Identification of protein antigens of group B streptococci, with special reference to the Ibc antigens.

Abstract

The protein antigens of prototypes of 5 types of group B streptococcal strains were extracted with HCl or Triton X-100, separated by sodium dodecyl sulfate polyacrylamide electrophoresis, transferred to nitrocellulose and examined by immunochemical staining. The Ibc proteins are shown to consist of at least 2 distinct protein antigens and their breakdown products. One antigen, the beta antigen, exists primarily as a 130,000 MW protein that is also able to bind human IgA. The alpha antigen, which has no known function, appears as a number of proteins of various MW from 20,000-120,000. Another set of antigens, the R protein antigens of type III strains, was identified as a group of acid-labile proteins varying in MW from 100,000-130,000. Two previously undescribed antigens were found that are common to all 5 group B types.