Antigenic composition of an endocarditis-associated isolate of Streptococcus faecalis and identification of its glycoprotein antigens by ligand blotting with lectins

Abstract

The antigenic composition of an endocarditis-associated isolate of Streptococcus faecalis was studied by immunoblotting of whole cells and cell walls from sodium-dodecyl sulphate polyacrylamide gels on to nitrocellulose and detection with serum from patients and hyperimmune rabbit serum. A major envelope protein antigen of mol. wt 53 X 10(3) detected with patient's serum was also present in three urinary strains of Str. faecalis and a laboratory strain of Str. faecalis ss. zymogenes but not in Staphylococcus aureus. Other common antigens of Str. faecalis were of mol. wt (10(3)) 65, 63, 56, 49.5, 30 and 21. Two other protein antigens (43 and 37 X 10(3) mol. wt) reacted strongly with asparagus pea lectin-peroxidase conjugate indicating the presence of fucosyl residues. Other lectin-peroxidase conjugates were used to demonstrate the presence of various glycosyl residues on envelope proteins. Growth of Str. faecalis in serum to mimic in-vivo growth conditions in endocarditis infections dramatically altered the antigenic patterns. Only two major antigens of mol. wt (10(3)) 56 and 53 reacted with sera from endocarditis patients. These antigens may, therefore, be of diagnostic or protective potential.