A Method for Removing Contaminating Protein during Purification of Human Papillomavirus Type 18 L1 Protein from Saccharomyces cerevisiae

Human papillomavirus (HPV) types 16 and 18 are the main targets in the field of prophylactic vaccines for preventing cervical cancer. L1 protein, the major capsid protein of HPV, self-assembles into virus-like particles (VLP), which are the major component of prophylactic vaccines. To obtain highly purified L1 protein, contaminants must be removed by several chromatography steps. However, this requires a great deal of time and labor, and results in loss of large amounts of the target protein. Therefore, we have sought to develop an efficient method for removing contaminants prior to chromatography during the purification of HPV18 L1 protein from Saccharomyces cerevisiae. For this purpose the contaminating proteins were removed by an ammonium sulfate precipitation step and further removed by a removal of precipitated contaminants step. Purification of the L1 protein by chromatography was significantly improved by the removal of precipitated contaminants step. In the present work we developed two one-step chromatography methods (heparin and cation-exchange chromatography), and HPV18 L1 proteins purified by both methods self-assembled into VLP. The two chromatographic purification methods are simpler and more convenient than previous methods and are widely applicable to work with VLPs.