Monocytes, particularly nonclassical ones, lose their opsonic and nonopsonic phagocytosis capacity during pediatric cerebral malaria

IntroductionInnate immunity is crucial to reducing parasite burden and contributing to survival in severe malaria. Monocytes are key actors in the innate response and, like macrophages, are plastic cells whose function and phenotype are regulated by the signals from the microenvironment. In the context of cerebral malaria (CM), monocyte response constitutes an important issue to understand. We previously demonstrated that decreased percentages of nonclassical monocytes were associated with death outcomes in CM children. In the current study, we postulated that monocyte phagocytosis function is impacted by the severity of malaria infection.MethodsTo study this hypothesis, we compared the opsonic and nonopsonic phagocytosis capacity of circulant monocytes from Beninese children with uncomplicated malaria (UM) and CM. For the CM group, samples were obtained at inclusion (D0) and 3 and 30 days after treatment (D3, D30). The phagocytosis capacity of monocytes and their subsets was characterized by flow cytometry and transcriptional profiling by studying genes known for their functional implication in infected-red blood cell (iRBC) elimination or immune escape.ResultsOur results confirm our hypothesis and highlight the higher capacity of nonclassical monocytes to phagocyte iRBC. We also confirm that a low number of nonclassical monocytes is associated with CM outcome when compared to UM, suggesting a mobilization of this subpopulation to the cerebral inflammatory site. Finally, our results suggest the implication of the inhibitory receptors LILRB1, LILRB2, and Tim3 in phagocytosis control.DiscussionTaken together, these data provide a better understanding of the interplay between monocytes and malaria infection in the pathogenicity of CM

Infections with Plasmodium falciparum during pregnancy affect VAR2CSA DBL-5 domain-specific T cell cytokine responses

Background: Current knowledge of human immunological responses to pregnancy-associated malaria-specific Plasmodium falciparum protein VAR2CSA concerns almost exclusively B cell-driven antibody-mediated activity. Knowledge of VAR2CSA-specific T cell-mediated activity is minimal by comparison, with only a single published report of a study investigating VAR2CSA-derived peptide-specific T cell responses. The study described here represents an attempt to redress this balance. Methods: Within the framework of a cohort study of 1037 pregnant Beninese, sub-groups were selected on the basis of the documented presence/absence of infection with P. falciparum and conducted detailed immunological assessments both at inclusion into the study and at delivery. Peripheral blood mononuclear cells were isolated, stimulated in vitro, and VAR2CSA DBL-5 domain-specific, IFN-gamma-secreting T-cell frequencies and cytokine responses were quantified using flow cytometric techniques. Multivariate analyses were used to determine primarily whether the T cell-mediated DBL5-specific activity measured was associated with infection by P. falciparum adjusted for gravidity, anaemia and other cofactors. Results: Infections with P. falciparum detected at inclusion were associated with enhanced non-specific TNF responses, whilst diminished non-specific and DBL-5-specific IL-10 responses were associated with infections detected at delivery. Infections during pregnancy led to enhanced non-specific and DBL-5-specific IFN-gamma responses detectable at delivery but to concomitantly lower DBL-5-specific CD8+ IFN-gamma responses. Prospective assessments indicated that non-specific pro-inflammatory responses detectable at inclusion in the study were associated with the occurrence of infections subsequently during pregnancy. Conclusions: The findings represent a first step in elucidating the quantity and quality of cellular immunological responses to VAR2CSA, which will help in the development of the primary vaccine candidate for prevention of pregnancy-associated malaria

Dynamics of Submicroscopic Plasmodium falciparum Infections Throughout Pregnancy: A Preconception Cohort Study in Benin.

BACKGROUND: In the context of global malaria elimination efforts, special attention is being paid to submicroscopic Plasmodium falciparum infections. In pregnant, sub-Saharan African women, such infections are more prevalent than microscopic infections, and are thought to have adverse effects on both mothers' and newborns' health. However, no study has studied the dynamics and determinants of these infections throughout pregnancy. Retard de Croissance Intra-uterin et Paludisme (RECIPAL), a preconception cohort study carried out in Benin between 2014 and 2017, represented a unique opportunity to assess this issue. METHODS: We used data from 273 pregnant Beninese women who were followed-up from preconception to delivery. We studied the dynamics of and factors influencing submicroscopic (and microscopic) P. falciparum infections during the 3 trimesters of pregnancy, using an ordinal logistic mixed model. RESULTS: The incidence rate of submicroscopic P. falciparum infections during pregnancy was 12.7 per 100 person-months (95% confidence interval [CI] 10.8-14.9), compared to 6.7 per 100 person-months (95% CI 5.5-8.1) for microscopic infections. The prevalences were highest in the first trimester for both submicroscopic and microscopic infections. After adjustment for potential confounding factors, we found that those of young age and those with a submicroscopic P. falciparum infection prior to pregnancy were at significantly higher risks of submicroscopic and microscopic infections throughout pregnancy, with a more pronounced effect in the first trimester of pregnancy. CONCLUSIONS: The first trimester of pregnancy is a particularly high-risk period for P. falciparum infection during pregnancy, especially for the youngest women. Malaria prevention tools covering the preconception period and early pregnancy are urgently needed to better protect pregnant women and their newborns

Семантичні зміни в лексичному складі російської та української мов

Использование вычислительной техники и радиоэлектроники способствовало формированию специальной группы лексических единиц. Номинация новых явлений и понятий является актуальной проблемой нынешнего этапа развития языка. Изменение семантического наполнения – это один из способов решения данной проблемы. Расширение или сужение семантического объема слов способствует обогащению лексической системы, а именно терминологии.Використання обчислювальної техніки та радіоелектроніки спричинило формування спеціальної групи лексичних одиниць. Номінація нових явищ та понять є актуальною проблемою теперішнього етапу розвитку мови. Зміна семантичного об'єму – це один із засобів вирішення даної проблеми. Звуження або розширення семантичного наповнення сприяє збагаченню лексичної системи, а саме термінології.Using of radio-electronic devices forced the formation of a special group of lexical units. The nomination of new processes and notions is an actual problem of today's language development. Semantic changes of existing units is one of the decisions of the problem. Widening and narrowing of semantic meanings promotes the enrichment of lexical system, especially the system of terminology

Malaria Infections and Placental Blood Flow: A Doppler Ultrasound Study From a Preconception Cohort in Benin

BACKGROUND: Malaria in pregnancy (MiP) has been associated with fetal growth restriction, the underlying pathogenic mechanisms of which remain poorly understood. Malaria in pregnancy is suspected to induce abnormalities in placental vascularization, leading to impaired placental development. Our study evaluated MIP's effect on uterine artery (UtA) and umbilical artery (UA) blood flow. METHODS: The analysis included 253 Beninese women followed throughout pregnancy and screened monthly for submicroscopic and microscopic malaria. Uterine artery Doppler measurement was performed once between 21 and 25 weeks' gestation (wg), and UA Doppler measurement was performed 1-3 times from 28 wg. Linear and logistic regression models were used to assess the effect of malaria infections on UtA Doppler indicators (pulsatility index and presence of a notch), whereas a logistic mixed model was used to assess the association between malaria infections and abnormal UA Doppler (defined as Z-score ≥2 standard deviation or absent/reversed UA end-diastolic flow). RESULTS: Primigravidae represented 7.5% of the study population; 42.3% of women had at least 1 microscopic infection during pregnancy, and 29.6% had at least 1 submicroscopic infection (and no microscopic infection). Both microscopic and submicroscopic infections before Doppler measurement were associated with the presence of a notch (adjusted odds ratio [aOR] 4.5, 95% confidence interval [CI] = 1.2-16.3 and aOR 3.3, 95% CI = .9-11.9, respectively). No associations were found between malaria before the Doppler measurement and abnormal UA Doppler. CONCLUSIONS: Malaria infections in the first half of pregnancy impair placental blood flow. This highlights the need to prevent malaria from the very beginning of pregnancy

Analyse du système hôte-parasite chez le patient pour un traitement adapté du neuropaludisme

Analysis of host-parasite interaction in cerebral malaria patients for appropriate treatment. Cerebral malaria, a fatal neurological complication of Plasmodium falciparum infection, occurs mainly in children under the age of five in sub-Saharan Africa. Despite treatment with intravenous artesunate, mortality remains high. A better understanding of the pathophysiology of cerebral malaria will enable us to envisage new, more suitable types of treatment. A cohort of Beninese children presenting with either uncomplicated malaria (UM) or cerebral malaria (CM) was set up. Children with CM were followed up at three days and 1 month (D3, D30) after their inclusion in the study (D0). This thesis focused on three aspects of the host response through the following questions: 1) Is endothelial activation impacted by the type of parasite infecting the host? 2) Is the monocyte response affected during cerebral malaria? and 3) Can we identify specific biomarkers of death during cerebral malaria? Using a co-culture model (Hbec-5i and infected red blood cells -iRBCs- from patients), we showed́ by RT-qPCR that cytoadherence of infected red blood cells from children with CM to endothelial cells increased the expression level of the Nrf2 gene on the endothelial cells. Comparison between clinical groups (CM and UM) of endothelial activation biomarkers measured in co-culture supernatants (with or without contact between the two cell types) showed no significant difference. These results suggest that cytoadherence of iRBCs to ECs alone is not sufficient to induce the production of activation biomarkers by ECs. Concerning the impact of cerebral malaria on monocyte response, the results showed a decrease in the proportion of non-classical monocytes and an alteration in the phagocytosis capacity of total monocytes during acute cerebral malaria (D0), followed by a return to a normal distribution at D3 and then D30. Non-classical monocytes showed a better opsonic and non-opsonic phagocytosis capacity compared with the phagocytosis capacity of the classical and intermediate monocytes. Transcriptional profiling of monocytes revealed that malaria severity was associated with altered expression of CD16, CR1, CR3, TLR2, involved in opsonic phagocytosis, and Tim3, involved in modulating parasite clearance. These results suggest that non-classical monocytes play a key role in the immune response set up during cerebral malaria, and that monocyte function would be controlled at the transcriptomic level. Further studies are required to identify the origin of these control mechanisms. Finally, plasma and urinary biomarkers were measured in children suffering from cerebral malaria. Univariate analysis revealed associations between the occurrence of death from CM and elevated plasma levels of TNF, IL-1, IL-10, CXCL9, Granzyme B, angiopoietin-2 and low levels of urinary PGEM. After multivariate logistic regression analysis, IL-8 appeared to be strongly associated with the occurrence of death for a plasma concentration 57.5 pg/mL at D0 followed by a rapid decreasing at D3 and D30 in surviving children. Biomarkers kinetics (D0, D3, D30) enabled us to distinguish a marker profiles of disease aggravation and resolution. This work reveals that cerebral malaria generates an activation of the antioxidant response by the vascular endothelium, as well as an alteration of the monocyte response via the diminished capacity of non-classical monocytes to eliminate iRBCs by phagocytosis. Furthermore, IL-8 as a biomarker associated with death also underlines the importance of the neutrophil response during cerebral malaria.Le neuropaludisme, complication neurologique mortelle du paludisme à Plasmodium falciparum, survient principalement chez les enfants de moins de cinq ans en Afrique sub-saharienne. Malgré un traitement à l'artésunate intraveineux, la mortalité reste élevée. Une meilleure connaissance de la physiopathologie du neuropaludisme permettra donc d'envisager de nouveaux types de traitements plus adaptés. Une cohorte d'enfants béninois présentant soit un paludisme simple (UM), soit un neuropaludisme (CM) a été constituée. Les enfants présentant un CM ont fait l'objet d'un suivi à trois jours et un mois (J3, J30) après leur inclusion dans l'étude (J0). Ce travail de thèse a porté sur trois aspects de la réponse de l'hôte au travers des questions suivantes : 1) L'activation endothéliale est-elle impactée par le type de parasite infectant?, 2) La réponse monocytaire est-elle affectée au cours du neuropaludisme ? et, 3) Peut-on identifier des biomarqueurs spécifiques de la survenue du décès au cours du neuropaludisme ? En utilisant un modèle de co-culture (Hbec-5i et globules rouges infectés - GRi - issus des patients), nous avons montré par RT-qPCR que la cytoadhérence des globules rouges parasités, issus d'enfants souffrant de CM, aux CEs augmentait le niveau d'expression du gène Nrf2 sur ces dernières. La comparaison entre groupes cliniques (CM et UM) des biomarqueurs d'activation endothéliale mesurés dans les surnageants de co-culture (avec ou sans contact entre les deux types cellulaires) n'a montré aucune différence significative. Ces résultats suggèrent que la cytoadhérence des GRi aux CEs ne suffit pas à elle seule à induire la production de biomarqueurs d'activation par les CEs. Concernant l'impact du neuroplaudisme sur la réponse monocytaire, les résultats ont montré une diminution de la proportion des monocytes non-classiques et une altération de la capacité de phagocytose des monocytes totaux au cours de la phase aiguë du neuropaludisme (J0), suivie d'un retour à une répartition normale à J3 puis J30. Les monocytes non-classiques ont montré une meilleure capacité de phagocytose opsonique et non-opsonique comparée à la capacité des monocytes classiques et intermédiaires. L'étude du profil transcriptionnel des monocytes a révélé que la sévérité du paludisme était associée à une altération de l'expression des gènes CD16, CR1, CR3, TLR2, impliqués dans la phagocytose opsonique, et de Tim3, impliqué dans la modulation de la clairance parasitaire. Ces résultats suggèrent que les monocytes non-classiques sont des acteurs clés de la réponse immune mise en place au cours du neuropaludisme et que la fonction des monocytes serait contrôlée au niveau transcriptomique. Des études supplémentaires sont nécessaires pour identifier l'origine de ces mécanismes de contrôle. Enfin, des biomarqueurs plasmatiques et urinaires ont été mesurés chez les enfants souffrant d'un neuropaludisme. L'analyse univariée a révélé des associations entre la survenue du décès par neuropaludisme et des taux plasmatiques élevés de TNF, IL-1, IL-8, IL-10, CXCL9, Granzyme B, angiopoïétine-2 et des taux faibles de PGEM urinaire. Après une analyse en régression logistique multivariée, l'IL-8 est apparue comme fortement associée à la survenue de décès pour une concentration plasmatique 57.5 pg/mL à J0 suivi d'une rapide diminution à J3 et J30 chez les enfants survivants. La cinétique des biomarqueurs (J0, J3, J30) a permis de distinguer un profil d'aggravation de la maladie d'une part et un profil de résolution de d'autre part. Ces travaux révèlent que le neuropaludisme engendre une activation de la réponse antioxydante par l'endothélium vasculaire, ainsi qu'une altération de la réponse monocytaire via la diminution de la capacité des monocytes non-classiques à éliminer les GRi par phagocytose. En outre, l'IL-8 comme biomarqueur associé au décès souligne également l'importance de la réponse neutrophile au cours du neuropaludisme

PfEMP1 A-Type ICAM-1-Binding Domains Are Not Associated with Cerebral Malaria in Beninese Children

International audiencePfEMP1 is the major antigen involved in Plasmodium falciparum-infected erythrocyte sequestration in cerebrovascular endothelium. While some PfEMP1 domains have been associated with clinical phenotypes of malaria, formal associations between the expression of a specific domain and the adhesion properties of clinical isolates are limited. In this context, 73 cerebral malaria (CM) and 98 uncomplicated malaria (UM) Beninese children were recruited. We attempted to correlate the cytoadherence phenotype of Plasmodium falciparum isolates with the clinical presentation and the expression of specific PfEMP1 domains. Cytoadherence level on Hbec-5i and CHO-ICAM-1 cell lines and var genes expression were measured. We also investigated the prevalence of the ICAM-1-binding amino acid motif and dual receptor-binding domains, described as a potential determinant of cerebral malaria pathophysiology. We finally evaluated IgG levels against PfEMP1 recombinant domains (CIDRα1.4, DBLβ3, and CIDRα1.4-DBLβ3). CM isolates displayed higher cytoadherence levels on both cell lines, and we found a correlation between CIDRα1.4-DBLβ1/3 domain expression and CHO-ICAM-1 cytoadherence level. Endothelial protein C receptor (EPCR)-binding domains were overexpressed in CM isolates compared to UM whereas no difference was found in ICAM-1-binding DBLβ1/3 domain expression. Surprisingly, both CM and UM isolates expressed ICAM-1-binding motif and dual receptor-binding domains. There was no difference in IgG response against DBLβ3 between CM and UM isolates expressing ICAM-1-binding DBLβ1/3 domain. It raises questions about the role of this motif in CM pathophysiology, and further studies are needed, especially on the role of DBLβ1/3 without the ICAM-1-binding motif.IMPORTANCE Cerebral malaria pathophysiology remains unknown despite extensive research. PfEMP1 proteins have been identified as the main Plasmodium antigen involved in cerebrovascular endothelium sequestration, but it is unclear which var gene domain is involved in Plasmodium cytoadhesion. EPCR binding is a major determinant of cerebral malaria whereas the ICAM-1-binding role is still questioned. Our study confirmed the EPCR-binding role in CM pathophysiology with a major overexpression of EPCR-binding domains in CM isolates. In contrast, ICAM-1-binding involvement appears less obvious with A-type ICAM-1-binding and dual receptor-binding domain expression in both CM and UM isolates. We did not find any variations in ICAM-1-binding motif sequences in CM compared to UM isolates. UM and CM patients infected with isolates expressing the ICAM-1-binding motif displayed similar IgG levels against DBLβ3 recombinant protein. Our study raises interrogations about the role of these domains in CM physiopathology and questions their use in vaccine strategies against cerebral malaria. Copyrigh

Transcriptome Analysis of Plasmodium falciparum Isolates From Benin Reveals Specific Gene Expression Associated With Cerebral Malaria

International audienceAbstract Cerebral malaria (CM) is the severest form of Plasmodium falciparum infection. Children under 5 years old are those most vulnerable to CM, and they consequently have the highest risk of malaria-related death. Parasite-associated factors leading to CM are not yet fully elucidated. We therefore sought to characterize the gene expression profile associated with CM, using RNA sequencing data from 15 CM and 15 uncomplicated malaria isolates from Benin. Cerebral malaria parasites displayed reduced circulation times, possibly related to higher cytoadherence capacity. Consistent with the latter, we detected increased var genes abundance in CM isolates. Differential expression analyses showed that distinct transcriptome profiles are signatures of malaria severity. Genes involved in adhesion, excluding variant surface antigens, were dysregulated, supporting the idea of increased cytoadhesion capacity of CM parasites. Finally, we found dysregulated expression of genes in the entry into host pathway that may reflect greater erythrocyte invasion capacity of CM parasites

Suboptimal Intermittent Preventive Treatment in Pregnancy (IPTp) is Associated With an Increased Risk of Submicroscopic Plasmodium falciparum Infection in Pregnant Women: A Prospective Cohort Study in Benin

BACKGROUND: Harmful maternal and neonatal health outcomes result from malaria in pregnancy, the prevention of which primarily relies on intermittent preventive treatment in pregnancy (IPTp) with sulfadoxine-pyrimethamine (SP). The World Health Organization recommends IPTp-SP in sub-Saharan Africa, but implementation is highly heterogeneous and often suboptimal in terms of the number of doses and their timing. In this study, we assessed the impact of this heterogeneity on malaria in pregnancy, mainly with respect to submicroscopic Plasmodium falciparum infections. METHODS: We used data from 273 Beninese women followed throughout pregnancy. Screening for P. falciparum infections, using both microscopy-based and polymerase chain reaction (PCR)-based methods, was performed monthly, and information on IPTp-SP doses was collected. Gestational age was estimated by repeated ultrasound scans. Using a negative binomial model, we investigated the effect of IPTp-SP doses and timing after 17 weeks of gestation on the number of P. falciparum infections, focusing on submicroscopic infections detectable only by PCR. RESULTS: At least 2 IPTp-SP doses were taken by 77.3% of the women. The median gestational age at the first IPTp-SP dose was 22 weeks. A late first IPTp-SP dose (>21.2 weeks) was marginally associated with an increased number of P. falciparum infections (adjusted incidence rate ratio [aIRR] = 1.3; P = .098). The number of IPTp-SP doses was not associated with the number of submicroscopic infections (aIRR = 1.2, P = .543). CONCLUSIONS: A late first IPTp-SP dose failed to provide optimal protection against P. falciparum, especially submicroscopic infections. This highlights the need for a new antimalarial drug for IPTp that could be taken early in pregnancy.Impact du paludisme précoce au cours de la grossesse sur la croissance fœtale au Béni

Pre-conception serum ferritin concentrations are associated with metal concentrations in blood during pregnancy: A cohort study in Benin

BACKGROUND: Iron deficiency is a common nutritional deficiency that impacts maternal health and fetal development and is also associated with increased uptake of toxic metals. Women in sub-Saharan Africa are highly exposed to both iron deficiency and metals in the environment. As research on the developmental origins of health and disease increasingly shows impacts of pre-conception maternal health on pregnancy and fetal health, these environmental exposures are of concern. OBJECTIVES: This study investigated the association between iron status pre-pregnancy and blood metal concentrations in the first trimester of pregnancy with potential implications for iron supplementation. METHODS: Pre-conception and first trimester blood samples taken from 262 Beninese women were tested for serum ferritin, inflammation markers, manganese (Mn), cadmium (Cd), lead (Pb), copper, zinc, selenium, mercury and arsenic. Associations between serum ferritin adjusted for inflammation and metal concentrations were analyzed using multivariate linear regression. RESULTS: Women with iron deficiency before conception (13%) were more likely to remain iron deficient in the first trimester (4%) (adjusted OR = 41.2, 95%CI 6.2; 275.0) even within the context of routine iron supplementation during pregnancy. Lower pre-pregnancy serum ferritin concentrations were significantly related to higher concentrations of Mn, Cd and Pb in the first trimester. Every 1% increase in serum ferritin concentration was associated with a 0.13% decrease in Mn (adjusted β = -0.13, 95%CI -0.18; -0.07), a 0.22% decrease in Cd (adjusted β = -0.22, 95%CI -0.28; -0.15) and a 0.06% decrease in Pb concentration (adjusted β = -0.06, 95%CI -0.12; -0.006). DISCUSSION: These results suggest that increasing iron stores prior to pregnancy may prevent excessive uptake of toxic concentrations of the metals Mn, Cd and Pb and argue in favour of testing the effects of iron supplementation prior to pregnancy on metal concentrations.Impact du paludisme précoce au cours de la grossesse sur la croissance fœtale au Béni