Host response in a vector transmission model of monocytotropic ehrlichiosis (P3353)

Abstract

Abstract Ehrlichioses are emerging infectious diseases affecting veterinary and human hosts. Studies reveal potential pathogenic mechanisms of infection; however, not much is known about the role of the vector on disease establishment, as demonstrated by a needle-challenged vaccine but failed in field challenge by infected ticks. We have developed a tick transmission model for ehrlichial infection to study the vector-pathogen-host interaction. We infected mice by intravenous (IV) and intradermal (ID) routes and compared the subsequent infection with tick transmission of the newly described E. muris-like agent. We collected samples during the course of infection to evaluate bacterial levels in tissues and antibody production to characterize the differences induced by the route of infection. Our results showed bacterial levels and distribution patterns comparable between mice experimentally infected by the ID or IV route. Higher IgM antibody levels were observed in the early stage of infection in mice infected by tick transmission compared to ID and IV routes. Moreover, IgG antibody levels in tick-transmitted ehrlichiosis were higher than in ID inoculated mice and much higher than in IV infection, which showed only low levels during both early and later phases of infection. These initial results suggest important differences in host processing and presentation of ehrlichial antigen due to the route of infection, which will be further explored in our vaccine development research.