Three contiguous lipoprotein genes in Pasteurella haemolytica A1 which are homologous to a lipoprotein gene in Haemophilus influenzae type b.

An Escherichia coli clone carrying the recombinant plasmid pPH24 has been found to express highly immunoreactive antigens of Pasteurella haemolytica A1. Two or three antigens of approximately 30 kDa were located to both the inner and outer membranes of the E. coli clone and in P. haemolytica A1. From the insert DNA of 8.2 kbp on pPH24, a fragment of 4.6 kbp was found to code for these antigens. Nucleotide sequence analysis of the 4.6-kbp DNA identified three genes (designated plpA, -B, and -C) arranged in tandem which code for three proteins, Plp1, -2, and -3, with predicted molecular masses of 30.1, 30.3, and 29.0 kDa, respectively. Comparison of the nucleic acid sequence of plpA, -B, and -C with GenBank sequences showed extensive homology with a Haemophilus influenzae 28-kDa lipoprotein gene. [14C]palmitate labelling coupled with glybomycin inhibition experiments showed that Plp1, -2, and -3 are also lipoproteins. In addition, plpA, -B, and -C were found to be present only in A biotypes of P. haemolytica by Southern blot analysis. Since Plp1, -2, and -3 were found to be antigenic components in a culture supernatant vaccine, they could be candidates for further investigation as vaccine components.