Characterisation of Eubacterium cell wall: peptidoglycan structure determines arthritogenicity

Objective-To elucidate factors involved in the arthritogenicity of bacteria l cell walls. Methods-For characterisation of an arthritogenic Eubacterium aerofaciens ce ll wall, peptidoglycan-polysaccharide (PG-PS) polymers were isolated by rem oving cell wall associated proteins (CWPs), PG and PS moieties were separat ed, and an attempt was made to de-O-acetylate PG-PS. The cell wall of E lim osum was used as a non-arthritogenic control. The chemical composition of t hese cell wall preparations was analysed by gas chromatography-mass spectro metry. Also, their ability to resist lysozyme degradation and to sustain ex perimental chronic arthritis was tested. Results-The observations made with the cell wall of E aerofaciens, an anaer obic habitant of the human intestine, were compared with those reported fro m a pathogenic Streptococcus, showing that in both strains a complex consis ting of PG-PS is required for the induction of chronic arthritis. The PS mo iety most probably protects PG from enzyme degradation, allowing prolonged tissue persistence and leading to the chronic synovial inflammation. CWPs a ttached to PG-PS are not necessary for this function. O-Acetylation of PG, which is required for arthritogenicity of the streptococcal cell wall, seem s not to be present in the arthritogenic E aerofaciens PG or only occurs to a small degree; attempts to de-O-acylate the E aerofaciens cell wall did n ot affect its arthritogenicity or lysozyme resistance. Conclusion-The results obtained indicate that the source of bacterial cell wall plays no part in the chemical or structural requirements for PG to ind uce chronic cell wall arthritis in the rats; the chemical structure of the PG moiety is decisive.