Bac to Bac System Efficiency for Preparing HPV Type ۱۶ Virus-Like Particle Vaccine

Today, the human papillomavirus (HPV) L۱ protein is the main target in the construction of prophylactic HPV vaccines. The production of virus-like particles (VLPs) that closely resemble the natural structure of the HPV۱۶ virus and induce high levels of virus-neutralizing antibodies in animals and humans is facilitated by the expression of HPV۱۶-L۱ protein in eukaryotic cells. The Bac-to-Bac system has been previously used to produce high levels of recombinant proteins. In this study, we utilized this expression system to generate HPV۱۶-L۱ VLPs in Spodoptra frugipedra (Sf۹) insect cells. The wild-type L۱ gene of papillomavirus type ۱۶ was selected from Gene Bank and placed in bacmid structure after codon optimization using pFast Bac vector. The recombinant baculovirus containing HPV-۱۶/L۱ gene was then provided using the Bac-to-Bac system. It should be mentioned that the vector was transfected into the Sf۹ cell. The cells were then lysed and the expression of L۱ protein was revealed by SDS-PAGE and confirmed by Western Blot. The L۱ purification was performed through Ni-NTA chromatography. The VLP formation of papillomavirus L۱ protein was visualized by transmission electron microscopy. The expressed recombinant L۱ was ~۶۰ KD on SDS-PAGE which was identified in western blot by a specific anti-L۱ monoclonal antibody. The electron microscopy confirmed the assembly of VLPs. Results of this study showed that the production of this protein at the industrial level can be optimized using a baculovirus/Sf۹ system. The characteristics and advantages of this system are promising and it is a suitable candidate for protein synthesis.

Keywords:

Baculovirus , HPV , L۱ , Protein purification , Sf۹ , vaccine