Study of the chemical and immunogenic properties of the capsular Staphylococcus aureus antigen. 2. Evaluation of the immunogenic properties of the capsular antigen in experiments in vitro

: Albino mice were immunized with a purified capsular antigen isolated from the S. aureus strain 1193/74. The presence of specific anticapsular antibodies in the sera of animals were determined by two methods: 1) by conversion of diffuse growth of a homologous strain into compact one, and 2) by determination of opsonic index in phagocytosis of homologous staphylococci by human neutrophils. It was revealed that antibodies converting the microbical growth were absent in the sera of normal mice and reached the highest level after the second antigen injection; opsonins were present in the sera of normal mice in widely varying quantities; their maximal level was noted after the 3rd immunization.