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Combined immunoprecipitation and agglutination for the detection of the heterodimeric molecule: human chorionic
1Department of Clinical Immunology, Faculty of Associated Medical Sciences, Chiang Mai University, Thailand.
Insights
A novel method detects intact human chorionic gonadotropin (hCG) by combining immunoprecipitation and agglutination. This technique accurately identifies the heterodimeric form, overcoming limitations of previous hemagglutination assays for Profasi hCG detection.
Area of Science:
- Biochemistry
- Immunology
- Assay Development
Background:
- Accurate detection of intact human chorionic gonadotropin (hCG) is crucial.
- Existing methods like reversed passive hemagglutination (RPHA) face challenges in distinguishing heterodimeric hCG from free beta subunits.
Purpose of the Study:
- To develop a reliable method for detecting intact heterodimeric hCG, specifically Profasi hCG (P-hCG).
- To overcome the cross-reactivity issues observed in single-particle hemagglutination assays.
Main Methods:
- Utilized double-particle RPHA with monoclonal antibodies against hCG alpha (ALC-1) and beta (BEL-5) subunits.
- Developed a novel 'combined immunoprecipitation and agglutination' assay.
- Employed hemagglutination inhibition to identify interfering substances.
Main Results:
- Initial RPHA showed positive results for P-hCG but also cross-reacted with free beta subunit hCG.
- Identified beta-multimer hCG as a cause of false positives.
- The combined immunoprecipitation and agglutination method successfully eliminated free beta subunits and multimers.
- The new assay specifically detected P-hCG, differentiating it from free beta subunit hCG and human luteinizing hormone (hLH).
Conclusions:
- The developed 'combined immunoprecipitation and agglutination' assay provides a specific and accurate method for detecting intact heterodimeric hCG.
- This method serves as a model for detecting other heterodimeric molecules using basic immunological techniques.
Abstract:
Double-particle reversed passive hemagglutination (RPHA) was performed for the detection of an intact heterodimeric form of human chorionic gonadotropin (intact hCG) composed in Profasi hCG (P-hCG). This technique relied on two mixed types of human O RBC, which were individually coated with two distinct monoclonal antibodies that recognized alpha or beta subunit of hCG, i.e. ALC-1 and BEL-5, respectively. The positive hemagglutination result was achieved by this technique. However, in the BEL-5 coated single-particle control system, positive results for both P-hCG and beta subunit hCG solution were realized. The occurrence of beta-multimer hCG was a causative molecule revealed by the hemagglutination inhibition technique. Thereby, the novel method called "combined immunoprecipitation and agglutination" was developed to overcome this problem. The free beta subunit together with the betamultimer hCG were eliminated from other forms presented in P-hCG after using the ALC-1 coated particles. The precipitated particles, which captured the heterodimer hCG molecule, reacted further with soluble BEL-5 to subsequently form a trellis. A positive result was obtained only with P-hCG, but not with beta subunit hCG or hLH. This study is inferable as a model for the detection of heterodimeric molecule by an elementary method.
