Protection of mice against group Bstreptococcus type Ia by IgG components of a rabbit antiserum

Sera obtained from human volunteers at 6 weeks after vaccination with highly purified type III polysaccharide antigen prepared from a group B Streptococcus, strain M732, were found to protect neonatal rats from otherwise lethal infection by the homologous strain. The specific antibody content of the sera, expressed in micrograms of antibody protein per milliliter, was determined by an enzyme-linked immunosorbent assay in conjunction with quantitative precipitin analysis. For two sera studied in detail, the protective dose of antibody for 50% of the animals was 0.4 micrograms. Immune serum obtained from a volunteer who received type II polysaccharide vaccine was not protective against type III infection. Absorption of anti-type III serum by quantitative precipitation of antibodies with type III polysaccharide completely removed the passive protective activity of the serum. The results show that antibodies induced in humans by purified type II polysaccharide give serotype-specific protection in an animal model of neonatal infection.

mentioning

confidence: 99%

Type-specific protection of neonatal rats from lethal group B streptococcal infection by immune sera obtained from human volunteers vaccinated with type III-specific polysaccharide

Cueninck¹,

Eisenstein²,

McIntosh³

et al. 1982

“…Acquired immunity to group B streptococcal infection in human neonates (4,5) and to experimental group B streptococcal infection in mice (7,10,25) and in neonatal rats (12,19) has been associated with antibody to the type-specific polysaccharides or proteins of the organism, and the opsonic activity of type-specific antibodies has been demonstrated in vitro (1,6,14,22).…”

mentioning

confidence: 99%

Quantitation of in vitro opsonic activity of human antibody induced by a vaccine consisting of the type III-specific polysaccharide of group B streptococcus

Cueninck¹,

Eisenstein²,

McIntosh³

et al. 1983

Human antibody, induced by a vaccine consisting of undegraded and highly purified extracellular type III-specific polysaccharide of group B streptococcus, was shown to increase the rate of phagocyte-mediated killing of bacteria of the homologous type. The bactericidal effect was mediated by type III-specific antibody and was complement dependent. An assay which permitted quantitation of "opsonic activity" was developed. In this assay, loss of CFUs occurred at a constant rate, and the rate constant was used as a measure of opsonic activity of antisera. A linear relationship between type III-specific antibody concentration (40 to 500 ng/ml) and the rate constant of killing was observed. When sets of immune sera were tested, some sera reacted anomalously, mediating significantly higher or lower rates than expected on the basis of their antibody content. Since type III-specific antibody in immune sera was found almost exclusively in the immunoglobulin G class, we hypothesize that differences in immunoglobulin G subclass distribution of specific antibody may have been the source of this variation.were sedimented with dextran (Dextran T500; Pharmacia Fine Chemicals, Piscataway, N.J.), and PMN were isolated from the leucocyte-rich plasma by densi-1155 on August 1, 2020 by guest http://iai.asm.org/ Downloaded from

“…Acquired immunity to natural group B streptococcal infection in human neonates (3,7) and to experimental infection in mice (9,12,30,31) and in neonatal rats (14,19) has been associated with antibody to the type-specific polysaccharides or proteins of these organisms. The opsonic value of antibodies with these specificities has been demonstrated in in vitro assays (1,8,18,19,21).…”

mentioning

confidence: 99%

Isolation, chemical composition, and molecular size of extracellular type II and type Ia polysaccharides of group B streptococci

Cueninck¹,

Greber²,

Eisenstein³

et al. 1983

Polysaccharides carrying the type IIand type Ia-specific determinants of Lancefield group B streptococci were isolated and purified by anion-exchange chromatography and gel filtration from the supernatant culture medium after growth of strain 18RS21/67/1 (type II) and strain DS/1204/78 (type Ia), respectively. The average molecular weights of these polysaccharides were 97,000 (type II) and 94,000 (type Ia), as determined by reducing end group analyses. These molecular weights were in reasonably good agreement with molecular weights determined by gel filtration at high ionic strength on calibrated columns. The polysaccharides did not cross-react with antisera specific for the other typespecific determinants or with group B-specific antisera. Their content of galactose, glucose, glucosamine, and neuraminic acid (the last two calculated as Nacetyl derivatives) accounted for over 96% of their dry weight. The two polysaccharides differed from each other (and from type III polysaccharide) in their relative content of these monosaccharides. The molar ratios of galactose, glucose, and neuraminic acid to glucosamine were 3.3:2.3:1.35:1.0 for the type II polysaccharide and 2.0:0.8:1.4:1.0 for the type Ia polysaccharide. The results obtained indicate that these extraceliular type II and Ia polysaccharides contain larger amounts of neuraminic acid than can be accounted for by previously proposed structures of their repeating units.