bac to bac system efficiency for preparing hpv type 16 virus-like particle vaccine

today, the human papillomavirus (hpv) l1 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 hpv16 virus and induce high levels of virus-neutralizing antibodies in animals and humans is facilitated by the expression of hpv16-l1 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 hpv16-l1 vlps in spodoptra frugipedra (sf9) insect cells. the wild-type l1 gene of papillomavirus type 16 was selected from gene bank and placed in bacmid structure after codon optimization using pfast bac vector. the recombinant baculovirus containing hpv-16/l1 gene was then provided using the bac-to-bac system. it should be mentioned that the vector was transfected into the sf9 cell. the cells were then lysed and the expression of l1 protein was revealed by sds-page and confirmed by western blot. the l1 purification was performed through ni-nta chromatography. the vlp formation of papillomavirus l1 protein was visualized by transmission electron microscopy. the expressed recombinant l1 was ~60 kd on sds-page which was identified in western blot by a specific anti-l1 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/sf9 system. the characteristics and advantages of this system are promising and it is a suitable candidate for protein synthesis.