Cell growth conditions and purification methods are important in determining biopharmaceutical activity. However, in studies aimed at manufacturing virus-like particles (VLPs) for the purpose of creating a prophylactic vaccine and antigen for human papillomavirus (HPV), the effects of the presence of a resin-bound ligand during purification have never been investigated. In this study, we compared the structural integrity and immunogenicity of two kinds of VLPs derived from HPV type 16 (HPV16 VLPs): one VLP was purified by heparin chromatography (hHPV16 VLP) and the other by cation-exchange chromatography (cHPV16 VLP). The reactivity of anti-HPV16 neutralizing monoclonal antibodies (H16.V5 and H16.E70) towards hHPV16 VLP were significantly higher than the observed cHPV16 VLP reactivities, implying that hHPV16 VLP possesses a greater number of neutralizing epitopes and has a greater potential to elicit anti-HPV16 neutralizing antibodies. After the application of heparin chromatography, HPV16 VLP has a higher affinity for H16.V5 and H16.E70. This result indicates that heparin chromatography is valuable in selecting functional HPV16 VLPs. In regard to VLP immunogenicity, the anti-HPV16 L1 IgG and neutralizing antibody levels elicited by immunizations of mice with hHPV16 VLPs were higher than those elicited by cHPV16 VLP with and without adjuvant. Therefore, the ability of hHPV16 VLP to elicit humoral immune responses was superior to that of cHPV16 VLP. We conclude that the specific chromatographic technique employed for the purification of HPV16 VLPs is an important factor in determining the structural characteristics and immunogenicity of column-purified VLPs.
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, selfassembles 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.
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