Viral load of episomal and integrated forms of human papillomavirus type 33 in high-grade squamous intraepithelial lesions of the uterine cervix

The association between total and integrated HPV-33 DNA loads and high-grade squamous intraepithelial lesions (HSIL) of the uterine cervix was investigated. Of 5,347 women recruited in 4 studies, 89 (64 without SIL, 7 low-grade SIL (LSIL), 15 HSIL, 3 unknown grade) were infected by HPV-33. HPV-33 E6, HPV-33 E2 and beta-globin DNA were measured with real-time PCR that allowed to assess total (E6), episomal (E2) and integrated (E6-E2) HPV-33 viral loads. HPV-33 E6/E2 ratios >/=>/=2.0 suggesting the presence of integrated HPV-33 were obtained for 28.6% (n = 18) of women without SIL and 21.4% (n = 3) of women with HSIL (p = 0.74). Although median viral loads were similar, there was a trend toward having a greater proportion of women with HSIL in the fourth quartile (>/=>/=10(6.69) copies/mug DNA) of total HPV-33 viral loads compared to normal women. Controlling for age, site, ethnicity and LCR polymorphism by logistic regression, HPV-33 total loads in the fourth quartile {odds ratio (OR) 4.5 [95% confidence interval (CI) 1.2-17.3]; p = 0.03} and episomal loads in the fourth quartile (>/=>/=10(6.64) copies/mug DNA) [OR 3.9 (95% CI 1.1-13.2); p = 0.05] but not integrated HPV-33 load in the fourth quartile [OR 1.0 (95% CI 0.3-3.3); p = 0.50] were associated with HSIL. Controlling for age, study site and SIL grade, HPV-33 episomal load [OR 0.2 (95% CI 0.1-0.5), p = 0.0004] was associated with the presence of HPV-33 integration. High episomal loads in HSIL and the presence of integration in women without SIL are likely to weaken the usefulness of HPV load of integrated forms in clinical practice.