Location: Arthropod-borne Animal Diseases ResearchTitle: Role of mammalian immune responses in vector-enhanced orbiviral transmission
|RUDER, MARK - University Of Georgia|
Submitted to: American Society of Tropical Medicine and Hygiene
Publication Type: Abstract Only
Publication Acceptance Date: 9/5/2017
Publication Date: 11/5/2017
Citation: Drolet, B.S., Lehiy, C.J., Reister-Hendricks, L.M., Ruder, M.G., McVey, D.S. 2017. Role of mammalian immune responses in vector-enhanced orbiviral transmission. American Society of Tropical Medicine and Hygiene. 1:1.
Technical Abstract: Culicoides sonorensis biting midges are vectors of several emerging and re-emerging orbiviruses including bluetongue, epizootic hemorrhagic disease, and African horse sickness viruses. They feed primarily on domestic sheep and cattle, but opportunistically feed on a variety of wildlife and on humans. The ability to obtain blood meals from this wide host range speaks to the versatility of midge salivary components, 45 of which we recently identified including anti-hemostatic factors and protease inhibitors, as well as proteins to immunomodulate host defenses. The extreme efficiency with which Culicoides midges can transmit orbiviruses, and the basis of anecdotal evidence for vector-enhanced orbivirus transmission by midge feeding, are unclear. One reason is that very little is known about the natural effects of Culicoides bites on mammalian hosts, particularly in the initial hours post feeding; a critical time for transmitted viral particles to establish infection. To gain insight as to why C. sonorensis are such efficient vectors for orbiviruses, we used a mouse model to characterize immune responses in the first three days after midge feeding. Analysis of skin, lymph node cell populations and cytokines by histology, flow cytometry, and real time PCR indicated a Th-mediated cellular response with significant mast cell activation, hemorrhaging, edema and vasodilation, as well as rapid dermal infiltration of CD16/32+ granulocytes, known infection targets of orbiviruses. In contrast to the hostile mammalian immunological environment we hypothesized would confront any bite-transmitted virus particles, effects on the dermal vasculature and lymphoid tissues in response to midge feeding led to a local, then systemic immunological state highly favorable for orbivirus infection and dissemination. The interactions of these beneficial innate immune responses with bite-transmitted virus is likely key to the transmission competency of this vector and play an important role in vector-enhanced transmission. These beneficial elicited responses may well extrapolate to other competent vector – arboviral disease associations.