AQ with sulfadoxine-pyrimethamine (AQ+SP), AQ with artesunate (AQ+AS), and artemether-lumefantrine (AL) in a six-dose regimen. Effectiveness was measured in terms of resource savings and cases of malaria averted (based on parasitological failure rates at days 14 and 28). All costs to providers and to patients and their families were estimated and uncertain variables were subjected to univariate sensitivity analysis. Incremental analysis comparing each combination to monotherapy (AQ) revealed that from a societal perspective AL was most cost-effective at day 14. At day 28 the difference between AL and AQ+AS was negligible; both resulted in a gross savings of approximately US$1.70 or a net saving of US$22.40 per case averted. Varying the accuracy of diagnosis and the subsistence wage rate used to value unpaid work had a significant effect on the number of cases averted and on programme costs, respectively, but this did not change the finding that AL and AQ+AS dominate monotherapy. CONCLUSIONS: In an area of high drug resistance, there is evidence that AL and AQ+AS are the most cost-effective drugs despite being the most expensive, because they are significantly more effective than other options and therefore reduce the need for further treatment. This is not necessarily the case in parts of Africa where recrudescence following SP and AQ treatment (and their combination) is lower so that the relative advantage of ACTs is smaller, or where diagnostic services are not accurate and as a result much of the drug goes to those who do not have malaria

Randomized Trial of Artesunate+Amodiaquine, Sulfadoxine-Pyrimethamine+Amodiaquine, Chlorproguanal-Dapsone and SP for Malaria in Pregnancy in Tanzania

Malaria in pregnancy is serious, and drug resistance in Africa is spreading. Drugs have greater risks in pregnancy and determining the safety and efficacy of drugs in pregnancy is therefore a priority. This study set out to determine the efficacy and safety of several antimalarial drugs and combinations in pregnant women with uncomplicated malaria.Pregnant women with non-severe, slide proven, falciparum malaria were randomised to one of 4 regimes: sulfadoxine-pyrimethamine [SP]; chlorproguanil-dapsone [CD]; SP+amodiaquine [SP+AQ] or amodiaquine+artesunate [AQ+AS]. Randomisation was on a 1ratio2ratio2ratio2 ratio. Women were admitted for treatment, and followed at days 7, 14, 21, 28 after the start of treatment, at delivery and 6 weeks after delivery to determine adverse events, clinical and parasitological outcomes. Primary outcome was parasitological failure by day 28.1433 pregnant women were screened, of whom 272 met entry criteria and were randomised; 28 to SP, 81 to CD, 80 to SP+AQ and 83 to AQ+AS. Follow-up to day 28 post treatment was 251/272 (92%), and to 6 weeks following delivery 91%. By day 28 parasitological failure rates were 4/26 (15%, 95%CI 4-35) in the SP, 18/77 (23%, 95%CI 14-34) in the CD, 1/73 (1% 95%CI 7-0.001) in the SP+AQ and 7/75 (9% 95%CI 4-18) in the AQ+AS arms respectively. After correction by molecular markers for reinfection the parasitological failure rates at day 28 were 18% for CD, 1% for SP+AQ and 4.5% for AQ+AS. There were two maternal deaths during the trial. There was no apparent excess of stillbirths or adverse birth outcomes in any arm. Parasitological responses were strikingly better in pregnant women than in children treated with the same drugs at this site.Failure rates with monotherapy were unacceptably high. The two combinations tested were efficacious and appeared safe. It should not be assumed that efficacy in pregnancy is the same as in children.ClinicalTrials.gov NCT00146731

Skeletal muscle fibre type and enzymatic activity in adult offspring following placental and peripheral malaria exposure in foetal life

BackgroundMaternal malaria may restrict foetal growth. Impaired utero-placental blood flow due to malaria infection may cause hypoxia-induced altered skeletal muscle fibre type distribution in the offspring, which may contribute to insulin resistance and impaired glucose metabolism. This study assessed muscle fibre distribution 20 years after placental and/or peripheral in-utero malaria exposure compared to no exposure, i.e., PPM+, PM+, and M-, respectively.MethodsWe traced 101 men and women offspring of mothers who participated in a malaria chemosuppression study in Muheza, Tanzania. Of 76 eligible participants, 50 individuals (29 men and 21 women) had skeletal muscle biopsy taken from m. vastus lateralis in the right leg. As previously reported, fasting and 30 min post-oral glucose challenge plasma glucose values were higher, and insulin secretion disposition index was lower, in the PPM+ group. Aerobic capacity (fitness) was estimated by an indirect VO2max test on a stationary bicycle. Muscle fibre sub-type (myosin heavy chain, MHC) distribution was analysed, as were muscle enzyme activities (citrate synthase (CS), 3-hydroxyacyl-CoA dehydrogenase, myophosphorylase, phosphofructokinase, lactate dehydrogenase, and creatine kinase activities. Between-group analyses were adjusted for MHC-I %.ResultsNo differences in aerobic capacity were found between groups. Despite subtle elevations of plasma glucose levels in the PPM+ group, there was no difference in MHC sub-types or muscle enzymatic activities between the malaria-exposed and non-exposed groups.ConclusionThe current study did not show differences in MHC towards glycolytic sub-types or enzymatic activity across the sub-groups. The results support the notion of the mild elevations of plasma glucose levels in people exposed to placental malaria in pregnancy being due to compromised pancreatic insulin secretion rather than insulin resistance

Maternal Malaria and Gravidity Interact to Modify Infant Susceptibility to Malaria

BACKGROUND: In endemic areas, placental malaria due to Plasmodium falciparum is most frequent and severe in first-time mothers, and increases the risk of infant mortality in their offspring. Placental malaria may increase the susceptibility of infants to malaria parasitemia, but evidence for this effect is inconclusive. METHODS AND FINDINGS: During 2002–2004, we monitored parasitemia in 453 infants, including 69 who were born to mothers with placental malaria, in a region of northeastern Tanzania where malaria transmission is intense. We used a Cox proportional hazards model to evaluate the time from birth to first parasitemia, and a generalized estimating equations logistic regression model to evaluate risk of any parasitemia throughout the first year of life. Compared with infants whose mothers did not have placental malaria at delivery (“PM-negative”), offspring of mothers with placental malaria at delivery (“PM-positive”) were 41% more likely to experience their first parasitemia at a younger age (adjusted hazard ratio [AHR] = 1.41, 95% confidence interval [CI] 1.01–1.99). The odds of parasitemia throughout infancy were strongly modified by the interaction between placental malaria and gravidity (p for interaction = 0.008, Type 3 likelihood ratio test). Offspring of PM-negative primigravidae had lower odds of parasitemia during infancy (adjusted odds ratio [AOR] = 0.67, 95% CI 0.50–0.91) than offspring of PM-negative multigravidae, and offspring of PM-positive primigravidae had the lowest odds (AOR = 0.21, 95% CI 0.09–0.47). In contrast, offspring of PM-positive multigravidae had significantly higher odds of parasitemia (AOR = 1.59, 95% CI 1.16–2.17). CONCLUSION: Although parasitemia is more frequent in primigravid than multigravid women, the converse is true in their offspring, especially in offspring of PM-positive women. While placental malaria is known to increase mortality risk for first-born infants, it surprisingly reduced their risk of parasitemia in this study. Placental malaria of multigravidae, on the other hand, is a strong risk factor for parasitemia during infancy, and therefore preventive antimalarial chemotherapy administered to multigravid women close to term may reduce the frequency of parasitemia in their offspring

High Throughput Functional Assays of the Variant Antigen PfEMP1 Reveal a Single Domain in the 3D7 Plasmodium falciparum Genome that Binds ICAM1 with High Affinity and Is Targeted by Naturally Acquired Neutralizing Antibodies

Plasmodium falciparum–infected erythrocytes bind endothelial receptors to sequester in vascular beds, and binding to ICAM1 has been implicated in cerebral malaria. Binding to ICAM1 may be mediated by the variant surface antigen family PfEMP1: for example, 6 of 21 DBLβC2 domains from the IT4 strain PfEMP1 repertoire were shown to bind ICAM1, and the PfEMP1 containing these 6 domains are all classified as Group B or C type. In this study, we surveyed binding of ICAM1 to 16 DBLβC2 domains of the 3D7 strain PfEMP1 repertoire, using a high throughput Bioplex assay format. Only one DBL2βC2 domain from the Group A PfEMP1 PF11_0521 showed strong specific binding. Among these 16 domains, DBL2βC2PF11_0521 best preserved the residues previously identified as conserved in ICAM1-binding versus non-binding domains. Our analyses further highlighted the potential role of conserved residues within predominantly non-conserved flexible loops in adhesion, and, therefore, as targets for intervention. Our studies also suggest that the structural/functional DBLβC2 domain involved in ICAM1 binding includes about 80 amino acid residues upstream of the previously suggested DBLβC2 domain. DBL2βC2PF11_0521 binding to ICAM1 was inhibited by immune sera from east Africa but not by control US sera. Neutralizing antibodies were uncommon in children but common in immune adults from east Africa. Inhibition of binding was much more efficient than reversal of binding, indicating a strong interaction between DBL2βC2PF11_0521 and ICAM1. Our high throughput approach will significantly accelerate studies of PfEMP1 binding domains and protective antibody responses

Combination of probenecid-sulphadoxine-pyrimethamine for intermittent preventive treatment in pregnancy

The antifolate sulphadoxine-pyrimethamine (SP) has been used in the intermittent prevention of malaria in pregnancy (IPTp). SP is an ideal choice for IPTp, however, as resistance of Plasmodium falciparum to SP increases, data are accumulating that SP may no longer provide benefit in areas of high-level resistance. Probenecid was initially used as an adjunctive therapy to increase the blood concentration of penicillin; it has since been used to augment concentrations of other drugs, including antifolates. The addition of probenecid has been shown to increase the treatment efficacy of SP against malaria, suggesting that the combination of probenecid plus SP may prolong the useful lifespan of SP as an effective agent for IPTp. Here, the literature on the pharmacokinetics, adverse reactions, interactions and available data on the use of these drugs in pregnancy is reviewed, and the possible utility of an SP-probenecid combination is discussed. This article concludes by calling for further research into this potentially useful combination

An unusual presentation of placental malaria: a single persisting nidus of sequestered parasites.

Placental malaria caused by Plasmodium falciparum is a public health concern in tropical countries. Peripheral blood smears to detect placental malaria are often negative, and recrudescences are common during pregnancy. We performed placental histology on a series of first-time mothers delivering in an area endemic for P falciparum. A single nidus of malaria-infected erythrocytes was identified by placental histology in a single intervillous space from a woman who had no other evidence of peripheral or placental blood parasitemia. This finding suggests ring stage-infected erythrocytes sequester in vivo, or P falciparum can persist as a dormant blood stage form