Signal transduction induced in Trypanosoma cruzi metacyclic trypomastigotes during the invasion of mammalian cells

Penetration of Trypanosoma cruzi into mammalian cells depends on the activation of the parasite's protein tyrosine kinase and on the increase in cytosolic Ca2+ concentration. We used metacyclic trypomastigotes, the T. cruzi developmental forms that initiate infection in mammalian hosts, to investigate the association of these two events and to identify the various components of the parasite signal transduction pathway involved in host cell invasion. We have found that i) both the protein tyrosine kinase activation, as measured by phosphorylation of a 175-kDa protein (p175), and Ca2+ mobilization were induced in the metacyclic forms by the HeLa cell extract but not by the extract of T. cruzi-resistant K562 cells; ii) treatment of parasites with the tyrosine kinase inhibitor genistein blocked both p175 phosphorylation and the increase in cytosolic Ca2+ concentration; iii) the recombinant protein J18, which contains the full-length sequence of gp82, a metacyclic stage surface glycoprotein involved in target cell invasion, interfered with tyrosine kinase and Ca2+ responses, whereas the monoclonal antibody 3F6 directed at gp82 induced parasite p175 phosphorylation and Ca2+ mobilization; iv) treatment of metacyclic forms with phospholipase C inhibitor U73122 blocked Ca2+ signaling and impaired the ability of the parasites to enter HeLa cells, and v) drugs such as heparin, a competitive IP3-receptor blocker, caffeine, which affects Ca2+ release from IP3-sensitive stores, in addition to thapsigargin, which depletes intracellular Ca2+ compartments and lithium ion, reduced the parasite infectivity. Taken together, these data suggest that protein tyrosine kinase, phospholipase C and IP3 are involved in the signaling cascade that is initiated on the parasite cell surface by gp82 and leads to Ca2+ mobilization required for target cell invasion.Universidade Federal de São Paulo, Escola Paulista Med, Dept Microbiol Immunol & ParasitolUNIFESPSciEL

Candida albicans Modulates Host Defense by Biosynthesizing the Pro-Resolving Mediator Resolvin E1

Candida albicans is an opportunistic fungal pathogen of humans that resides commensally on epithelial surfaces, but can cause inflammation when pathogenic. Resolvins are a class of anti-inflammatory lipids derived from omega-3 polyunsaturated fatty acids (PUFA) that attenuate neutrophil migration during the resolution phase of inflammation. In this report we demonstrate that C. albicans biosynthesizes resolvins that are chemically identical to those produced by human cells. In contrast to the trans-cellular biosynthesis of human Resolvin E1 (RvE1), RvE1 biosynthesis in C. albicans occurs in the absence of other cellular partners. C. albicans biosynthesis of RvE1 is sensitive to lipoxygenase and cytochrome P450 monoxygenase inhibitors. We show that 10nM RvE1 reduces neutrophil chemotaxis in response to IL-8; 1nM RvE1 enhanced phagocytosis of Candida by human neutrophils, as well as intracellular ROS generation and killing, while having no direct affect on neutrophil motility. In a mouse model of systemic candidiasis, RvE1 stimulated clearance of the fungus from circulating blood. These results reveal an inter-species chemical signaling system that modulates host immune functions and may play a role in balancing host carriage of commensal and pathogenic C. albicans

Candida albicans Modulates Host Defense by Biosynthesizing the Pro-Resolving Mediator Resolvin E1

Candida albicans is an opportunistic fungal pathogen of humans that resides commensally on epithelial surfaces, but can cause inflammation when pathogenic. Resolvins are a class of anti-inflammatory lipids derived from omega-3 polyunsaturated fatty acids (PUFA) that attenuate neutrophil migration during the resolution phase of inflammation. In this report we demonstrate that C. albicans biosynthesizes resolvins that are chemically identical to those produced by human cells. In contrast to the trans-cellular biosynthesis of human Resolvin E1 (RvE1), RvE1 biosynthesis in C. albicans occurs in the absence of other cellular partners. C. albicans biosynthesis of RvE1 is sensitive to lipoxygenase and cytochrome P450 monoxygenase inhibitors. We show that 10nM RvE1 reduces neutrophil chemotaxis in response to IL-8; 1nM RvE1 enhanced phagocytosis of Candida by human neutrophils, as well as intracellular ROS generation and killing, while having no direct affect on neutrophil motility. In a mouse model of systemic candidiasis, RvE1 stimulated clearance of the fungus from circulating blood. These results reveal an inter-species chemical signaling system that modulates host immune functions and may play a role in balancing host carriage of commensal and pathogenic C. albicans

Human rhinovirus infection causes different DNA methylation changes in nasal epithelial cells from healthy and asthmatic subjects

BACKGROUND: Mechanisms underlying the development of virus-induced asthma exacerbations remain unclear. To investigate if epigenetic mechanisms could be involved in virus-induced asthma exacerbations, we undertook DNA methylation profiling in asthmatic and healthy nasal epithelial cells (NECs) during Human Rhinovirus (HRV) infection in vitro. METHODS: Global and loci-specific methylation profiles were determined via Alu element and Infinium Human Methylation 450 K microarray, respectively. Principal components analysis identified the genomic loci influenced the most by disease-status and infection. Real-time PCR and pyrosequencing were used to confirm gene expression and DNA methylation, respectively. RESULTS: HRV infection significantly increased global DNA methylation in cells from asthmatic subjects only (43.6% to 44.1%, p = 0.04). Microarray analysis revealed 389 differentially methylated loci either based on disease status, or caused by virus infection. There were disease-associated DNA methylation patterns that were not affected by HRV infection as well as HRV-induced DNA methylation changes that were unique to each group. A common methylation locus stood out in response to HRV infection in both groups, where the small nucleolar RNA, H/ACA box 12 (SNORA12) is located. Further analysis indicated that a relationship existed between SNORA12 DNA methylation and gene expression in response to HRV infection. CONCLUSIONS: We describe for the first time that Human rhinovirus infection causes DNA methylation changes in airway epithelial cells that differ between asthmatic and healthy subjects. These epigenetic differences may possibly explain the mechanism by which respiratory viruses cause asthma exacerbations

Estudos de freqüência, morfologia e diagnóstico de Entamoeba gingivalis, Gros, 1849

Realizamos estudos de freqüência de Entamoeba gingivalis entre 100 pacientes atendidos nos ambulatórios odontológicos da Ufiiversidade Federal de Uberlândia (UFU), utilizando-se esfregaços corados pela técnica de Papanicolaou modificado, revelando um expressivo índice de 62% de positividade. A afinidade do corante pelo conteúdo vacuolarfagocítico impede uma nítida visualização das cromatinas central e periférica do núcleo do parasita. Lavados bucais de outros 10 pacientes foram utilizados para avaliar em qual método parasitológico de diagnóstico (a fresco e em coloração por hematoxilina férrica, Giemsa e Papanicolaou) ocorre melhor visualização do parasita. O exame afresco do sedimento do lavado bucal revelou 100% de positividade e nítida visualização do parasita. Nenhuma técnica de coloração dos esfregaços se mostrou adequada, apresentando o núcleo freqüentemente mascarado pelos vacúolos fagocíticos. Em preparações coradas por azul de toluidina e na microscopia eletrônica de transmissão pode-se observar caracteres morfológicos típicos do protozoário

Experimental infection of Calomys callosus (Rodentia, Cricetidae) by Toxoplasma gondii

Calomys callosus, Rengger 1830 (Rodentia, Cricetidae), a wild rodent found in Central Brazil, was studied to investigate its susceptibility to Toxoplasma gondii experimental infection and its humoral immune response against this protozoa. The electrophoretic profile of the serum proteins of C. callosus showed that IgG, which shows no affinity to Protein A, has higher cross reactivity with rat IgG than with IgG from other rodents. The susceptibility assay was performed by inoculation groups of animals with various suspensions of T. gondii tachyzoites from 10^2 to 10^6 parasites. All animals died between 3 and 9 days after infection and the kinetics of antibody synthesis was determined. Basically, they recognized predominantly the immunodominant antigen SAG-1 (P30). The immunohistochemistry assays revealed that the liver was the most heavily infected organ, followed by the spleen, lungs, intestine, brain and kidneys. It can be concluded that C. callosus is an excellent experimental model for acute phase of Toxoplasma infection

Experimental infection of Calomys callosus (Rodentia, Cricetidae) by Toxoplasma gondii

Calomys callosus, Rengger 1830 (Rodentia, Cricetidae), a wild rodent found in Central Brazil, was studied to investigate its susceptibility to Toxoplasma gondii experimental infection and its humoral immune response against this protozoa. The electrophoretic profile of the serum proteins of C. callosus showed that IgG, which shows no affinity to Protein A, has higher cross reactivity with rat IgG than with IgG from other rodents. The susceptibility assay was performed by inoculation groups of animals with various suspensions of T. gondii tachyzoites from 10^2 to 10^6 parasites. All animals died between 3 and 9 days after infection and the kinetics of antibody synthesis was determined. Basically, they recognized predominantly the immunodominant antigen SAG-1 (P30). The immunohistochemistry assays revealed that the liver was the most heavily infected organ, followed by the spleen, lungs, intestine, brain and kidneys. It can be concluded that C. callosus is an excellent experimental model for acute phase of Toxoplasma infection