Provided herein are compositions and methods for eliciting an immune response against Porphyromonas gingivalis. The compositions and methods relate to P. gingivalis polypeptides and fragments and variants thereof and the corresponding polynucleotides which are useful in the diagnosis, prevention and therapy of P. gingivalis infections (e.g. periodontitis). Antibodies against the polypeptides and compositions and methods including these antibodies are also disclosed. The disclosure also describes methods for the detection, prevention and treatment of P. gingivalis infection (e.g. periodontitis).