Detection of anticapsular antibodies to Bacteroides asaccharolyticus in serum from rabbits and humans by use of an enzyme-linked immunosorbent assay.

A sensitive serologic test, the enzyme-linked immunosorbent assay (ELISA), was used to detect serum IgG antibodies directed specifically to a capsular antigen of Bacteroides asaccharolyticus (previously known as Bacteroides melaninogenicus subspecies asaccharolyticus). Anticapsular IgG was measured in 30 specimens of rabbit serum after the animals were immunized with whole B. asaccharolyticus, the two subspecies of B. melaninogenicus, and several other bacterial species. Species-specific anticapsular IgG was demonstrated (P less than 0.001). Levels of anticapsular IgG greater than control levels were likewise detected in serum from two humans, including one patient who had periodontitis and from whom B. asaccharolyticus was isolated, and a laboratory worker who had extensive exposure over a two-year period to B. asaccharolyticus. The ELISA was found to be a relatively simple, sensitive tool for measurement of serum IgG. Its application to detection of immunoglobulins of other classes, including secretory IgA, is anticipated, provided adequate standardization methods are used.