Specific antibodies to the N-termini of the interpeptide bridges of peptidoglycan

Antibodies to staphylococcal peptidoglycan and its peptide epitopes, teichoic acid, and lipoteichoic acid in sera from blood donors and patients with staphylococcal infections

Antibodies to the staphylococcal antigens peptidoglycan, beta-ribitol teichoic acid, and lipoteichoic acid, as well as to the peptidoglycan epitopes L-Lys-D-Ala-D-Ala, L-Lys-D-Ala, and pentaglycine, were found over a wide range of concentrations in sera from both blood donors and patients with verified or suspected staphylococcal infections. The patient group was heterogeneous with regard to both age and type of staphylococcal infections, being representative for sera sent to our laboratory. In single-antigen assays antibodies to pentaglycine had the highest predictive positive value (67%), although only 32% of the patients had elevated levels of such antibodies. Combinations of test antigens could yield positive predictive values as high as 100%, but then the fraction of positive sera was low. Indeed, the fraction of patient sera which was positive in multiple-antigen tests never exceeded 61%. The clinical usefulness of these seroassays for identifying Staphylococcus aureus as a causative agent was limited, owing to the considerable overlap in the range of antibody concentrations between patient and blood donor sera.

Monoclonal antibodies evoked by the free oligopeptide (Gly)5 reacting specifically with peptidoglycan from staphylococci

Murine monoclonal antibodies reactive with the Staphylococcus aureus peptidoglycan (PG) epitope (Gly)5 were obtained using the synthetic oligopeptide (Gly)5 in its free form as immunogen. The selected monoclonal antibodies were of the IgM kappa isotype and reacted specifically with PG from S. aureus and Staphylococcus epidermidis, but gave no reaction with PG from Streptococcus pyogenes, Bacillus subtilis and Micrococcus lysodeikticus. Affinity chromatography showed that the antibodies were reactive with the N-terminus of the (Gly)5 peptide. These monoclonal antibodies can be used for the detection of staphylococcal PG in solution.

Antibodies to various bacterial cell wall peptidoglycans in human and rabbit sera

Sera from patients with verified systemic staphylococcal infection contained antibodies reactive with peptidoglycan (PG) from Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pyogenes, Micrococcus lysodeikticus, Bacillus subtilis, and Escherichia coli. The presence of anti-PG cross-reactive antibodies was verified in patient sera by inhibition studies with the various bacterial PGs. Antibodies to nonstaphylococcal PGs were also elevated in sera from rabbits immunized with S. aureus PG. Antibodies to S. aureus PG were removed with the synthetic peptide analogs of S. aureus PG, the L-Lys-D-Ala-D-Ala, L-Lys-D-Ala, and (Gly)5 determinants, as well as with an S. aureus PG peptide fragment containing the determinants D-Ala-D-Ala and L-Lys-D-Ala. Isolated antibodies to the PG peptides, both synthetic and native, were reactive with S. aureus and S. epidermidis PGs. The antibodies to the D-Ala-D-Ala and the L-Lys-D-Ala determinants were also reactive with S. pyogenes PG, but not with PGs from M. lysodeikticus, B. subtilis, and E. coli.

Immunoelectron microscopic studies on the localization of peptidoglycan peptide subunit pentapeptides in bacterial cell walls

The peptide subunit pentapeptide H-L-Ala-D-Glu(L-Lys-D-Ala-D-Ala-OH)-NH2 of peptidoglycan was localized in the cell walls of several Gram-positive bacteria employing the indirect immunoferritin technique. Specific antibodies to the D-alanyl-D-alanine moiety of non-crosslinked peptide subunit pentapeptide were raised in rabbits by immunization with synthetic immunogen albumin-(CH2CO-Gly-L-Ala-L-Ala-D-Ala-D-Ala-OH)39. Specificity of these antibodies for the peptide subunit pentapeptide and not for the peptide subunit tetrapeptide was corroborated in a Farr-type radio-active hapten binding assay. Specificity of labelling with ferritin was established by immunoelectron microscopic controls, and by the excellent correlation between specific labelling of cells with ferritin and the particular peptidoglycan primary structure of bacterial strains investigated. Cells of Lactobacillus gasseri, Streptococcus pyogenes and Staphylococcus aureus revealing non-crosslinked peptide subunit pentapeptides in their peptidoglycans could specifically be labelled. Lactobacillus acidophilus and Bacillus subtilis, on the contrary, missing such pentapeptides, failed in labelling. The implication of this method to possibly localize the points of attack of penicillin or cycloserine is discussed.