Chlamydia pneumoniae Serology: Importance of Methodology in Patients with Coronary Heart Disease and Healthy Individuals

Abstract

Most publications on the relationship between infection with Chlamydia pneumoniae and coronary heart disease (CHD) propose an association, but negative studies are also reported. Seroepidemiological studies vary in the use of different serological methods, different cutoff limits, different sampling times in relation to acute cardiac events, and different clinical stages of CHD. We wanted to compare three different commercially available methods for measuring Chlamydia antibodies to see how the choice of method influenced the prevalence of seropositive individuals in CHD patients and in healthy individuals and to see if sampling time in relation to an acute cardiac event or the stage of atherothrombotic disease influenced the results. Blood samples from 197 CHD patients and 197 individually matched healthy control individuals were tested at baseline and after 6 months; the mean age was 55 years in both groups, and 18% were women. Among the CHD patients, 166 were included at a median of 16 days after an acute cardiac event and 31 had chronic disease with the latest acute event being >3 months earlier. The difference in prevalence of antibodies between the CHD patients and the healthy controls was significant when Chlamydia lipopolysaccharide antibodies were measured, while no significant differences between the study groups were observed by the two methods detecting Chlamydia pneumoniae major outer membrane protein antibodies. The number of seropositive individuals was quite similar at inclusion and 6 months later, and no significant differences were observed between patients with a recent cardiac event and those with a more remote cardiac event. We conclude that the choice of serological method is of major importance when evaluating a possible relationship between C. pneumoniae and CHD.The old hypothesis that atherosclerosis could be caused by infectious agents has received new attention during the last 15 years, and Chlamydia pneumoniae is one of the main pathogens under suspicion. Since Saikku et al. (31) proposed an association between C. pneumoniae and coronary heart disease (CHD), many reports from different countries have been published, with diverging results (10,11,14,17,25,37). Although some investigations are based on direct immunofluorescence or PCR demonstrating C. pneumoniae in situ in the atherosclerotic plaque, most studies are based on serology, using different methods to detect human antibodies against the organism. Two basic methods are used: microimmunofluorescence tests (MIF) or enzyme immunoassays (EIA and ELISA techniques). Some tests detect antibodies to the species-specific major outer membrane proteins (MOMP), and some detect antibodies to the chlamydia lipopolysaccharide (LPS), which is common to Chlamydia pneumoniae, Chlamydia trachomatis, and Chlamydia psittaci. Furthermore, the titer end points used as cutoff values for seropositivity when comparing various groups differ in various studies.The aim of the present study was to compare three different, commonly used methods for measuri...

Comparison of Eleven Commercial Tests for Chlamydia pneumoniae -Specific Immunoglobulin G in Asymptomatic Healthy Individuals

“…All these samples also had IgG antibodies, and in total, 70% of the IgG-positive samples were IgA positive as well. Schumacher et al have also been reported a lower prevalence of IgA than of IgG in healthy controls (44). Therefore, detection of IgG seems to be the more sensitive method for determination of the seroprevalence of anti-C. pneumoniae antibodies in a healthy population.…”

“…We found 30 (54%) of the truepositive samples to be positive by rELISA. In addition, it has been found that rELISA detects a lower prevalence of Chlamydia-specific IgG antibodies than MIF does in patients with chronic obstructive pulmonary disease and coronary heart disease (44,46). Most of the samples which were found to be positive by the rELISA had high antibody titers by MIF, which might indicate a very recent infection.…”

Importance of Methodology in Determination of Chlamydia pneumoniae Seropositivity in Healthy Subjects and in Patients with Coronary Atherosclerosis

“…The MC rELISA was used for Chlamydia LPS analysis and therefore was not able to differentiate between antibodies against the different Chlamydia species, e.g., C. pneumoniae, C. trachomatis, and C. psittaci. However, discordant serological results between MIF and the MC rELISA should not necessarily be ascribed to the Chlamydia species specificity versus the genus specificity of the tests, since differences could also exist in the human immunological response, as suggested by Schumacher et al (25). In addition, cross-reactions between the different chlamydial species have recently been reported with the MIF test, bringing into question the specificity of the reference test.…”

Involvement of Chlamydia pneumoniae in Atherosclerosis: More Evidence for Lack of Evidence

“…In contrast to MIF tests, enzyme immunoassays are easier to perform, less time-consuming, and more objective because of the photometric reading involved. Nevertheless, three recent studies have demonstrated that the link between C. pneumoniae and coronary artery disease depends on the serologic method chosen to measure the C. pneumoniae antibodies (29,45,62).In summary, although initial reports were positive, the later ones, often prospectively designed and adjusted for known cardiovascular risk factors, showed a negative or weak positive association overall between seropositivity for C. pneumoniae and atherosclerosis. Importantly, methodology has a strong impact on the link between C. pneumoniae and atherosclerosis.…”

“…In contrast to MIF tests, enzyme immunoassays are easier to perform, less time-consuming, and more objective because of the photometric reading involved. Nevertheless, three recent studies have demonstrated that the link between C. pneumoniae and coronary artery disease depends on the serologic method chosen to measure the C. pneumoniae antibodies (29,45,62).…”