Aerosols were generated via nebulization of a Brucella suspension (∼ 5 × 10 9 CFU/ml in PBS) into a Madison Chamber (Madison, Wisconsin) according to the manufacturer's instructions (Kahl-McDonagh et al., 2007) . The aerosol chamber was located in a biosafety level 3 (BSL3) facility in the Laboratory Animal Research and Resources (LARR) building staffed and managed by the CMP at Texas A&M University. To assure personal safety, the principal investigator implemented a strict safety protocol, and all procedures were approved by the IBC and IACUC. Following aerosol exposure, one group of mice (n = 5) were immediately euthanized via carbon dioxide inhalation and the lungs collected to determine the infecting dose (Kahl-McDonagh et al., 2007) . At 1, 2, 4, 6, 8 , and 10 weeks after exposure, mice were euthanized and lung, spleen and liver were collected and homogenized in 1 ml each of sterile water containing 0.5% (v/v) Tween-20. One hundred microliters of appropriate dilution of the homogenized tissue were plated on Farrell's selective medium plates followed by incubation at 37 • C for at least 3 days. The experimental limit of detection was determined to be 10 CFU per lung, spleen or gram of live, and the results described represent the accumulated data from 4 independent aerosol exposures.