Contribution of variable domains to the stability of humanized IgG1 monoclonal antibodies
Temperature-induced unfolding of three humanized IgG1 monoclonal antibodies and their Fab and Fc fragments was monitored by differential scanning calorimetry at neutral pH. With some exceptions, the thermogram of the intact antibody presents two peaks and the transition with the larger experimental enthalpy contains the contribution from the Fab fragments. Although the measured enthalpy was similar for all three Fab fragments studied, the apparent melting temperatures were found to vary significantly, even for Fab fragments originating from the same human germline.
Introduction
The rapid growth of the therapeutic antibody market has increased the interest in modeling of the antibody structure and in understanding the factors that affect the function and the stability of antibodies. As of 2006 there were 18 monoclonal antibodies approved for therapeutic use in US, and 14 of them were molecules of the IgG isotype.1 Among these, 50% are humanized IgG1 anti-bodies. The antibody molecule (Figure 1) is formed by two identical heavy chains (~450 residues each) and two identical light chains (~220 residues each).
