The Rubella Virus IgG (Avidity) ELISA Kit (ab247202) is designed to indicate the avidity of rubella-specific IgG in human serum or plasma (citrate, heparin) to differentiate between acute and past infections.
The qualitative immunoenzy Matic determination of specific antibodies is based on the ELISA (enzyme-linked immunosorbent assay) technique. The microplates are coated with specific antigens to bind the corresponding antibodies in the sample (double pipetting). After washing the wells to remove all unbound sample material, one well is incubated with Avidity Reagent and the corresponding well with Wash Buffer.
The avidity reagent removes low avidity antibodies from antigens, while high avidity antibodies are still bound to specific antigens. After a second wash step to remove the remaining avidity reagent and low avidity antibodies, a horseradish peroxidase (HRP) labeled conjugate is added. This conjugate binds to the captured antibodies. In a third washing step, the unbound conjugate is removed.
The immune complex formed by the bound conjugate is visualized by adding tetramethylbenzidine (TMB) substrate which gives a blue reaction product. The intensity of this product is proportional to the number of specific antibodies in the sample. Sulfuric acid is added to stop the reaction. This produces a yellow endpoint color. The absorbance at 450/620 nm is read using an ELISA microwell plate reader.
The presence of IgG antibodies to the rubella virus indicates the onset of infection but does not distinguish between recent and past infections. Virus-specific IgM antibodies are first detected in approximately ten days and peak approximately four weeks after infection. They can persist for several months after acute infections.
Based on the evidence that antibody avidity gradually increases after exposure to an immunogen, IgG antibody avidity can be used as a marker to distinguish recent from long-term primary infections. Avidity describes the binding strength of a specific antibody to its antigen. Low avidity IgG antibodies indicate a primary infection, whereas the presence of high avid IgG antibodies indicates persistence or reactivation of infection.