Long-Term Levels of Cross-Reactive Antibodies following HPV Immunization

Prophylactic human papillomavirus (HPV) vaccines have shown to generate type-specific antibodies against infection with HPV 16 (proto-type HPV vaccine), HPV16/18 (Cervarix), and HPV 6/11/16/18 (Gardasil). These vaccines also appear to partially protect from infection with HPVs closely related to the targeted types, however, the duration of protection provided by both type-specific and cross-reactive antibodies is unknown. It is hypothesized that HPV vaccine-generated cross-reactive antibodies will wane more quickly than will type-specific antibodies. To characterize cross-reactive antibodies in women following HPV vaccination, 863 sera were collected from 353 women who were followed for up to 8.5 years post-HPV16 vaccination. The average number of visits was 2.47; 251 women visited the clinic more than once. Using glutathione-s-transferase-HPV L1 fusion proteins bound to glutathione-casein coated Luminex beads, antibody levels to multiple HPV types will be measured. Fusion proteins of types closely related to HPV 16 (31L1, 33L1, 35L1, 52L1, 58L1 and 67L1) and HPV 18 (39L1, 45L1, 59L1 and 68L1) will be used, as will the other vaccine types (6L1 and 11L1) and more distantly related types within the genus alpha (2L1, 51L1 and 56L1). Additionally, one HPV from a different genus (1L1 genus Mu)will be used for comparison. We will compare the level of antibodies for each non-vaccine HPV type with the level of antibodies to HPV types targeted by the HPV16/18 vaccine or the HPV 6/11/16/18 vaccine. Additionally, the change in antibody levels over time will be calculated to determine if cross-reactive antibodies wane more rapidly than vaccine-type antibodies.