Protein D, the glycerophosphodiester phosphodiesterase from Haemophilus influenzae with affinity for human immunoglobulin D, influences virulence in a rat otitis model

Håkan Janson, Åsa Melhus, Ann Hermansson, Arne Forsgren

Research output: Contribution to journalArticlepeer-review

Abstract

A mutant lacking the ability to express the surface-exposed lipoprotein protein D was constructed by linker insertion and deletion mutagenesis of a cloned DNA insert containing the protein D structural gene from a nontypeable Haemophilus influenzae strain (NTHi). An isogenic NTHi mutant was isolated after transformation of genetically competent bacteria. The transformant was unreactive to a protein D-specific monoclonal antibody in a colony immunoassay. In addition, the mutant lacked the ability to synthesize detectable levels of protein D by protein staining, immunoblot methods, glycerophosphodiester phosphodiesterase activity, and binding studies of radiolabelled immunoglobulin D. The isogenic protein D-deficient mutant was compared with its parental strain for its ability to induce experimental otitis media in rats challenged with bacteria. An approximately 100-times-higher concentration of the mutant compared with that of the wild-type strain was required in order to cause otitis among all rats challenged with that given dose. The protein D mutant exhibited a generation time that was equal to that of the wild-type strain in complex broth medium. No difference in lipopolysaccharide expression was found between the mutant and the parental strain. These results suggest that protein D may influence the pathogenesis of NTHi in the upper respiratory tract.
Original languageEnglish
Pages (from-to)4848-4854
JournalInfection and Immunity
Volume62
Issue number11
Publication statusPublished - 1994

Subject classification (UKÄ)

  • Otorhinolaryngology
  • Microbiology in the medical area

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