VLP Production from Recombinant L1/L2 HPV-16 Protein Expressed in Pichia Pastoris

Human papillomavirus 16 is considered a causative agent of genital cancers. Since there is no decisive treatment, the only approach is vaccination of high-risk group.

This study aimed to produce a chimeric L1/L2 protein in Pichia Pastoris system.

To develop VLPs of chimeric L1/L2 protein HPV-16, first, a cross-neutralizing epitope of HPV-16 L2 gene was inserted into L1 HPV-16 gene. Then the chimeric L1/L2 HPV-16 was inserted in pPICZA plasmid and expressed in Pichia pastoris (P. pastoris). The final purification of VLPs was carried out by ultra-centrifugation (130000 g) using 10-40% sucrose density gradient for 4 h at 4 °C. The SDS-PAGE and western blot assay was carried out for L1-HPV-16 and L2-HPV- 16 proteins separately. Amount of 55ng of the purified VLPs was coated to the wells of ELISA for detection of L1 HPV-16 antibody and L2-HPV-16 antibody by ELISA test separately using commercial L1-HPV-16 and L2-HPV-16 antibodies. The sera of 16 patients positive for HPV-16 and 85 sera negative for HPV infections were tested for detection of HPV-16 antibody by ELISA test and the results were compared with commercial test kit.

The formation and purified VLPs were observed by TEM and AFM. The result of purified VLPs by SDS-PAGE showed a band of 60 KD and confirmed by western blot assay. The results of ELISA for detection of L1-HPV-16 antibody and L2 -HPV-16 antibody showed positive reaction which displayed similar sensitivity with commercial test kit.

The present study will pave the way for producing recombinant pan-HPV vaccine.