Production of Recombinant Polyepitopic HPV16-E6 Antigen: the Effects of various Strains and Expression Conditions

Cervical cancer is the leading cause of morbidity and cancer mortality in women throughout the world and persistent infection with human papillomavirus (HPV) is the main etiology for the development of this cancer. Peptide vaccines derived from E6 and E7 oncogenes are promising candidates for HPV vaccine production due to their safety, high stability, and ease of production. In the current study, expression strains such as Escherichia coli BL21 (DE3), BL21 (DE3)-AI, Rosetta, C41 (DE3), and BL21 (DE3)-pLysS were applied for poly epitopic E6 expression and the effects of temperature, induction time, and inducer concentration on the expression level of recombinant HPV16-E6 polypeptide protein were examined in the mentioned strains.

In the present study, the optimized gene of E6 recombinant protein was cloned into pET28a vector under the control of T7 promoter and the resulting plasmid was successfully transformed into Escherichia coli strains BL21 (DE3), BL21 (DE3)-AI, Rosetta, C41 (DE3), and BL21 (DE3)-pLysS. Then, the ability of these strains to express the desired recombinant protein in different conditions was compared.  Two temperatures of 25 ° C and 37 ° C, IPTG concentrations between 0.1 and 1.0 mM, and different incubation times were selected to examine the expression level of recombinant E6 protein in these strains.

The highest level of expression was obtained in Escherichia coli BL21 (DE3) -AI strain inducing at Optical Density (OD) of 0.9, 0.1 mM IPTG, and 16 hours induction at 25 °C.

The results of this study can be used to produce E6 protein as a vaccine candidate in the treatment of HPV-related cancers.