Expression, purification and characterization of a recombinant fusion protein based on the human papillomavirus-16 E7 antigen

A fusion protein comprising a cell penetrating and immunostimulatory peptide corresponding to residues 32 to 51 of the Limulus polyphemus protein linked to human papillomavirus (HPV)-16 E7 antigen (LALF(32-51)-E7) was expressed in E. coli BL21 (DE3) cells. The recombinant protein in E. coli accounted for approximately 18% of the total cellular protein and purified with a single affinity chromatographic step. Yields of approximately 38 mg purified LALF(32-51)-E7 per liter of induced culture was obtained with an overall 52% recovery and constitutes a promising setting for the future production and scaling-up. Purified protein was characterized as soluble aggregates with molecular weight larger than 670 kDa, which is considered an important property to increase the immunogenicity of an antigen preparation. The recombinant fusion protein LALF(32-51)-E7 will be a promising vaccine candidate for the treatment of HPV-16 related malignancies.