Discriminatory effect of anti-Pr-β-hCG-TT antibodies on the neutralization of the biological activity of placental and pituitary gonadotropins

Serum from monkeys and human subjects immunized with an anti-hCG vaccine, Pr-β-hCG-TT, have been analyzed for their capacity to neutralize hCG/LH induced biological effects in two test systems. The monkey antiserum blocked completely the hCG induced ovulation in mice, but the same amount of the antiserum and even two-fold higher concentrations, did not reduce the number of ovulating animals on priming with ovine LH. The immunized monkey and the human sera were competent to neutralise the hCG induced testosterone production in Leydig cells. The monkey and seven out of twelve human sera did not interfere in the hLH action on these cells. Five human sera, however, showed varying degree of inhibition of hLH induced steroidogenesis in this sensitive bioassay. These subjects nevertheless maintained regular menstrual cycles and serum progesterone levels in the luteal phase were consonant with ovulation. In a subject whose serum had shown a fairly high degree of cross-reaction with hLH in Leydig cell bioassay, estradial, hLH and progesterone levels were determined on different days throughout a menstrual cycle. The hormonal profiles were normal.