Gingipains are cysteine proteases composed of lysine-gingipain (Kgp), arginine-gingipain A (RgpA), and arginine-gingipain B (RgpB), which have been identified in the brains of patients with AD, and their levels are correlated with tau and ubiquitin pathology (Dominy et al., 2019). This evidence concerns the gene MAPT and Alzheimer disease.