Abstract
How human papillomavirus (HPV) vaccines elicit robust and enduring neutralizing antibody (nAb) responses is unknown, yet such information is valuable to vaccinology. In addition to the major capsid protein, L1, the 4-valent HPV vaccine reportedly also contains recombinant L1 DNA. Nucleic acids in vaccines can enhance antibody responses, but whether L1 DNA enhances HPV vaccine antibody responses is understudied. We tested whether 9-valent HPV (9vHPV) vaccine lots contained L1 DNA and if peak or long-term 9vHPV vaccine-elicited nAb responses were dependent on DNA sensors TLR9, AIM2, or cGAS, or STING or MyD88, the adaptors for cGAS and TLR9, respectively. To quantify L1 DNA, we extracted total nucleic acid per 9vHPV dose and applied singleplex quantitative PCR to amplify HPV6/11/16/18/31/33/45/52/58 L1 sequences. Wildtype mice (wt; C57BL/6J) or mice deficient in DNA sensing pathways (TLR9(-/-), AIM2(-/-), cGAS(-/-), STING(gt/gt), MyD88(-/-)) were administered 9vHPV vaccine or equivalent adjuvant only at 0, 4, and 12 weeks. We measured serum HPV16 and HPV18 nAb titers at 16, 26, 40, and 53-56 weeks and HPV16- and HPV18-specific bone marrow plasma cell responses at 53-56 weeks. We detected 5-44 and 104-351 copies of HPV6 and HPV18 L1 DNA per 9vHPV vaccine dose, but no other types (n=3 lots). We found no consistent difference in geometric mean nAb titers between mice strains that received 9vHPV at any time point tested or in median HPV16- or HPV18-specific plasma cell frequencies. Thus, we conclude the magnitude and durability of nAb responses to 9vHPV vaccination do not depend on DNA sensing pathways.