Bacillus pumilus polysaccharide cross-reactive with meningococcal group A polysaccharide

Area of Science:

• Microbiology
• Immunology
• Biochemistry

Background:

• Bacillus pumilus Sh-17, an enteric bacterium, has been linked to natural immunity against meningococcal group A.
• Meningococcal group A polysaccharide is a key target for immune responses.

Purpose of the Study:

• To isolate and characterize the polysaccharide from Bacillus pumilus Sh-17.
• To investigate the structural basis for the antigenic cross-reactivity between B. pumilus polysaccharide and meningococcal group A polysaccharide.

Main Methods:

• Isolation and chemical analysis of the polysaccharide from B. pumilus Sh-17.
• Immunological assays including precipitation reactions with meningococcal group A antiserum.
• Chemical treatments such as periodate oxidation and mild acid hydrolysis to probe structural components.

Main Results:

• A polysaccharide composed of (1-6)-N-acetyl-manosamine-1-phosphate, glycerol phosphate teichoic acid, and mucopeptide was isolated from B. pumilus Sh-17.
• The poly-(1-6)-N-acetyl-mannosamine-1-phosphate component was identified as responsible for the cross-reaction.
• Periodate oxidation and mild acid treatment abolished the precipitating activity, confirming the role of N-acetyl-mannosamine phosphate.

Conclusions:

• The N-acetyl-mannosamine phosphate homopolymer in B. pumilus Sh-17 polysaccharide is antigenically and structurally related to meningococcal group A polysaccharide.
• This structural similarity explains the observed cross-reactivity and potential for natural immunity.