THE EFFECTS OF TICK SALIVA ON THE DENDRITIC CELL- INTERACTION, IN VIVO

Thomas Shelite, R. Fang, M.D., Ph.D., N. Ismail, M.D., Ph.D., and D. H. Walker, M.D.

Department of Pathology, UTMB

Background: The inhibition of DC maturation and differentiation in the presence of tick saliva could attenuate the host’s initial immune response to tick infestation and thus provide a window of opportunity for dissemination of tick-borne pathogens. The role of tick saliva in rickettsial disease is unknown. Objective: The objective of this proposal is to elucidate the cellular and immunological events that occur early in R. conorii infection. Methods: BMDCs were isolated from C3H/HeN and C57BL/6 mice, which are susceptible and resistant to R. conorii infection, respectively. R. conorii-infected BMDCs were exposed to saliva from Rhipicephalus sanguineus ticks, the natural vector of R. conorii. Samples were then stained and prepared for FACS. Results: Tick saliva significantly enhanced the expression levels of MHC-II and the co-stimulatory molecule CD86 on R. conorii-infected DCs from C3H/HeN mice without increasing the expression level of MHC class I, B220, and CD8. In contrast, expression levels of MHC class II, CD86 and MHC-I on DCs of C57BL/6 mice were unaltered. The expression levels of B220 and CD8 were increased in untreated R. conorii-infected DCs of both resistant and susceptible mice. Conclusions: Tick saliva inhibited the expression of B220 on infected DCs of resistant C57BL/6 mice, implying decreased differentiation into plasmacytoid DCs potentially inhibiting the innate immune system of C57BL/6 mice during rickettsial infection.

Supported by the Department of Pathology and NIH RO1 AI 21242.