Prokaryotic Expression of Fusion Gene of Cat Recombinant Allergen Fel d 1 with Hepatitis B Core Antigen

To expose the cat recombinant allergen Fel d 1 protein on the outer surface of hepatitis B core antigen（HBcAg）virus-like particles（VLPs), the recombinant Fel d 1（rFel d 1）was created by linking the two genes chain 1 and chain 2 that composed the Fel d 1 protein. Then the rFel d 1 sequence was inserted into the HBcAg c/e1 loop area, replacing the amino acids between D78 and E83 in HBcAg c/e1 loop area. We successfully constructed the prokaryotic expression vector pET28a-HBcAg-rFel d 1 via gene codon optimization and synthesis. The recombinant plasmid pET28a-HBcAg-rFel d 1 was transformed into E.coli BL21(DE3）cells, then induced by IPTG, purified by Ni-NTA affinity chromatography and tested by SDS-PAGE, Western blotting and transmission electron microscopy（TEM). The fusion protein HBcAg-rFel d 1 was expressed successfully in E. coli expression system and the pure fusion protein HBcAg-rFel d 1 was purified by Ni-NTA affinity chromatography. Further, TEM confirmed the fusion protein HBcAg-rFel d 1 could assemble into VLPs. The fusion protein HBcAg-rFel d 1 could assemble into VLPs spontaneously, which laid a solid foundation for the research of the preventive and therapeutic vaccines for cat allergy.