Changes in Specificity and Electrophoretic Mobility of the Precipitating Antibodies present in the Serum of Cattle recovering from Foot-and-Mouth Disease

Abstract

GRAVES¹ has shown by agar gel diffusion tests that quantitative differences exist among three different field samples (Channel Island, Ven. 1 and M.11) belonging to the same immunological type (Vallée O) of foot-and-mouth disease virus. He noticed, however, that these sub-type differences could not be clearly shown when early convalescent cattle serum (7–14 days) was used for the tests. This was due to the almost equal reaction of the immune serum with the heterologous as well as the homologous virus sub-type. During an examination of the nature of this cross-reaction by immunoelectrophoresis some interesting observations have been made regarding the mobility of the antibodies present in the sera during early convalescence. Cattle sera collected 7, 14 and 21 days after infection with the Channel Island sub-type of the virus were separated electrophoretically in agar by the method of Williams and Grabar². The separated serum proteins were then allowed to diffuse towards the homologous Channel Island virus on one side or the heterologous sub-type M.11 on the other. The 7-day convalescent serum gave a precipitin line with both sub-types of the virus whereas the 14 and 21 days sera precipitated only with the homologous Channel Island virus (Fig. 1). In addition to this cross-reaction it was observed that the precipitin lines formed by the 14 and 21 days sera were longer and nearer to the cathode than those formed by the 7 day serum.