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>> Epidemiologic Study of anti HPV16/18 seropositivity and subsequent risk of HPV16 and 18 infections

17:15 PM - 17:30 PM

Room 517a

Mahboobeh Safaeian1, Carolina Porras2, Mark Schiffman1, Ana Cecilia Rodriguez2, Sholom Wacholder1, Paula Gonzalez2, Wim Quint3, Valérie Xhenseval4, Rolando Herrero2, Allan Hildesheim1.

1National Cancer Institute, National Institutes of Health, Bethesda, MD, USA; 2Proyecto Epidemiológico Guanacaste, Fundación INCIENSA, San José, Costa Rica; 3DDL Diagnostic Laboratory, Voorburg, The Netherlands; 4GlaxoSmithKline Biologicals, Rixensart, Belgium .

Background: We examined whether women with antibodies elicited against natural infections with human papillomavirus (HPV) 16 or HPV18 are at reduced risk of subsequent new detection of homologous HPV genotypes compared to seronegative women. We also examined this association for HPV31 and 45, closely related genotypes to HPV16 and 18, respectively, with some cross-protection reported following HPV16/18 vaccination.

Methods: Data are from the control arm of the ongoing NCI-sponsored, randomized, HPV16/18 Costa Rica Vaccine Trial. Two overlapping analytic groups included women who were baseline cervical HPV16 DNA-negative (n=2813) and/or cervical HPV18 DNA-negative (n=2950). The main outcome was detection of new cervical HPV16 or HPV18 DNA using a type-specific HPV-DNA assay over 4 years follow-up. We compared rate ratios of newly detected cervical HPV16 or HPV18 infection among HPV-seropositives and seronegatives, determined using a polyclonal ELISA assay.

Results: We detected 291 new HPV16 infections during 7,843 person-years (PY) (crude-incidence (IR):3.7/100PY [95% confidence interval (95%CI):3.3-4.2]); and 178 new HPV18 infection during 8,407 PYs (IR:2.1/100PY [95%CI:1.8-2.4]). After controlling for risk factors associated with newly detected HPV infection, women with the highest HPV16 antibody tertile had a significantly reduced risk for subsequent infection with HPV16 (adjusted rate ratio (ARR):0.50, 95%CI:0.26-0.86 compared to HPV16-seronegatives). Similarly, women in the highest HPV18 antibody tertile had a significantly reduced risk for subsequent infection with HPV18 (ARR:0.36, 95%CI:0.14-0.76 compared to HPV18-seronegatives). We did not observe any association between enrollment HPV16 serostatus and incident HPV31 infection (IR:0.96, 95%CI:0.55-1.58 with the highest tertile, compared to HPV16- seronegatives) or HPV18 and subsequent HPV45 infection (IR:1.16, 95%CI:0.64-1.94 with the highest tertile, compared to HPV18-seronegatives).

Conclusions: In this cohort of more than 2,500 sexually-active women, those with high antibody levels of HPV16 and HPV18 following natural infection had a significantly reduced risk of subsequent new HPV16 and HPV18 infection, though protection was partial.

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