Fusobacterium nucleatum envelope protein FomA is immunogenic and binds to the salivary statherin-derived peptide

Area of Science:

• Microbiology
• Oral Health
• Immunology

Background:

• Statherin, a human salivary protein, contains a YQPVPE peptide crucial for binding Fusobacterium nucleatum.
• Understanding the molecular interactions between salivary proteins and oral bacteria is key to preventing dental plaque formation.

Purpose of the Study:

• To identify the specific protein in Fusobacterium nucleatum responsible for binding to the statherin-derived YQPVPE peptide.
• To investigate the potential of targeting this interaction for preventing Fusobacterium nucleatum colonization and biofilm formation.

Main Methods:

• Purification and characterization of a 40-kDa cell envelope protein from Fusobacterium nucleatum.
• Amino acid sequencing and homology analysis to identify the protein.
• Generation of a FomA-deficient mutant to assess binding.
• Immunization studies in mice using the purified protein and cholera toxin (CT) as a mucosal adjuvant.
• In vitro assessment of saliva's ability to block bacterial binding.

Main Results:

• A 40-kDa cell envelope protein (40-kDa CE) of Fusobacterium nucleatum was identified as specifically binding to the YQPVPE peptide with a high affinity (4.30 x 10^6).
• The 40-kDa CE showed high homology to FomA, a major porin protein of Fusobacterium nucleatum; a FomA-deficient mutant failed to bind the peptide.
• Nasal immunization with FomA and CT induced specific mucosal IgA and plasma IgG/IgA antibodies.
• Saliva from immunized mice inhibited the in vitro binding of Fusobacterium nucleatum to statherin-coated surfaces.

Conclusions:

• The FomA protein of Fusobacterium nucleatum directly binds to the statherin-derived YQPVPE peptide.
• Targeting FomA through specific immunity, particularly mucosal immunity, shows promise for preventing Fusobacterium nucleatum adhesion and subsequent oral biofilm formation.