PASSIVE PROTECTION OF CALVES WITH PASTEURELLA-HAEMOLYTICA ANTISERUM

Four colostrum-deprived calves each were immunized passively with anti sera to whole Pasteurella haemolytica, leukotoxin-containing supernata nts of P haemolytica, P haemolytica lipopolysaccharide, or newborn cal f serum. Calves were challenge exposed intrabronchially with 5 X 10(9) P haemolytica, and 24 hours later, the resulting lesions were evaluat ed. The greatest protection against challenge exposure was provided by the antiserum to whole P haemolytica (lesion score = 6.3), whereas ne wborn calf serum provided the least protection (lesion score = 28.3). Calves that received antiserum to P haemolytica supernatants were mode rately protected (lesion score = 16.3), and the antiserum to lipopolys accharide provided minimal protection (lesion score = 21.8). Antibodie s that were unique to whole P haemolytica antiserum and produced dense bands on immunoblots were detected to antigens at 66, 50, and 30 kd. Antibodies in the supernatant preparation that produced prominent band s reacted to antigens between 100 and 90 kd. Collectively, antibodies to these antigens may be responsible for enhancing resistance to exper imentally induced pneumonic pasteurellosis. Antibodies to antigens in P haemolytica lipopolysaccharide provided little to no protection.