A Streptococcus agalactiae R protein analysed by polyclonal and monoclonal antibodies.
Unexpected cross-reactivity between two Streptococcus agalactiae (GBS) isolates formed the basis for purification of a GBS protein called the Ra antigen, and raising of murine monoclonal antibody (MAb) against Ra. The Ra protein was resistant to trypsin digestion, susceptible to pepsin digestion, formed a ladder-like pattern of lines with a periodicity of approximately 8 kD on immunoblotting, was surface-localized in GBS strains, and was variably expressed by GBS. These characteristics provided evidence that the Ra antigen belonged to the R proteins of GBS. By testing of reference GBS isolates and antiserum, including an anti-R4 protein serum, cross-reactivity was recorded consistent with the assumption that Ra is a R4 protein. The Ra/R4 protein also showed cross-reactivity with a previously described GBS protein called protein Rib (J. Exp. Med. 177: 1593-1603, 1993). Several characteristics of the Ra/R4 protein were similar to those of the GBS protein c alpha, but the two proteins showed no cross-reactivity. The anti-Ra/R4 MAb has proved useful in serosubtype determination of GBS of known serotype and should be a valuable tool for studying the immunobiological function of antibodies targetting the surface-localized Ra/R4 protein.
Department of Microbiology, Faculty of Medicine, Regional Hospital, University of Trondheim, Norway.
L
L
Bevanger
A I
AI
Kvam
J A
JA
Maeland
D000906:Antibodies; D001426:Bacterial Proteins / Q000032:analysis* / Q000302:isolation & purification; D004797:Enzyme-Linked Immunosorbent Assay; D015151:Immunoblotting; D013292:Streptococcus agalactiae / Q000378:metabolism*
D000906:Antibodies; D001426:Bacterial Proteins