Bacterial Comparisons: How Anaplasma phagocytophilum and Borrelia burgdorferi Effect the Secretion of Vesicles in their Vector, and the Immune Response of their Host

Lyme disease and Human Granulocytic Anaplasmosis (HGA) are the two most reported tick-borne diseases in the US. Nevertheless, what happens locally at the skin during transmission of Anaplasma phagocytophilum, the causative agent of HGA, is poorly defined. In this study, RNAseq analysis of the bite sites of A. phagocytophilum infected ticks compared uninfected ticks indicate that many immune related genes are upregulated during A. phagocytophilum transmission, particularly those related to the IFN-γ, NF-κB and JAK/STAT signaling pathways. Multiple cytokines and chemokines were also upregulated. The production of extracellular vesicles from A. phagocytophilum and B. burgdorferi infected tick midguts and salivary glands was observed, with A. phagocytophilum infection resulting in extracellular vesicles 50-150 nm in diameter being significantly reduced in both organs. B. burgdorferi infection reduced midgut vesicles but produced no significant change in salivary glands. Overall, these results indicate that the response of the host and the vector to different pathogens is unique