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Immunochemistry of pneumococcal types II, V, and VI. II. Inhibition tests in the type VI precipitating system
Abstract:
Rebers, Paul A. (Rutgers University, New Brunswick, N. J.), Esther Hurwitz, and Michael Heidelberger. Immunochemistry of pneumococcal types II, V, and VI. II. Inhibition tests in the type VI precipitating system. J. Bacteriol. 82:920-926. 1961.-As in other immune systems involving polysaccharides, rabbit antibodies but not those engendered in the horse were found sensitive to degradation of type VI pneumococcal (Pn) polysaccharide (SVI), and were readily inhibited by fragments of SVI. Large amounts, 30 to 111 mumoles, of most sugars gave up to 15% inhibition, while sugar and polyol phosphates inhibited as much as 25%, with little relation to their presence or absence in SVI. The phosphate-free repeating unit of SVI was a good inhibitor, its phosphate monoester was better, and the "trimer" still better. The "trimer" precipitated most of the antibodies from horse anti-Pn VI.Although inhibition of precipitation of SVI anti-Pn horse sera could not be demonstrated with fragments of SVI, cross-reactions of antibodies in the horse sera could be inhibited. Precipitation of SII was inhibited by low concentrations of l-rhamnose, while even high concentrations of the other sugar components of SII and SVI were ineffective. Precipitation by guar gum was inhibited by galactose and alpha- and beta-methyl-galactopyranosides, also by rhamnose, although guar gum does not contain this sugar, while SVI, the antigenic determinant, does.
Insights
Rabbit antibodies, unlike horse antibodies, are sensitive to type VI pneumococcal polysaccharide fragments. Specific sugar structures, particularly the "trimer," effectively inhibited precipitation in horse anti-Pn VI sera.
Area of Science:
- Immunochemistry
- Microbial Polysaccharides
- Antibody-Antigen Interactions
Background:
- Pneumococcal polysaccharides (Pn) are key antigens in bacterial immunity.
- Understanding the immunochemical properties of different pneumococcal types is crucial for vaccine development.
- Previous studies indicated variability in antibody responses to polysaccharides based on host species.
Purpose of the Study:
- To investigate the immunochemical inhibition of type VI pneumococcal (Pn) polysaccharide (SVI) precipitation by various sugars and fragments.
- To compare the sensitivity of rabbit and horse antibodies to SVI degradation products.
- To elucidate the role of specific chemical structures in antibody cross-reactivity.
Main Methods:
- Precipitation inhibition assays were performed using SVI and anti-Pn VI sera from rabbits and horses.
- Various monosaccharides, sugar phosphates, and polysaccharide fragments were tested as inhibitors.
- Cross-reactivity inhibition tests were conducted with different polysaccharide antigens and their potential inhibitors.
Main Results:
- Rabbit antibodies were sensitive to SVI degradation and inhibited by fragments, unlike horse antibodies.
- Phosphate-free repeating units, monoesters, and trimers of SVI showed increasing inhibitory capacity.
- Horse anti-Pn VI antibodies showed cross-reactions inhibited by l-rhamnose for SII precipitation and galactose/methyl-galactopyranosides for guar gum precipitation.
Conclusions:
- Antibody sensitivity to polysaccharide fragments varies significantly between host species (rabbit vs. horse).
- Specific structural features of pneumococcal polysaccharides, like the SVI "trimer," are critical for antibody binding and precipitation.
- Cross-reactivity patterns suggest distinct antigenic determinants and highlight the role of specific sugars like l-rhamnose in immune responses.
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