Comparison of enzyme linked immunosorbent assay and enzyme linked fluorescence immunoassay for detection of antibodies against Chlamydia trachomatis

Enzyme immunoassay with enhanced specificity for detection of antibodies to Chlamydia trachomatis

Two different methods for preventing the binding of cross-reacting antibodies to the genus-reactive chlamydial lipopolysaccharide (LPS) were used to improve the specificity of an enzyme immunoassay for the determination of antibodies to Chlamydia trachomatis. Coated elementary bodies were treated with either sodium periodate, to oxidize the antigenic sites of the LPS, or Triton X-100, to extract the LPS. By using these new enzyme immunoassays, the standard enzyme immunoassay, and the whole inclusion fluorescence (WIF) assay, antibodies to C. trachomatis were determined in sera from different groups of patients and controls. Paired serum samples from patients with culture-proven urogenital C. trachomatis infections showed similar responses in all three assays. Paired serum samples from patients with Chlamydia psittaci infections showed similar responses in the WIF assay and the standard enzyme immunoassay, whereas significantly reduced titers were obtained in the enzyme immunoassays with treated antigen, especially in the convalescent-phase serum samples. Serum samples from patients with symptoms suggestive of infection with C. trachomatis, pregnant women, and blood donors were evaluated by all three types of assays. Eighty percent of the significant reductions in immunoglobulin G (IgG), IgA, and IgM titers were observed in sera with WIF assay titers in the lower classes (IgG, 1: < or = 256; IgA, 1: < or = 32; IgM, 1: < or = 16). From these results we conclude that oxidation of the antigen by sodium periodate is a simple and effective method of producing an enzyme immunoassay with enhanced specificity that could be useful for diagnostic purposes and seroepidemiological studies.

Comparison of different serological methods for the determination of antibodies to Chlamydia psittaci in pigeon sera

Several methods for detecting antibodies to Chlamydia psittaci using sera from pigeons were compared with regard to their sensitivity, specificity and efficacy. The reference method used was indirect immunofluorescence (IFI), which uses as antigen intracellular inclusions in McCoy cell monolayers. Indirect micro-immunofluorescence (MIF) using as antigen C. psittaci cultured on yolk sacs of embryonated eggs, direct and indirect complement fixation tests (CFT and ICFT, respectively), and enzyme-linked immunosorbent assay (ELISA) were compared to the reference method. Indirect micro-immunofluorescence proved to be the most efficient method, while ELISA was the most sensitive, though showing a very low specificity. No statistically significant difference was found in comparing the two complement fixation tests. The use of ICFT to check for the negative results obtained in CFT is questioned. Possible reasons for the different results with the methods used are discussed.

Detection of IgG, IgM and IgA antibodies in patients with uncomplicated Chlamydia trachomatis infection: a comparison between enzyme linked immunofluorescent assay and isolation in cell culture

The diagnostic value of serum IgG, IgM and IgA in patients with uncomplicated urogenital Chlamydia trachomatis infection was compared with isolation in cell culture. C. trachomatis specific antibodies were determined with an enzyme linked immunofluorescent assay using elementary bodies from C. trachomatis serotypes E,F,H,I,J and LGV2 as antigens. At least two sera from each patient were tested and cultures were also established on the same day. Excluding the IgM titres in men, significantly more IgG, IgA and IgM and combinations of these antibodies were observed in culture positive patients. The sensitivity with which IgG titres in men or IgG and/or IgM titres in men and women could be determined, was significantly lower using C. trachomatis LGV2 as the only antigen than when all 6 antigens were used. The presence of 10 or more leucocytes in the urine sediment of men correlated positively with an IgG or an IgG and/or IgM titre.

Laboratory techniques for the diagnosis of chlamydial infections

Yolk-sac inoculation of embryonated eggs was superseded 25 years ago by the use of cell cultures (often McCoy) for the isolation of Chlamydia trachomatis. Centrifugation of specimens onto the cell monolayers was shown to increase sensitivity, but little of late has further improved sensitivity which is at least ten-fold greater than that of eggs. However, culture is slow and labour intensive so that non-cultural techniques without these drawbacks have come to dominate. Direct fluorescent antibody (DFA) tests are rapid and have sensitivities that range from 70% to 100% for men and 68% to 100% for women, and specificities that range from 87% to 99% for men and 82% to 100% for women; if the tests are read by competent observers the values are at the top end of the ranges. The detection rate may be enhanced even further by relatively low-speed centrifugation of specimens before staining. Skilled reading is not a feature of enzyme immunoassays (EIAs) which according to the literature have sensitivities that range from 62% to 97% for men and 64% to 100% for women, and specificities that range from 92% to 100% for men and 89% to 100% for women. However, comparison against poor reference tests is responsible for most of the higher values and the clinician should not be misled into believing that EIAs have excellent sensitivity; the lower values in the ranges are closer to reality. Furthermore, EIAs that are being designed for use by general practitioners should be regarded with the greatest caution since lack of sensitivity means that chlamydia-positive patients will go undetected. The polymerase chain reaction (PCR) is not bedevilled by insensitivity but it is no more sensitive than the most sensitive cell culture or DFA tests. PCR is unsuitable for routine diagnosis but has a place as a research tool. For men, examination of "first-catch" urine samples by the best of the non-cultural procedures provides an acceptable non-invasive approach to diagnosis; for women, the value of examining urine may be less, but needs to be thoroughly tested. However, there is little doubt that a Cytobrush used to obtain cervical specimens holds no practical advantage over a swab. Serological tests are reliant on the provision of paired sera for making a diagnosis; high antibody titres in single sera may be suggestive of an aetiological association in deep-seated chlamydial infections (epididymitis, arthritis, salpingitis, etc), but unequivocal interpretation is unusual, particularly in an individual case, since the distinction between a current and past infection is problematical.

Chlamydia trachomatis infections in infants

In recent years considerable progress has been made in understanding chlamydial infections. The spectrum of pediatric Chlamydia trachomatis infection includes neonatal inclusion conjunctivitis, infantile pneumonia, occasional respiratory or genital tract infections in older children and sexually transmitted diseases in adolescents. The role of maternal chlamydial infection in prematurity and in perinatal death is currently an area of active study. We outline the current knowledge of the biologic characteristics of C. trachomatis, the epidemiologic features of chlamydial infection, and the clinical aspects, diagnosis and treatment of neonatal chlamydial infections.

Immunodiagnosis of ocular chlamydial infection

The diagnostic roles of enzyme immunoassay and indirect immunofluorescence tests were studied in 99 patients with various grades of active trachoma and in 72 patients with inactive trachoma. Normal individuals and patients with non-specific chronic conjunctivitis were used as a control group. Chlamydial antigens were detected in the conjunctival swabs from a large proportion of patients with severe or moderate trachoma. Cases with 'antigen-negative' but clinically severe trachoma showed presence of specific IgG in the blood, thus indicating that serological tests may complement the ELISA test for the detection of chlamydia in infected tissues. The nature of cellular reaction in the conjunctiva seems to be related to the severity of trachoma and presence of the infective organism. 'Antigen-negative' trachoma thus represents either an error of diagnosis or limited sensitivity of currently available immunologic techniques, or a predominantly hypersensitivity state triggered by transient tissue parasitism. Recombinant DNA technology and chronobiologic study of infiltrating lymphocytes are likely to provide some insight in such cases.

Immunocytochemical demonstration of Chlamydia infection in the urogenital tracts

The peroxidase-antiperoxidase (PAP) technique was applied in cellular samples for the detection of chlamydial infection. Urethral scrapings were obtained from 316 males with clinically suspected urethritis. Positive PAP staining was detected in 118 (37%) of 316 tested. Cellular samples from the endocervix of 25 (54%) of 46 female contacts of males with positive Chlamydia-infected cells had positive Chlamydia-PAP staining. Chlamydia was also found in 12 (25%) of 48 male with gonorrhea. Serum IgG antibodies against Chlamydia trachomatis were evaluated using an enzyme-linked immunosorbent assay. A total of 29 out of 73 patients had positive Chlamydia serology; of these, 21 were positive for PAP staining, and eight were negative. The determination of Chlamydia antigen by means of the PAP technique appears to be a satisfactory method for detecting Chlamydia in male and female genital specimens; also, the procedure can be done readily in most laboratory settings.

Relationship between Chlamydia trachomatis infection and elevated serum immunoglobulin M levels in premature infants

Serum immunoglobulin M (IgM) antibodies to Chlamydia trachomatis and to human cytomegalovirus (CMV) were detected by enzyme-linked fluorescence assay and enzyme-linked immunosorbent assay, respectively in 19 premature infants with chronic lung diseases, in 43 extremely low birth weight premature infants and in 123 neonates with elevated serum IgM levels. Ten of the 19 premature infants with chronic lung diseases had elevated serum IgM levels, and five had IgM antibodies to Chlamydia trachomatis. Three of the 43 extremely low birth weight premature infants had elevated serum IgM levels, and two had IgM antibodies to Chlamydia trachomatis. Three of the 123 neonates with elevated serum IgM levels (excluding those with chronic lung diseases and extremely low birth weight) had IgM antibodies to CMV. These results suggest that chronic lung diseases in low birth weight infants might be caused by intrauterine Chlamydia trachomatis infection.

Chronic respiratory disease in premature infants caused by Chlamydia trachomatis

The relation between chronic respiratory disease and infection with Chlamydia trachomatis in premature infants was investigated to ascertain the aetiological importance of intrauterine C trachomatis infection and chronic respiratory disease in premature infants. Serum IgM antibodies against C trachomatis were determined by enzyme linked fluorescence assay. Sections of lung tissues obtained by biopsy and at necropsy were also tested for the presence of antigens using fluorescein conjugated monoclonal antibodies to C trachomatis. Of 16 sera from premature infants with chronic respiratory diseases clinically diagnosed as bronchopulmonary dysplasia or the Wilson-Mikity syndrome, five had IgM antibodies to C trachomatis L2 strain by enzyme linked fluorescence assay (titre greater than or equal to 1/500). Of 37 sera from premature infants with extremely low birth weights, two had IgM antibodies to C trachomatis. No specific IgM antibody was detected in 31 neonates who showed raised serum IgM concentrations but who did not have respiratory tract symptoms. C trachomatis was identified from two specimens of lung tissue obtained at necropsy from premature infants with chronic respiratory disease positive for IgM antibody. These findings indicate the aetiological importance of intrauterine C trachomatis infection in chronic respiratory disease in premature infants.

Detection of IgM antibodies against Chlamydia trachomatis by enzyme linked fluorescence immunoassay

A simple, sensitive enzyme linked fluorescence immunoassay has been developed to detect IgM antibodies against Chlamydia trachomatis. Reticulate bodies and elementary bodies from C trachomatis L2/434 Bu strain were isolated and used as antigens in the assay. Of 113 serum samples obtained from infants with pneumonia, 27 (23.9%) had IgM antibodies to C trachomatis L2 reticulate bodies and nine (8.0%) had IgM antibodies to C trachomatis L2 elementary bodies (titre greater than or equal to 1/500). Specific IgM antibodies were not detected in 20 control serum samples obtained from healthy adults and children. The possible use of enzyme linked fluorescence assay to determine IgM antibodies in the serodiagnosis of C trachomatis infection is discussed.