Quantitative Determination of Antibody to Gonococcal Pili. CHANGES IN ANTIBODY LEVELS WITH GONOCOCCAL INFECTION

Abstract

A B S T R A C T 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 MgCli, followed by dissolution in 0.01 M Tris pH 8, 0.01 M NaNs. 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 '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 /Ag/ml with a geometric mean of 0.5 ,ug/ml. This geometric mean antibody activity was significantly lower than the geometric mean for asymptomatically infected males (1.0 isg/ml, P < 0.002), males with symptomatic gonococcal anterior urethritis (1.6 ug/ml, P <0.001), or asymptomatically infected females (4.2 Ag/ml, P<0.001). Antibody appeared in elevated levels (> 1.6 Lg/ml) 2-3 wk after infection and returned toward control levels 1 or more months after treatment. Antibody levels higher than 1.6 Ag/ml were found in 26 (50%) of 52 males with gonococcal anterior urethritis, in 10 (33%) of 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.

Antigenic heterogeneity of gonococcal pili.

“…These two strains were of different gonococcal serotypes as tested and described by Johnston and Gotschlich (5) . Different serotypes of gonococci were picked to insure that the gonococcal strains studied were distinctly different, since previous studies indicated antigenic similarity of pili from many gonococci (2,3) .…”

“…Colony type 2 gonococci were grown in liquid culture as previously described (2,6) . At the height of log phase growth, the liquid culture was briefly sheared in an omnimixer (Dupont Instruments, Sorval Operations, Newtown, Conn .)…”

“…Further evidence of shared antigens on many gonococcal pili was obtained with a radioactive antigen-binding assay using 'III-labeled purified gonococcal pili of strain 2686. This assay detected elevated antibody levels to 2686 pili in serum from 60 to 80% of patients with gonococcal infection (2,3) and in serum from each of two groups of chimpanzees immunized with distinctly different strains of gonococci (4) . However, no studies have been reported that directly compare purified pili from different strains of gonococci.…”

“…Studies with a fluoresceinconjugated globulin fraction of rabbit antiserum to purified gonococcal pili of strain 2686 suggested common antigenicity among gonococcal pili of 18 strains tested from the New York City area (2) . Further evidence of shared antigens on many gonococcal pili was obtained with a radioactive antigen-binding assay using 'III-labeled purified gonococcal pili of strain 2686.…”

The Surface Properties of Neisseria gonorrhoeae: Isolation of the Major Components of the Outer Membrane

“…Pili, which are associated with enhanced virulence in humans (Kellogg et al, 1963), are responsible for increased attachment in vitro, probably by overcoming the initial electrostatic repulsive force between the gonococcus and its host cell (Heckels et al, 1976). Raised levels of anti-pilus antibodies have been reported in patients with gonorrhoea, an observation which suggests that the detection of such antibodies might provide a serological screening system (Buchanan et al, 1973).…”