| Description |
Rabbits produce a capsular antibody that can be detected by the specific capsular reaction test, precipitin test and the hemagglutination test. Detection of capsular antibody in mouse serum by these test was unsuccessful. Antibody in mouse sera was detected by the Roger bacterial agglutination test using mouse anti-sera and dilutions of a six hour broth culture of S. aureaus, strain NB-1, as antigen. By this method it was found that germ free mice had a titer of 1:10 or less and pools of human serum collected in the winter and summer months and a titer of 1:160 and 1:640 respectively. These titers of germ free mouse serum and pooled human serum were unaltered by absorption with S. aureaus, strain NV-1, or Escherichia coli organisms. Five hundred µgms of capsular material was found to be the optimal dose for antibody production in the mouse. Mice having a pre-immunization titer of 1:160 or less gave a better antibody response to capsular material than mice with a pre-immunization titer of 1:320 or more. It is believed that mice with a high pre-immune titer went into a negative phase or a state of antibody suppression following immunization with capsular material It would appear that capsular material is an agglutinogen that is strongly antigenic in rabbits. In mice the antibody titer reaches its maximum in two to three weeks and returns to the pre-immune level in four to six weeks. The antibody produced in conventional mice was found to be specific for S. aureus. It was absorbed out of serum by a heavy suspension of S. aureus, strain NB-1, and not absorbed by a heavy suspension of Escherichia coli. Total protein determinations and electrophoretic analysis of serum from mice immunized with capsular material showed an average decreased total protein with a decrease in the beta globulin and an increase in the gamma globulin. The increase in the gamma fraction is believed to be due to an increase in the IgG1 fraction. Since this fraction does not appear in mice for periods up to 30 to 60 days, it is possible the early IgG1 globulin is being measured by the Boger method and is not being detected by the other serological tests used in this work. There is no evidence that IgM antibodies fail to react in conventional test but according to Fahey (1962), Berlin (1964) and Pike (1967) these IgM antibodies are slow to react, have poor avidity and are more temperature sensitive than the IgG antibodies. The decrease in total serum protein following immunization with capsular material may have been due to an induced negative phase following immunization with capsular material. Mice immunized with a Whole cell suspension of S. aureus, strain NB-1, demonstrated a greater rise in serum gamma globulin than that produced by capsular material. This greater stimulation may have been due to other components of whole cells or to failure of isolated capsular material to function as an antigen. Studies of hyperimmune ascites fluids produced in mice by the K II strain of ascites tumor cell produced serological and chemical findings similar to those of serum. Even through large amounts of hyperimmune ascetic fluid were obtained the results of the protein determinations were similar to those of serum. There was an overall average decreased in total protein and a corresponding increase in the albumin and globulin fractions giving an albumin:globulin ratio similar to that of serum. Mice immunized with whole cells of strain NV-1 produced gama globulin in their ascetic fluid that was two one-half times that found in normal mice and mice immunized with capsular material had only 25% more gamma globulin in their ascetic fluid than the normal mice. Ascited fluids produced in mice immunized with whole NB-1 organism were absorbed with homologous organism at 4? C for seven days. Electrophoretic studies on the absorbed ascites fluid showed a reduction in the gamma globulin fraction of 50%. This suggests that the increased gamma globulin present before may have been antibody. One LD50 of S. aureus, strain NB-1, was estimated to be 7.8 x107 organisms. One LD50 of the Smith variant strain 872 was estimated to be less than 106 organism. The proposed reason for this difference in LD50's for the two organisms is that the Smith variant strain 872 in possible not as widespread in nature. Therefore the mice might have less contact with strain 872 and would have a low antibody titer to it. It is also possible that capsular antigens of strain 872 are different from the NB-1 strain and hence immunization of the mouse does not stimulate specific antibodies protecting against the Smith variant 872, It was found that capsular material in less than microgram amounts seemed to sensitize mice to lethal inoculations of live vaccine. Serologically and electrophoretically they had an elevated gamma globulin but immunologically there was negligible protection against a lethal challenge. |
