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PMID:24835392

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Citation

Fleury, C, Su, YC, Hallström, T, Sandblad, L, Zipfel, PF and Riesbeck, K (2014) Identification of a Haemophilus influenzae factor H-Binding lipoprotein involved in serum resistance. J. Immunol. 192:5913-23

Abstract

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.

Links

PubMed Online version:10.4049/jimmunol.1303449

Keywords

Bacterial Proteins/chemistry; Bacterial Proteins/genetics; Bacterial Proteins/immunology; Blood Bactericidal Activity/immunology; Complement Factor H/immunology; Female; Haemophilus influenzae/chemistry; Haemophilus influenzae/genetics; Haemophilus influenzae/immunology; Humans; Lipoproteins/chemistry; Lipoproteins/genetics; Lipoproteins/immunology; Male; Mutation; Recombinant Proteins/chemistry; Recombinant Proteins/genetics; Recombinant Proteins/immunology

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

HAEIF:A0A024A2C9

located_in

GO:0009986: cell surface

ECO:0000314: direct assay evidence used in manual assertion

C

Seeded From UniProt

complete

HAEIF:A0A024A2C9

involved_in

GO:1903659: regulation of complement-dependent cytotoxicity

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete

HAEIF:A0A024A2C9

enables

GO:0005515: protein binding

ECO:0000353: physical interaction evidence used in manual assertion

UniProtKB:P08603

F

Seeded From UniProt

complete

HUMAN:CFAH

enables

GO:0005515: protein binding

ECO:0000353: physical interaction evidence used in manual assertion

UniProtKB:A0A024A2C9

F

Seeded From UniProt

complete

HUMAN:CFAH

involved_in

GO:0006956: complement activation

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete

Notes

See also

References

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