In Silico Structural Prediction and Production of a Chimeric Recombinant Dickkopf-1 (DKK-1) Antigen

Dickkopf (DKK) family of proteins are known as antagonists for the Wnt-β-catenin signaling pathway. It is suggested that the Dickkopf-1 (DKK-1) has a role in several diseases such as hepatocellular carcinomas, hepatoblastomas, Wilms’ tumors, lung cancer and Myeloma bone disease. The aim of the present study was to produce a chimeric-recombinant DKK-1 protein in order to induce immune response against the antigen. The recombinant Dickkopf-1 (rDKK-1) protein was designed using bioinformatics analysis. The standard methods were used for cloning, expression and purification. The structure of recombinant protein was analyzed by spectroscopy methods. Enzyme-linked immunosorbent assay (ELISA) and Western blotting were performed to confirm the recombinant protein using a commercial anti-DKK-1 (whole protein) polyclonal antibody. The immunogenicity of the recombinant DKK-1 was assessed by immunizing, intraperitoneally, BALB/C mice four times with the 31-kDa and 45-kDa purified rDKK-1 cloned in pET28a and pET32a vectors respectively. The antibody titer was measured in due course of time. Stronger immunogenic parts of the protein were selected based on in-silico predictions and recombinant protein was successfully designed. The chimeric gene was sub-cloned, expressed, purified and refolded. The purified protein was confirmed by Western blotting and ELISA. The three dimensional structural was confirmed by CD spectrum and predicted structures by bioinformatics tools, revealed the stability of helix structures. rDKK-1 protein was capable of inducing immune response with high titer antibody and  excessive humoral immune response. No significant difference was observed between immunization by 31-kDa and 45-kDa antigen.