Provided herein are methods and immunogenic compositions useful for protecting mammals from infection and pathology of P. gingivalis. Specifically, arginine-specific proteases of Porphyromonas gingivalis and peptides derived therefrom offer protection against infection. Immunogenic compositions comprising a 50 kDa arginine-specific protease, the high molecular weight complex or peptides from one of the foregoing proteins are capable of protecting against P. gingivalis infection and/or gingivitis and/or periodontitis caused thereby in mammals, including humans.