Impact of foetus and mother on IFN-gamma-induced indoleamine 2,3-dioxygenase and inducible nitric oxide synthase expression in murine placenta following Toxoplasma gondii infection.

IFN-gamma production is a hallmark of acute infection with the protozoan parasite Toxoplasma gondii. The tryptophan-catabolising enzyme indoleamine 2,3-dioxygenase (IDO), as well as inducible nitric oxide synthase (NOS2) are induced by IFN-gamma and can play extremely diverse roles in immune regulation, defence against pathogens and physiological homeostasis. We investigated the regulation of these two central enzymes in the placenta during acute infection of pregnant female mice. Using IFN-gamma receptor knockout (IFNgammaR-/-) mice, we showed that IDO is not constitutively expressed in term placentas. In contrast, NOS2 expression was observed, largely dependent on IFN-gamma signalling. Upon infection with the avirulent PRU strain of T. gondii, IDO mRNA expression was induced in an IFNgammaR-dependent manner. Surprisingly, NOS2 mRNA was severely suppressed. Importantly, we showed in crossing experiments of heterozygote (IFNgammaR+/-) mothers with IFNgammaR-/- males and vice versa that IDO expression largely depends on the presence of IFN-gamma receptors on foetal cells, and to a lesser extent on maternal cells. Immunohistochemical analysis localised foetal IDO production to invasive trophoblasts within the maternal part of the placenta. The placental vascular endothelium only stained positive when the mothers possessed functional IFN-gamma receptors. In contrast, placental NOS2 expression, but also its suppression following infection, seems to be largely dependent on IFN-gamma signalling in maternal cells. Neither factor appears to regulate placental T. gondii growth, as we observed no difference in parasite numbers between (+/-) and (-/-) foetuses. Taken together, our results demonstrate the crucial role of the foetus in placental IDO, but not NOS2, production following T. gondii infection.

A new ELISA kit which uses a combination of Plasmodium falciparum extract and recombinant Plasmodium vivax antigens as an alternative to IFAT for detection of malaria antibodies.

BACKGROUND: The methods most commonly used to measure malarial antibody titres are the Indirect Fluorescence Antibody Test (IFAT), regarded as the gold standard, and the Enzyme-Linked ImmunoSorbent Assay (ELISA). The objective here was to assess the diagnostic performance, i.e. the sensitivity and specificity, of a new malaria antibody ELISA kit in comparison to IFAT. This new ELISA kit, the ELISA malaria antibody test (DiaMed), uses a combination of crude soluble Plasmodium falciparum extract and recombinant Plasmodium vivax antigens. METHODS: Two groups were used: 95 samples from malaria patients to assess the clinical sensitivity and 2,152 samples from blood donors, who had not been exposed to malaria, to assess the clinical specificity. RESULTS: The DiaMed ELISA test kit had a clinical sensitivity of 84.2% and a clinical specificity of 99.6% as compared with 70.5% and 99.6% respectively, using the IFAT method. The ELISA method was more sensitive than the IFAT method for P. vivax infections (75% vs. 25%). However, in 923 malaria risk donors the analytical sensitivity of the ELISA test was 40% and its specificity 98.3%, performances impaired by large numbers of equivocal results non-concordant between ELISA and IFAT. When the overall analytical performances of ELISA was compared to IFAT, the ELISA efficiency J index was 0.84 versus 0.71 for IFAT. Overall analytical sensitivity was 93.1% and the analytical specificity 96.7%. Overall agreement between the two methods reached 0.97 with a reliability k index of 0.64. CONCLUSION: The DiaMed ELISA test kit shows a good correlation with IFAT for analytical and clinical parameters. It may be an interesting method to replace the IFAT especially in blood banks, but further extensive investigations are needed to examine the analytical performance of the assay, especially in a blood bank setting.