Gingipains are cysteine proteases consisting of arginine-gingipain A (RgpA), arginine-gingipain B (RgpB), and lysine-gingipain (Kgp);27,39 these are well-known key pathogens of periodontitis, associated with multiple systemic diseases such as diabetes mellitus and Alzheimer’s disease (AD).28 This evidence concerns the gene CTSB and Alzheimer disease.