Oral Immunization with RecombinantStreptococcus gordoniiExpressingPorphyromonas gingivalisFimA Domains

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Abstract
Porphyromonas gingivalis, a gram-negative anaerobe, is implicated in the etiology of adult periodontitis.P. gingivalisfimbriae are one of several critical surface virulence factors involved in both bacterial adherence and inflammation.P. gingivalisfimbrillin (FimA), the major subunit protein of fimbriae, is considered an important antigen for vaccine development againstP. gingivalis-associated periodontitis. We have previously shown that biologically active domains ofP. gingivalisfimbrillin can be expressed on the surface of the human commensal bacteriumStreptococcus gordonii. In this study, we examined the effects of oral coimmunization of germfree rats with twoS. gordoniirecombinants expressing N (residues 55 to 145)- and C (residues 226 to 337)-terminal epitopes ofP. gingivalisFimA to elicit FimA-specific immune responses. The effectiveness of immunization in protecting against alveolar bone loss followingP. gingivalisinfection was also evaluated. The results of this study show that the oral delivery ofP. gingivalisFimA epitopes viaS. gordoniivectors resulted in the induction of FimA-specific serum (immunoglobulin G [IgG] and IgA) and salivary (IgA) antibody responses and that the immune responses were protective against subsequentP. gingivalis-induced alveolar bone loss. These results support the potential usefulness of theS. gordoniivectors expressingP. gingivalisfimbrillin as a mucosal vaccine against adult periodontitis.