A comparison of serological tests for the diagnosis of gonorrhoea

Evaluation of a serum gonococcal antibody test

The authors evaluated the Gonosticon Dri-Dot system as a tool for the determination of the prevalence of gonococcal serum antibody in two female populations. This paper discusses their findings.

Application of immuno-blotting to the differentiation of specific antibodies in gonorrhoea

The technique of immuno-blotting was used to examine the specificity of serum antibodies in patients with gonorrhoea and to define the significant antigenic determinant present in the desoxycholate extracts of gonococcal cell walls used previously for serological diagnosis. IgG but not IgA antibody was directed predominantly against lipopolysaccharide. Antibodies to outer membrane proteins were not found as frequently as expected. There was a suggestion from the results that antibodies to antigen PI was more common in systemic than in local infections.

Gonococcal serology. A comparison of three different tests

Three serological tests for the detection of gonococcal antibodies were compared: an enzyme-linked immunosorbent assay (ELISA), an indirect haemagglutination reaction (IHA), and a gonococcal complement-fixation test (GCFT). The ELISA was performed with gonococcal pili of a Rotterdam strain (1443) as antigen, the IHA with pilus antigen of an American strain (2686, Buchanan), and the GCFT with whole gonococci of a single strain (46695, Oliver) as antigen. The tests were performed on sera from the same groups of Dutch patients; samples of sera were taken at the first examination and generally 11-22 days later. The ELISA and the IHA were more sensitive than the GCFT. The specificity of the tests was equal in low-risk groups, but the GCFT was slightly more specific in high-risk groups. The ELISA and the IHA did not differ in sensitivity and specificity. The agreement between the ELISA and IHA for patients with uncomplicated gonorrhoea was low (chi = 0.44), but the agreement between the GCFT and the two pilus assays was less (chi = 0.26 and 0.20). The sensitivities were highest for sera from patients with oropharyngeal gonorrhoea or with gonococcal complications; again the ELISA and the IHA were more sensitive than the GCFT.

Serological diagnosis of gonorrhoea by an enzyme-linked immunosorbent assay (Elisa)

IgG antibody to an outer membrane protein extracted from Neisseria gonorrhoeae was measured in patients with gonorrhoea. The level in such patients was significantly higher than in normal controls or in patients with other conditions who were attending the clinic for sexually transmitted diseases. Significantly higher antibody levels were detectable in half the patients within a few days of infection and in a similar proportion of carriers--both male and female. Men with rectal gonorrhoea had particularly high antibody levels. Sixteen per cent of presumptively normal men and 11% of normal women gave positive results but the actual false positive rate could be lower.

Cell-mediated immune response in gonococcal infections

Peripheral blood lymphocyte (PBL) transformation stimulated by gonococcal and meningococcal antigens was studied in 29 men and 21 women with uncomplicated gonorrhoea. The blastogenic responses of PBLs from these men and women were substantially higher than from normal controls. Cross-reactivity between Neisseria gonorrhoeae and Neisseria meningitidis was manifested by the PBL transformation responses in patients with gonorrhoea to non-purified meningococcal antigen (MGC-I). In both male and female patients the PBLs were stimulated by non-purified gonococcal antigen (GC-I) and by non-purified meningococcal antigen. The extent of the blastogenic response in women was much greater than in men. Partial purification of these antigens by gel chromatography resulted in reduced cross-reactive responses to the semi-purified meningococcal antigen (MGC-II). Female patients demonstrated marked stimulation with the semi-purified gonococcal antigen (GC-II), while male patients showed slight stimulation with GC-II. It is possible that cell-mediated immunity may act to limit the spread of gonococcal infection beyond the genital mucous membranes.

Fluorescent antibody test for the serological diagnosis of gonorrhea

An indirect fluorescent antibody technique has been developed for the serological diagnosis of gonorrhea. The selected strain(s) of Neisseria gonorrhoeae possesses a heat-labile surface antigen (L-antigen). Sera are diluted 1:10, and an aliquot is hear inactivated at 59 C for 30 min. The treated and untreated aliquots are then examined for human immunoglobulin G anti-L-antigen. In a prelimiary study of 495 sera, 95% of those from women with a bacteriologically confirmed diagnosis of gorrhea and 87% of those from male patients were reactive in this test, whereas only 1.4% fo the sera from presumably normal individuals were reactive.

Specificity of human serum antibodies against endotoxin from N. gonorrhoeae

Sera from patients with gonorrhoea were used to study the specificity of human antibodies against determinant a of endotoxin from gonococcal strains 8551, V, and VII. The sera were tested by an indirect haemagglutination technique before and after absorption with endotoxin from the same strains. The sera were used untreated and treated with mercaptoethanol (ME). The untreated and ME-treated sera showed antibody activity against all the a determinants when examined unabsorbed. After absorption with any of the endotoxin preparations the sera usually demonstrated antibody activity against one or both of the other preparations. The pattern of reactivity thus observed differed from one serum to another. Treatment of sera with ME resulted in an altered pattern of reactivity of four of the five sera. The results indicate multispecificity of human antibodies against the a determinants.

Antenatal screening for candidiasis, trichomoniasis, and gonorrhoea

Gonorrhoea was not found to be a problem in antenatal patients. It was found in only one out of 625 women, thus confirming other British surveys which do not agree with the North American figures. Candidiasis is commoner than trichomoniasis (27.4 and 4.7 per cent. prevalence respectively) and culture of a high vaginal swab is more effective as a means of diagnosis than a cervical cytology smear. The two conditions seldom occur together. The detection rate for Candida increases with gestation, but not with age, parity, or premarital and extramarital conception. The species isolated was predominantly Candida albicans. Trichomonads are detected in culture of a high vaginal swab more often than in a cervical cytology smear. Detection does not increase with age, parity, or gestation, but does increase with premarital and extramarital conception. It is difficult to diagnose clinically the cause of vaginal discharge in a pregnant woman.

Mercaptoethanol-resistant human serum antibodies reacting with endotoxin from Neisseria gonorrhoeae

Sera from fifty patients with gonorrhoea, thirty with non-specific urethritis, and eighty blood donors were treated with mercaptoethanol (ME) and examined by the indirect haemagglutination test for antibodies against endotoxin from gonococci. Erythrocytes sensitized with determinant a of endotoxin from Strains 8551, V, and VII, or determinant b from Strain V were used. The percentage of sera active in the haemagglutination test was much higher in the gonorrhoea group than in the controls. The geometric mean titre was also significantly higher in the gonorrhoea group. This applied for all four antigens used. Results obtained in an anti-globulin test indicated that the titre of ME-treated serum was determined by IgG antibodies against the endotoxin. Many sera had titres which varied according to the strain origin of the antigen used in the test. The sensitivity of tests for antibodies was increased by using endotoxin from several different strains of gonococci for the examination of each serum. A simplified procedure for determination of antibodies against endotoxin from different strains of gonococci was elaborated.

Studies in venereal disease. II. Improved diagnosis of gonorrhoea by the parallel use of conventional and L-phase media for culture

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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.