Abstract SY23-02: Host immune responses to HPV and HPV vaccines

Abstract

Abstract Human papillomavirus (HPV) infection is the cause of multiple cancers in both women and men. There are three different licensed HPV prophylactic vaccines. Currently licensed L1 virus-like particles (VLP)–based HPV vaccines target two to nine different HPV types and have demonstrated excellent efficacy against the targeted HPV types and associated disease. Host immune responses to HPV vaccines and infection will be presented and discussed. Briefly, HPV vaccines induce nearly 100% seroconversion to all HPV types included in the vaccine. High titers of high-affinity anti-L1 IgG antibodies, to the HPV types included in the vaccine, are generated after vaccination, and these persist for several years after vaccination at levels considerably higher than those observed in natural infection. Although correlates of vaccine protection have not been identified, neutralizing antibodies are believed to be the main effectors of protection against HPV infection. Vaccine-induced antibodies are detectable not only in serum but also at mucosal sites of infection, such as the cervix and oral cavity. Local HPV-specific antibody levels, although lower, correlate well with circulating levels. Immunogenicity data have shown noninferiority of antibody responses after two doses of HPV vaccine, and the recommended number of vaccine doses was recently reduced from three to two. There is some evidence suggesting that even one dose of the bivalent HPV vaccine may provide similar protection to the recommended dose regimens. Antibody levels following one dose of the bivalent vaccine, although lower, have been shown to be stable over 4 years of follow-up and vaccine recipients remained HPV16/18 seropositive, suggesting that a single dose of the bivalent vaccine may provide durable protection against infection. The robust immunogenicity of the HPV vaccines contrasts with the immune responses observed after natural infection, in which seroconversion has been shown in only a percentage of individuals with incident HPV infection. Furthermore, levels of antibodies induced by vaccination are much higher than the levels observed after infection and appear to be preserved over time. A better understanding of long-term protection of the vaccine as well as a more comprehensive evaluation of correlates of immune protection against HPV infection are still needed. Citation Format: Ligia Pinto. Host immune responses to HPV and HPV vaccines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr SY23-02. doi:10.1158/1538-7445.AM2017-SY23-02