Tick salivary glands contain many molecules with potential applications as new antimicrobials, which are urgently needed. We generated a fully annotated transcriptome, obtained with 454 sequencing technology, for salivary glands of various developmental stages of Rhipicephalus microplus, the cattle tick. A corresponding proteome was constructed with MudPIT. In these we found many coding sequences and peptides for putative secreted antimicrobial peptides (AMPs). The AMPs are distributed in several families, each with several members: defensins, hebrains, Trypsin inhibitor-like-TIL domain containing AMPs, longicornisin and a family with intermediate similarities to neutrophil elastase inhibitors and AMPs. Pathogen recognition proteins such as ficolin and lipid interacting ML domains were also identified. Nothing is known about the biological activity of these putative AMPs and how they compare with each other in antimicrobial potency and specificity. In order to identify new antimicrobials we will synthesize peptides guided by >80 coding full length sequences containing signal peptides that were bioinformatically mined from the transcriptome of salivary glands of R. microplus. In the case of larger TIL-domain proteins, we will express recombinant proteins. These peptides and proteins will be tested in standard assays of inhibition of microbial growth in order to determine their minimum inhibitory concentrations. They will also be tested in standard assays of stability under ranges of temperatures and pH. Toxicity for mammalian hosts will be initially assessed by means of standard lytic assays for red blood cells. Peptides will synthesized by service contracts. We expect to identify several candidate AMPs for development as new antimicrobials. Keywords: Antimicrobial peptides (AMP), Saliva; Ticks; Rhipicephalus microplus.
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