Q. de Mast

Assessment of Urinary Concentrations of Hepcidin Provides Novel Insight into Disturbances in Iron Homeostasis during Malarial Infection

Disturbances in iron homeostasis are frequently observed in individuals with malaria. To study the effect of malaria and its treatment on iron homeostasis and to provide a mechanistic explanation for observed alterations in iron distribution, we studied the course of the iron regulatory hormone hepcidin in anemic Tanzanian children with febrile Plasmodium falciparum malaria. Before initiation of antimalarial treatment, urinary concentrations of hepcidin were strongly elevated and were associated with iron maldistribution, as was suggested by the presence of hypoferremia and high serum concentrations of ferritin. Antimalarial treatment resulted in a rapid decrease in urinary concentrations of hepcidin and reversal of the hypoferremia. Exploration of regulatory pathways of hepcidin production by analysis of iron, erythropoietic, and inflammatory indices suggested that reduced erythropoietic activity and inflammation stimulated hepcidin production. We conclude that high concentrations of hepcidin explain the observed disturbances in host iron homeostasis associated with malaria and may contribute to malarial anemia and an impaired erythropoietic response to iron supplementation.

Platelet function alterations in dengue are associated with plasma leakage

Severe dengue is characterised by thrombocytopenia, plasma leakage and bleeding. Platelets are important for preservation of endothelial integrity. We hypothesised that platelet activation with secondary platelet dysfunction contribute to plasma leakage. In adult Indonesian patients with acute dengue, we measured platelet activation status and the response to the platelet agonist TRAP using flow cytometer-based assays. Patients were monitored daily for plasma leakage by ultrasonography. Acute dengue was associated with platelet activation with an increased expression of the activated fibrinogen receptor (αIIbβ3), the lysosomal marker CD63 and the alpha-granule marker CD62P (P-selectin). Upon maximal platelet activation by TRAP, platelet function defects were observed with a significantly reduced maximal activated αIIbβ3 and CD63 expression and reduced platelet-monocyte and platelet-neutrophil complexes. Patients in the lowest tertile of activated αIIbβ3 and CD63 expression had an odds ratio for plasma leakage of 5.2 (95% confidence interval [CI] 1.3-22.7) and 3.9 (95% CI 1.1-13.7), respectively, compared to the highest tertile. Platelet-derived serotonin has previously been related to plasma leakage and we found increased intra-platelet serotonin concentrations in our patients. In conclusion, platelet activation with platelet function alterations can be found in patients with acute dengue and this may contribute to dengue-associated plasma leakage.

A decrease of plasma macrophage migration inhibitory factor concentration is associated with lower numbers of circulating lymphocytes in experimental Plasmodium falciparum malaria.

Macrophage migration inhibitory factor (MIF) has recently been implicated in the pathogenesis of malarial anaemia. However, field studies have reported contradictory results on circulating MIF concentrations in patients with clinically overt Plasmodium falciparum malaria. We determined plasma MIF levels over time in 10 healthy volunteers during experimental P. falciparum infection. Under fully controlled conditions, MIF levels decreased significantly during early blood‐stage infection and reached a nadir at day 8 post‐infection. A decrease in the number of circulating lymphocytes, which are an important source of MIF production, paralleled the decrease in MIF levels. Monocyte/macrophage counts remained unchanged. At MIF nadir, the anti‐inflammatory cytokine interleukin (IL)‐10, which is an inhibitor of T‐cell MIF production, was detectable in only 2 of 10 volunteers. Plasma concentrations of the pro‐inflammatory cytokines IL‐8 and IL‐1β were only marginally elevated. We conclude that circulating MIF levels decrease early in blood‐stage malaria as a result of the decline in circulating lymphocytes.

von Willebrand factor activation, granzyme-B and thrombocytopenia in meningococcal disease

Summary.  Background: During invasive meningococcal disease, severe thrombocytopenia is strongly associated with a poor outcome. Objectives: In order to elucidate the pathophysiological mechanism behind the development of thrombocytopenia, we studied the role of von Willebrand factor (VWF) in meningococcal disease. Patients/methods: Thirty‐two children with severe meningococcal disease admitted to our university hospital were included in this study. VWF and related parameters were measured and results were correlated with the development of shock and thrombocytopenia. Results: At admission, all patients had increased levels of (active) VWF and VWF propeptide. The highest VWF propeptide levels were observed in patients with shock, indicating acute endothelial activation. Although VWF propeptide levels in patients with shock, with or without thrombocytopenia, were similar, increased active VWF was significantly lower in patients with thrombocytopenia as compared with patients without thrombocytopenia. ADAMTS13 was moderately decreased. However, the VWF multimeric pattern was minimally increased. We assume that these findings are explained by VWF consumption and perhaps by granzyme B (GrB). In vitro experiments showed that GrB is able to cleave VWF multimers in plasma, whereas GrB was high in patients with shock, who developed thrombocytopenia. Conclusions: Our results demonstrate that consumption of VWF, derived from endothelial cells, could be a key feature of meningococcal disease and primary to the development of thrombocytopenia during shock.

Differential effects of platelets and platelet inhibition by ticagrelor on TLR2- and TLR4-mediated inflammatory responses

Platelets and platelet-monocyte interaction play an important role in inflammation. Both pro- and anti-inflammatory effects of platelet inhibition have been reported in animal models. This study aimed to investigate the effect of platelets and platelet inhibition by the new P2Y12 receptor antagonist ticagrelor on monocyte function, as assessed by cytokine responses to Toll-like Receptor (TLR) ligands. In a set of in vitro experiments, peripheral blood mononuclear cells (PBMC) incubated with the TLR2 ligand Pam3CSK4 produced less cytokines in the presence of platelets, whereas platelets increased the production of cytokines when PBMC were exposed to TLR4 ligand lipopolysaccharide (LPS). These effects of platelets were dependent on direct platelet-leukocyte aggregation and for the Pam3CSK4-induced response, on phagocytosis of platelets by monocytes. In a double blind, placebo-controlled crossover trial in healthy volunteers, a single oral dosage of 180 mg ticagrelor reduced platelet-monocyte complex (PMC) formation. This was associated with an increase in pro-inflammatory cytokines in blood exposed to Pam3CSK4, but a decrease in these cytokines in blood exposed to LPS. These findings show that platelets differentially modulate TLR2- and TLR4-mediated cytokine responses of PBMC. Through inhibition of platelet-leukocyte interaction, P2Y12 receptor antagonists may either exert a pro- or anti-inflammatory effect during infections depending on the TLR primarily involved.

Reduced platelet hyperreactivity and platelet-monocyte aggregation in HIV-infected individuals receiving a raltegravir-based regimen

Objective:Platelets are key cells in atherosclerosis and acute cardiovascular events. Platelet hyperreactivity and increased platelet-monocyte aggregation (PMA) are found in HIV-infected patients and may contribute to the excess cardiovascular risk. The integrase inhibitor raltegravir (RAL) has been associated with better residual viral suppression and reduction in inflammatory and coagulation biomarkers. The aim of our study was to investigate whether RAL-treated patients have reduced platelet reactivity and PMA. Design and methods:We performed a cross-sectional study involving 80 virologically suppressed adult HIV1-infected patients on a RAL-based (n = 25), nonnucleoside reverse transcriptase inhibitor (NNRTI)-based (n = 30) or a protease inhibitor based (n = 25) regimen and 30 healthy controls. Platelet reactivity was determined by measuring platelet P-selectin expression and the binding of fibrinogen to platelets to stimulation with two concentrations of ADP. PMA was determined by measuring the expression of the platelet marker CD42b on CD14 positive cells. Results:HIV-infected individuals had higher platelet reactivity and PMA than controls. RAL-treated individuals showed significantly lower P-selectin expression to stimulation with low (P = 0.026 vs. NNRTI and P = 0.005 vs. protease inhibitor group) and high-dose ADP (P = 0.009 vs. NNRTI and P = 0.003 vs. protease inhibitor group). A similar trend for was found for fibrinogen binding, although only the difference in P-selectin expression between RAL and protease inhibitor treated patients reached statistical significance (P = 0.038). PMA was also lower in the RAL group than in the NNRTI (P = 0.037) and protease inhibitor (P = 0.034) groups. Conclusion:Use of a RAL-based regimen was associated with a reduction in persistent HIV-induced platelet hyperreactivity and PMA compared with NNRTI and protease inhibitor based regimen.

Hematologic parameters predicting a response to oral iron therapy in chronic inflammation

In anemic patients with chronic inflammatory conditions, the assessment of iron status and the selection of those who may benefit from iron therapy frequently presents diagnostic challenges.[1][1],[2][2] Traditional biochemical iron parameters, such as ferritin, serum iron and transferrin, are

Ferritin levels during structured treatment interruption of highly active antiretroviral therapy

The aim of the study was to investigate the influence of highly active antiretroviral therapy (HAART) on iron status and, conversely, the influence of iron status on the response to HAART.

Persisting arthralgia due to Mayaro virus infection in a traveler from Brazil: Is there a risk for attendants to the 2014 FIFA World Cup?

The 2014 FIFA World Cup and the 2016 Olympic Games will attract large groups of visitors to Brazil. These visitors will be at risk for different arboviral infections, some of which not well known outside endemic areas. We report a case of a 52-year-old Dutch woman who presented with persistent arthralgia due to a Mayaro virus (MAYV) infection which she contracted in the Amazon basin in Brazil. MAYV is a mosquito-borne alphavirus which primarily circulates in humid tropical forests of South America. Infections are rarely reported in travelers and are characterized by an acute febrile illness which is often followed by a prolonged and sometimes incapacitating polyarthralgia. Both travelers and physicians should be aware of the risk of these arboviral infections and the importance of mosquito bite prevention should be stressed.

A randomised trial on the effect of anti-platelet therapy on the systemic inflammatory response in human endotoxaemia

The use of acetylsalicylic acid (ASA) is associated with improved outcome in patients with sepsis, and P2Y12 inhibitors have been suggested to also have immunomodulatory effects. Therefore, we evaluated the effects of clinically relevant combinations of antiplatelet therapy on the immune response in experimental endotoxaemia in humans in vivo. Forty healthy subjects were randomised to seven days of placebo, placebo with ASA, ticagrelor and ASA, or clopidogrel and ASA treatment. Systemic inflammation was elicited at day seven by intravenous administration of Escherichia coli endotoxin. ASA treatment profoundly augmented the plasma concentration of pro-inflammatory cytokines, but did not affect anti-inflammatory cytokines. Addition of either P2Y12 antagonist to ASA did not affect any of the circulating cytokines, except for an attenuation of the ASA-induced increase in TNFα by ticagrelor. Systemic inflammation increased plasma adenosine, without differences between groups, and although P2Y12 inhibition impaired platelet reactivity, there was no correlation with cytokine responses.