Antigenic heterogeneity of Bacteroides intermedius as recognized by monoclonal antibodies.

Four hybrid cell lines secreting monoclonal antibodies against antigens of Bacteroides intermedius were generated by fusing murine NSI cells with splenocytes from a rat immunized with B. intermedius strain OMZ248. An enzyme-linked immunosorbent assay was used to analyze the distribution of the recognized antigens on 39 strains from various Bacteroides species and on 5 strains from other genera. Only Bacteroides species B. intermedius, B. loescheii, B. melaninogenicus, and B. corporis were found to express at least one of the recognized antigens. Strains of the two asaccharolytic black-pigmenting Bacteroides species were negative. Among the strains capable of binding to one or more of the monoclonal antibodies, five groups with different reactivity patterns could be distinguished. Two of the monoclonal antibodies were specific for B. intermedius. The B. intermedius strains were metabolically almost identical, expressed at least three of the recognized antigens, and fell into three distinct antibody reactivity groups, suggesting a tentative separation of this species into three new serogroups. Oral and nonoral isolates of B. intermedius were, however, not distinguished by the monoclonal antibodies. One monoclonal antibody was directed against an antigen strongly expressed on all saccharolytic black-pigmenting Bacteroides strains tested so far, thus confirming the previously noted antigenic relationship between the species which had emerged from the former B. melaninogenicus subsp. intermedius and B. melaninogenicus subsp. melaninogenicus groups.