The present invention relates to soluble P. gingivalis polypeptides derived from PG32 and PG33 and to polynucleotides encoding these polypeptides. The P. gingivalis polypeptides and nucleotides can be used in compositions for use in raising an immune response in a subject against P. gingivalis and treating or preventing or reducing the severity of the condition known as periodontitis or in other conditions related to infection with P. gingivalis.