Low doses of flagellin-L2 multimer vaccines protect against challenge with diverse papillomavirus genotypes

Kirill Kalnin, Timothy Tibbitts, Yanhua Yan, Svetlana Stegalkina, Lihua Shen, Victor Costa, Robert Sabharwal, Stephen F. Anderson, Patricia M. Day, Neil Christensen, John T. Schiller, Subhashini Jagu, Richard B.S. Roden, Jeffrey Almond, Harold Kleanthous

Research output: Contribution to journalArticlepeer-review

37 Scopus citations


Genetically modified bacterial flagellin (Fla), a Toll-like receptor-5 (TLR5) ligand, was evaluated as a fusion partner for human papillomavirus (HPV) L2-based immunogens in two animal challenge models; either cutaneous inoculation of rabbits with HPV 'quasivirions' containing cottontail rabbit papillomavirus (CRPV) genomes that induce warts, or intra-vaginal inoculation of mice with HPV 'pseudovirions' encapsidating a luciferase reporter plasmid and measurement of bioluminescence to determine infectivity. An Escherichia coli production system was developed for flagellin-L2 (Fla-L2) fusions containing either monomeric HPV-16 L2 a.a. 11(× 11-200) or oligomeric L2 comprising a fusion of the a.a. 11-88 peptides of five (Fla~5 × 11-88) or eight (Fla~8 × 11-88) genital HPV types. Immunogenicity and bioactivity of Fla-L2 constructs were assessed using an in vitro neutralization and cell-based TLR-5 binding assay, respectively. Efficacy was evaluated following active immunization of rabbits or mice administered 3 intramuscular doses of Fla-L2 recombinants without exogenous adjuvant, followed by challenge. In addition, passive immunization studies of naïve rabbits with serial dilutions of pooled immune sera were used to determine End-Point Protection Titers (EPPT) for each formulation against a broader spectrum of HPV quasivirions. Efficacy was assessed for up to 10 weeks on the basis of wart volume induced following challenge and results compared to licensed L1-VLP vaccines (Gardasil and Cervarix). Following active immunization at doses as low as 1. μg, Fla-L2 fusions afforded complete protection against infection (mice) and disease (rabbits) following either homologous or heterologous HPV challenge. Passive immunization with anti-L2 immune sera discriminated between the different vaccine candidates under evaluation, demonstrated the protective role of antibody and suggested the superiority of this oligomeric L2-TLR5 agonist fusion approach compared to L1-based vaccines in its ability to cross-protect against non-vaccine HPV types.

Original languageEnglish (US)
Pages (from-to)3540-3547
Number of pages8
Issue number28
StatePublished - Jun 12 2014

All Science Journal Classification (ASJC) codes

  • Molecular Medicine
  • General Immunology and Microbiology
  • General Veterinary
  • Public Health, Environmental and Occupational Health
  • Infectious Diseases


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