In vitro delayed response to dihydroartemisinin of malaria parasites infecting sickle cell erythocytes.

BACKGROUND: Decreased efficacy of artemisinin-based combination therapy (ACT) for Plasmodium falciparum malaria has been previously reported in patients with sickle cell disease (SCD). The main purpose of this study was to investigate the in vitro susceptibility of isolates to dihydro-artemisinin (DHA) to provide a hypothesis to explain this treatment failure. METHODS: Isolates were collected from patients attending health centres in Abidjan with uncomplicated P. falciparum malaria. The haemoglobin type has been identified and in vitro drug sensitivity tests were conducted with the ring stage assay and maturation inhibition assay. RESULTS: 134 isolates were obtained. Parasitaemia and haemoglobin levels at inclusion were lower in patients with haemoglobin HbSS and HbSC than in patients with normal HbAA. After ex vivo RSA and drug inhibition assays, the lowest rate of parasitic growth was found with isolates from HbAS red cells. Conversely, a significantly higher survival rate of parasites ranging from 15 to 34% were observed in isolates from HbSS. Isolates with in vitro reduced DHA sensitivity correlate with lower RBC count and haematocrit and higher parasitaemia at inclusion compared to those with isolates with normal DHA sensitivity. However, this decrease of in vitro sensitivity to DHA was not associated with Kelch 13-Propeller gene polymorphism. CONCLUSION: This study highlights an in vitro decreased sensitivity to DHA, for isolates collected from HbSS patients, not related to the Pfkelch13 gene mutations. These results are in line with recent studies pointing out the role of the redox context in the efficacy of the drug. Indeed, SCD red cells harbour a highly different ionic and redox context in comparison with normal red cells. This study offers new insights into the understanding of artemisinin selective pressure on the malaria parasite in the context of haemoglobinopathies in Africa.

Influence of Host-Related Factors and Exposure to Mosquito Bites on the Dynamics of Antibody Response to Plasmodium falciparum Antigens.

Humoral immunity to Plasmodium falciparum is acquired after repeated infections, and can lead to clinical protection. This study aimed to evaluate how human-, parasite-, and environment-related determinants can modulate the dynamics of IgG responses to Plasmodium falciparum after an infection. Individuals (n = 68, average age = 8.2 years) with uncomplicated malaria were treated with ACT and followed up for 42 days. IgG responses to P. falciparum merozoite antigens (PfMSP1, PfMSP3, PfAMA1, PfGLURP-R0), to whole schizont extract (PfSchz), and to Anopheles gSG6-P1 and Aedes Nterm-34 kDa salivary peptides were measured. Regression analyses were used to identify factors that influence the dynamics of IgG response to P. falciparum antigen between D0 and D42, including demographic and biological factors and the level of exposure to mosquito bites. The dynamics of IgG response to P. falciparum differed according to the antigen. According to multivariate analysis, IgG responses to PfSchz and to PfGLURP-R0 appear to be affected by exposure to Aedes saliva and are associated with age, parasite density, and anti-Plasmodium pre-existing immune response at study inclusion. The present work shows that human exposure to Aedes saliva may contribute, in addition to other factors, to the regulation of anti-Plasmodium immune responses during a natural infection.

Artemisinin derivative-containing therapies and abnormal hemoglobin: Do we need to adapt the treatment?

BACKGROUND: Artemisinin-based treatment in malaria patients with abnormal hemoglobin may be ineffective because of their genetic particularity, which could lead to resistance. The main purpose of this study was to assess the effect of artemisinin derivatives on in vivo parasite clearance according to erythrocyte variants. In vivo response was investigated through retrospective data obtained over a 42-day artemether-lumefantrine/artesunate amodiaquine efficacy protocol conducted from 2012 to 2016. RESULTS: A total of 770 patients in Côte d'Ivoire attending the hospitals of Anonkoua-koute (Abidjan), Petit Paris (Korhogo), Libreville (Man), Dar es salam (Bouaké), Ayamé and Yamoussoukro with acute uncomplicated falciparum malaria were selected for successful hemoglobin typing. HbAS, HbSS, HbAC, and HbSC genotypes were found. Parasite clearance time was obtained for 414 patients. In the population with abnormal hemoglobin, parasite densities on admission and parasite clearance rates were significantly lower in the HbSC group compared to HbAA (p = 0.02 and p = 0.007, respectively). After PCR correction on day 42, the acute treatment rate was 100% for each group. Parasite half-life and time for initial parasitaemia to decline by 50 and 99% were longer for the HbSC group (p < 0.05). The study also investigated the prevalence of K13-propeller polymorphisms across different hemoglobin genotype groups. A total of 185 and 63 samples were sequenced in the HbAA group and patients with abnormal Hb, respectively. Only two nonsynonymous mutations D559N and V510M were found in the HbAA group. CONCLUSION: Although this study proved good efficacy of artemether-lumefantrine and artesunate amodiaquine in the treatment of uncomplicated Plasmodium falciparum malaria in patients with abnormal hemoglobin, the increased delay of parasite clearance may represent a threat to health in these patients in relation with sickle cell crisis, which could support selection of parasites resistant to artemisinin.

TITLE: Thérapies contenant des dérivés de l'artémisinine et hémoglobine anormale : faut-il adapter le traitement ? ABSTRACT: Contexte : Le traitement à base d'artémisinine chez les patients atteints de paludisme et présentant une hémoglobine anormale peut être inefficace en raison de leur particularité génétique, ce qui pourrait entraîner une résistance. L'objectif principal de cette étude était d'évaluer in vivo l'effet des dérivés de l'artémisinine sur la clairance du parasite en fonction des variantes érythrocytaires. La réponse in vivo a été étudiée à travers des données rétrospectives obtenues au cours d'un protocole d'efficacité de 42 jours artéméther-luméfantrine/artésunate-amodiaquine mené dans les années 2012 à 2016. Résultats : Un total de 770 patients en Côte d'Ivoire fréquentant les hôpitaux d'Anonkoua-koute (Abidjan), Petit Paris (Korhogo), Libreville (Man), Dar es salam (Bouaké), Ayamé et Yamoussoukro, présentant un paludisme aigu non compliqué à falciparum ont été sélectionnés pour un typage réussi de l'hémoglobine. Les génotypes HbAS, HbSS, HbAC et HbSC ont été trouvés. Le temps de clairance du parasite a été obtenu pour 414 patients. Dans la population avec une hémoglobine anormale, les densités parasitaires à l'admission et le taux de clairance parasitaire étaient significativement plus faibles dans le groupe HbSC par rapport au groupe HbAA (respectivement, p = 0,02 et p = 0,007). Le RCPA était de 100 % pour chaque groupe après correction par PCR au jour 42. La demi-vie du parasite et le temps nécessaire pour que la parasitémie initiale diminue de 50 et 99 % étaient plus longs pour le groupe HbSC (p < 0,05). L'étude a également examiné la prévalence des polymorphismes du gène K13 dans différents groupes de génotype d'hémoglobine. Un total de 185 et 63 échantillons ont été séquencés respectivement dans le groupe HbAA et chez les patients présentant une Hb anormale. Seules deux mutations non synonymes D559N et V510M ont été trouvées dans le groupe HbAA. Conclusion : Bien que cette étude ait prouvé la bonne efficacité de l'artéméther-luméfantrine et de l'artésunate amodiaquine dans le traitement du paludisme simple à Plasmodium falciparum chez les patients présentant une hémoglobine anormale, le retard accru de clairance parasitaire peut représenter une menace pour la santé de ces patients en relation avec la crise drépanocytaire, et peut favoriser la sélection de parasites résistants à l'artémisinine.

Risk factors for placental malaria and associated low birth weight in a rural high malaria transmission setting of Cote d'Ivoire.

BACKGROUND: Placental malaria (PM) is associated with increased risk of both maternal and neonatal adverse outcomes. The objective of this study was to assess risks factors associated with PM including intermittent preventive treatment with sulfadoxine-pyrimethamine (IPTp-SP). METHODS: A cross-sectional study was conducted at Ayame hospital in the southern region of Cote d'Ivoire between August 2016 and March 2017. Sociodemographic baseline characteristic and antenatal data were obtained from the mother's antenatal card and included timing and number of IPTp-SP doses. Newborn characteristics were recorded.Peripheral blood as well as placental and cord blood were used to prepare thick and thin blood films. In addition, pieces of placental tissues were used to prepare impression smears. Regression logistics were used to study factors associated with PM and low birth weight (LBW) (<2.500 g). RESULTS: Three hundred delivered women were enrolled in the study. The mean age of the participants was 25 ± 6.5 years and most participants were multigravida (52.8%). The coverage rate of IPTp-SP with the full three doses recommended was 27.8%. Overall, 7.3% (22/300) of women examined had PM detected by microscopy using impression smear (22/300). Multivariate analysis showed that significant risks factors of PM were maternal peripheral parasitemia at delivery (P < 0.0001), residence (P = 0.03), and not sleeping under long-lasting insecticide treated nets (LLINs) (P = 0.006). LBW infants were born to 22.7% (5/22) of women with PM and 13.3% (37/278) of women without PM (P = 0.47). Only primiparous was associated with LBW in the multivariable analysis (P = 0.04). CONCLUSION: The prevalence of PM was 7.3%. Low parity, residence and not using LLINs and maternal peripheral parasitemia were identified as risks factors. PM was associated with LBW. Implementation of IPTp-SP should be improved by the National Malaria Control Program in rural settings.

Coverage and efficacy of intermittent preventive treatment with sulphadoxine pyrimethamine against malaria in pregnancy in Côte d'Ivoire five years after its implementation.

BACKGROUND: The World Health Organization (WHO) recommends for sub-Saharan Africa a package of prompt and effective case-management combined with the delivery of insecticide-treated nets (ITN) and intermittent preventive treatment during pregnancy (IPTp) with sulphadoxine-pyrimethamine (SP) through the national antenatal care (ANC) programs. Implemented in Côte d'Ivoire around 2005, few Data on IPTp coverage and efficacy in the country are available. METHODS: A multicentre, cross-sectional survey was conducted in Côte d'Ivoire from September 2009 to May 2010 at six urban and rural antenatal clinics. IPTp-sp coverage, Socio-economic and obstetrical data of mothers and neonate birth weights were documented. Peripheral blood as well as placental and cord blood were used to prepare thick and thin blood films. In addition, pieces of placental tissues were used to prepare impression smears and maternal haemoglobin concentration was measured. Regression logistics were used to study factors associated with placental malaria and LBW (<2.500 grams). RESULTS: A total of 1317 delivered women were enrolled with a median age of 26 years. A proportion of 43.28% of the women had received at least two doses of IPTsp during the current pregnancy although a high proportion (90.4%) of women received antenatal care and made enough visits (≥2). Variability in the results was observed depending on the type of area (rural/urban). Plasmodium falciparum was detected in the peripheral blood of 97 women (7.3%) and in the placenta of 119 women (9%). LBW infants were born to 18.8% (22/107) of women with placental malaria and 8.5% (103/1097) of women without placental malaria. LBW was associated with placental malaria. CONCLUSIONS: This study found relative low coverage of IPTp in the study areas which supported findings that high ANC attendance does not guarantee high IPTp coverage. Urgent efforts are required to improve service delivery of this important intervention.