Structural and antigenic characterization of a novel genotype of Mfa1 fimbriae in Porphyromonas gingivalis

Abstract

Background

Mfa1 fimbriae of the periodontal pathogen Porphyromonas gingivalis are responsible for biofilm formation and comprise five proteins: Mfa1–5. Two major genotypes, mfa1⁷⁰ and mfa1⁵³, encode major fimbrillin. The mfa1⁷⁰ genotype is further divided into the mfa1^70A and mfa1^70B subtypes. The properties of the novel mfa1^70B remain unclear.

Methods

Fimbriae were purified from P. gingivalis strains JI-1 (mfa1^70A), 1439 (mfa1^70B), and Ando (mfa1⁵³), and their components and their structures were analyzed. Protein expression and variability in the antigenic specificity of fimbrillins were compared using Coomassie staining and western blotting using polyclonal antibodies against Mfa1^70A, Mfa1^70B, and Mfa1⁵³ proteins. Cell surface expression levels of fimbriae were analyzed by filtration enzyme-linked immunosorbent assays.

Results

The composition and structure of the purified Mfa1 fimbriae of 1439 was similar to that of JI-1. However, each Mfa1 protein of differential subtype/genotype was specifically detected by western blotting. Mfa1^70B fimbriae were expressed in several strains such as 1439, JKG9, B42, 1436, and Kyudai-3. Differential protein expression and antigenic heterogeneities were detected in Mfa2–5 between strains.

Conclusion

Mfa1 fimbriae from the mfa1^70A and mfa1^70B genotypes indicated an antigenic differencesuggesting the mfa1^70B, is to be utilized for the novel classification of P. gingivalis.