RG2-VLP: a Vaccine Designed to Broadly Protect against Anogenital and Skin Human Papillomaviruses Causing Human Cancer

Abstract

Licensed preventive HPV vaccines are composed of VLPs derived by expression of major capsid protein L1. They confer protection generally restricted to infection by the alpha HPVs targeted by the up-to-9-valent vaccine, and their associated anogenital cancers and genital warts, but do not target beta HPV that are associated with CSCC in EV and immunocompromised patients. The family of human papillomaviruses (HPV) includes over 400 genotypes. Genus alpha genotypes generally infect the anogenital mucosa, and a subset of these HPV are a necessary, but not sufficient, cause of cervical cancer. Of the 13 high-risk (HR) and 11 intermediate-risk (IR) HPV associated with cervical cancer, genotypes 16 and 18 cause 50% and 20% of cases, respectively, whereas HPV16 dominates in other anogenital and oropharyngeal cancers. A plethora of beta HPVs are associated with cutaneous squamous cell carcinoma (CSCC), especially in sun-exposed skin sites of epidermodysplasia verruciformis (EV), AIDS, and immunosuppressed patients. Licensed L1 virus-like particle (VLP) vaccines, such as Gardasil 9, target a subset of alpha HPV but no beta HPV. To comprehensively target both alpha- and beta HPVs, we developed a two-component VLP vaccine, RG2-VLP, in which L2 protective epitopes derived from a conserved alpha HPV epitope (amino acids 17 to 36 of HPV16 L2) and a consensus beta HPV sequence in the same region are displayed within the DE loop of HPV16 and HPV18 L1 VLP, respectively. Unlike vaccination with Gardasil 9, vaccination of wild-type and EV model mice (Tmc6(Delta/Delta) or Tmc8(Delta/Delta)) with RG2-VLP induced robust L2-specific antibody titers and protected against beta-type HPV5. RG2-VLP protected rabbits against 17 alpha HPV, including those not covered by Gardasil 9. HPV16- and HPV18-specific neutralizing antibody responses were similar between RG2-VLP- and Gardasil 9-vaccinated animals. However, only transfer of RG2-VLP antiserum effectively protected naive mice from challenge with all beta HPVs tested. Taken together, these observations suggest RG2-VLP's potential as a broad-spectrum vaccine to prevent alpha HPV-driven anogenital, oropharyngeal, and beta HPV-associated cutaneous cancers. IMPORTANCE Licensed preventive HPV vaccines are composed of VLPs derived by expression of major capsid protein L1. They confer protection generally restricted to infection by the alpha HPVs targeted by the up-to-9-valent vaccine, and their associated anogenital cancers and genital warts, but do not target beta HPV that are associated with CSCC in EV and immunocompromised patients. We describe the development of a two-antigen vaccine protective in animal models against known oncogenic alpha HPVs as well as diverse beta HPVs by incorporation into HPV16 and HPV18 L1 VLP of 20-amino-acid conserved protective epitopes derived from minor capsid protein L2.