Expression of biologically active human chorionic gonadotropin and its subunits by recombinant vaccinia virus

Vaccinia virus (VV) expression vector was used to clone the genes for coding α and β subunits of human chorionic gonadotropin (hCG). Recombinant viruses VSL3 and VSS1 containing these genes were selected as blue coloured plaques on the basis of co-expression of Escherichia coli β-galactosidase in the infected cells. CV-1 cells when infected with VSL3 or VSS1 secreted 2.4 and 1.8 μg of α and βhCG subunits, respectively, per 3×106 cells after 24 h of infection. The subunit proteins expressed individually had immunoreactivity with monoclonal and polyclonal antibodies specific to hCG. The subunit hormonal peptides associated with each other during co-infection to form the complete hCG dimer, which was biologically active as evident from the induction of steroidogenesis in a mouse Leydig cell system