Date of Award

5-2016

Degree Type

Honors College Thesis

Department

Biological Sciences

First Advisor

Shahid Karim, Ph.D.

Advisor Department

Biological Sciences

Abstract

Ticks secrete a plethora of pharmacologically active molecules in their saliva while feeding. These allow the tick to feed upon a host over prolonged periods of time in an itch free and painless attachment. The exact mechanism of pain suppression by the tick has barely been investigated. In this study, two angiotensin converting enzymes (ACEs), members of the metalloprotease family, are identified as potentially responsible for the degradation of pro-inflammatory peptides. It is hypothesized that these tick ACEs block the function of bradykinin through degradation of the peptide, contributing to the tick’s ability to conduct a pain and itch-free host attachment for prolonged periods of time. To elucidate the functions of the target tick molecules, the time dependent and tissue specific transcriptional gene expression has been investigated by qRT-PCR. Furthermore, an RNAi knockdown approach was used to assess the ability of saliva to degrade bradykinin in an in vitro assay. To measure degradation in ACE deficient saliva, HPLC was used to monitor bradykinin breakdown. Upon knockdown of the target genes, the ticks showed significantly reduced blood intake and the vertebrate host became highly agitated. It was observed through a HPLC of the saliva that the knockdown produced a markedly different pattern of degradation. This data, both quantitative and qualitative, shows that these genes have functional roles for bradykinin degradation and tick feeding. Therefore, these highly conserved genes are attractive targets for tick control measures, or as a novel source of analgesics for medical application.

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