Construction and characterisation of a recombinant fowlpox virus that expresses the human papilloma virus L1 protein

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RESEARCH

Open Access

Construction and characterisation of a recombinant fowlpox virus that expresses the human papilloma virus L1 protein Carlo Zanotto1†, Eleana Pozzi1†, Sole Pacchioni1, Massimiliano Bissa1, Carlo De Giuli Morghen1,3 and Antonia Radaelli2,3*

Abstract Background: Human papilloma virus (HPV)-16 is the most prevalent high-risk mucosal genotype. Virus-like-particle (VLP)-based immunogens developed recently have proven to be successful as prophylactic HPV vaccines, but are still too expensive for developing countries. Although vaccinia viruses expressing the HPV-16 L1 protein (HPV-L1) have been studied, fowlpox-based recombinants represent efficient and safer vectors for immunocompromised hosts due to their ability to elicit a complete immune response and their natural host-range restriction to avian species. Methods: A new fowlpox virus recombinant encoding HPV-L1 (FPL1) was engineered and evaluated for the correct expression of HPV-L1 in vitro, using RT-PCR, immunoprecipitation, Western blotting, electron microscopy, immunofluorescence, and real-time PCR assays. Results: The FPL1 recombinant correctly expresses HPV-L1 in mammalian cells, which are non-permissive for the replication of this vector. Conclusion: This FPL1 recombinant represents an appropriate immunogen for expression of HPV-L1 in human cells. The final aim is to develop a safe, immunogenic, and less expensive prophylactic vaccine against HPV.

Background Cervical cancer caused by human papilloma virus (HPV) is the second leading cause of malignancies in women worldwide, and the first in developing countries. Persistent infection with one of the approximately fifteen highrisk oncogenic HPV types can cause the onset of cervical intraepithelial neoplasia and progression to invasive cervical cancer [1]. Approximately 500,000 cases are diagnosed every year, resulting in 274,000 deaths [2,3]. The absence of specific antiviral drugs has stimulated the search for prophylactic vaccines against HPV-16 and HPV-18, which are the HPV genotypes that are most commonly associated with the disease. In particular, HPV-16 is by far the most prevalent high-risk mucosal genotype, and, as it is present in around 50% of all * Correspondence: [email protected] † Contributed equally 2 Department of Pharmacological Sciences, University of Milan, 20133 Milan, Italy Full list of author information is available at the end of the article

cervical cancers [1,4,5], it has been the focus of many recent vaccine developments. Although therapeutic vaccines are of high priority for the control of progression to neoplasia in subjects who are already infected, prophylactic vaccines are important to limit the diffusion of infection. They are therefore the best choice for intervention against HPVs, as they can neutralise the incoming virus and prevent disease progression. The preparation of a new vaccine has been hampered for a long time because of the restricted host range of the virus and its selective tropism for differentiated squamous epithelium, which makes i