Vaccination reduces virus load in upper and lower airways following virulent BRSV challenge.

<p>Four groups of 5 calves were vaccinated as described in Fig. 1 and challenged with BRSV, 5 weeks after vaccination, on post-infection day (PID) 0. Two weeks before challenge, one calf (c5) was euthanized due to traumatic injury. The figure presents mean viral load in nasal swabs collected from PID 0 to PID 7 in panel A and post-mortem bronchoalveolar lavage (BAL) in panel B, as determined by BRSV F-gene RT-PCR after total RNA extraction, and is expressed as TCID₅₀ equivalent, calculated from standard dilution series of virus with a known TCID₅₀. The area under mean curves in panel A represents the accumulated detected virus shed (AVS): calves immunized with either ΔSHrBRSV or SUMont had significantly lower AVS (1.4±2.2 eqTCID₅₀, p≤0.005 and 3.6±2.6 eqTCID₅₀, p≤0.05 respectively), compared to calves immunized with either SUAbis (7.9±3.4 eqTCID₅₀) or adjuvant alone (11.0±2.2 eqTCID₅₀). Statistically significant difference with Student’s <i>t</i>-test are indicated by asterisks and the corresponding groups; p≤0.05 (*); p≤0.01 (**); p≤0.005 (***); p≤0.001 (****).