Stability and plasticity also module affinity maturation of anti-protein antibodies

ACIERNO, JUAN PABLO; KLINKE, SEBASTIÁN; BRADEN, BRADFORD C; GOLDBAUM, FERNANDO ALBERTO; CAUERFF, ANA

Rosario, Santa Fé, Argentina

Congreso; XLII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2006

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Affinity maturation of antibodies against protein antigens is carried out accompanying the switch process from IgM to IgG isotype. The study of the molecular basis of affinity maturation mechanism is important to understand aspects of the humoral immune response and also for biotechnological and biomedical applications. We study two anti-lisozyme antibodies derived from the same germ lines genes recognizing the same epitope on HEL surface. The first antibody, D44.1 was obtained after a short immunization plan, and the second, mAb F10.6.6 was obtained after a long term immunization plan. F10.6.6 has a ~103 increase in affinity for antigen over D44.1. Several spectroscopic and calorimetric studies were performed in order to characterize both binding and stability. We found that Fv F10.6.6 has an increased thermal and chemical stability than D44.1 and that contacts made by VH domain contribute to the association rates while the VL domain contacts module the dissociation rates. We also tested ANS binding to Fvs molecules, finding a correlation between stability and ANS binding: the more stable the protein, the lesser the light emitted by the probe. Thus, an improvement of the variable domain stability that increases the plasticity of the VH-VL interaction results in the improvement of the binding properties of the antibody towards the antigen.