Fig. 1

Summary of potential mechanisms associating the VMB with cervical disease. a VMB structure appears to be associated with acquisition and persistence of HPV infection, and CST II in particular is associated with most rapid clearance of an acute HPV infection. b Dysbiosis can result in a proinflammatory environment, which can facilitate several of the necessary steps in viral transformation including E6 and E7 expression, genomic instability, viral integration and telomerase activation, which are necessary for carcinogenesis. c Higher diversity with lower Lactobacillus spp. content has been associated with increasing severity of CIN. Particular species associated with high diversity VMBs may produce sialidases which cause mucus breakdown, predisposing the cervical epithelium to tissue damage, as well as producing biological amines which are responsible for oxidative stress; a key mechanism in carcinogenesis. Certain species Lactobacillus spp. have been shown to mop up these amines, and therefore their presence may reduce the risk of oxidative damage. L. iners does not appear to share many of the protective mechanisms of other Lactobacillus species and therefore appears intermediate in its ability to prevent cervical disease