Peromyscus leucopus, Mus musculus, and humans have distinct transcriptomic responses to larval Ixodes scapularis bites.

Ixodes scapularis are an important vector for at least six tick-borne human pathogens, including the predominant North American Lyme disease spirochete Borrelia burgdorferi. The ability for these ticks to survive in nature is credited, in part, to their ability to feed on a variety of hosts without excessive activation of the vertebrate immune system. While the ability for nymphal ticks to feed on a variety of hosts has been well-documented, the host-parasite interactions between larval I. scapularis and different vertebrate hosts is relatively unexplored. Here we report on the changes in the vertebrate transcriptome present at the larval tick bite site using the natural I. scapularis host Peromyscus leucopus, a non-natural rodent host Mus musculus (BALB/c), and humans. We note substantially less evidence of inflammation in P. leucopus compared to BALB/c mice and pronounced evidence of inflammation in humans. These data suggest that larval I. scapularis may have a reduced ability to suppress host immunity in non-natural hosts and expand our overall understanding of I. scapularis feeding. Overall design: A heated 1:4 mixture of melted beeswax to rosin gum mixture was used to attach a modified microcentrifuge tube lined with mesh between the shaved shoulder blades of each rodent. Ten I. scapularis larvae (National Tick Research and Education Resource, Oklahoma State University) were placed inside the mesh cap. Mice were singly housed in cages surrounded by a water moat for 48 hours. The tick containment chamber was carefully removed, and a 2-mm punch biopsy was taken surrounding a single feeding tick and transferred immediately RNAlater, stored overnight at room temperature, and then frozen at –80oC until use. Biopsies were intentionally restricted to regions away from the edge of the tick containment chamber where damage from removal could skew results. A second biopsy was taken on the outside of the tick containment chamber as a matched control.