THE USE OF MONOCLONAL-ANTIBODIES FOR STUDYING THE BIOLOGICAL PROPERTIES OF STAPHYLOCOCCUS-AUREUS ENDO-BETA-N-ACETYLGLUCOSAMINIDASE

Staphylococcus aureus endo-beta-N-acetylglucosaminidase (SaG) has been suggested to function as a virulence determinant which interferes wit h the host cellular immune response. To further characterize the biolo gical properties of SaG, monoclonal antibodies (mAbs) were raised agai nst purified SaG. Four IgG1 subclass mAbs were obtained, none of which reacted with the reduced, sodium dodecyl sulphate pretreated or boile d enzyme. The ability of the mAbs to react with the enzymes present in supernatants obtained from 197 S. aureus strains indicated that they recognized epitopes which are highly conserved; bacteriolytic enzymes produced by staphylococci other than S. aureus did not show any cross- reactivity. After pretreatment of SaG with mAbs (mAb-SaG molar ratios varying from 1 to 20), it was shown that all selected mAbs caused, at a mAb: SaG molar ratio of 10, a 90% inhibition of SaG bacteriolytic ac tivity and a statistically significant reduction of its ability to int erfere with phagocytosis by human polymorphonuclear leukocytes. All se lected mAbs reacted with several commercially available exo-beta-N-ace tylglucosaminidases; mAb C1/10-11 also reacted with chicken and turkey egg muramidases and, at a mAb:SaG molar ratio of 10, inhibited their bacteriolytic activity by 97%. This suggests that one or more epitopes present in the above exo-glucosaminidases and muramidases share some degree of homology with others present in SaG.