Vaccine Challenge
After completion of the 22-wk repletion period, a novel vaccine challenge was used to assess immune response. The vaccine challenge was completed over 7 wk. Vaccination and sampling time points for the vaccine challenge are described in Fig. 1. The OVA (Sigma, Saint Louis, MO) vaccines were prepared under sterile conditions in a laminar flow hood (Biological Safety Cabinets; NuAire, Plymouth, MN). The OVA was dissolved in sterile physiological saline (Butler, Lexington, KY) at a concentration appropriate to allow the final vaccine volume to be 1 mL (i.e., 10 mg OVA/mL). The vaccine was administered intramuscularly in the pectoral muscle after thorough cleaning of the area with ethanol.