BACULOVIRUS-INSECT CELL PRODUCTION OF BIOACTIVE CHORIOGONADOTROPIN-IMMUNOGLOBULIN-G HEAVY-CHAIN FUSION PROTEINS IN SHEEP

A hybrid cDNA encoding a fusion protein between the beta subunit of hC G (beta hCG) and constant domains of a mouse IgG heavy chain (CH1-3) w as inserted into a baculovirus expression vector. Insect cells transfe cted with foreign DNA synthesized multimeric forms of fusion protein t hat inhibited hCG-induced steroid hormone secretion by mouse Leydig tu mor cells. Leydig cells were lysed by beta hCG-CH1-3 in the presence o f complement. Intravenous injection of beta hCG-CH1-3 in rams was asso ciated with testicular mononuclear leukocyte infiltration, interstitia l tissue damage, and a transient depression in circulatory testosteron e (levels returned to normal within 2 wk). It appears that targeted ce ll-killing can be mediated by recombinant proteins composed of the rec eptor-binding moiety of hormones and truncated effector (Fc) regions o f lethal antibodies.