Background: Bos indicus and B. taurus bovines present variable, heritable levels of immune resistance to the cattle tick, Rhipicephalus microplus. Previous studies of these contrasting phenotypes of infestation show that they are associated with different profiles of local inflammation and different patterns of gene expression at the site of tick bites. Neutrophils contribute to local inflammation by producing neutrophil extracellular traps (NETs), which are structures composed of decondensed chromatin and antimicrobial proteins. We observed that skin from infested bovines presents molecular signatures of NETs; the process is more intense in skin from resistant bovines. In addition, salivary glands from R. microplus produce ectonucleotidases and inhibitors of neutrophil elastase and tick salivary glands have nuclease activity, suggesting that ticks have mechanisms to escape from NETs. Furthermore, infested, susceptible bovines present high levels of nucleotides in their serum. Objetives: Confirm and further elucidate the role of NETs against R. microplus in our model of contrasting phenotypes. Experimental design: We will examine if there are immunohistochemical signatures of NET production in local inflammation and verify if there are quantitative differences in expression of genes encoding products related to formation of NETs in infested skin using a PCR array. We will also verify the effect of silencing genes that encode tick elastase inhibitors and ectonucleotidases on tick biology and on local inflammation at the site of tick bites site in susceptible bovines. Expected Results: to understand the role of neutrophils and NETs in the anti-tick response in bovines.
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