High-level production of human papillomavirus (HPV) type 16 L1 in Escherichia coli

Human papillomavirus (HPV), a non-enveloped, double-stranded DNA tumor virus, is a primary etiological agent of cervical cancer development. As a potential tool for prophylactic vaccination, the development of virus-like particles (VLPs) containing the HPV16 L1 capsid protein is highly desired. In this study, we developed a high-level expression system of the HPV16 L1 in Escherichia coli for the purpose of VLP development. The native gene of HPV16 L1 has many rare codons that cause the early termination of translation and result in the production of truncated forms. First, we optimized the codon of the HPV16 L1 gene to the preferable codons of E. coli, and we succeeded in producing the full-size HPV16 L1 protein without early termination. Next, to find the best host for the production of HPV16 L1, we examined a total of eight E. coli strains, and E. coli BL21(DE3) with the highest yield among the strains was selected. With the selected host-vector system, we did a fed-batch cultivation in a lab-scale bioreactor. Two different feeding solutions (complex and defined feeding solutions) were examined and, when the complex feeding solution was used, a 6-fold higher production yield (4.6 g/l) was obtained compared with that with the defined feeding solution.