Signaling pathways involved in the immune response of the cattle tick Rhipicephalus microplus

Abstract

The cattle tick Rhipicephalus microplus (Acari: Ixodidae)is an ectoparasite of veterinary importance in Brazil, with an annual economic loss of $2 billion it causes to the cattle industry, resulting in reduction in weight and milk production of affected animals as well as a decrease in animal fertility. Also, this tick species is a vector of the intracellular bacteria Anaplasma marginale, the etiological agent of bovine anaplasmosis. For the effective control of this disease, it is essential to understand the vector-pathogen relationship. However, at present, little is known about how the tick immune system counteracts bacterial infections. Thus, the aim of the present study is i. to analyze the role of the intracellular signaling pathways TOLL, IMD and JAK/STAT in the control of A. marginale as well as other microorganisms not vectored by the tick host using a tick embryo cell culture line (BME26), ii. to investigate how these signaling pathways are involved in the production of antimicrobial peptides (AMPs) and iii. to verify whether AMPs produced are involved in the control of bacterial infections. To accomplish this, some components of these signaling pathways will be silenced through RNA interference (RNAi), after which the tick cell culture will be experimentally infected with A. marginale, Enterobacter cloacae, Micrococcus luteus and Saccharomyces cerevisiae and infection levels will be determined through RT-qPCR and CFU counting by direct bacterial plating. Importantly, we aim to gain insight into the signaling pathways involved in tick immune responses against pathogen infections, in order to identify new control targets for this ectoparasite and for the control of the pathogens transmitted by this tick species.