Production of Human Papillomavirus Type-16 L1 VLP in Pichia pastoris

Human papillomavirus-16 (HPV-16) is primary etiological agent of invasive cervical cancer development in the world population. There is no treatment for HPV infection. As a possible tool for prophylactic vaccination, the development of virus-like particles (VLPs) comprising the HPV-16 L1 capsid protein is highly preferred. The expression of HPV-16 L1 gene was carried out in Pichia pastoris. It was done as a promising vaccine candidate against HVP-16 infection for developing countries. The codon optimization for HPV-16 L1 gene was done and synthesized in pPICZA plasmid. The expression of HPV-16 L1 was evaluated in P. pastoris after induction with methanol. The purification of HPV-16 VLPs was accomplished by the ultra-centrifugation using the sucrose density gradient. The sera of 101 subjects including 16 patients positive for HPV-16 and 85 individuals negative for HPV-16 were tested by ELISA assay using anti-HPV-16 antibodies. The results of ELISA test have depicted no false positive and no false negative as compared with commercial ELISA kit. The results of HPV-16 L1 expression in P. pastoris showed a band of about 56 kDa by SDS-PAGE, and were confirmed by Western-blot assay. The formation of VLP and the self-assembly of HPV-16 L1 major capsid protein in VLP was observed by transmission electron and atomic force microscopies.