MOLECULAR-CLONING, EXPRESSION, AND SEQUENCE OF THE PILIN GENE FROM NONTYPABLE HAEMOPHILUS-INFLUENZAE M37

Nontypeable Haemophilus influenzae M37 adheres to human buccal epithelial cells and exhibits mannoseresistant hemagglutination of human erythrocytes. An isogenic variant of this strain which was deficient in hemagglutination was isolated. A protein with an apparent molecular weight of 22,000 was present in the sodium dodecyl sulfate-polyacrylamide gel profile of sarcosyl-insoluble proteins from the hemagglutination-proficient strain but was absent from the profile of the isogenic hemagglutination-deficient variant. A monoclonal antibody which reacts with the hemagglutination-proficient isolate but not with the hemagglutination-deficient isolate has been characterized. This monoclonal antibody was employed in an affinity column for purification of the protein as well as to screen a genomic library for recombinant clones expressing the gene. Several clones which contained overlapping genomic fragments were identified by reaction with the monoclonal antibody. The gene for the 22-kDa protein was subcloned and sequenced. The gene for the type b pilin from H. influenzae type b strain MinnA was also cloned and sequenced. The DNA sequence of the strain MinnA gene was identical to that reported previously for two other type b strains. The DNA sequence of the strain M37 gene is 77% identical to that of the type b pilin gene, and the derived amino acid sequence is 68% identical to that of the type b pilin.