Hao-Chia Chen

Limitation of the specific serum radioimmunoassay for human chorionic gonadotropin in the management of trophoblastic neoplasms

Two cases of recurrent trophoblastic disease are presented in which human chorionic gonadotropin was detected in assays of urine concentrates at a time when serum levels were undetectable by a sensitive and specific beta-subunit radioimmunoassay. The potential greater usefulness of measurements of urinary concentrates is discussed.

Diagnosis of pregnancy in chimpanzees using the nonhuman primate pregnancy test kit.

The usefulness of The Nonhuman Primate Pregnancy Test kit for diagnosis of pregnancy in chimpanzees was determined. This hemagglutination inhibition test for urinary chorionic gonadotropin accurately indicated conception by positive responses in 151 to 153 specimens collected between 20 and 133 days after the estimated day of fertilization. The rate of false positive responses did not exceed 1%.

Limitations and Problems of hCG-Specific Antisera

Production of antisera against intact hCG, its subunits or the unique carboxyl-terminal glycopeptide of the β-subunit, and subsequent development of radioimmunoassay systems based on these antisera, have been shown to be highly valuable for basic and clinical investigations related to pregnancy, trophoblastic neoplasms, and some non-trophoblastic neoplasms. Unlike in vitro and in vivo bioassays, and radioimmunoassays using an antiserum against hCG, radioimmunoassay systems based on either a selected antiserum against the highly purified 8-subunit of hCG or the carboxyl-terminal peptide of hCGβ (known as Sb6 and H93, respectively) permit differentiation of hCG from the structurally similar hLH. However, despite their advantages these hCG-specific radioimmunoassay systems have exhibited a number of limitations in practice. In the light of recent developments such as the finding of small amounts of hCG or hCG-like substances in biological fluids and non-placental tissues of normal subjects, and the use of antifertility vaccines employing hCGβ or a portion of its molecule as antigen, the necessity of understanding such limitations become apparent.

A simple and effective solvent system for elution of gonadotropins from concanavalin A affinity chromatography

Elution of gonadotropins and other glycoproteins from concanavalin A has been previously performed with competitive ligands such as α-methyl-d-mannopyranoside and α-methyl-d-glucopyranoside. In comparative studies we found that 1 m NH4OH was a highly effective eluent solution and gave nearly complete recovery of gonadotropin as revealed by protein contents, immunological, and biological activities. Advantages of 1 m NH4OH over the sugar derivatives are its low cost and volatile nature, and its ability to irreversibly inactivate concanavalin A. The use of this system permits further steps of purification to be performed directly or after lyophilization without dialysis.

Antigenic similarities to HCG subunits among chorionic gonadotropins of nonhuman primates.

Comparison of antigenic similarity between human chorionic gonadotropin (HCG) subunits and the chorionic gonadotropins of six species of nonhuman primates indicates marked similarity of antigenic determinants between both subunits of HCG and the chorionic gonadotropins of chimpanzees, gorillas, and orangutans. Antisera to HCG subunits (alpha or beta) did not cross-react with the chorionic gonadotropins of baboons, macaques, or marmosets. Because of the relative availability of chimpanzees for laboratory studies, we suggest that chimpanzees may be the optimal nonhuman primate model for determining the advisability of vaccinations in man using conjugates of HCG fragments to achieve fertility control or for suppression of HCG-producing neoplasms.