Vero (African green monkey kidney fibroblast) cells and BHK-21 (baby hamster kidney fibroblast) cells were cultured as described previously (Goodman et al. 2014 (link)). Briefly, cells were maintained at 37°C in Dulbecco’s modified Eagle’s medium (DMEM; Life Technologies, Grand Island, NY) with 8% fetal bovine serum (FBS; Atlas Biologicals, Fort Collins, CO), 1 mM sodium pyruvate (Life Technologies), 27 mM sodium bicarbonate (Life Technologies), 0.1 mM gentamicin (Lonza, Walkersville, MD), and 1 μM amphotericin B (Sigma-Aldrich, St. Louis, MO). Aedes albopictus mosquito C6/36 cells were maintained at 28°C in DMEM (Life Technologies) with 10% FBS (Atlas Biologicals), 0.1 mM nonessential amino acids (Life Technologies), 1 mM sodium pyruvate (Life Technologies), 9 mM sodium bicarbonate (Life Technologies), and 0.1 mM gentamicin (Lonza). ISE6 tick cells, derived from I. scapularis embryonated eggs, were obtained from Ulrike Munderloh (University of Minnesota) and maintained at 32°C, as previously described (Munderloh et al. 1994 (link)).