Protective capacity of the Pasteurella haemolytica transferrin-binding proteins TbpA and TbpB in cattle

The transferrin-binding proteins TbpA and TbpB from Pasteurella haemolytica biotype A serotype 1 were tested for their ability to confer protection ag ainst experimental P. haemolytica infection when administered to calves in vaccine formulations containing one or both antigens. Vaccine groups includ ed TbpB (single immunization), TbpB (two immunizations), TbpA, TbpA+TbpB an d a placebo. AII animals that received TbpB had measurable antibody titres against the antigen at the time of challenge, while those that received Tbp A did not show an antibody response. The TbpA+TbpB group showed the best pr otection against experimental challenge. Protection correlated with anti-Tb pB antibody levels, The enhanced protection in the TbpA+TbpB group suggests TbpA contributed to protection through the induction of a non-antibody-med iated immune response. Sera from the TbpB-immunized animals was cross-react ive with TbpBs from other P. haemolytica serotypes. (C) 1999 Academic Press .