CLONING AND EXPRESSION OF THE MORAXELLA-CATARRHALIS LACTOFERRIN RECEPTOR GENES

The lactoferrin receptor genes from two strains of Moraxella catarrhal is have been cloned and sequenced. The lfr genes are arranged as lbpB followed by lbpA, a gene arrangement found in lactoferrin and transfer rin receptor operons from several bacterial species. In addition, a th ird open reading frame, orf3, is located one nucleotide downstream of lbpA. The deduced lactoferrin binding protein A (LbpA) sequences from the two strains were found to be 99% identical, the LbpB sequences wer e 92% identical, and the ORF3 proteins were 98% identical. The lbpB ge ne was PCR amplified and sequenced from a third strain of M. catarrhal is, and the encoded protein was found to be 77% identical and 84% simi lar to the other LbpB proteins. Recombinant LbpA and LbpB proteins wer e expressed from Escherichia coil, and antisera raised to the purified proteins were used to assess antigenic conservation in a panel of M. catarrhalis strains. The recombinant proteins were tested for the abil ity to bind human lactoferrin following gel electrophoresis and electr oblotting, and rLbpB, but not rLbpA, was found to bind lactoferrin. Ba ctericidal antibody activity was measured, and while the anti-rLbpA an tiserum was not bactericidal, the anti-rLbpB antisera were found to be weakly bactericidal. Thus, LbpB may have potential as a vaccine candi date.