Human Papillomavirus 16 E6 Antibodies in Individuals Without Diagnosed Cancer: A Pooled Analysis.

Background: The increasing incidence of oropharyngeal cancer in many developed countries has been attributed to human papillomavirus type 16 (HPV16) infections. Recently, HPV16 E6 serology has been identified as a promising early marker for oropharyngeal cancer. Therefore, characterization of HPV16 E6 seropositivity among individuals without cancer is warranted. Methods: 4,666 controls were pooled from several studies of cancer and HPV seropositivity, all tested within the same laboratory. HPV16 E6 seropositive controls were classified as having i) moderate (mean fluorescent intensity [MFI]≥484 & <1000) or ii) high seroreactivity (MFI≥1000). Associations of moderate and high HPV16 E6 seroreactivity with i) demographic risk factors; and seropositivity for ii) other HPV16 proteins (E1, E2, E4, E7 and L1) and iii) E6 proteins from non-HPV16 types (HPV6, 11, 18, 31, 33, 45 and 52) were evaluated. Results: Thirty-two (0.7%) HPV16 E6 seropositive controls were identified; 17 (0.4%) with moderate and 15 (0.3%) with high seroreactivity. High HPV16 E6 seroreactivity was associated with former smoking (odds ratio [OR] 5.5 [95% confidence interval [CI]:1.2-51.8]), and seropositivity against HPV16 L1 (OR 4.8, 95%CI:1.3-15.4); E2 (OR 7.7, 95%CI:1.4-29.1); multiple HPV16 proteins (OR 25.3, 95%CI:2.6-119.6 for 3 HPV16 proteins beside E6) and HPV33 E6 (OR 17.7, 95%CI:1.9-81.8). No associations were observed with moderate HPV16 E6 seroreactivity. Conclusions: High HPV16 E6 seroreactivity is rare among individuals without diagnosed cancer and was not explained by demographic factors. Impact: Some HPV16 E6 seropositive individuals without diagnosed HPV-driven cancer, especially those with seropositivity against other HPV16 proteins, may harbor a biologically relevant HPV16 infection.