Identification of Immunodominant T-lymphocyte Epitope Peptides in HPV 1, 2 and 3 L1 Protein for Novel Cutaneous Wart Vaccine

Abstract

Background: Common warts and flat warts are caused by the human papillomavirus (HPV). Peak incidence of wart infection occurs in schoolchildren aged 12-16, where prevalence can be as high as 20%. Traditional treatments aimed at destruction of wart tissue have low clearance rates and high recurrence rates. Occasional reports have even shown warts becoming malignant and progressing into verrucous carcinoma. Current licensed HPV vaccines largely target higher-risk oncogenic HPV types, but do not provide coverage of low-risk types associated with warts. To date, little attention has been given to the development of effective, anti-viral wart treatments. Objective: This study aims to identify immunodominant T-lymphocyte epitopes from the L1 major capsid protein of HPV 1, 2 and 3, a foundational step in bioengineering a peptide-based vaccine for warts. Methods: Cytotoxic T-cell and helper T-cell epitopes were predicted using an array of immunoinformatic tools against a reference panel of frequently observed MHC-I and MHC-II alleles. Predicted peptides were ranked based on IC50 and IFN-γ Inducer Scores, respectively, and top performing epitopes were synthesized and subjected to in vitro screening by IFN-γ enzyme-linked immunosorbent spot assay (ELISpot). Independent trials were conducted using PBMCs of healthy volunteers. Final chosen peptides were fused with flexible GS linkers in silico to design a novel polypeptide vaccine. Results: Seven immunodominant peptides screened from 44 predicted peptides were included in the vaccine design, selected to elicit specific immune responses across MHC class I and class II, and across HPV types. Evaluation of the vaccine′s properties suggest that the vaccine is stable, non-allergenic, and provides near complete global population coverage (>99%). Solubility prediction and rare codon analysis indicate that the DNA sequence encoding the vaccine is suitable for high level expression in Escherichia coli. Conclusions: In sum, this study demonstrates the potential and lays the framework for the development of a peptide-based vaccine against warts.