IgG1 and IgG2 immunoglobulins to Bacteroides (Fusiformis) nodosus protease in infected and immunized sheep.

Sheep experimentally infected with foot rot developed antibodies that neutralized the proteolytic activity of Bacteroides nodosus culture filtrates in vitro. Similar antibody activity developed in sheep vaccinated against foot rot. In both cases the antibody was initially only associated with the IgG2 fraction of serum, but with time there was an increase in the proportion associated with IgG1. A subsidiary protein peak devoid of antiprotease activity was observed in elution profiles of affected and vaccinated sheep.