Simplified serological test for antibodies to Chlamydia trachomatis

Development and evaluation of an enzyme-linked immunosorbent assay (ELISA), using chlamydial group antigen, to detect antibodies, to Chlamydia trachomatis

Chlamydial group antigen was extracted from Chlamydia trachomatis strain SA2(f) and used as the antigen for an ELISA. The assay was reproducible since chlamydial antibody titres differed by no more than twofold when sera were tested on up to eight occasions. In tests on sera from 75 patients attending venereal disease or rheumatology clinics, the results of the ELISA and of a microimmunofluorescence (MIF) technique were similar for 61 of the sera, that is an 81% agreement. However, the ELISA was a little more sensitive than the MIF technique and at least tenfold more sensitive than the complement fixation procedure. Chlamydial IgG antibody at a titre of 1/greater than or equal to 16 was detected by the ELISA in 6% of children's sera, in 20% of sera from adult patients attending hospital with non-venereal diseases and in 85% of sera from persons attending venereal disease or rheumatology clinics. IgM and IgG antibodies were detected also by the ELISA in the sera of chimpanzees and marmosets which had been infected genitally with C trachomatis and, in general, the titres were greater than those recorded by the MIF test. The value of the ELISA in comparison with the MIF test is discussed.

Genital-tract infection and disease in nude and immunologically competent mice after inoculation of a human strain of Chlamydia trachomatis

A fast, human strain of Chlamydia trachomatis was introduced into the uterus of progesterone-treated CBA mice and congenic CBA nude mice through the uterine wall or via the cervical canal. The numbers of inclusions produced by samples taken from the vagina of the nude mice were significantly greater (P less than 0.05) than those produced by samples from immunologically competent normal mice. However, the infection was self-limited, lasting about 60 days, and there was no statistical difference in its duration in the nude and normal mice despite the failure of the former to mount a chlamydial antibody response. In contrast, 14 of 18 normal mice had developed a 4-fold or greater rise in the titre of IgG antibody 14 days after inoculation. A serum titre of 1:512 or greater was attained in 15 of these mice, and high titres persisted for 69 days or longer after inoculation. The numbers of polymorphonuclear leucocytes in vaginal smears from both normal and nude mice increased by 12 days after inoculation, indicating an inflammatory cell response. However, interpretation of the cellular response after the 40th day was difficult because of recommencement of the oestrous cycle. The results indicate that T lymphocytes and T-lymphocyte-dependent antibody have little effect on the course of the self-limited chlamydial genital infection.

Chlamydial serum IgG antibodies in patients with acute salpingitis measured by an enzyme-linked immunosorbent assay

An enzyme-linked immunosorbent assay (ELISA) for the detection of serum IgG antibodies to Chlamydia trachomatis has been developed. The C. trachomatis subtype LGV-2 was used as antigen. The ELISA was reproducible and its sensitivity and specificity compared well with that of the single-antigen immunofluorescence test (r = 0.83). 29 (85%) of the 34 patients with acute salpingitis had chlamydial serum IgG antibodies measured by the ELISA technique. The detection level in single blood donor specimens was 30%. Among the 34 patients with acute salpingitis, 16 paired serum specimens showed a fourfold or greater rise/fall in antibody titres, and 12 of these belonged to the 19 who harboured C. trachomatis in the lower genital tract.

Chlamydial secretory IgA antibodies in human milk

Colostrum from 10 of 30 randomly chosen women contained IgA antibodies to Chlamydia trachomatis as shown by an enzyme-linked immunosorbent assay and a single-antigen immunofluorescence test. Specific colostral IgA was present only in seropositive women. In addition, Chlamydial-specific IgA was also detected in milk from 5 of 6 women who were shown to harbour C. trachomatis in the lower genital tract during delivery. There was a close correlation between chlamydial-specific IgA and the chlamydial secretory immunoglobulin titres in colostrum and milk samples but not between chlamydial IgA titres and the total secretory IgA content. No agreement was observed between the specific IgA antibodies in milk and corresponding serum samples. It is suggested that chlamydial-specific IgA in milk is induced by genital infections.

Chlamydia trachomatis: serological diagnosis

Satisfactory methods for the serodiagnosis of Chlamydia trachomatis have been widely discussed in recent years. Until a decade ago, the complement-fixation test measuring group-specific antibody was the most widely applied technique. However, despite showing relatively high diagnostic sensitivity in systemic chlamydial infections, it is of little value in the serodiagnosis of localized chlamydial oculo-genital infections or of trachoma. The more recently developed microimmunofluorescence (micro-IF) test is not only a very sensitive technique, but can also reach a high degree of serodiagnostic specificity in certain chlamydial infections. Unlike the complement-fixation test, it measures type-specific antibody which may be directed against one or more C trachomatis serotypes. By nature, chlamydia infections often lead to high background rates of antibody in affected populations. Interpretation of serological results may therefore be difficult, particularly when only single-serum samples are available. However, in seroepidemiological work, in the study of transmission patterns and in the detection of predominant serotypes in a community, the micro-IF test is especially valuable, and if results are interpreted with care, the test may also serve as an indicator of chlamydial infection. The predictability, sensitivity and specificity of serological tests for C. trachomatis will be discussed.

Immunity to reinfection of the genital tract of marmosets with Chlamydia trachomatis

Eleven marmosets inoculated intra-vaginally with either of 2 serotypes (D/E and H) of Chlamydia trachomatis developed a self-limited infection which persisted usually for 10-42 days. Animals re-inoculated on one or more occasions were, however, infected generally for a shorter duration, usually 3-7 days. Curtailed infections were observed after re-inoculation with either the same or a different serotype, indicating that immunity was not serotype specific but cross-protective. IgM and/or IgG chlamydial antibody, measured by micro-immunofluorescence, developed in most of the marmosets on primary infection and was not serotype specific. The antibody titres were boosted on re-infection and there was a correlation between pre-existing high antibody titres and infections of short duration. Chlamydial infection of the genital tract was accompanied by acute inflammation which persisted in about half of the immune animals for up to several weeks despite rapid clearance of the organisms. These features of the experimental infection should help to provide a greater understanding of the immunobiology and pathogenesis of chlamydial genital-tract infections of humans.

A microbiological study of non-gonococcal proctitis in passive male homosexuals

In a study of 180 male homosexual patients attending a venereal disease clinic, a correlation was sought between symptoms and signs of proctitis and the isolation of Neisseria gonorrhoeae, group B streptococci, Chlamydia trachomatis, Ureaplasma urealyticum, Mycoplasma hominis and herpes simplex virus. Faecal specimens were examined for enteric pathogens and serological tests for hepatitis B virus, syphilitic and chlamydial infections were performed.

There was no association between proctitis, as diagnosed by examination of a Gram-stained rectal smear, and the isolation of any micro-organism or detection of a positive serological test. There was, in addition, no association between any symptom or abnormal physical sign and any positive microbiological findings. Since 23% of patients from whom N. gonorrhoeae was isolated had no abnormal physical signs, it is difficult to assign a pathogenic role to other micro-organisms isolated from patients with and without clinical signs of proctitis. Approaches to further investigation of the problem are discussed.

Clinical and microbiological study of non-gonococcal urethritis with particular reference to non-chlamydial disease

A double-blind placebo-controlled study of minocycline in 221 men with non-gonococcal urethritis (NGU) was undertaken. Techniques were used which enabled diagnoses of chlamydial and mycoplasmal infections to be made within 24 hours of a patient attending a clinic. All patients from whom Chlamydia trachomatis was isolated were treated with minocycline, while patients from whom Ureaplasma urealyticum or Mycoplasma hominis was isolated, or from whom no micro-organisms were isolated, were treated on a double-blind basis with either minocycline or placebo. Chlamydia were isolated from 77 (35%) patients and were eradicated by minocycline from 76 (99%). Ureaplasmas were isolated initially from 96 (43%) patients. Treatment with minocycline eradicated them from 43 of 52 (83%) patients, and they disappeared from six of 31 (19%) patients who were treated with placebo. After one week significantly more patients had responded clinically to minocycline than to placebo. The response to minocycline was not influenced by the microbiological status of the patients, which suggests that ureaplasmas are playing a similar role to chlamydia in the pathogenesis of the disease and that an antibiotic-sensitive micro-organism may be producing disease in the isolate-negative group. An immunological approach is required to resolve the problem of the persistent urethral inflammation which occurred despite eradication of the micro-organisms.

Microbiological, serological, and histopathological features of experimental Chlamydia trachomatis urethritis in chimpanzees

A laboratory-passaged genital strain of Chlamydia trachomatis and two unpassaged genital strains from patients with nongonococcal urethritis were inoculated intraurethrally into three young male chimpanzees. Chlamydia were recovered from the urethra of two animals and specific antibody responses were detected in all of them. Furthermore, a urethral polymorphonuclear leucocyte response, but not an overt discharge, occurred in all the chimpanzees about 1-2 weeks after inoculation. None of these events occurred in a chimpanzee inoculated with medium only. At necropsy three months after inoculation the submucosa of the urethra of one chimpanzee was densely infiltrated with small round cells. This suggests that a similar chronic lymphocytic response may occur in human chlamydial infection of the urethra.

Evidence of Chlamydia trachomatis infection in sexually acquired reactive arthritis

Thirty male patients with sexually acquired reactive arthritis (SARA) have been studied at the time of their initial presentation and thereafter. Chlamydia trachomatis was isolated from the urethral exudate of 9 (36.0%) of the 25 patients from whom urethral specimens were taken, and elevated titres of IgM antibody of C. trachomatis were detected in 11 (36.6%) of the 30 initial sera. Thirteen (43.3%) of the patients has a positive urethral culture and/or elevated titre of IgM antibody, and it is therefore suggested that 43.3% of these patients suffered an acute chlamydial infection at or near the time of the onset of their joint disease. The demonstration of 4-fold or greater rises and/or falls in IgM antibody titre (8 patients) and IgG antibody titre (6 patients) in a group of 15 men studied throughout the course of their disease strongly supports this conclusion. A positive urethral culture and/or raised titre of IgM serum antibody was also detected in 25 (50%) of 50 men with uncomplicated nongonococcal urethritis (NGU), suggesting that the prevalence of chlamydial infections in the 2 conditions is similar. Titres of IgG serum antibody to C. trachomatis were, however, significantly higher in patients with SARA than in those with NGU or other rheumatic diseases, and in healthy controls. The geometric mean titres (GMT) of IgG serum antibody in patients with SARA, NGU, rheumatoid arthritis, ankylosing spondylitis, systemic lupus erythematosus, and in healthy controls were 1:47.5, 1:8.6, 1:2.2, 1;2.2, 1:3.5, and 1:1.4, respectively. These findings suggest that an exaggerated antibody response to acute infection by C. trachomatis may be an important factor in the development of SARA in some but not all patients.

Experimental infection of the marmoset genital tract with Chlamydia trachomatis

A strain of Chlamydia trachomatis isolated in McCoy cells from the urethra of a patient suffering from non-gonococcal urethritis was inoculated into the vagina of 8 female marmosets. Chlamydiae were isolated repeatedly for 10-42 days from the lower genital tract of 7 of the marmosets. Six of the infected animals developed an acute inflammatory reaction in the genital tract and chlamydial inclusions in epithelial cells were seen in smears from 2 of them. In addition, each of 6 infected marmosets examined developed humoral antibodies to C. trachomatis. In contrast, 3 control animals inoculated intravaginally with chlamydia-free McCoy cells showed no evidence of chlamydial infection. Since the marmoset is small and easily bred in captivity, it should provide a useful model for studying the mechanisms of chlamydial pathogenicity.

The rôle of Chlamydia trachomatis in genital-tract and associated diseases

Images

Reticulate bodies as single antigen in Chlamydia trachomatis serology with microimmunofluorescence

Formalin-fixed, purified reticulate bodies (RB) of Chlamydia trachomatis immunotype C/TW-3/OT were used as a serological test antigen in the microimmunofluorescence test. The sensitivity and specificity of the RB antigen were compared to elementary bodies (EB) used as antigens in the detection of C. trachomatis antibodies in human sera by microimmunofluorescence. RB reacted with all known C. trachomatis immunotypes with the same sensitivity as the homotypic EB. In routine serology with sera and endocervical secretions, the RB antigen had a sensitivity similar to that of the EB in detecting serum antibodies, endocervical secretion antibodies, and antibodies of immunoglobulin M and G classes. No false-positive reactions were detected with control sera. All positive reactions showed type-specific antibodies against an EB immunotype. RB seemed to demonstrate chlamydial group reactivity; sera from 10 psittacosis patients diagnosed clinically and serologically by complement fixation showed five positive, three equivocal, and two negative reactions. By immunofluorescence, RB appeared as distinct rings demonstrating uniform peripheral surface fluorescence at their rims. The EB appeared as pinpoint-sized dots. C/TW-3/OT RB used as a single test anitgen should provide a simple and sensitive serological assay for the detection of C. trachomatis antibody.

Formalinized Chlamydia trachomatis organisms as antigen in the micro-immunofluorescence test

Chlamydia trachomatis organisms grown in HeLa 229 cell cultures were purified and formalinized for use in the micro-immunofluorescence test. As test antigens, they were stable when stored unfrozen at 4 degrees C for a long period of time without loss of type specificity and sensitivity.

Low frequency of chlamydial antibodies in patients with Crohn's disease and ulcerative colitis

Serum samples from 55 patients with Crohn's disease and from 23 patients with ulcerative colitis were tested for antibodies to Chlamydia trachomatis immunotypes by a micro-immunofluorescence technique. Antibody titres of 1:8 or greater against several immunotypes were detected in 14.5% of patients with Crohn's disease and in 21.7% of those with ulcerative colitis. These figures resemble the incidence in a healthy, non-venereal-disease population. Furthermore, there was no correlation between the presence of antibody and such factors as duration of symptoms, localisation of disease, or disease activity. These findings indicate that there is no reason to believe that Crohn's disease involves chlamydiae or that examination for chlamydial antibody is helpful in diagnosis.

Single-antigen immunofluorescence test for chlamydial antibodies

A simple method is presented for producing large numbers of inclusions of Chlamydia trachomatis serotype L2 in cell cultures on slides for immunofluorescence antibody staining. Preliminary results with a total of 1,241 human sera from different groups were consistent with findings by earlier methods: 82% of chlamydia-positive men with nongonococcal urethritis had antibodies at titers of greater than or equal to 8, with a geometric mean titer (GMT) of 44.9; 68.5% of chlamydia-negative men with nongonococcal urethritis had titers of greater than or equal to 8, with a GMT of 38.6; 27% of male blood donors had titers of greater than or equal to 8, with a GMT of 19.6; 95.0% of chlamydia-positive women had titers of greater than or equal to 8, with a GMT of 80.3; 67.0% of chlamydia-negative partners of men with nongonococcal urethritis had titers of greater than or equal to 8, with a GMT of 47.0; 50.2% of control women had titers of greater than or equal to 8, with a GMT of 27.7% and 8.1% of children (aged 1 to 15 years) had titers of greater than or equal to 8, with a GMT of 17.8.