Expression of recombinant Cap antigen of porcine circovirus type 2 in the chloroplast of Chlamydomonas reinhardtii

The capsid (Cap) protein encoded by the <i>ORF2</i> gene of porcine circovirus type 2 is the major immunogen for the development of vaccines and can effectively reduce the incidence of porcine circovirus-associated diseases. In order to explore an efficient expression pathway of the recombinant Cap protein, using the <i>Chlamydomonas reinhardtii</i> chloroplast as the expression platform of the Cap protein, <i>C. reinhardtii</i> chloroplast expression vector pCR02 of the optimized <i>ORF2</i> gene was constructed and transferred into the <i>C. reinhardtii</i> chloroplast using the biolistic bombardment method. After multiple rounds of resistance screening and culturing, PCR, RT-PCR, Western blotting, and ELISA were used to detect the <i>ORF2</i> gene and the expression of the Cap protein in <i>C. reinhardtii</i> transformants. The results of the study showed that the <i>ORF2</i> antigen gene had been correctly integrated into the specific site of the <i>C. reinhardtii</i> chloroplast genome, and the Cap protein was effectively expressed. These results suggested that the <i>C. reinhardtii</i> chloroplast is a potential platform for the production of recombinant antigen proteins and provided important support for exploring new production pathways of recombinant pharmaceutical proteins.