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. 1999 Sep;67(9):4346-51.
doi: 10.1128/IAI.67.9.4346-4351.1999.

Detection of intrastrain antigenic variation of Bacteroides fragilis surface polysaccharides by monoclonal antibody labelling

S Patrick  1 , D Gilpin, L Stevenson
Affiliations

Detection of intrastrain antigenic variation of Bacteroides fragilis surface polysaccharides by monoclonal antibody labelling

S Patrick et al. Infect Immun. 1999 Sep.

Abstract

Bacteroides fragilis is a constituent of the normal resident microbiota of the human intestine and is the gram-negative obligately anaerobic bacterium most frequently isolated from clinical infection. Surface polysaccharides are implicated as potential virulence determinants. We present evidence of within strain immunochemical variation of surface polysaccharides in populations that are noncapsulate by light microscopy as determined by monoclonal antibody labelling. Expression of individual epitopes can be enriched from a population of an individual strain by use of immunomagnetic beads. Also, individual colonies in which either >94% or <7% of the bacteria carry an individual epitope retain this level of expression when subcultured into broth. In broth cultures where >94% of the bacteria carry a given epitope, there is no enrichment for other epitopes recognized by different polysaccharide-specific monoclonal antibodies. This intrastrain variation has important implications for the development of potential vaccines or immunodiagnostic tests.

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Figures

FIG. 1
FIG. 1
Immunoblots of hot phenol-water extracts from B. fragilis NCTC 9343 after PAGE reacted with rabbit anti-B. fragilis NCTC 9343 common antigen antiserum (track 1), rabbit anti-B. fragilis NCTC 9344 common antigen antiserum (track 2), and MAbs QUBF 12 (track 3), QUBF 5 (track 4), QUBF 6 (track 5), QUBF 7 (track 6), and QUBF 8 (track 7).
FIG. 2
FIG. 2
Light micrographs of B. fragilis NCTC 9343, prepared from single colonies, immunolabelled with both mouse MAb plus anti-mouse TRITC conjugate and rabbit anti-B. fragilis polyclonal antiserum plus anti-rabbit FITC conjugate viewed (100× objective) with fluorescein filters (a) and the same field viewed with rhodamine filters (b). (i) Colony labelled with MAb QUBF 6 in which 95% or more of the bacteria are labelled; (ii) another colony labelled with MAb QUBF 6 in which only a small proportion of the total bacterial population is labelled.
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