Humoral immune responses. Average bRSV antibody titers, with standard deviations (A, B, and C), measured at 3-week intervals (dpi 0, 20, 41, 69, 83, 104, and 125), on the day of challenge administration (dpi 146), and at the end of the experiment (dpi 156). PBS group (♦), six mock-immunized calves; FI-bRSV group (▪), six calves immunized with FI bRSV; L-bRSV group (▴), six calves immunized with live bRSV. (D) IgE antibody responses detected in the IgE DAS ELISA. Corrected OD values were transformed to percentages of a standard positive serum. Only FI-bRSV-immunized calves were found to be IgE positive. Each line represents a calf immunized with FI-bRSV vaccine. VN, virus neutralizing.