Expression Analysis of Recombinant Equine Chorionic Gonadotropin in Three Host Systems: E. coli BL21C, Sf insect cell lysate and COS-1 mammalian cells

Abstract

Mammalian cells are the recommended host for recombinant eukaryotic protein production aimed at incorporation of post-translational modifications for downstream applications. The bacterial system and insect cells are widely used because of ease of technical methodology, economics of production, purification and yield of final protein. The present research objective was expression of recombinant reproductive hormones of animal origin and study of their immunogenic potential for reproductive applications. The equine Chorionic Gonadotropin (eCG) is one of the most heavily glycosylated protein amongst all glycoprotein hormone family. Hence, experiments were carried out to observe its expression in the three most popular host systems and it led to comparative studies for their post-translational modifications. The Pregnant Mare Serum Gonadotropin (PMSG, also called as eCG) gene was cloned in TOPO-TA vector, pIX 4.0 and pTARGET vectors accordingly and expression analysis in E. coli BL21C, Sf insect cell lysate and COS-1 cells was carried out. We observed diverse sizes of recombinant proteins in SDS-PAGE analysis which indicated post-translational modification in mammalian expression system towards the linking of tags as well as side chains in respective host cells. Basic diagnostic immunogenicity tests showed encouraging results, however, no significant in vivo and in vitro activity was observed for the expressed reCG in all the employed host systems.