A Haemophilus influenzae IgA protease-like protein promotes intimate interaction with human epithelial cells

Mol Microbiol. 1994 Oct;14(2):217-33. doi: 10.1111/j.1365-2958.1994.tb01283.x.


Haemophilus influenzae represents a common cause of human disease and an important source of morbidity and mortality. Disease caused by this organism begins with colonization of the upper respiratory tract. Several studies indicate that H. influenzae is capable of binding to and entering cultured human cells, properties which are potentially of relevance to the process of colonization. In the present study, we isolated an H. influenzae gene designated hap, which is associated with the capacity for in vitro attachment and entry. Analysis of the derived amino acid sequence of hap demonstrated significant homology with the serine-type IgA1 proteases expressed by H. influenzae and Neisseria gonorrhoeae. It is notable that the hap product shares the catalytic domain of the IgA1 proteases and appears to be processed and secreted in an analogous manner. We speculate that the hap gene product is an important determinant of colonization, perhaps enabling the organism to evade the local immune response and thereby persist within the respiratory tract.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Bacterial Adhesion
  • Bacterial Outer Membrane Proteins / chemistry
  • Bacterial Outer Membrane Proteins / genetics*
  • Bacterial Outer Membrane Proteins / metabolism
  • Cell Line
  • Cloning, Molecular
  • DNA Transposable Elements
  • Epithelial Cells
  • Epithelium / microbiology*
  • Genes, Bacterial
  • Haemophilus influenzae / enzymology
  • Haemophilus influenzae / genetics*
  • Haemophilus influenzae / physiology
  • Humans
  • Molecular Sequence Data
  • Molecular Weight
  • Mutagenesis
  • Mutagenesis, Insertional
  • Peptide Hydrolases / chemistry
  • Peptide Hydrolases / genetics*
  • Peptide Hydrolases / metabolism
  • Sequence Homology, Amino Acid
  • Serine Endopeptidases*


  • Bacterial Outer Membrane Proteins
  • DNA Transposable Elements
  • Hap protein, Hemophilus influenzae
  • Peptide Hydrolases
  • Serine Endopeptidases
  • IgA-specific serine endopeptidase

Associated data

  • GENBANK/U11024