The group B streptococcus (GBS) is the leading cause of septicaemia and meningitis in newborns. We are studying two GBS surface proteins, Rib and alpha, which elicit protective immunity and are members of the same protein family. About 90% of all GBS strains express Rib or alpha, and a combination of these proteins works well as a vaccine in a mouse model. It would be an advantage if a single protein could be used. Different chimeric proteins, derived from Rib and alpha, will therefore be constructed and analyzed for ability to elicit protective immunity.
The role of Rib and alpha in pathogenesis is unknown. The function of Rib may be of particular interest, because Rib is expressed by all GBS strains of serotype III, which cause most cases of meningitis. Our hypothesis is that Rib promotes binding to epithelial or endothelial cells. If Rib indeed can be shown to act as an adhesin, attempts will be made to identify the corresponding human receptor. The results may provide information of general interest with regard to meningitis.
It is unknown why certain children contract GBS disease. Possibly, these children are poorly protected, because of low levels of maternal antibodies to GBS surface structures. We have initiated a study, aimed at analyzing the level of antibodies to GBS proteins in newborns with GBS disease. If these children, and their mothers, have low antibody levels, it might become possible to identify a risk group among pregnant women, and prevention of disease in the child.
Results from this study have been published in scientific journals as follows:
Larsson C, Holmgren J, Lindahl G, Bergquist C.
Intranasal immunization of mice with group B streptococcal protein rib and cholera toxin B subunit confers protection against lethal infection.
Infect Immun 2004 Feb;72(2):1184-7.
Lindahl G, Stalhammar-Carlemalm M, Areschoug T.
Surface proteins of Streptococcus agalactiae and related proteins in other bacterial pathogens.
Clin Microbiol Rev 2005 Jan;18(1):102-27.
Waldemarsson J, Areschoug T, Lindahl G, Johnsson E,
The streptococcal Blr and Slr proteins define a family of surface proteins with leucine-rich repeats: camouflaging by other surface structures.
J Bacteriol 2006 Jan;188(2):378-88.
Larsson C, Lindroth M, Nordin P, Stalhammar-Carlemalm M, Lindahl G, Krantz I.
Association between low concentrations of antibodies to protein alpha and Rib and invasive neonatal group B streptococcal infection.
Arch Dis Child Fetal Neonatal Ed 2006 Nov;91(6):F403-8.