Chimeric L2-Based Virus-Like Particle (VLP) Vaccines Targeting Cutaneous Human Papillomaviruses (HPV)

Bettina Huber,Neil Christensen,Reinhard Kirnbauer,Christoph Jindra,Saeed Shafti-Keramat,Christina Schellenbacher,Lawrence Banks

doi:10.1371/journal.pone.0169533

Bettina Huber, Neil Christensen + Show 5 more

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https://doi.org/10.1371/journal.pone.0169533

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Abstract

Common cutaneous human papillomavirus (HPV) types induce skin warts, whereas species beta HPV are implicated, together with UV-radiation, in the development of non-melanoma skin cancer (NMSC) in immunosuppressed patients. Licensed HPV vaccines contain virus-like particles (VLP) self-assembled from L1 major capsid proteins that provide type-restricted protection against mucosal HPV infections causing cervical and other ano-genital and oro-pharyngeal carcinomas and warts (condylomas), but do not target heterologous HPV. Experimental papillomavirus vaccines have been designed based on L2 minor capsid proteins that contain type-common neutralization epitopes, to broaden protection to heterologous mucosal and cutaneous HPV types. Repetitive display of the HPV16 L2 cross-neutralization epitope RG1 (amino acids (aa) 17–36) on the surface of HPV16 L1 VLP has greatly enhanced immunogenicity of the L2 peptide. To more directly target cutaneous HPV, L1 fusion proteins were designed that incorporate the RG1 homolog of beta HPV17, the beta HPV5 L2 peptide aa53-72, or the common cutaneous HPV4 RG1 homolog, inserted into DE surface loops of HPV1, 5, 16 or 18 L1 VLP scaffolds. Baculovirus expressed chimeric proteins self-assembled into VLP and VLP-raised NZW rabbit immune sera were evaluated by ELISA and L1- and L2-based pseudovirion (PsV) neutralizing assays, including 12 novel beta PsV types. Chimeric VLP displaying the HPV17 RG1 epitope, but not the HPV5L2 aa53-72 epitope, induced cross-neutralizing humoral immune responses to beta HPV. In vivo cross-protection was evaluated by passive serum transfer in a murine PsV challenge model. Immune sera to HPV16L1-17RG1 VLP (cross-) protected against beta HPV5/20/24/38/96/16 (but not type 76), while antisera to HPV5L1-17RG1 VLP cross-protected against HPV20/24/96 only, and sera to HPV1L1-4RG1 VLP cross-protected against HPV4 challenge. In conclusion, RG1-based VLP are promising next generation vaccine candidates to target cutaneous HPV infections.

Highlights

Papillomaviruses (PV) are a diverse group of non-enveloped, double-stranded, species-specific DNA viruses with strict epithelial tissue tropism
Chimeric L1-L2 fusion genes were designed that encode L1 capsid proteins of hr mucosal HPV16 or HPV18, hr cutaneous beta HPV5, or common cutaneous HPV1 L1 as scaffold to present L2 peptides via the DE surface loop
The HPV16 L1 scaffold has previously proven highly efficient in epitope display, though presenting the RG1 epitope of beta HPV17 by beta HPV5 L1 might be more advantageous in providing high-titer type-specific immunity to HPV5

Summary

Introduction

Papillomaviruses (PV) are a diverse group of non-enveloped, double-stranded, species-specific DNA viruses with strict epithelial tissue tropism. While genus alpha contains HPV types that infect mucosal or cutaneous epithelia, types of the other genera predominantly infect the skin, site specificity is not complete [2]. Alpha HPV infections cause ano-genital warts (condylomata acuminata), and persistent infection with hr types may cause cervical cancers (CxCa), most anal cancers, and a subset of vaginal, vulvar, penile, and oro-pharyngeal (tonsil and base of tongue) cancers. About 13 mucosal hr types, in particular HPV16 and 18, account for practically all CxCa cases worldwide, while lr HPV, most often HPV6 and 11, cause benign genital warts and, infrequently, recurrent laryngeal papillomatosis. Common cutaneous types HPV1, 2, 3, 4, 10, 27, 57 induce benign common and palmo-plantar warts, a frequent nuisance in children, and in adults and immunosuppressed patients, causing a significant burden to health care systems [3]. In immunosuppressed patients including HIV positive and organ transplant recipients (OTR), warts are more numerous, tend to persist, are more difficult to treat and prevalence increases with time of immunosuppression [5,6,7]

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