Effect of red blood cell variants on childhood malaria in Mali: a prospective cohort study

Red blood cell (RBC) variants protect African children from severe Plasmodium falciparum malaria. Their individual and interactive impacts on mild disease and parasite density, and their modification by age-dependent immunity, are poorly understood

Peritoneal Sclerosis in a Patient on Long-term Continuous Ambulatory Peritoneal Dialysis (CAPD). : An Autopsy Case.

若年性ネフロン癆による慢性腎不全でCAPD (continuous ambulatory peritoneal dialysis)導入し, 6年6ヵ月後に死亡した20歳男性の1剖検例を報告した。CAPD導入数カ月後, 腹膜炎による除水能低下を起こしたが, 約5ヵ月後に回復した。CAPD導入1年5ヵ月以降重症な腹膜炎罹患により除水能低下状態が遷延したが, 次第に回復した。しかし, 体液貯留傾向のため, 3年2ヵ月後より高張透析液を使用し除水量の増加を得たが, 3年9ヵ月後に不可逆的な除水能低下状態となった。一方, クレアチニンの透析排液/血漿濃度比(D/P)から見た溶質除去能は, その約半年後まで保たれており, 血清クレアチニン値の上昇は軽度であった。剖検にて腹膜の線維性肥厚と高度の内腔狭窄を伴う動静脈硬化を認め, 腹膜硬化症と診断した。本例の腹膜硬化症は, 頻回の腹膜炎と高張透析液の使用が主な原因と考えられた。腹膜機能を長期に維持するためには, 腹膜炎の予防と高張透析液の使用を最小限にすることが重要と考えられた。A 20-year-old man, treated with continuous ambulatory peritoneal dialysis (CAPD) for 6.5 years because of-end-stage renal disease due to juvenile nephronophthysis, died of ultrafiltration failure, and the morphological examination of peritoneum was carried out at autopsy. Nine episodes of peritonitis developed, and ultrafiltration transiently decreased after each episodes. At 2 years after the start of CAPD, severe peritonitis occurred, and then his body weight and blood pressure gradually increased. At 4 years after the beginning of CAPD, when hyperosmotic dialysate was frequently used, ultrafiltration was irreversively deteriorated. On the other hand, creatinine dialysate/plasma ratio remained within normal limits for about several months, and the increase in the level of serum creatinine was very little. The peritoneum obtained at autopsy revealed marked fibrous thickening as well as the conspicuous luminal narrowing of arteries and veins due to intimal thickening. The development of peritoneal sclerosis seemed to be related with the frequency and severity of peritonitis and the use of hyperosmotic dialysate

α-Thalassemia Impairs the Cytoadherence of Plasmodium falciparum-Infected Erythrocytes

α-Thalassemia results from decreased production of α-globin chains that make up part of hemoglobin tetramers (Hb; α(2)β(2)) and affects up to 50% of individuals in some regions of sub-Saharan Africa. Heterozygous (-α/αα) and homozygous (-α/-α) genotypes are associated with reduced risk of severe Plasmodium falciparum malaria, but the mechanism of this protection remains obscure. We hypothesized that α-thalassemia impairs the adherence of parasitized red blood cells (RBCs) to microvascular endothelial cells (MVECs) and monocytes--two interactions that are centrally involved in the pathogenesis of severe disease.We obtained P. falciparum isolates directly from Malian children with malaria and used them to infect αα/αα (normal), -α/αα and -α/-α RBCs. We also used laboratory-adapted P. falciparum clones to infect -/-α RBCs obtained from patients with HbH disease. Following a single cycle of parasite invasion and maturation to the trophozoite stage, we tested the ability of parasitized RBCs to bind MVECs and monocytes. Compared to parasitized αα/αα RBCs, we found that parasitized -α/αα, -α/-α and -/-α RBCs showed, respectively, 22%, 43% and 63% reductions in binding to MVECs and 13%, 33% and 63% reductions in binding to monocytes. α-Thalassemia was associated with abnormal display of P. falciparum erythrocyte membrane protein 1 (PfEMP1), the parasite's main cytoadherence ligand and virulence factor, on the surface of parasitized RBCs.Parasitized α-thalassemic RBCs show PfEMP1 display abnormalities that are reminiscent of those on the surface of parasitized sickle HbS and HbC RBCs. Our data suggest a model of malaria protection in which α-thalassemia ameliorates the pro-inflammatory effects of cytoadherence. Our findings also raise the possibility that other unstable hemoglobins such as HbE and unpaired α-globin chains (in the case of β-thalassemia) protect against life-threatening malaria by a similar mechanism

Home visits versus fixed-site care by community health workers and child survival: a cluster-randomized trial, Mali

ObjectiveTo test the effect of proactive home visits by trained community health workers (CHWs) on child survival.MethodsWe conducted a two arm, parallel, unmasked cluster-randomized trial in 137 village-clusters in rural Mali. From February 2017 to January 2020, 31 761 children enrolled at the trial start or at birth. Village-clusters received either primary care services by CHWs providing regular home visits (intervention) or by CHWs providing care at a fixed site (control). In both arms, user fees were removed and primary health centres received staffing and infrastructure improvements before trial start. Using lifetime birth histories from women aged 15-49 years surveyed annually, we estimated incidence rate ratios (IRR) for intention-to-treat and per-protocol effects on under-five mortality using Poisson regression models.FindingsOver three years, we observed 52 970 person-years (27 332 in intervention arm; 25 638 in control arm). During the trial, 909 children in the intervention arm and 827 children in the control arm died. The under-five mortality rate declined from 142.8 (95% CI: 133.3-152.9) to 56.7 (95% CI: 48.5-66.4) deaths per 1000 live births in the intervention arm; and from 154.3 (95% CI: 144.3-164.9) to 54.9 (95% CI: 45.2-64.5) deaths per 1000 live births in the control arm. Intention-to-treat (IRR: 1.02; 95% CI: 0.88-1.19) and per-protocol estimates (IRR: 1.01; 95% CI: 0.87-1.18) showed no difference between study arms.ConclusionThough proactive home visits did not reduce under-five mortality, system-strengthening measures may have contributed to the decline in under-five mortality in both arms

Host age and Plasmodium falciparum multiclonality are associated with gametocyte prevalence: a 1-year prospective cohort study

Abstract Background Since Plasmodium falciparum transmission relies exclusively on sexual-stage parasites, several malaria control strategies aim to disrupt this step of the life cycle. Thus, a better understanding of which individuals constitute the primary gametocyte reservoir within an endemic population, and the temporal dynamics of gametocyte carriage, especially in seasonal transmission settings, will not only support the effective implementation of current transmission control programmes, but also inform the design of more targeted strategies. Methods A 1-year prospective cohort study was initiated in June 2013 with the goal of assessing the longitudinal dynamics of P. falciparum gametocyte carriage in a village in Mali with intense seasonal malaria transmission. A cohort of 500 individuals aged 1–65 years was recruited for this study. Gametocyte prevalence was measured monthly using Pfs25-specific RT-PCR, and analysed for the effects of host age and gender, seasonality, and multiclonality of P. falciparum infection over 1 year. Results Most P. falciparum infections (51–89%) in this population were accompanied by gametocytaemia throughout the 1-year period. Gametocyte prevalence among P. falciparum-positive individuals (proportion of gametocyte positive infections) was associated with age (p = 0.003) but not with seasonality (wet vs. dry) or gender. The proportion of gametocyte positive infections were similarly high in children aged 1–17 years (74–82% on median among 5 age groups), while older individuals had relatively lower proportion, and those aged > 35 years (median of 43%) had significantly lower than those aged 1–17 years (p < 0.05). Plasmodium falciparum-positive individuals with gametocytaemia were found to have significantly higher P. falciparum multiclonality than those without gametocytaemia (p < 0.033 in two different analyses). Conclusions Taken together, these results suggest that a substantial proportion of Pf-positive individuals carries gametocytes throughout the year, and that age is a significant determinant of gametocyte prevalence among these P. falciparum-positive individuals. Furthermore, the presence of multiple P. falciparum genotypes in an infection, a common feature of P. falciparum infections in high transmission areas, is associated with gametocyte prevalence

Relationship between malaria incidence and IgG levels to Plasmodium falciparum merozoite antigens in Malian children: impact of hemoglobins S and C.

Heterozygous hemoglobin (Hb) AS (sickle-cell trait) and HbAC are hypothesized to protect against Plasmodium falciparum malaria in part by enhancing naturally-acquired immunity to this disease. To investigate this hypothesis, we compared antibody levels to four merozoite antigens from the P. falciparum 3D7 clone (apical membrane antigen 1, AMA1-3D7; merozoite surface protein 1, MSP1-3D7; 175 kDa erythrocyte-binding antigen, EBA175-3D7; and merozoite surface protein 2, MSP2-3D7) in a cohort of 103 HbAA, 73 HbAS and 30 HbAC children aged 3 to 11 years in a malaria-endemic area of Mali. In the 2009 transmission season we found that HbAS, but not HbAC, significantly reduced the risk of malaria compared to HbAA. IgG levels to MSP1 and MSP2 at the start of this transmission season inversely correlated with malaria incidence after adjusting for age and Hb type. However, HbAS children had significantly lower IgG levels to EBA175 and MSP2 compared to HbAA children. On the other hand, HbAC children had similar IgG levels to all four antigens. The parasite growth-inhibitory activity of purified IgG samples did not differ significantly by Hb type. Changes in antigen-specific IgG levels during the 2009 transmission and 2010 dry seasons also did not differ by Hb type, and none of these IgG levels dropped significantly during the dry season. These data suggest that sickle-cell trait does not reduce the risk of malaria by enhancing the acquisition of IgG responses to merozoite antigens

L'Auto-vélo : automobilisme, cyclisme, athlétisme, yachting, aérostation, escrime, hippisme / dir. Henri Desgranges

14 septembre 19181918/09/14 (A19,N6445)

Community case management to accelerate access to healthcare in Mali: A realist process evaluation nested within a cluster randomised trial

The Proactive Community Case Management (ProCCM) trial in Mali reinforced the health system across both arms with user fee removal, professional Community Health Workers (CHWs), and upgraded primary health centres (PHCs)-and randomized village-clusters to receive proactive home visits by CHWs (intervention) or fixed site-based services by passive CHWs (control). Across both arms, sick children's 24-hour treatment and pregnant women's four or more antenatal visits doubled, and under-five mortality halved, over three years compared to baseline. In the intervention arm, proactive CHW home visits had modest effects on children's curative and women's antenatal care utilization, but no effect on under-five mortality, compared to the control arm. We aimed to explain these results by examining implementation, mechanisms, and context in both arms. We conducted a process evaluation with a mixed method convergent design that included 79 in-depth interviews with providers and participants over two time-points, surveys with 195 providers, and secondary analyses of clinical data. We embedded realist approaches in novel ways to test, refine, and consolidate theories about how ProCCM worked, generating three context-intervention-actor-mechanism-outcome nodes that unfolded in a cascade. First, removing user fees and deploying professional CHWs in every cluster enabled participants to seek health sector care promptly and created a context of facilitated access. Second, health systems support to all CHWs and PHCs enabled equitable, respectful, quality healthcare, which motivated increased, rapid utilization. Third, proactive CHW home visits facilitated CHWs and participants to deliver and seek care, and build relationships, trust, and expectations, but these mechanisms were also activated in both arms. Addressing multiple structural barriers to care, user fee removal, professional CHWs, and upgraded clinics interacted with providers' and patients' agency to achieve rapid care and child survival in both arms. Proactive home visits expedited or compounded mechanisms that were activated and changed the context across arms

A potential role for plasma uric acid in the endothelial pathology of Plasmodium falciparum malaria.

BACKGROUND: Inflammatory cytokinemia and systemic activation of the microvascular endothelium are central to the pathogenesis of Plasmodium falciparum malaria. Recently, 'parasite-derived' uric acid (UA) was shown to activate human immune cells in vitro, and plasma UA levels were associated with inflammatory cytokine levels and disease severity in Malian children with malaria. Since UA is associated with endothelial inflammation in non-malaria diseases, we hypothesized that elevated UA levels contribute to the endothelial pathology of P. falciparum malaria. METHODOLOGY/PRINCIPAL FINDINGS: We measured levels of UA and soluble forms of intercellular adhesion molecule-1 (sICAM-1), vascular cell adhesion molecule-1 (sVCAM-1), E-selectin (sE-Selectin), thrombomodulin (sTM), tissue factor (sTF) and vascular endothelial growth factor (VEGF) in the plasma of Malian children aged 0.5-17 years with uncomplicated malaria (UM, n = 487) and non-cerebral severe malaria (NCSM, n = 68). In 69 of these children, we measured these same factors once when they experienced a malaria episode and twice when they were healthy (i.e., before and after the malaria transmission season). We found that levels of UA, sICAM-1, sVCAM-1, sE-Selectin and sTM increase during a malaria episode and return to basal levels at the end of the transmission season (p<0.0001). Plasma levels of UA and these four endothelial biomarkers correlate with parasite density and disease severity. In children with UM, UA levels correlate with parasite density (r = 0.092, p = 0.043), sICAM-1 (r = 0.255, p<0.0001) and sTM (r = 0.175, p = 0.0001) levels. After adjusting for parasite density, UA levels predict sTM levels. CONCLUSIONS/SIGNIFICANCE: Elevated UA levels may contribute to malaria pathogenesis by damaging endothelium and promoting a procoagulant state. The correlation between UA levels and parasite densities suggests that parasitized erythrocytes are one possible source of excess UA. UA-induced shedding of endothelial TM may represent a novel mechanism of malaria pathogenesis, in which activated thrombin induces fibrin deposition and platelet aggregation in microvessels. This protocol is registered at clinicaltrials.gov (NCT00669084)

Distribution and morphology of knobs on the surface of parasitized RBCs.

<p>Atomic force micrographs (AFMs) of parasitized −α/αα (HE) (<b>a,d</b>) and −α/−α (HO) (<b>b,e</b>) RBCs obtained from naturally-parasitized Malian children with malaria and −/−α (HH) (<b>c,f</b>) RBCs infected with a laboratory-adapted <i>P. falciparum</i> clone showing normal (<b>a,b</b>) or abnormal (<b>c–f</b>) knob distributions and morphologies. AFM images are representative of 32, 10 and 18 images of parasites in −α/αα, −/−αα and −/−α RBCs. Inlays show YOYO-1-stained parasites that correspond to those imaged by AFM. Comparison AFMs of parasitized HbA, HbC and HbS RBCs have been reported previously <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037214#pone.0037214-Arie1" target="_blank">[22]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037214#pone.0037214-Cholera1" target="_blank">[37]</a>.</p