Measuring serum antibody to human papillomavirus following infection or vaccination

The family of human papillomaviruses (HPVs) includes more than 130 genotypes, many of which infect the genital tract, and these can be classified as low risk or high risk for induction of genital neoplasia. Two prophylactic vaccines are currently available for the prevention of genital HPV infection: a quadrivalent (Gardasil); Merck & Co. Inc) and a bivalent (Cervarix; GlaxoSmithKline) vaccine. Protection against HPV infection and associated disease is observed for at least 6.4 years following immunization with the bivalent vaccine and for at least 8.5 years with the HPV 16L1 virus-like particle of the quadrivalent vaccine. HPV vaccines induce robust immune memory, as evidenced by recall of responses after revaccination, suggesting that immunization will afford long-lasting protection. An immunological marker for ongoing protection from infection would provide information to help establish best-practice deployment of these vaccines. However, while HPV-specific antibody is likely the major mechanism of protection against HPV infection following immunization, available serological assays provide only a partial characterization of immune status, and no measured immune response has been shown to define immediate or future protection against HPV infection or associated disease. Future research efforts should therefore be directed towards correlating measures of virus-specific immune memory with continued protection against infection with the HPV types in the available vaccines, and towards determining the duration of cross-protection afforded by these vaccines against HPV types other than those incorporated in the vaccines.