A body of evidence by in vitro studies and in vivo genetically modified mouse models demonstrates that extracellular cyclophilin A is involved in inflammatory diseases such as viral infection [30,45,66,67,68,69], periodontitis [70], and atherosclerosis [69] by means of promoting cell chemotaxis and cell migration (especially leukocyte chemotaxis), and eventually enhancing inflammation [32]. Here, PPIA is linked to viral infectious disease.