Expression, purification and immunological characterization of the transforming protein E7, from cervical cancer‐associated human papillomavirus type 16

E7 is the major oncogenic protein produced in cervical cancer‐associated human papillomavirus type 16 (HPV16). This protein was expressed in Escherichia coli as a glutathione‐S‐transferase (GST) fusion protein. E7‐enriched inclusion bodies were collected from bacterial lysates, were solubilized in 10  M urea, and the protein was purified using anion exchange column chromatography. After removal of endotoxin with serial Triton X‐114 extractions, material of high purity (about 90%) was obtained, which is suitable for use in a human clinical trial. This material was immunogenic, and when used as a vaccine, protected mice against challenge with an HPV16 E7 DNA transfected tumour cell line. Based on this observation, the E7GST fusion protein is currently being used in a human clinical trial of a vaccine against HPV16‐induced cervical cancer. This fusion protein could be cleaved with thrombin to remove the GST fusion part and further purified by preparative SDS gel electrophoresis to obtain free E7 with > 98% purity.