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Mol Microbiol. 2014 Oct;94(1):89-106. doi: 10.1111/mmi.12741. Epub 2014 Aug 18.

Binding of human factor H to outer membrane protein P5 of non-typeable Haemophilus influenzae contributes to complement resistance.

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Department of Microbiology, University of Pennsylvania, Philadelphia, PA, USA; Department of Pediatrics, Laboratory of Pediatric Infectious Diseases, Radboud University Medical Center, Nijmegen, The Netherlands.


Non-typeable Haemophilus influenzae is an opportunistic pathogen of the human upper respiratory tract and is often found to cause inflammatory diseases that include sinusitis, otitis media and exacerbations of chronic obstructive pulmonary disease. To persist in the inflammatory milieu during infection, non-typeable H. influenzae must resist the antimicrobial activity of the human complement system. Here, we used Tn-seq to identify genes important for resistance to complement-mediated killing. This screen identified outer membrane protein P5 in evasion of the alternative pathway of complement activation. Outer membrane protein P5 was shown to bind human complement regulatory protein factor H directly, thereby, preventing complement factor C3 deposition on the surface of the bacterium. Furthermore, we show that amino acid variation within surface-exposed regions within outer membrane P5 affected the level of factor H binding between individual strains.

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