title: The Ibc proteins of group B streptococci: isolation of the alpha and beta antigens by immunosorbent chromatography and test for human serum antibodies against the two antigens.
abstract: The Ibc protein fraction from group B streptococci contains at least two antigens, named alpha and beta. Rabbit antisera to each of these antigens were used to prepare affinity-purified alpha and beta antigens. Analysis of the purified antigens by SDS-PAGE showed at least three weakly stained proteins in the alpha antigen - and multiple protein bands in the beta antigen preparation. Conditions for optimalization of ELISA for testing of human serum antibodies against these antigens were investigated. When tested at a dilution of 1 in 200, ELISA activity corresponding to an OD405 greater than 0.2 was shown by 11.2 per cent of 157 blood donor sera in tests with the alpha antigen, and 77.7 per cent with the beta antigen. Increasing antibody activity against the alpha antigen was shown by a patient with septicaemia caused by an alpha antigen-producing strain. The antigens were immunoblotted and tested against human and rabbit antibodies. With the alpha antigen, antibodies from both species produced a diffuse stained area, and with the beta antigen multiple stained bands, some of which were colinear with the human and rabbit antibody. Thus, antibodies to the beta antigen of group B streptococci are present in a large proportion of the healthy population. These antibodies may be important in the protection against group B streptococcal disease.
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000032:analysis*; D000942:Antigens, Bacterial / Q000302:isolation & purification*; D001426:Bacterial Proteins / Q000276:immunology* / Q000302:isolation & purification; D002846:Chromatography, Affinity; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007163:Immunosorbent Techniques; D008297:Male; D008970:Molecular Weight; D011817:Rabbits; D018805:Sepsis / Q000276:immunology; D013292:Streptococcus agalactiae / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001426:Bacterial Proteins