Streptococcus agalactiae has emerged as a major cause of neonatal sepsis and late-onset meningitis in infants. Despite the sensitivity of this organism to antibiotics, the high attack rate and rapid onset of disease results in high morbidity (50%) and mortality (20%). The polysaccharide bacterial capsule of group B Streptococcus (GBS) is well studied and plays an important role in both virulence and immunity. However, vaccines prepared from these capsular antigens are not fully protective in humans. A family of polypeptides, called C proteins, has been described in GBS that appears to play a role in both virulence and immunity. To identify and characterize proteins that are involved in immunity and virulence of GBS, a recombinant DNA library of chromosomal DNA from GBS was prepared in E. coli. A plasmid-based expression vector was developed for cloning bacterial chromosomal DNA that has several advantages over libraries constructed with gt11. This library is being screened for expression of GBS proteins with antisera to GBS proteins that have been shown to be protective in a mouse lethality model. Five genes have been isolated form GBS whose gene products react with protective antisera prepared against GBS proteins. Interestingly, four of these gene products do not appear to be present in GBS strains that do not carry the C proteins. An animal model is used to determine if the cloned gene products elicit protective antibodies. Those GBS proteins that elicit protective antibodies are, by definition, C proteins. Preliminary biochemical and immunological characterization of the gene products of the clones suggests that at least two genes encoding C proteins have been isolated. The overall goals of this project are to identify and characterize the structure, function, regulation and expression of genes associated with the C protein(s). To determine the role of these genes in pathogenesis, isogenic strains of GBS will be prepared with these genes deleted. The immunity and virulence of these mutants will be evaluated in an animal model. C proteins expressed from the cloned genes will be isolated and their role in immunity studied. The long term goal is to study the potential of these proteins to serve as a polypeptide backbone for GBS capsular polysaccharides and to develop an effective conjugate vaccine against GBS.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
First Independent Research Support & Transition (FIRST) Awards (R29)
Project #
5R29AI028500-04
Application #
3455251
Study Section
Bacteriology and Mycology Subcommittee 2 (BM)
Project Start
1990-03-01
Project End
1995-02-28
Budget Start
1993-03-01
Budget End
1994-02-28
Support Year
4
Fiscal Year
1993
Total Cost
Indirect Cost
Name
Brigham and Women's Hospital
Department
Type
DUNS #
071723621
City
Boston
State
MA
Country
United States
Zip Code
02115
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Kling, D E; Gravekamp, C; Madoff, L C et al. (1997) Characterization of two distinct opsonic and protective epitopes within the alpha C protein of the group B Streptococcus. Infect Immun 65:1462-7
Li, J; Kasper, D L; Ausubel, F M et al. (1997) Inactivation of the alpha C protein antigen gene, bca, by a novel shuttle/suicide vector results in attenuation of virulence and immunity in group B Streptococcus. Proc Natl Acad Sci U S A 94:13251-6
Gravekamp, C; Horensky, D S; Michel, J L et al. (1996) Variation in repeat number within the alpha C protein of group B streptococci alters antigenicity and protective epitopes. Infect Immun 64:3576-83
Madoff, L C; Michel, J L; Gong, E W et al. (1996) Group B streptococci escape host immunity by deletion of tandem repeat elements of the alpha C protein. Proc Natl Acad Sci U S A 93:4131-6
Michel, J L; Madoff, L C; Olson, K et al. (1992) Large, identical, tandem repeating units in the C protein alpha antigen gene, bca, of group B streptococci. Proc Natl Acad Sci U S A 89:10060-4
Madoff, L C; Michel, J L; Gong, E W et al. (1992) Protection of neonatal mice from group B streptococcal infection by maternal immunization with beta C protein. Infect Immun 60:4989-94
Michel, J L; Madoff, L C; Kling, D E et al. (1991) Cloned alpha and beta C-protein antigens of group B streptococci elicit protective immunity. Infect Immun 59:2023-8
Madoff, L C; Michel, J L; Kasper, D L (1991) A monoclonal antibody identifies a protective C-protein alpha-antigen epitope in group B streptococci. Infect Immun 59:204-10
Madoff, L C; Hori, S; Michel, J L et al. (1991) Phenotypic diversity in the alpha C protein of group B streptococci. Infect Immun 59:2638-44