Proteolytic action of Legionella pneumophila on human serum proteins

Proteolysis by four strains of Legionella pneumophila, the etiological agent of Legionnaires disease, was studied by the method of immunoelectrophoresis. Twenty-three human serum proteins were tested as substrates. Five proteins were degraded: alpha 1-acid glycoprotein, alpha 1-antichymotrypsin, beta-lipoprotein, beta 1E-globulin, and beta 2-glycoprotein-I. Moreover, the degradation of alpha 1-antichymotrypsin was demonstrated by investigation of an enzyme-blocking test. It is suggested that the proteolytic activity of L. pneumophila may bear some relationship to its pathogenic activity.