Antibodies to inhibin and conjugates produced therefrom

Abstract

A 32,000-Dalton protein with inhibin activity is isolated from porcine follicular fluid which is composed of two chains having molecular weights of about 18,000 and about 14,000 Daltons, which are bound together by disulfide bonding. Microsequencing revealed the NH.sub.2 -terminal portion of the 18 kD chain to be Ser-Thr-Ala-Pro-Leu-Pro-Trp-Pro-Trp-Ser-Pro-Ala-Ala-Leu-Arg-Leu-Leu-Gln-Ar g- Pro-Pro-Glu-Glu-Pro-Ala-Val and of the 14 kD chain to be Gly-Leu-Glu-Cys with the next 21 residues believed to be Asp-Gly-Ser-His-Asn-Leu-Asp-Ser-Arg-Gln-Gln-Phe-Phe-Ile-Asp-Phe-Arg-Leu-Il e-G y-Trp. This 32 kD protein specifically inhibits basal secretion of FSH, but not of LH. Antibodies raised against a synthetic replicate of the N-terminal six residues of the 18 kD chain are effective to reduce the activity of highly purified 32 kD inhibin and may be administered to mammalian animals for the purpose of neutralizing endogenous inhibin and thereby increasing gonadotropin secretion. The antibodies are also useful in immunoassays to determine inhibin levels in mammalian fluids. To generate the antibodies, short chain peptides are synthesized which mimic portions of natural mammalian inhibin protein chains, the synthetic peptides are conjugated to large carrier molecules and the conjugates are used as inoculum to induce a mammalian immune system to produce inhibin-reactive antibodies.