Kinetics of the humoral immune responses of rabbits and sheep immunized with BoHV-4CMV-IgKE2-14ΔTK. Sera collected from rabbits (a) and sheep (b) before immunization (time 0) and after immunization (time 1, 2, 3, 4 and 5) were evaluated for anti-BVD neutralizing antibodies by serum neutralization (SN) test. Serum neutralizing antibodies against BVDV are expressed as the reciprocal of the highest dilution of the serum that inhibited the development of virus-induced CPE in MDBK cells. Virus neutralization (VN) titers of 2 (log2) were considered to be positive. In both panels, each value represents the mean response of 3 rabbits (a) (** = P < 0.001, * = P < 0,05) or 4 sheep (b) (** = P < 0.001, * = P < 0,05). Each test was repeated 3 times and statistical significance was evaluated by Student's t test.