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The zwitterionic type I Streptococcus pneumoniae polysaccharide does not induce memory B cell formation in humans
Johannes Trück1, Rajeka Lazarus, Elizabeth A Clutterbuck
1Department of Paediatrics, University of Oxford, and the NIHR Oxford Biomedical Research Centre, Oxford, United Kingdom. johannes.truck@paediatrics.ox.ac.uk
Immunobiology
|June 19, 2012
Summary
Type 1 Streptococcus pneumoniae polysaccharide (Sp1), a zwitterionic polysaccharide (ZPS), surprisingly depleted memory B cells post-vaccination. This suggests Sp1 does not follow typical thymus-dependent immune responses via the MHC-II pathway.
Area of Science:
- Immunology
- Vaccinology
- Microbial Pathogenesis
Background:
- Pneumococcal polysaccharides are typically T-independent antigens.
- Type 1 Streptococcus pneumoniae polysaccharide (Sp1) is a zwitterionic polysaccharide (ZPS).
- Previous studies suggested Sp1 elicits thymus-dependent (TD) immune responses via MHC-II presentation.
Purpose of the Study:
- To investigate memory B cell responses to Sp1 after vaccination.
- To determine if Sp1 elicits a TD immune response in humans.
Main Methods:
- Analysis of peripheral blood mononuclear cells from adults in a randomized clinical trial.
- Assessment of serotype 1 antigen-specific memory B cells before and after vaccination with a 23-valent pneumococcal polysaccharide vaccine.
Main Results:
- Vaccination with the Sp1-containing vaccine led to a significant depletion of pre-existing serotype 1 antigen-specific memory B cells compared to baseline.
- This contrasts with the expected expansion of antigen-specific memory B cells in a typical TD response.
Conclusions:
- The observed depletion of memory B cells suggests Sp1 is not processed and presented via the classical MHC-II pathway as a TD antigen.
- This finding challenges the previous understanding of Sp1-induced immune responses and indicates a non-classical mechanism.
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