Using proteome databases and exploiting the concept that a rare sequence is a potential epitope, epitopic sequences derived from Porphyromonas gingivalis fimA type I protein were examined for pentapeptide sequence similarity score to the human proteome. We obtained data showing that most of the linear bacterial determinants are (or are formed by) peptide fragment(s) absent (or rarely found) in the human proteins. These results seem to confirm the hypothesis that low-sequence similarity may contribute to shape the epitope repertoire and provides a potential tool for designing new immunotherapeutic approaches to apply in Porphyromonas gingivalis infected periodontitis.