Protection studies on winter dysentery caused by bovine coronavirus in cattle using antigens prepared from infected cell lysates

Cells infected with bovine coronavirus (BCV) were solubilized with Triton X -100 to yield a cell lysate (CL) antigen having high hemagglutinating (HA) titers. The antigen gave high HA titers using rat erythrocytes, suggesting that ii contained large amounts of hemagglutinin esterase (HE) antigen. The CL antigen, combined with an oil adjuvant, was tested for protective and a ntibody-inducing activities in cattle. Four groups (2 cattle/group) of catt le were inoculated with CL antigen having HA titers of 16 000, 4000, 1000, and 250. Another group served as untreated controls. Two intramuscular inoc ulations were given at an interval of 3 wk. The animals were challenged wit h virus 1 wk after the second inoculation. The groups immunized with the CL antigen having an HA titer of 4000 or 16 000 produced hemagglutination inh ibition (HI) antibody titers of > 320 and serum neutralizing (SN) antibody titers of > 1280. These groups of animals showed no clinical abnormalities after challenge. In the groups immunized with CL antigen at an HA titer of 1000 or 250, HI antibody titers were 40 to 160 and SN titers were 80 to 640 . The cattle with HI antibody titers of greater than or equal to 160 and th e SN titers of greater than or equal to 640 showed no clinical signs, but t he cattle with the HI antibody titer < 80 and the SN antibody titer < 160 d eveloped watery diarrhea and fever after challenge. These results indicate that CL antigen with high HA titer induces antibody production in cattle th at provides effective protection against winter dysentery.