Preparation and mass spectrometric study of egg yolk antibody (IgY) against rabies virus

Rabies virus was used as the antigen to immunize laying chickens. Anti-rabi es virus immunoglobulin Y(IgY) was isolated from yolks of the eggs laid by these chickens using a two-step salt precipitation and one-step gel filtrat ion protocol. The purified IgY was reduced with dithiothreitol, and heavy c hains (HC) and light chains (LC) were obtained. In addition, the purified I gY was digested with pepsin and the fragment with specific antigen binding properties (Fab) was produced. Using matrix-assisted laser desorption/ioniz ation mass spectrometry (MALDI-TOFMS), the average molecular weights of IgY , HC, LC, and Fab were determined as 167 250, 65 105, 18 660, and 45,359 Da , respectively. IgY has two structural differences compared with mammalian IgGs. First, the molecular weight of the heavy chain of IgY is larger than that of its mammalian counterpart, while the molecular weight of the light chain of IgY is smaller. Second, upon pepsin digestion, anti-rabies virus I gY is degraded into Feb, in contrast to mammalian IgG, which has been repor ted to be degraded into F(ab')(2) under the same conditions. Copyright (C) 2001 John Wiley & Sons, Ltd.