Purification and characterization of Haemophilus influenzae pili, and their structural and serological relatedness to Escherichia coli P and mannose-sensitive pili.

Open Access
Publisher Website
Google Scholar
Abstract
H. influenzae pili were purified, and their physical and serological properties were examined. The solution properties of the pili were determined, and then a purification scheme involving repeated cycles of precipitation and solubilization was developed. The purified pili from 1 type b isolate (A02) were found to consist of multiple copies of a 25,000 MW subunit. Amino-terminal sequence analysis of A02 pili was carried out to 40 amino acid residues, and a remarkable degree of sequence homology was found with E. coli P and mannose-sensitive (MS) pili (27.5 and 25% homology, respectively). Purified A02 pili were found to be highly immunogenic, and serological analysis by enzyme-linked immunosorbent assay [ELISA] and whole piliated cell agglutination revealed significant cross-reactivity between A02 pilus antiserum and the pili of 7 other H. influenzae strains tested (heterologous titers = 2-100% of the homologous titer). Cross-reactivity was also observed between the H. influenzae pili (5 of 8 strains tested) and the P pili from E. coli strians HU849 and 3669; no cross-reactivity was detected with MS pili from E. coli strain H10407 and C94. The structural similarities between H. influenzae and E. coli P and MS pili suggest a common gene ancestry.