ANTIGENIC HETEROGENEITY AND MOLECULAR ANALYSIS OF COPB OF MORAXELLA (BRANHAMELLA) CATARRHALIS

Outer membrane protein (OMP) CopB, an iron-repressible 8P-kDa major OM P of Moraxella (Branhamella) catarrhalis has been a major focus of inv estigation, To assess CopB as a potential vaccine antigen, we elucidat ed the degree of antigenic and sequence heterogeneity in this protein among strains of M, catarrhalis. Two monoclonal antibodies, 1F5 and 2. 9F, which bind to surface-exposed epitopes on CopB recognized 60 and 7 0% of the strains, respectively, The degree of sequence heterogeneity in CopB was assessed by cloning and sequencing the CopB gene from two different strains of M, catarrhalis and comparing with the published s equence, There was 92 to 96% homology between the sequences at the nuc leotide level and 90 to 95% homology at the amino acid level, The vari ability in the protein-sequence is confined mainly to three moderately variable regions, Restriction fragment length polymorphism (RFLP) ana lysis of the CopB genes obtained from 20 diverse strains by PCR was pe rformed, Ninety percent of the potential restriction sites in the cons tant regions and 47% of the potential restriction sites in the variabl e regions were present in the 20 strains, indicating that the pattern of variable and constant areas in the CopB gene is a general pattern a mong strains of hi. catarrhalis, We conclude that the CopB gene is lar gely conserved among strains of M, catarrhalis and contains discrete r egions which show moderate heterogeneity among strains.