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Haemophilus influenzae acquires vitronectin via the ubiquitous Protein F to subvert host innate immunity.

Author

Summary, in English

Acquisition of the complement inhibitor vitronectin (Vn) is important for the respiratory tract pathogen nontypeable Haemophilus influenzae (NTHi) to escape complement-mediated killing. NTHi actively recruits Vn, and we previously showed that this interaction involves Protein E (PE). Here we describe a second Vn-binding protein, a 30 kDa Yersinia YfeA homologue designated as Protein F (PF). An isogenic NTHi 3655Δhpf mutant devoid of PF displayed a reduced binding of Vn, and was consequently more sensitive to killing by human serum compared with the wild type. Surface expression of PF on Escherichia coli conferred binding of Vn that resulted in a serum resistant phenotype. Molecular analyses revealed that the N-terminal of PF (Lys23-Glu48) bound to the C-terminal of Vn (Phe352-Ser374) without disrupting the inhibitory role of Vn on the membrane attack complex. The PF-Vn complex actively delayed C9 deposition on PF-expressing bacteria. Comparative studies of binding affinity and multiple mutants demonstrated that both PE and PF contribute individually to NTHi serum survival. PF was highly conserved and ubiquitously expressed in a series of randomly selected NTHi clinical isolates (n = 18). In conclusion, the multifaceted binding of Vn is beneficial for NTHi survival in serum and may contribute to successful colonization and consequently infection.

Publishing year

2013

Language

English

Pages

1245-1266

Publication/Series

Molecular Microbiology

Volume

87

Issue

6

Document type

Journal article

Publisher

Wiley-Blackwell

Topic

  • Microbiology in the medical area

Keywords

  • Bacterial Proteins/genetics
  • Blood Bactericidal Activity
  • Gene Deletion
  • Haemophilus influenzae/genetics
  • Humans
  • Immune Evasion
  • Immunity, Innate
  • Microbial Viability
  • Protein Binding
  • Protein Interaction Mapping
  • Vitronectin/metabolism

Status

Published

Research group

  • Clinical Microbiology, Malmö
  • Protein Chemistry, Malmö

ISBN/ISSN/Other

  • ISSN: 1365-2958