Antigen Degradation in Human Colon Ecosystems: Host’s ABO blood type influences enteric bacterial degradation of a cell surface antigen on Escherichia coli O86

Abstract

Strains of human enteric bacteria produce enzymes that degrade the oligosaccharide moieties of gut mucin glycoproteins. To determine whether these bacterial enzymes also degrade related heteroglycan antigens on the cell walls of enteric bacteria we studied the ability of enzymes in fecal extracts and anaerobic fecal cultures to degrade a cell surface antigen on Escherichia coli O86. This antigen is structurally and immunologically similar to oligosaccharides containing human blood group B antigenic determinant α-D-(1-3)-galactopyranosyl moieties. Enzyme activity in fecal extracts and fecal cultures degraded the B-like antigen from the surface of E. coli O86, but degradation was slower than degradation of B antigen from salivary mucin glycoproteins, and the rate varied among individual subjects. One determinant of degradation rate was the host’s blood type. Fecal extracts and cultures from 4 of 6 blood group B secretors caused ≥ 94% loss of B-like antigen from the bacteria in 24 hr, but only 1 fecal extract and no fecal culture from 10 group A or O secretors degraded it this rapidly from the cells. A bacterial B-degrading α-galactosidase is probably responsible for loss of antigen from E. coli O86 during incubation with fecal extract since galactose was released concurrently from the cells and added galactose inhibited the loss. These results suggest that: (1) cell surface antigens on enteric bacteria may normally be degraded by bacterial enzymes in the human colon, and (2) bacterial enzyme adaptation to blood group antigens in the host’s gut mucins enhances degradation of similar structures on enteric bacteria.