Following reports of increased IgE in severe malaria and hypothesizing that helminth coinfections could modify its outcome, we conducted a retrospective case-control study to establish whether helminths affect the evolution of Plasmodium falciparum malaria. Some 182 severe cases, 315 mild controls and 40 controls with circulating schizonts were examined for intestinal helminths. Comparing cerebral malaria with mild controls, Ascaris lumbricoides was associated with a protective adjusted odds ratio (OR) of 0.58 (0. 32-1.03) P = 0.06, for coinfection with Ascaris and Necator americanus, OR = 0.39 (0.17-0.88) P = 0.02. Protection followed a dose-effect trend (P = 0.008). When comparing cerebral malaria cases and controls with circulating schizonts the OR was 0.25 (0.009-0.67) P = 0.006. We hypothesized that Ascaris infected patients may have had decreased cyto-adherence, possibly through endothelial cell receptor downregulation and/or decreased splenic clearance leading to the absence of selection of virulent P. falciparum strains. IgE-anti-IgE immune complexes resulting from helminth preinfection may have an important role in influencing clinical presentation of severe malaria, and in establishing malaria tolerance, through the CD23/NO pathway.

Serum IgE concentrations and the expression of the low-affinity receptor for IgE (FceRHl/CD23) Nitric oxide (NO) generated by activated murine macrophages is cytostatic or cytotoxic for a variety of pathogens, including Leishmania major, Plasmodium falciparum, Schistosoma mansoni, Trypanosoma cruzi, and Toxoplasma gondii (1-6). NO is generated from the oxidation of the terminal guanido nitrogen atom(s) of L-arginine by an NADPH-dependent enzyme, the NO synthase (NOS) (7-9). In murine macrophages, NOS activity is induced by lipopolysaccharide (LPS) (9) IgE-IC) or by a specific monoclonal antibody (mAb) to CD23 (CD23 mAb) promotes the generation of cGMP. Simultaneous measurement of the generation of nitrite (NO-j) indicated that the enhanced production of cGMP is consequent to activation of the L-arginine:NO pathway.The low-affinity receptor for IgE (FceRII/CD23) is also expressed on normal human monocytes/macrophages after their activation in vivo (22,23). Studies in patients infected with Leishmania braziliensis or in disease-free, immunoreactive donors have shown both in situ CD23 expression and serum IgE concentrations to be increased in these conditions (23). We have, therefore, studied whether cell activation through ligation of the membrane receptor CD23 induces the L-arginine:NO pathway and results in leishmanicidal activity in human macrophages. MATERIALS AND METHODSReagents. The following reagents were used: recombinant human interleukin 4 (IL-4; a gift from J. Banchereau, Schering-Plough); IFN--y (a gift from J. M. Mencia-Huerta, Institut Beaufour, Paris); TNF-a and anti-TNF-a mAb (Genzyme); human IgE (Stallergene, Paris), and goat anti-human IgE (Nordic, Tilburg, The Netherlands). Polymyxin B, LPS (Escherichia coli 055, L-2880), NG-monomethyl-L-arginine (L-NMMA), D-NMMA, L-arginine, D-arginine, superoxide dismutase (SOD), and catalase were all obtained from Sigma.Cells. Human mononuclear cells were obtained by Ficoll gradient separation of peripheral blood leukocytes from healthy volunteers. Monocytes were separated from lymphocytes by adherence to plastic dishes coated with fetal calf serum as described (24). After this procedure, >90% of cells expressed CD14 antigen and displayed cytochemical characteristics of monocytes (24). The cells were then incubated in Dulbecco's modified Eagle's medium (DMEM) supplemented with nonessential L-amino acids, sodium pyruvate, glutamine, penicillin, streptomycin, and 10% (vol/vol) fetal calf serum (all from GIBCO). The culture medium was routinely controlled for the absence of a direct activation effect on human monocytes (CD23 expression and TNF-a production as activation Abbreviations: mAb, monoclonal antibody; CD23 mAb, anti-CD23 mAb; IgE-IC, IgE-anti-IgE immune complexes; L-NMMA, NA3-monomethyl-L-arginine; LPS, lipopolysaccharide; NOS, NO synthase; iNOS, inducible NOS; IFN-y, interferon y; IL, interleukin; TNF-a, tumor necrosis factor ai; SOD, superoxide dismutase; HPRT, hypoxanthine phosphoribosyltransferase. tTo whom reprint requests should be ad...

During Plasmodium falciparum infection leading to cerebral malaria, cytokine production and cytoadherence of parasitized erythrocytes (PRBCs) to postcapillary venules are involved. We demonstrate that PRBC adhesion induces apoptosis in human endothelial cells (HLECs). PRBC adhesion modulated HLEC gene expression in tumor necrosis factor-alpha superfamily genes (Fas, Fas L, and DR-6) and apoptosis-related genes (Bad, Bax, caspase-3,SARP 2, DFF45/ICAD, IFN-gamma receptor 2, Bcl-w, Bik, and iNOS). Apoptosis was confirmed by (1) morphological modifications by electron microscopy, (2) annexin V binding, (3) DNA degradation, by measuring intracytoplasmic nucleosomes, and (4) caspase activity. The apoptotic stimulus was physical contact between HLECs and PRBCs and not parasite-secreted molecules. In addition, it was found that cytoplasmic (caspase 8) and mitochondrial (caspase 9) pathways were involved in this process. These data not only describe the direct apoptotic effect of PRBC adhesion on endothelial cells but also provide new useful tools that allow an evaluation of potential pharmaceuticals.