Levels of soluble CD163 and severity of malaria in children in Ghana.

CD163 is an acute-phase-regulated monocyte/macrophage membrane receptor expressed late in inflammation. It is involved in the haptoglobin-mediated removal of free hemoglobin from plasma, has been identified as a naturally soluble plasma glycoprotein with potential anti-inflammatory properties, and is possibly linked to an individual's haptoglobin phenotype. High levels of soluble CD163 (sCD163) in a malaria episode may therefore downregulate inflammation and curb disease severity. In order to verify this, the relationships between sCD163 levels, malaria severity, and selected inflammatory mediators (tumor necrosis factor alpha [TNF-alpha], interleukin-6 [IL-6], and IL-10) were assessed by enzyme-linked immunosorbent assay using plasma samples obtained from pediatric malaria patients with uncomplicated malaria (UM [n = 38]), cerebral malaria (CM [n = 52]), and severe malarial anemia (SA [n = 55]) during two consecutive malaria transmission seasons (2002 and 2003). Median sCD163 levels were higher in UM (11.9 microg/ml) patients than in SA (7.7 microg/ml; P = 0.010) and CM (8.0 microg/ml; P = 0.031) patients. Levels of sCD163 were also higher in all patient groups than in a group of 81 age-matched healthy controls. The higher sCD163/TNF-alpha ratio in UM patients, coupled with the fact that sCD163 levels correlated with TNF-alpha levels in UM patients but not in CM and SA patients, suggests inflammatory dysregulation in the complicated cases. The study showed that sCD163 levels are elevated during acute malaria. High sCD163 levels in UM patients may be due to the induction of higher-level anti-inflammatory responses, enabling them to avoid disease complications. It is also possible that UM patients simply lost their CD163 receptors from macrophages in inflammatory sites while complicated-malaria patients still had their receptors attached to activated macrophages, reflecting ongoing and higher-level inflammation associated with complicated malaria.

Complement activation in Ghanaian children with severe Plasmodium falciparum malaria.

BACKGROUND: Severe anaemia (SA), intravascular haemolysis (IVH) and respiratory distress (RD) are severe forms of Plasmodium falciparum malaria, with RD reported to be of prognostic importance in African children with malarial anaemia. Complement factors have been implicated in the mechanism leading to excess anaemia in acute P. falciparum infection. METHODS: The direct Coombs test (DCT) and flow cytometry were used to investigate the mean levels of RBC-bound complement fragments (C3d and C3balphabeta) and the regulatory proteins [complement receptor 1 (CD35) and decay accelerating factor (CD55)] in children with discrete clinical forms of P. falciparum malaria. The relationship between the findings and clinical parameters including coma, haemoglobin (Hb) levels and RD were investigated. RESULTS: Of the 484 samples tested, 131(27%) were positive in DCT, out of which 115/131 (87.8%) were positive for C3d alone while 16/131 (12.2%) were positive for either IgG alone or both. 67.4% of the study population were below 5 years of age and DCT positivity was more common in this age group relative to children who were 5 years or older (Odds ratio, OR = 3.8; 95%CI, 2.2-6.7, p < 0.001). DCT correlated significantly with RD (beta = -304, p = 0.006), but multiple regression analysis revealed that, Hb (beta = -0.341, p = 0.012) and coma (beta = -0.256, p = 0.034) were stronger predictors of RD than DCT (beta = 0.228, p = 0.061). DCT was also not associated with IVH, p = 0.19, while spleen size was inversely correlated with Hb (r = -402, p = 0.001). Flow cytometry showed similar mean fluorescent intensity (MFI) values of CD35, CD55 and C3balphabeta levels on the surfaces of RBC in patients and asymptomatic controls (AC). However, binding of C3balphabeta correlated significantly with CD35 or CD55 (p < 0.001). CONCLUSION: These results suggest that complement activation contributed to anaemia in acute childhood P. falciparum malaria, possibly through induction of erythrophagocytosis and haemolysis. In contrast to other studies, this study did not find association between levels of the complement regulatory proteins, CD35 and CD55 and malarial anaemia. These findings suggest that complement activation could also be involved in the pathogenesis of RD but larger studies are needed to confirm this finding.

V beta profiles in African children with acute cerebral or uncomplicated malaria: very focused changes among a remarkable global stability.

T cells are thought to play a critical role in cerebral malaria pathogenesis. However, available evidences are restricted to rodent models in which V beta specific T cell expansion has been associated with neurological syndrome suggesting involvement of superantigens or dominant antigens. Using flow cytometry, we studied the peripheral V beta T cell repertoire of Ghanaian children with cerebral malaria, uncomplicated malaria and asymptomatic control children, to look for either expansion or deletion of specific V beta associated with cerebral malaria. At admission, the general pattern of the repertoire of the patients was very similar, with no major distortion compared to the control group a part a significant increase of the frequency of the V beta 21.3 subset correlating with disease severity and attributed to the CD4 subset. During convalescence very limited fluctuations were observed including a significant decrease of the V beta 21.3 subset and increase of the V beta 20 subset, a subset not detected at admission. The remarkable stability of the V beta repertoire observed in acute malaria either cerebral or uncomplicated argues against the idea that cerebral malaria would result from a T cell-mediated inflammatory shock syndrome driven by some dominant super-antigenic activity(ies). The significance of the reproducible increase of the CD4+V beta 21.3T cell subset deserves further investigations.

Bone marrow suppression and severe anaemia associated with persistent Plasmodium falciparum infection in African children with microscopically undetectable parasitaemia.

BACKGROUND: Severe anaemia can develop in the aftermath of Plasmodium falciparum malaria because of protracted bone marrow suppression, possibly due to residual subpatent parasites. MATERIALS AND METHODS: Blood was collected from patients with recent malaria and negative malaria microscopy. Detection of the Plasmodium antigens, lactate dehydrogenase (Optimal), aldolase and histidine rich protein 2 (Now malaria) were used to differentiate between patients with (1) no malaria, (2) recent cleared malaria, (3) persistent P. falciparum infection. Red cell distribution width (RDW), plasma levels of soluble transferrin receptor (sTfR) and erythropoietin (EPO) were measured as markers of erythropoiesis. Interleukin (IL) 10 and tumour necrosis factor (TNF)alpha were used as inflammation markers. RESULTS: EPO was correlated with haemoglobin, irrespective of malaria (R = -0.36, P < 0.001). Persistent P. falciparum infection, but not recent malaria without residual parasites, was associated with bone marrow suppression i.e., low RDW (P < 0.001 vs. P = 0.56) and sTfR (P = 0.02 vs. P = 0.36). TNF-alpha and IL-10 levels were not associated with bone marrow suppression. CONCLUSION: In the treatment of malaria, complete eradication of parasites may prevent subsequent development of anaemia. Severely anaemic children may benefit from antimalarial treatment if antigen tests are positive, even when no parasites can be demonstrated by microscopy.

Plasma concentrations of soluble urokinase-type plasminogen activator receptor are increased in patients with malaria and are associated with a poor clinical or a fatal outcome.

BACKGROUND: Blood concentrations of soluble urokinase-type plasminogen activator receptor (suPAR) are increased in conditions with immune activation, and high concentrations of suPAR often predict a poor clinical outcome. This study explored the hypothesis that high plasma concentrations of suPAR are associated with disease severity in malaria. METHODS: At admission to the hospital, plasma concentrations of suPAR were measured by ELISA in samples from 645 African children with clinical symptoms of malaria: 478 had malaria, and 167 had a blood film negative for Plasmodium parasites. Fourteen healthy children were included for comparison. RESULTS: Plasma concentrations of suPAR were higher in patients with malaria (median, 7.90 ng/mL [interquartile range [IQR], 6.56-9.15 ng/mL]), compared with those in plasmodium-negative patients (median, 5.59 ng/mL [IQR, 4.54-8.16 ng/mL]; P < .001) and those in healthy children (3.94 ng/mL [IQR, 3.46-4.82 ng/mL]; P < .001). The highest concentrations were found in patients with malaria who died (P = .008) or had complicated malaria (P < .001). In univariate logistic regression analysis, a 1 ng/mL increase in plasma concentration of suPAR was associated with increased risk of mortality (odds ratio, 1.42 [95% confidence interval, 1.09-1.86]; P = .009). In multivariate linear regression analysis, lower platelet count, lower hemoglobin level, and higher neutrophil count were independently associated with a higher plasma concentration of suPAR. CONCLUSIONS: If the plasma concentration of suPAR reflects the extent of parasite-induced immune activation, this may explain why a high concentration of suPAR is associated with a poor clinical outcome in patients with malaria.