Duck Complement Factor H Binds to Outer Membrane Protein Omp24 of Riemerella anatipestifer

Area of Science:

• Microbiology
• Immunology
• Bacterial Pathogenesis

Background:

• Complement factor H (FH) is crucial for regulating the complement alternative pathway (AP).
• Pathogens often evade complement-mediated killing by recruiting host FH via surface proteins.
• The mechanism by which Riemerella anatipestifer evades complement is not fully understood.

Purpose of the Study:

• To identify Riemerella anatipestifer proteins that interact with host factor H.
• To determine the functional role of these interactions in bacterial virulence and complement evasion.

Main Methods:

• Affinity chromatography and mass spectrometry to identify FH-binding proteins.
• Prokaryotic expression and antibody preparation for candidate proteins.
• Indirect immunofluorescence, affinity blotting, and serum bactericidal assays to confirm binding and function.

Main Results:

• Three outer membrane proteins (Omp54, Omp53, Omp24) were identified as potential FH-binding proteins.
• Omp24 was confirmed to bind factor H.
• FH binding to Omp24 conferred resistance to the complement alternative pathway and enhanced R. anatipestifer survival in normal duck serum.

Conclusions:

• Riemerella anatipestifer Omp24 is a factor H-binding protein.
• The interaction between Omp24 and FH inhibits the complement alternative pathway.
• FH recruitment by Omp24 is a key mechanism for R. anatipestifer to resist host complement defense.