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Identification of a Haemophilus influenzae Factor H-Binding Lipoprotein Involved in Serum Resistance.

In English

Författare

Summary, in English

Haemophilus influenzae is a Gram-negative human pathogen that resides in the upper respiratory tract. Encapsulated H. influenzae type b (Hib) and type f (Hif) are the most common serotypes associated with invasive disease. H. influenzae displays various strategies to circumvent the host innate immune response, including the bactericidal effect of the complement system. In this study, we identified an H. influenzae lipoprotein having the ability to bind factor H (FH), the major regulator of the alternative pathway of complement activation. This protein, named protein H (PH), was surface exposed and was found in all clinical Hib and Hif isolates tested. Deletion of the gene encoding for PH (lph) in Hib and Hif significantly reduced the interaction between bacteria and FH. When Hib and Hif PH variants were separately expressed in nontypeable (unencapsulated) H. influenzae, which did not bind FH, an increased FH affinity was observed. We recombinantly expressed the two PH variants in Escherichia coli, and despite sharing only 56% identical amino acids, both FH-binding Haemophilus proteins similarly interacted with the complement regulator FH short consensus repeats 7 and 18-20. Importantly, Hib and Hif resistance against the bactericidal effect of human serum was significantly reduced when bacterial mutants devoid of PH were tested. In conclusion, we have characterized a hitherto unknown bacterial protein that is crucial for mediating an interaction between the human pathogen H. influenzae and FH. This novel interaction is important for H. influenzae resistance against complement activation and will consequently promote bacterial pathogenesis.

Publiceringsår

2014

Språk

Engelska

Sidor

5913-5923

Publikation/Tidskrift/Serie

Journal of Immunology

Volym

192

Issue

12

Dokumenttyp

Artikel i tidskrift

Förlag

American Association of Immunologists

Ämne

  • Immunology in the medical area

Status

Published

Forskningsgrupp

  • Clinical Microbiology, Malmö

ISBN/ISSN/Övrigt

  • ISSN: 1550-6606