Immunochemical studies with synthetic immunogens chemically related to peptidoglycan

Rabbits were immunized with synthetic immunogens HSA-(Gly-L-Ala-L-Ala-D-Ala-D-Ala)39 and HSA-(Gly-gamma-D-Glu-L-Ala-D-Ala-D-Ala)40, respectively. Antibodies against HSA-(Gly-L-Ala-L-Ala-D-Ala-D-Ala)39 showed a strong precipitin reaction with the homologous antigen, with HSA-(Gly-gamma-D-Glu-L-Ala-D-Ala-D-Ala)40 and with solubilized peptidoglycan containing peptide subunits with C-terminal D-alanyl-D-alanine. The albumin-peptide conjugates also cross-reacted with rabbit antisera to Streptococcus A-variant, which contain antibodies directed against the peptide moiety of peptidoglycan. The proof for identical determinant groups of peptidoglycan of Streptococcus A-variant and HSA-(Gly-L-Ala-L-Ala-D-Ala-D-Ala)39 was furnished by Ouchterlony gel diffusion studies and by the appropriate inhibition tests of the quantitative precipitin reaction. Immunization of rabbits with HSA-(Gly-gamma-D-Glu-L-Ala-D-Ala-D-Ala)40 yielded antisera which, besides the specificity of antisera to HSA-(Gly-L-Ala-L-Ala-D-Ala-D-Ala)39, showed an additional specificity.