GENETIC AND IMMUNOLOGICAL ANALYSES OF A 38KDA SURFACE-EXPOSED LIPOPROTEIN OF PASTEURELLA-HAEMOLYTICA A1

Pasteurella haemolytica serotype A1 is the bacterial pathogen most fre quently isolated from the lungs of cattle with bovine respiratory dise ase. As part of a study to characterize P. haemolytica antigens which are important in eliciting resistance to pneumonic pasteurellosis, we have cloned and sequenced the gene encoding a 38 kDa lipoprotein, Lpp3 8. The deduced amino acid sequence of Lpp38 is similar to those of the Escherichia polyamine transport proteins PotD (70%) and PotF (33%). P . haemolyrica Lpp38 is present in both inner membrane and outer membra ne fractions of the cell envelope, Susceptibility of Lpp38 to cleavage by extracellular proteases indicates that portions of the protein are surface-exposed. A protein of similar molecular mass in P. haemolytic a strains from all 12 serotypes of biotype A acid in an untypeable str ain was detected by an anti-Lpp38 monoclonal antibody. Lpp38 is recogn ized by sera from calves resistant to infection after natural exposure to P. haemolytica and by sera from calves protected against infection by vaccination with P. haemolytica A1 outer membranes or with live ba cteria, These data suggest a role for this protein in the development of immunity to P. haemolytica infection.