THE HUMORAL IMMUNE-RESPONSE IN CATTLE AFTER IMMUNIZATION WITH A MULTIVALENT IBR PI3 PASTEURELLA-HAEMOLYTICA A1 LEUKOTOXIN VACCINE/

A multivalent vaccine consisting of inactivated bovine herpes virus-1 (BHV-1), also known as infectious bovine rhinotracheitis virus (IBR), para-influenza type-3 virus (PI3) and the leukotoxin of Pasteurella ha emolytica A1, were combined with the addition of aluminium hydroxide a s adjuvant, and administered to post-weaned calves, and the serum test ed for seroconversion to each antigen. Two groups of calves (n = 150 a nd n = 68) were used and were randomly divided into three subgroups. T he first group of 150 calves were immunized with the multivalent vacci ne (three batches) to test its first-stage stability (vaccine 3 months old) and the second group were immunized with the same vaccine 1 year later, in order to test its immunogenicity. A significant increase in titres occurred after the day 0 and 28 immunizations, for each of the three antigens in the multivalent vaccine, as measured on days 0 and 42. Immunoconversion occurred after immunization with the 3-month- and 1-year-old vaccine. The immunogenic stability of antigens in the vacc ine was demonstrated after a 1-year period when the vaccine was kept a t 4-6 degrees C.