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Background: Infections with parasites of the Leishmania donovani complex result in clinical outcomes that range from asymptomatic infection to severe and fatal visceral leishmaniasis (VL). Neutrophils are major players of the immune response against Leishmania, but their contribution to distinct states of infection is unknown. Gene expression data suggest the activation of the NETosis pathway during human visceral leishmaniasis. Thus, we conducted an exploratory study to evaluate NET-related molecules in retrospective sera from VL patients, asymptomatic individuals and uninfected endemic controls. Results: We demonstrate that VL patients and asymptomatic individuals exhibit differential regulation of molecules associated with neutrophil extracellular traps (NET). These differences were observed at the transcriptional level of genes encoding NET-associated proteins; in quantifications of cell free DNA and metalloproteinase 9; and in enzymatic activity of DNAse and elastase. Moreover, multivariate analysis resulted in class-specific signatures, and ROC curves demonstrate the ability of these molecules in discriminating asymptomatic infection from uninfected controls. Conclusion: Molecules that are associated with NETs are differentially regulated between distinct states of infection with L. infantum, suggesting that NETs might have distinct roles depending on the clinical status of infection. Although unlikely to be exclusive for VL, these signatures can be useful to better characterize asymptomatic infections in endemic regions of this disease. [ABSTRACT FROM AUTHOR]

Background: Ticks secrete a cement cone composed of many salivary proteins, some of which are rich in the amino acid glycine in order to attach to their hosts' skin. Glycine-rich proteins (GRPs) are a large family of heterogeneous proteins that have different functions and features; noteworthy are their adhesive and tensile characteristics. These properties may be essential for successful attachment of the metastriate ticks to the host and the prolonged feeding necessary for engorgement. In this work, we analyzed Expressed Sequence Tags (ESTs) similar to GRPs from cDNA libraries constructed from salivary glands of adult female ticks representing three hard, metastriate species in order to verify if their expression correlated with biological differences such as the numbers of hosts ticks feed on during their parasitic life cycle, whether one (monoxenous parasite) or two or more (heteroxenous parasite), and the anatomy of their mouthparts, whether short (Brevirostrata) or long (Longirostrata). These ticks were the monoxenous Brevirostrata tick, Rhipicephalus (Boophilus) microplus, a heteroxenous Brevirostrata tick, Rhipicephalus sanguineus, and a heteroxenous Longirostrata tick, Amblyomma cajennense. To further investigate this relationship, we conducted phylogenetic analyses using sequences of GRPs from these ticks as well as from other species of Brevirostrata and Longirostrata ticks. Results: cDNA libraries from salivary glands of the monoxenous tick, R. microplus, contained more contigs of glycinerich proteins than the two representatives of heteroxenous ticks, R. sanguineus and A. cajennense (33 versus, respectively, 16 and 11). Transcripts of ESTs encoding GRPs were significantly more numerous in the salivary glands of the two Brevirostrata species when compared to the number of transcripts in the Longirostrata tick. The salivary gland libraries from Brevirostrata ticks contained numerous contigs significantly similar to silks of true spiders (17 and 8 in, respectively, R. microplus and R. sanguineus), whereas the Longirostrata tick contained only 4 contigs. The phylogenetic analyses of GRPs from various species of ticks showed that distinct clades encoding proteins with different biochemical properties are represented among species according to their biology. Conclusions: We found that different species of ticks rely on different types and amounts of GRPs in order to attach and feed on their hosts. Metastriate ticks with short mouthparts express more transcripts of GRPs than a tick with long mouthparts and the tick that feeds on a single host during its life cycle contain a greater variety of these proteins than ticks that feed on several hosts. [ABSTRACT FROM AUTHOR]