Immunochemistry of purified polysaccharide type antigens of group B streptococcal types Ia, Ib, and Ic

The type III polysaccharides of group B Streptococcus in its native state chemically consists of glucose, galactose, glucosamine, and sialic acid. The core of this polysaccharide lacks sialic acid and precipitates with type III antiserum to give a partial identity with the precipitate between the native antigen and this serum. The core determinant is immunochemically similar to the capsular polysaccharide of type XIV Streptococcus pneumoniae, while the native type III group B streptococcal polysaccharide does not cross-react with type XIV pneumococcal antiserum. In human sera, it is antibody directed to the native antigen which correlates very highly with opsonic immunity (r = 0.94) while a poorer correlation exists between antibody to the core antigen and opsonins (r = 0.51 P less than 0.001). In natural infections, as association exists between low levels of maternal antibody to the native antigen and risk of disease in the infant. This association is not true for antibody to the core structure, where both infected infants and their mothers have much higher levels of antibody to the core than the native antigens. Infected infants are also more likely to respond to infection by developing antibody to the native antigen. Immunization of 12 adults with multivalent pneumococcal polysaccharide induced significantly better antibody response to the core antigen than to the native, and this vaccine induced opsonic activity in only one recipient. Immunization of adults with type III group B streptococcal antigens induced antibody to the native determinant which correlated with opsonic activity. Therefore, it would appear that native group B streptococcal polysaccharides will provide the best candidate antigens for immunization.

Section: Methodsmentioning

confidence: 99%

Immunodeterminant specificity of human immunity to type III group B streptococcus.

Kasper¹,

Baker²,

Baltimore³

et al. 1979

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mentioning

confidence: 98%

Protection of mice from experimental infection with type III group B Streptococcus using monoclonal antibodies.

Egan

Pritchard

Dillon

et al. 1983

It is widely believed that antibodies to the group B streptococcal (GBS) typespecific polysaccharides are of major importance in human host defenses against GBS infection. All four of the type-specific polysaccharides elicit antibodies against at least two forms of the antigens: a complete antigen that contains Nacetylneuraminic acid (sialic acid) at the nonreducing ends of the side chains and an incomplete or nonsialated antigen (1-4). This was first demonstrated for the type II polysaccharide by Lancefield and Freimer (1) when they showed that rabbit antisera directed against either the complete or incomplete antigen would protect mice from a lethal challenge of live type II organisms. They were unable to carry out studies with type III GBS using similar passive protection tests because these organisms were not by themselves pathogenic for mice.The question of antibody specificity in protection against type III GBS infections remains controversial. There are conflicting reports regarding the protective properties of human and rabbit antibodies directed against the type III antigens and against the capsular polysaccharide of the type 14 pneumococcus, which cross-reacts with the incomplete GBS type III antigen (5). Although it is possible to select for certain specificities in anti-GBS serum by specific absorptions with purified antigens, as was done by Lancefield and Freimer (1), the polyclonal nature of antisera makes it difficult to clearly determine the immunoprotective effects of various specificities and different isotypes of the antibodies in question.Harris et al. (6) recently reported that mice could be protected against GBS types Ia, Ib, Ic, or II by antibody-producing tumors formed 2 wk after subscapular injection of hybridoma cells. The protection was serotype specific. Similar experiments could not be carried out using type III GBS because this serotype was not virulent in their mouse model. This report describes the production of mouse hybridoma antibodies of different isotypes directed against both sialated and nonsialated forms of the GBS type III polysaccharide. The protective properties of antibodies were examined under conditions where type III GBS were lethal for mice.

“…An additional serotype, type Ic, has been defined by Wilkinson and Eagon (7). Type Ic strains possess a polysaccharide antigen which is immunochemically identical to the type Ia antigen (11); in addition, type Ic strains have a protein antigen, the Ibc protein, which is found in all type Ib and Ic strains and infrequently in strains of type II and HI.…”

mentioning

confidence: 99%

“…However, these HCl-treated antigens are incomplete, lowmolecular weight substances which have previously been reported to contain varying quantities of glucose, galactose, and glucosamine. For the isolation of the type-specific antigens from serotypes Ia, Ib, Ic, and II, extraction with cold trichloracetic acid (TCA) results in more "complete" polysaccharides with a labile component identifiable as sialic acid (11,12,15). This sialic acid component accounted for approximately 12% of the dry weight of the type II-TCA antigen (12).…”

mentioning

confidence: 99%

Immunochemical characterization of the "native" type III polysaccharide of group B Streptococcus.

Baker¹,

Kasper²,

Davis³

1976

Since Lancefield's classification of beta-hemolytic Streptococcus in 1933 (1), organisms designated Group B have been reported as a cause of human disease. Their emergence as frequent neonatal pathogens, however, is an event of this decade. Two distinct types of illness that are related to age at onset (2,3) are described for neonates with infections due to Group B Streptococcus. The "early onset type" of infection occurs in neonates 5 days of age or less (2), results from intrapartum transmission of organisms from the maternal genital tract, and causes a mortality rate in excess of 50%. "Late onset type" infections, in contrast, are characterized by onset beyond the 10th day of life and are associated with purulent leptomeningitis, significantly lower mortality rates, and modes of transmission in addition to the mother-to-infant route (4).These two clinical syndromes have been related to certain serotypes. The serologic classification of Group B streptococci is based upon capillary precipitin tests with hyperimmune rabbit antisera and acid-extracted antigens (5). By this method, Group B streptococci can be divided into serotypes Ia, Ib, Ic, II, and III (5-7). Serotyping of strains has allowed the epidemiologic characterization of neonatal infection. Organisms isolated from asymptomatic mothers and neonates with Group B streptococci have virtually identical distributions of serotypes; 26% of strains are type Ia, Ib, or Ic; 38% are type II, and 36% are type III (8). This distribution of serotypes is similar among isolates from neonates who have early onset type septicemia without meningitis. However, neonates who have early onset type infection with meningitis and infants with late onset type infection have a striking predominance of type III isolates (:>80%) (8-10). These epidemiologic observations suggested that strains of Group B streptococci of serotype HI may possess invasive properties that allow meningeal penetration and the production of disease beyond the first few days of life.Lancefield has immunochemically characterized two polysaccharides from Group B Streptococcus: the group-specific B polysaccharide antigen common to all strains and the type-specific polysaccharide antigen which allows classification into four distinct serotypes: Ia, Ib, II, and III (5,6). These type-specific petysaccharides are believed to be *