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, mfa1 70 and mfa1 53 , encode major fimbrillin. The mfa1 70 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 (mfa1 53 ), 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 Mfa1 53 proteins. Cell surface expression levels of fimbriae were analyzed by filtration enzyme-linked immunosorbent assays. Results The composition and structures 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 mfa170A and mfa170B genotypes indicated an antigenic difference suggesting the mfa170B, is to be utilized for the novel classification of P. gingivalis.