Cloned alpha and beta C-protein antigens of group B streptococci elicit protective immunity.
Streptococcus agalactiae (group B streptococci [GBS]) is the leading cause of neonatal sepsis and meningitis in the United States. The surface-associated C proteins of GBS play a role in immunity, but their number, size, structure, function, and virulence properties have not been well characterized. A recombinant library of DNA fragments from GBS strain A909 (type Ia/C) was prepared in the plasmid pUX12, a specially constructed Escherichia coli expression vector. The library was screened with a rabbit antiserum shown to be protective for passive immunity to GBS infection in a mouse lethality model. Clones were divided into two distinct groups on the basis of DNA-DNA cross-hybridization, restriction enzyme analysis, and the expression of antigenic proteins in E. coli. A characteristic clone from each group was chosen for further study. Clone pJMS23 expresses gene products that biochemically and immunologically correspond to the trypsin-resistant, C-protein alpha antigen. Clone pJMS1 expresses a gene product that binds to immunoglobulin A and is similar to the trypsin-sensitive, C-protein beta antigen. Antisera raised in rabbits against E. coli containing each of the plasmid clones were able to elicit protective immunity in mice challenged by GBS strains carrying the C proteins but not by non-C-protein-bearing strains. Southern blot analysis shows no DNA homology between the clones, and there is no immunological cross-reactivity between the antigens they express. Therefore, pJMS23 and pJMS1 encode two different C proteins that define unique protective epitopes.
Channing Laboratory, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts.
J L
JL
Michel
L C
LC
Madoff
D E
DE
Kling
D L
DL
Kasper
F M
FM
Ausubel
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000276:immunology; D001428:Bacterial Vaccines; D001483:Base Sequence; D015153:Blotting, Western; D002352:Carrier Proteins / Q000235:genetics / Q000276:immunology*; D003001:Cloning, Molecular; D004251:DNA Transposable Elements / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics; D011817:Rabbits; D013290:Streptococcal Infections / Q000517:prevention & control*; D013292:Streptococcus agalactiae / Q000235:genetics* / Q000276:immunology
D001426:Bacterial Proteins; D001428:Bacterial Vaccines; D002352:Carrier Proteins; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; C039214:Ibc proteins, Streptococcus; C020723:citrate-binding transport protein