A preliminary evaluation of a new enzyme immunoassay to detect Chlamydia pneumoniae-specific antibodies

A review of serological tests to assist diagnosis of reactive arthritis: critical appraisal on methodologies

On a population-based level, the incidence of reactive arthritis (ReA) is 0.6–27/100,000. The definition of ReA varies and its pathogenesis is not yet clear. Attempts in basic immunology to suggest hypotheses for proliferation of forbidden B cell clones, molecular mimicry, and involvement of cross-reactive antibodies are helpful but not sufficient. Importantly, for the clinical diagnosis of the preceding infection, serology is widely used. Unfortunately, the accuracy of associations between serologic findings and clinical conclusions is plagued by poor standardization of methods. So far, few attempts have been done to examine the pitfalls of different approaches. Here, we review several serologic techniques, their performance and limitations. We will focus on serology for Yersinia, Campylobacter, Salmonella, Shigella, and Chlamydia trachomatis because these bacteria have a longer history of being associated with ReA. We also address controversies regarding the role of serology for some other bacteria linked to autoimmune disorders.

Chlamydia pneumoniae antibody levels before coronary events in the Helsinki Heart Study as measured by different methods

The lack of specific tests for the diagnosis of chronic Chlamydia pneumoniae infection has led to the use of enzyme immunoassay (EIA) instead of the gold standard, that is, microimmunofluorescence (MIF), in the measurement of C. pneumoniae antibodies. We assessed the predictive values of C. pneumoniae antibody levels and seroconversions measured by MIF and EIA for coronary events in the prospective Helsinki Heart Study. Sera from 239 cases with coronary events and 239 controls were available at the baseline and data from 210 cases and 211 controls before and after the event. The agreement between MIF and EIA antibody levels was best in high antibody titers. In conditional logistic regression analysis, only high IgA MIF titers (>/=40) at the baseline predicted future coronary events, and the participants with MIF seroconversion between consecutive sera had a higher (nonsignificant) risk for coronary events than the controls. The difference in the kinetics of EIA and MIF antibodies demonstrated that MIF should remain the gold standard.

Simkania negevensis and newly diagnosed asthma: a case-control study in 1- to 6-year-old children

BACKGROUND

Simkania negevensis is an intracellular bacterium, sharing many characteristics with Chlamydophila and Chlamydia species. S. negevensis infection has been associated with bronchiolitis in infants and with pneumonia and exacerbations of COPD in adults.

OBJECTIVE

The aim of the present study was to evaluate, in a case-control setting, whether S. negevensis serology had any association with the onset of asthma in children.

METHODS

S. negevensis-specific IgM, IgA and IgG antibodies were measured by microimmunofluorescence in 104 children below school-age with newly diagnosed asthma, and in 122 control children.

RESULTS

S. negevensis-specific IgM was detected in two (2%) cases and in nine (8%) of the controls. IgG was detected in 12 (12%) cases and 12 (10%) of the controls. IgA antibodies were absent in all children. The age distribution of the 35 children with S. negevensis-specific antibodies was even, the positivity rate being 11% in the 12- to 23-month-old group and 20-23% in the children aged between 2 and 5 years.

CONCLUSION

Although S. negevensis appears to cause infections in the Finnish preschool-aged population, there was no association with asthma.

Chlamydia pneumoniae and newly diagnosed asthma: a case-control study in 1 to 6-year-old children

OBJECTIVE

The aim of the study was to evaluate the association between antibodies to Chlamydia pneumoniae and the onset of asthma in children.

METHODOLOGY

In 1996-2000, 122 children aged 1-6 years, who were treated for new asthma as inpatients or outpatients in our hospital, were recruited. For each patient, two controls, matched by age, sex and municipality, were randomly selected from the same population. In 2000, 104 serum samples were available from patients (85%) and 120 from controls (49%) for microimmunofluorescence (MIF) assay for C. pneumoniae and C. trachomatis antibodies, and for enzyme immunoassay (EIA) for C. pneumoniae antibodies.

RESULTS

In EIA, the median IgG concentrations were 20 EIU (EIA units) in the patients, and 16 EIU in the controls. IgG was positive (> 30 EIU) in 37 (36%) patients and in 36 (31%) controls. IgA was positive (> 12 EIU) in four (4%) patients and in eight (7%) controls. In MIF, four (4%) patients and seven (6%) controls were IgG positive, and seven were also IgA positive. IgM antibodies were detected in four children by EIA, and in none by MIF.

CONCLUSION

IgG antibodies to C. pneumoniae, though common in 1 to 6-year-old children as detected by EIA, did not differ between newly diagnosed asthma patients and controls in this case-control study.

Etiology of community-acquired pneumonia in hospitalized school-age children: evidence for high prevalence of viral infections

BACKGROUND

Community-acquired pneumonia (CAP) in young children is most commonly associated with viral infections; however, the role of viruses in CAP of school-age children is still inconclusive.

METHODS

Seventy-five school-age children hospitalized with CAP were prospectively evaluated for the presence of viral and bacterial pathogens. Nasopharyngeal washes were examined by polymerase chain reaction for viruses and atypical bacteria. Antibody assays to detect bacterial pathogens in acute-phase and convalescent-phase serum samples were also performed.

RESULTS

A viral infection was identified in 65% of cases. Rhinovirus RNA was detected in 45% of patients; infection with another virus occurred in 31%. The most common bacterial pathogen was Mycoplasma pneumoniae, which was diagnosed in 35% of cases. Chlamydia pneumoniae DNA was not detected in any patient; results of serological tests were positive in only 2 patients (3%). Mixed infections were documented in 35% of patients, and the majority were a viral-bacterial combination.

CONCLUSIONS

The high prevalence of viral and mixed viral-bacterial infections supports the notion that the presence of a virus, acting either as a direct or an indirect pathogen, may be the rule rather than the exception in the development of CAP in school-age children requiring hospitalization.

Use of quantitative and objective enzyme immunoassays to investigate the possible association between Chlamydia pneumoniae and Mycoplasma pneumoniae antibodies and asthma

Sera from 150 consecutive patients with established asthma and 150 matched controls were examined for Chlamydia pneumoniae IgG and IgA with commercially available enzyme immunoassays (EIAs) detecting immune response solely to surface proteins of elementary bodies. The assays were also modified to measure combined immune response to surface proteins and family-specific lipopolysaccharide antigen. Mycoplasma pneumoniae IgG and IgA were measured with new commercial EIAs utilising P1-enriched protein fraction as an antigen. No statistically significant differences between the patient groups in terms of prevalence or levels of antibodies to either organism were found with these methods.

The reproducibility of an enzyme-linked immunosorbent assay for detection of Chlamydia pneumoniae-specific antibodies

With use of an enzyme-linked immunosorbent assay (ELISA), Chlamydia pneumoniae immunoglobulins were detected in a consecutive series of patients' sera (n = 122 for IgA and IgG; n = 138 for IgM). When the ELISA tests were repeated, the percentage disagreements were 12%, 16% and 10% for C. pneumoniae IgA, IgG and IgM, respectively. The reproducibility of the ELISA, expressed as kappa values, for IgA, IgG and IgM was 0.73, 0.60 and 0.53, respectively (p < 0.001). It was concluded that the ELISA had good reproducibility for detecting C. pneumoniae IgA, and moderately good reproducibility for detecting C. pneumoniae IgG and IgM.

Chlamydia antibody response in healthy volunteers immunized with nonchlamydial antigens: a randomized, double-blind, placebo-controlled study

Serological analysis is often used for the diagnosis of chlamydial infections. However, an increase in Chlamydia antibodies has been reported in patients with parvovirus and Mycoplasma infections. Whether this antibody response is the result of dual infection or nonchlamydial antigen stimulation is unknown. In a randomized study, 48 healthy volunteers either were immunized against yellow fever, polio, diphtheria, and tetanus (the group receiving intervention with nonchlamydial antigen) or received saline injections (the placebo group). The change in antibody levels was compared between the 2 groups. The Chlamydia recombinant lipopolysaccharide enzyme-linked immunosorbent assay (Medac) showed an increase in the antibody titer in the intervention group, compared with that in the control group (for immunoglobulin M, P=.004; for immunoglobulin A, P=.038; and for immunoglobulin G, P=.056), but no differences between study groups was found when the C. pneumoniae enzyme immunoassay (EIA; ThermoLabsystems), the C. pneumoniae EIA (Medac), and the microimmunofluorescence test (MRL) were used. An increase in antibodies to Chlamydia organisms can be measured after exposure to nonchlamydial antigens, depending on the test used.