Development of HPV 35 serology assays for assessment of immune responses to HPV 35 after infection and vaccination.

Human papillomavirus (HPV) 16 and HPV 18 are the two most common HPV types leading to cervical cancer; however, HPV 35 accounts for about 2% of invasive cervical cancers worldwide and a higher percentage in women of African ancestry. Further investigation into potential cross-protection against HPV 35 by current vaccines is needed to determine whether the addition of HPV 35 antigens to the next generation of vaccines is warranted. In this study, we developed and qualified serology assays to measure antibodies against HPV 35, including enzyme-linked immunosorbent assays (ELISA) and pseudovirion (PsV)-based neutralization assays (PBNA). HPV 35 virus-like particles (VLP) and HPV 35 PsV both containing L1 (late-expressed major capsid protein) and L2 (late-expressed minor capsid protein) were successfully produced and qualified for use in these methodologies. ELISA qualification established a cutoff of 9.8 ELISA Units/mL (EU/mL) and excellent reproducibility, with an intraclass correlation coefficient (ICC) of 0.995. The PBNA qualification indicated a cutoff of 10 was suitable for assessing neutralization and that the assay was highly specific and exhibited good reproducibility with an ICC of 0.931. Qualified HPV 35 binding and neutralization assays will allow us to understand if current vaccines induce neutralizing antibody responses against HPV 35, as well as assess next-generation vaccines for HPV 35 immunogenicity, with the goal of improving protection against HPV 35 associated cancers in vulnerable populations.