Inhibition of binding of sera from ovarian cyst patients to human chorionic gonadotropin and its subunits by ab212418 and SPM522 monoclonal antibodies.

Malignant ovarian tumor is a significant gynecological issue among women throughout the world. Early diagnosis, accurate prognosis of clinical course and efficacious therapy still remain a problem. Studies that preceded this work, prove that in the sera of ovarian cyst patients, there is a certain amount of naturally-occurring antibodies of IgG2 isotope, that bind to hCG and its subunits. It is important to evaluate specificity of paratopes of these antibodies for assessment of their protective capacity from ovarian cancer, early diagnosis of ovarian cancer and for developing new prognostic tests based on naturally-occurring antibodies. Main aim of the study was to assess the inhibition of binding of naturally-occurring IgG antibodies (present in blood of ovarian cyst patients) to hCG and its subunits by ab212418 and SPM522 monoclonal antibodies, which would give us a valuable information about specificity of paratopes of detected naturally-occurring antibodies. Research material and methods: We have studied sera from 10 patients with ovarian cyst. Patient selection was based on previous data of serum titration. Serum titration was done in order to assess binding to following antigens: hCG, hCGβ and hCGβCTP. Selection criteria included presence of naturally-occurring antibodies with binding abilities to tested antigens. Inhibition of binding to hCG, hCGβ and hCGβCTP by commercial, monoclonal antibodies was assessed via enzyme-linked immunoassay (ELISA). Results: Ability of commercial, monoclonal antibodies, that are specific for ovarian cyst mucins and cross-bind to hCG and its subunits, to inhibit naturally-occurring antibodies binding (present in serum of ovarian cyst patients) to hCGαβ, hCGβ and hCGβCTP was assessed. Results have demonstrated that specificity of naturally-occurring antibodies (present in ovarian cyst patients sera) differ from specificity of ab212418 (Abcam, U.S.) SPM522 (Novus Biological, U.S.) monoclonal antibodies. Conclusion: Naturally-occurring antibodies in the blood of ovarian cyst patients that bind to hCG and its subunits, are not specific for carbohydrate determinants (Gal1-3GalNAc and Gal 1-3(Fuc 1-4) GlcNAc) or binding affinity of tested commercial antibodies is weaker than avidity of binding of naturally-occurring antibodies to the same determinants.