Age-related changes of the cervix influence human papillomavirus type distribution

Approximately 15 human papillomavirus (HPV) types cause virtually all cervical cancer whereas other HPV types are unrelated to cancer. We were interested in whether some noncarcinogenic types differ from carcinogenic in their affinity for the cervical transformation zone, where nearly all HPV-induced cancers occur. To examine this possibility, we tested cervical specimens from 8,374 women without cervical precancer and cancer participating in a population-based study in Guanacaste for > 40 HPV types using PCR. We compared age-group specific prevalences of HPV types of the alpha 9 species, which are mainly carcinogenic and include HPV16, to the genetically distinct types of the alpha 3/alpha 15 species (e.g., HPV71), which are noncarcinogenic and common in vaginal specimens from hysterectomized women. We related HPV detection of each group to the location of the junction between the squamous epithelium of the ectocervix and vagina and the columnar epithelium of the endocervical canal. Models evaluated the independent effects of amount of exposed columnar epithelium (ectopy) and age on the presence of alpha 9 or alpha 3/alpha 15 types. Prevalence of alpha 9 types (7.6%) peaked in the youngest women, declined in middle-aged women, and then increased slightly in older women. By contrast, prevalence of alpha 3/alpha 15 types (7.6%) tended to remain invariant or to increase with increasing age. Detection of alpha 9 infections increased (P-trend < 0.0005) but alpha 3/alpha 15 infections decreased (Ptrend < 0.0005) with increasing exposure of the columnar epithelia. Older age and decreasing cervical ectopy were independently positively associated with having an alpha 3/alpha 15 infection compared with having an alpha 9 infection. These patterns need to be confirmed in other studies and populations. We suggest that these genetically distinct groups of HPV types may differ in tissue preferences, which may contribute to their differences in carcinogenic potential.