Detection of gonococcal antigens by an indirect sandwich enzyme-linked immunosorbent assay

The detection of gonococcal antigens by an indirect sandwich ELISA system is described. The feasibility of using rabbit antiserum raised against whole cells of Neisseria gonorrhoeae strain 9 to detect gonococcal lipopolysaccharide, whole cells, and outer membrane (OM) protein was investigated. OM protein was found to be the main antigen detectable with the antiserum in a direct ELISA system. A positive result in the indirect assay could be obtained with a minimum of 46 to 92 ng of gonococcal OM protein or with 6.6 X 10(3) cfu of N. gonorrhoeae. The sensitivity of the assay was found to be approximately eightfold lower with OM complex from a strain of N. meningitidis serogroup B for which the minimum amount of OM protein detected was 375 ng. Negative results were obtained with OM complex from Streptococcus agalactiae, Bacteroides bivius and Escherichia coli. The assay seems to be highly specific for gonococcal antigens. The sensitivity of the assay and its specificity commend it for further evaluation in the detection of gonococcal antigens in clinical specimens.