IgY Antibodies from Birds: A Review on Affinity and Avidity

SIMPLE SUMMARY: IgY antibodies are used in research and in the development of solutions for immunotherapy and the immunodiagnosis of human and animal diseases. Affinity and avidity are forces that describe the interaction between an antigen and antibody and are important characteristics for the biological function of IgY antibodies. Therefore, these measures are fundamental variables for the development of immunodiagnostic methodologies and immunotherapy based on IgY antibodies. In this review, we address factors that influence the affinity and avidity of IgY antibodies and the methodologies used for the determination of these strengths. We observed a low number of studies on the factors influencing the maturation of IgY affinity and avidity and a wide variation in the methodologies used to determine these variables. The development of studies characterising the factors that influence the maturation of IgY antibody affinity and avidity, with standardised methodologies for the determination of these forces, is of utmost importance. ABSTRACT: IgY antibodies are found in the blood and yolk of eggs. Several studies show the feasibility of utilising IgY for immunotherapy and immunodiagnosis. These antibodies have been studied because they fulfil the current needs for reducing, replacing, and improving the use of animals. Affinity and avidity represent the strength of the antigen–antibody interaction and directly influence antibody action. The aim of this review was to examine the factors that influence the affinity and avidity of IgY antibodies and the methodologies used to determine these variables. In birds, there are few studies on the maturation of antibody affinity and avidity, and these studies suggest that the use of an adjuvant-type of antigen, the animal lineage, the number of immunisations, and the time interfered with the affinity and avidity of IgY antibodies. Regarding the methodologies, most studies use chaotropic agents to determine the avidity index. Studies involving the solution phase and equilibrium titration reactions are also described. These results demonstrate the need for the standardisation of methodologies for the determination of affinity and avidity so that further studies can be performed to optimise the production of high avidity IgY antibodies.