||Porras C, Bennett C, Safaeian M, Coseo S, Rodríguez AC, González P, Hutchinson M, Jiménez S, Sherman ME, Wacholder S, Solomon D, van Doorn LJ, Bougelet C, Quint W, Schiffman M, Herrero R, Hildesheim A, Costa Rica HPV Vaccine Trial (CVT) Group, Alfaro M, Barrantes M, Bratti MC, Cárdenas F, Cortés B, Espinoza A, Estrada Y, González P, Guillén D, Herrero R, Jiménez SE, Morales J, Morera LA, Pérez E, Porras C, Rodriguez AC, Villegas M, Freer E, Bonilla J, Silva S, Atmella I, Ramírez M, Hildesheim A, Lowy DR, Macklin N, Schiffman M, Schiller JT, Sherman M, Solomon D, Wacholder S, Pinto L, Garcia-Pineres A, Eklund C, Hutchinson M, Quint W, van Doorn LJ
||BACKGROUND: Not all women infected with HPV-16/18 have detectable levels of HPV-16/18 antibodies, those who seroconvert develop low antibody levels, and seroconversion occurs typically several months post-infection. We evaluated determinants of seropositivity among 646 women infected with HPV-16 and/or HPV-18. METHODS: Data are from the enrollment visit of the NCI-sponsored Costa Rica HPV Vaccine Trial. Sera were tested for HPV-16/18 antibodies by ELISA; cervical specimens were tested for HPV DNA using HC2 and SPF10/LiPA25. Odds ratios (OR) and 95% confidence intervals (CI) were computed. RESULTS: Among HPV-16/18 DNA positives, seropositivity was 63.0% and 57.5%, respectively. Among HPV-16 DNA positives, seropositivity increased with lifetime number of sexual partners (p-trend = 0.01). Women with abnormal cytology and/or high viral load had a 1.63-2.79-fold increase in the detection of antibodies compared to women with normal cytology/low viral load. Current users of oral contraceptives had a 1.88-fold (95%CI, 1.14-3.09) increased detection of antibodies and current users of injectables had a 3.38-fold (95%CI, 1.39-8.23) increased detection compared to never users. Among HPV-18 DNA positive women, seropositivity was associated with current oral contraceptive use (OR 2.47; 95%CI 1.08-5.65). CONCLUSIONS: Factors associated with sustained HPV exposure (abnormal cytology, elevated HPV viral load, increasing lifetime partners) were predictive of HPV-16 seropositivity. Hormonal contraceptive use was associated with seropositivity suggesting an effect of hormones on immune responses to HPV. Patterns were less consistent for HPV-18. Follow up of incident HPV infections to evaluate seroconversion and their determinants is needed.