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Published on: September 25, 2014
Immunochemical studies on a Mycoplasma pneumoniae polysaccharide fraction: cross-reactions with type 23 and 32
Abstract:
Lipid-free polysaccharide fraction 2 extracted from Mycoplasma pneumoniae strain FH by Prescott et al. (J. Bacteriol. 91:2117-2115, 1966) was examined for its ability to cross-precipitate antibody from type-specific rabbit antipneumococcal sera types 1 to 34 inclusive. Cross-precipitation in type-specific pneumococcal anti-type 23 and anti-type 32 sera was examined in detail and could be attributed to a rhamnose-galactose-rich component of crude M. pneumoniae polysaccharide fraction 2 recovered from immunoprecipitates formed with anti-type 23 serum. Immunochemically isolated mycoplasma polysaccharide was found to contain glucose, galactose, rhamnose, and mannose in 1:14:5:4 molar proportions. Comparison of the ability of 6-O-alpha-L-rhamnosyl-D-glucose and free L-rhamnose to inhibit precepitation by homologous pneumococcal and heterologous mycoplasma polysaccharide antigens indicates a combining site specificity for anti-type 23 and anti-type 32 antibodies directed largely against the alpha-linked L-rhamnosyl determinants and the occurrence of alpha-L-rhamnosyl units in type 32 and M. pneumoniae polysaccharides. Hapten inhibition of the cross-precipitation of pneumococcal type 23 capsular polysaccharide in anti-type 32 serum helps to establish that cross-reactivity can be attributed to interaction of recurrent, alpha-L-rhamnosyl units of type 23 with anit-alpha-L-rhamnoside combining sites of anti-type 32 antibodies.
Insights
Mycoplasma pneumoniae polysaccharide fraction 2 cross-reacts with pneumococcal antibodies, specifically types 23 and 32. This cross-reactivity is due to shared alpha-L-rhamnosyl units in both Mycoplasma pneumoniae and Streptococcus pneumoniae polysaccharides.
Area of Science:
- Immunology
- Microbiology
- Carbohydrate Chemistry
Background:
- Mycoplasma pneumoniae polysaccharide fraction 2 was previously isolated and characterized.
- Type-specific rabbit antipneumococcal sera, types 1-34, were available for antibody analysis.
Purpose of the Study:
- To investigate the cross-precipitating ability of Mycoplasma pneumoniae polysaccharide fraction 2 with antipneumococcal sera.
- To identify the specific antigenic determinants responsible for observed cross-reactivity.
Main Methods:
- Cross-precipitation assays were performed between M. pneumoniae polysaccharide fraction 2 and various antipneumococcal sera.
- Immunoprecipitates were analyzed to isolate and characterize the Mycoplasma pneumoniae components involved.
- Hapten inhibition studies using specific sugars (L-rhamnose and a derivative) were conducted to probe antibody binding sites.
Main Results:
- M. pneumoniae polysaccharide fraction 2 exhibited cross-precipitation with anti-pneumococcal sera, particularly types 23 and 32.
- A rhamnose-galactose-rich component of the M. pneumoniae polysaccharide was identified in immunoprecipitates.
- Analysis revealed molar proportions of glucose, galactose, rhamnose, and mannose in the Mycoplasma polysaccharide.
- Hapten inhibition indicated that anti-type 23 and anti-type 32 antibodies recognize alpha-L-rhamnosyl determinants.
Conclusions:
- The cross-reactivity between M. pneumoniae polysaccharide and antipneumococcal antibodies is attributed to shared alpha-L-rhamnosyl units.
- Both type 32 pneumococcal polysaccharide and M. pneumoniae polysaccharide contain these immunodominant alpha-L-rhamnosyl units.
- Antibodies against type 23 and type 32 pneumococci share binding specificities with Mycoplasma pneumoniae polysaccharides.
