Serological properties of aqueous ether extracted endotoxin from Neisseria gonorrhoeae

Heterogeneity of molecular size and antigenic expression within lipooligosaccharides of individual strains of Neisseria gonorrhoeae and Neisseria meningitidis

We determined the Mr of neisserial lipooligosaccharides (LOS) by using discontinuous sodium dodecyl sulfate-polyacrylamide gel electrophoresis, minimal loading concentrations, and Salmonella isogenic rough mutant LOS as Mr standards. Salmonella LOS were resolved into three components. The migration distance of each component was linearly related to its theoretical Mr (r = 0.99). Neisserial LOS also contained multiple components whose calculated Mr ranged from 3,200 to 7,100. The relative abundance of components and their MrS varied greatly among strains. Meningococcal LOS were composed almost exclusively of two closely migrating components; gonococcal LOS were more heterogeneous. LOS from a gonococcus selected for resistance to a Pseudomonas pyocin contained only a single component that was different from and of intermediate Mr among the three components of the parent strain. A monoclonal antibody directed against the meningococcal L8 LOS epitope was used to determine whether heterogeneity of antigen expression reflected Mr heterogeneity. Single components of the L8 meningococcal LOS and of the LOS of 3 of 19 gonococcal strains bound the monoclonal antibody. Gonococcal LOS components that expressed the L8 epitope were of a similar Mr (4,800). Smaller components of these same LOS did not express the epitope.

Quantitative determination of antibody to gonococcal pili. Changes in antibody levels with gonococcal infection

Gonococcal pili, pure by the criteria of electron microscopic examination and polyacrylamide gel electrophoresis in sodium dodecyl sulfate, have been prepared by repeated cycles of precipitation with 0.1 M MgCl(2), followed by dissolution in 0.01 M Tris pH 8, 0.01 M NaN(3). Using a fluorescein-conjugated antibody prepared to pili from a single strain, pilar antigen(s) was found to be present in each of 18 strains of gonococci tested, and absent from strains of pilated meningococci, nonpathogenic Neisseria sp., and Escherichia coli. Purified pili, labeled with (125)I were used in an antigen binding assay to quantitatively measure antibody to pili in rabbit sera and in 561 human sera. The range of antibody activity for 133 persons unlikely to have experienced gonorrhea was 0.1-1.6 mug/ml with a geometric mean of 0.5 mug/ml. This geometric mean antibody activity was significantly lower than the geometric mean for asymptomatically infected males (1.0 mug/ml, P < 0.002), males with symptomatic gonococcal anterior urethritis (1.6 mug/ml, P < 0.001), or asymptomatically infected females (4.2 mug/ml, P < 0.001). Antibody appeared in elevated levels (> 1.6 mug/ml) 2-3 wk after infection and returned toward control levels 1 or more months after treatment. Antibody levels higher than 1.6 mug/ml were found in 26 (50%) of 52 males with gonococcal anterior urethritis, in 10 (33%) of 30 males with asymptomatic urethral infection and in 50 (89%) of 56 asymptomatically infected females. In a high-risk group of 103 females for whom culture results and antibody to pili were compared, 58 (57%) had elevated antibody levels to pili and 86% of the infected females were within this seropositive group. The antigen binding assay may provide a means to detect asymptomatic gonococcal infection in women.