Enzyme immunoassay to determine exposure to Chlamydia pneumoniae (strain TWAR)

Descripción de inmunógenos de Chlamydia pneumoniae reconocidos por el suero de sujetos con enfermedad arterial periférica

BACKGROUND AND OBJECTIVE

The relationship between antibodies to C. pneumoniae and presence of the bacteria was studied in individuals with peripheral arterial disease.

PATIENTS AND METHOD

An observational analytical, case-control study was performed in 118 patients (68 cases, 50 controls) to investigate immunoglobulin (Ig) G and A against C. pneumoniae in serum, using Western-blot (commercial and no commercial methods), ELISA and MIF; DNA of the bacteria in vascular tissue biopsy specimens was studied by polymerase chain reaction.

RESULTS

Using commercial Western-blot, significant presence of IgG anti-39 kDa and anti-54 kDa was found in cases and was related to MIF results and C. pneumoniae DNA findings; IgA anti-LPS, anti-92 kDa and anti-Hsp60 kDa were also found and related to DNA presence. Using no commercial Western-blot, significant presence of 128.8 and 9.2 kDa bands for IgG was detected in cases and associated with DNA presence; 70.8, 58.9, 47.9, 47.5, 18.4, 12.1, 10.6, 8.1, and 7.6 kDa bands for IgG were found in cases; and DNA was present when 54.6 and 1.1 kDa bands for IgG and 79.4, 50.1, and 18.4 kDa bands for IgA were also detected.

CONCLUSIONS

Using Western-blot, a greater serologic response was found against certain proteins of the bacteria in individuals with peripheral arterial disease. This may reflect an initial stage with presence of DNA and specific IgG. Subsequently, even in absence of the bacteria, an immunomediated disease may develop with presence of IgA and IgG.

Characterization of the humoral immune response to Chlamydia outer membrane protein 2 in chlamydial infection

Detection of antibodies to an outer membrane protein 2 (OMP2) by enzyme-linked immunosorbent assay (ELISA) by using either the Chlamydia trachomatis- or the Chlamydia pneumoniae-specific protein was investigated. OMP2 is an immunodominant antigen giving rise to antibody responses in humans infected with different C. trachomatis serovars (A to C and D to K) or with C. pneumoniae, which could be detected by OMP2 ELISA. OMP2 ELISA is not species specific, but antibody titers were usually higher on the homologous protein. The sensitivity of this assay was high but varied according to the "gold standard" applied. Levels of antibody to C. pneumoniae OMP2 as detected by ELISA seem to return to background or near-background values within a shorter period of time compared to antibodies to C. pneumoniae detected by microimmunofluorescence (MIF), making it more likely that positive results in ELISA reflect recent infection. Thus, OMP2 ELISA has distinct advantages over MIF and commercially available ELISAs and might be a useful tool for the serodiagnosis of chlamydial infection.

Chlamydia pneumoniae, Helicobacter pylori and cytomegalovirus infections and the risk of peripheral arterial disease in young women

Sero-epidemiological case control studies have observed positive relations between infections with Chlamydia pneumoniae, Helicobacter pylori or cytomegalovirus (CMV) and the occurrence of coronary artery disease (CAD) and stroke. Moreover, positive relations between 'infection burden' and CAD and the role of inflammation have recently been described. However, the relations between infection, inflammation and the occurrence of peripheral arterial disease (PAD) have not been reported so far. We performed a multi-centre population-based case-control study, using serum samples of 228 young female PAD patients and 643 control women to determine IgG antibody titres and C-reactive protein. The odds ratios for PAD in women with serological evidence for infection with C. pneumoniae, H. pylori or CMV were 2.0 (95% CI; 1.3-3.1), 1.6 (95% CI; 1.1-2.2) and 1.6 (95% CI; 1.1-2.3), respectively. The cumulative number of infections was positively related to the risk of PAD; the odds ratio was 1.5 (95% CI; 1.0-2.4), 2.7 (95% CI; 1.6-4.4) and 3.5 (95% CI; 1.5-8.1) for women with one, two or three infections, respectively. This increased risk, related to the 'infection burden', was found again in the subgroup of women with a high CRP level, but not in the subgroup with a low CRP level. Infections might be a causal component in the development of PAD. The risk of PAD is not only related to a single pathogen in particular, but also to the cumulative number of infections. The positive relation between 'infection burden' and PAD was only found in women with a high CRP level, which indicates that inflammation might be involved in the process that leads to PAD.

Evaluation of Chlamydia pneumoniae 43- and 53-kilodalton recombinant proteins for serodiagnosis by Western Blot

Chlamydia pneumoniae is a common cause of respiratory infection. It has also been shown to be associated with coronary heart disease. Two proteins that have been reported to be recognized frequently during human infection are proteins having molecular masses of 43 and 53 kDa. In order to develop a useful alternative serological test to the microimmunofluorescence (micro-IF) assay, recombinant 43-kDa and 53-kDa chlamydia-specific proteins were evaluated in dot blot and/or for comparison to the standard micro-IF test. Primers for amplification were derived from genome sequence information for two C. pneumoniae genes (CPn0809 and CPn0980) encoding 53-kDa proteins and four C. pneumoniae genes (CPn0562, CPn0927, CPn0928, and Cpn0929) encoding 43-kDa proteins of unknown function, which were Chlamydia specific and not found in Chlamydia trachomatis. The 53-kDa protein product of CPn0809 or the N-terminal 18-kDa portion had better specificity than any of the 43-kDa recombinants but was much less sensitive than micro-IF. In contrast, the 53-kDa protein encoded by CPn0980 was recognized by 11 of 12 (92%) acute-phase sera, 35 of 46 (76%) chronic sera, 0 of 12 micro-IF-negative sera (C. pneumoniae and C. trachomatis negative), and 1 of 12 (8%) C. pneumoniae negative, C. trachomatis positive sera. Thus, it appears that the 53-kDa protein encoded by CPn0980 has potential use for serodiagnosis of C. pneumoniae infection.

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

New enzyme immunoassays (EIAs) for determination of specific IgG, IgA, and IgM antibody titers to Chlamydia pneumoniae were evaluated independently in three research laboratories. Specificity of the EIAs was enhanced by removing LPS from the chlamydial antigen. The performance of these EIAs was evaluated in comparison with the microimmunofluorescence (MIF) test using specimens from: (i) a group of adult patients with community-acquired pneumonia (CAP) previously diagnosed as having an acute chlamydial infection by the complement fixation test or the whole inclusion fluorescence test; (ii) from a group of adult patients with acute respiratory tract infections; and (iii) from a group of young children consecutively presenting with acute respiratory tract infections. The MIF test and the EIAs detected acute infections in paired serum specimens from 12 of 14 patients from the first group. Eleven of these 12 patients were positive in both tests. The MIF test detected seven acute infections in single convalescence serum specimens from eight patients. Two of these were also positive in the EIAs. Paired serum specimens from the second group of adult patients (n=12) were collected during an epidemic of C. pneumoniae. The EIAs detected six acute infections. The MIF test detected two additional patients with acute infections. From the group of young children (n=30), the EIAs detected two patients with acute infections. Our conclusion from this preliminary evaluation is that these EIAs could be useful for laboratory diagnosis of acute C. pneumoniae infections. Comprehensive prospective studies should provide suitable data to calculate the sensitivity, specificity, and predictive values.

Antibodies to Chlamydia pneumoniae and clinical course in patients with unstable angina pectoris

Inflammation is one of the most important mechanisms that contribute to coronary artery disease (CAD). One of the micro-organisms that is mentioned as a source of the inflammation is Chlamydia pneumoniae. In this study, we investigated the relationship between titres of IgG and IgA antibodies to C. pneumoniae and the clinical course, during hospitalisation and during an 18-month follow-up, in 211 patients admitted to hospital with unstable angina pectoris. Slightly more patients who were refractory during their hospitalisation were positive for C. pneumoniae antibodies than patients who could be stabilised by drug treatment (53 vs. 43%, for IgG and 16 vs. 11% for IgA, respectively)(n.s.). In logistic regression analysis no significant predictive values were observed for the relationship between antibody titres and clinical course. The antibody titres to C. pneumoniae were lower in the unstable angina patients who had plasma levels of interleukin-10 (IL-10) above 5 pg/ml than in the patients with levels below 5 pg/ml, and higher in smokers than in non-smokers. No associations were observed between antibody titres to C. pneumoniae and C-reactive protein (CRP), interleukin-6 (IL-6), age, total cholesterol levels, fibrin degradation products (FDP), plasminogen activator inhibitor-1 (PAI-1) and erythrocyte sedimentation rate (ESR). In conclusion, there was no significant association between antibody titres to C. pneumoniae and risk of events during hospitalisation and the 18-month follow-up period in patients admitted for unstable angina pectoris.

The use of serologic tests for the diagnosis of chlamydial infections

Serology is commonly used for the diagnosis of acute Chlamydia pneumoniae infections and also for the diagnosis of complicated Chlamydia trachomatis infections. Furthermore, recent sero-epidemiological studies have linked C. pneumoniae infection with several diseases traditionally considered non-infectious. The objectives of this mini-review are to critically review and discuss some selected analytical and methodological aspects, controversies and current problems in chlamydial serodiagnosis. To illustrate our views we present some original data of the comparison of current technologies. The review of the literature revealed high variability in methodologies applied to different studies. This observation was supported by our own data, which explains occasional conflicting clinical interpretation. Although the microimmunofluorescence (MIF) technique is generally considered as the gold standard for serodiagnosis of chlamydial infections, assay conditions are highly variable and hence pose a major problem in the interpretation of the results. For instance, many recent studies linking C. pneumoniae and atherosclerosis have utilized MIF techniques with variable threshold criteria for the positivity, in combination with selection bias of cases and controls possibly leading to conflicting results. Variability of assay conditions is also a common problem with Western blots, and interpretation is problematic when both anti-C. pneumoniae and anti-C. trachomatis antibodies are present. Furthermore, there is a lot of disagreement in serological criteria applied to recently emerged enzyme immunoassay (EIA) techniques when these assays are used for acute and non-acute clinical conditions and their association with Chlamydiae. In conclusion, standardization of serological techniques and the development of uniform criteria for interpretation of serologic findings is necessary to increase our knowledge of the biology of Chlamydiae, pathogenesis of any chlamydial infection and chronic infections in particular.

Detection of Chlamydia species-specific serum antibodies by prior adsorption of common genus-specific antibodies

To establish a method for the detection of Chlamydia species-specific antibodies to the three species of Chlamydia responsible for human disease, the author attempted to remove Chlamydia genus-specific antibodies by prior adsorption with heterologous Chlamydia antigen. The effects of adsorption with heterologous antigen were investigated by the microplate immunofluorescence antibody technique. The Chlamydia genus-specific antibodies in immune animal sera were significantly reduced by prior adsorption with heterologous Chlamydia antigen. Chlamydia pecorum which does not infect humans was found to be useful for the adsorption. A preliminary test using Chlamydia trachomatis-infected human sera showed that this adsorption method with C. pecorum is applicable to the serodiagnosis of human Chlamydia infections.

Low prevalence of Chlamydia pneumoniae and Mycoplasma pneumoniae among patients with symptoms of respiratory tract infections in Dutch general practices

Acute respiratory disease is one of the most common reasons to consult a general practitioner. A substantial part of these diseases cannot be explained by an infection with a virus or a common pathogenic bacterium. To study this diagnostic deficit, the prevalence of Chlamydia pneumoniae and Mycoplasma pneumoniae infections was determined in two groups of patients consulting a general practitioner. DNA of C. pneumoniae and M. pneumoniae was detected by a polymerase chain reaction (PCR) in nose/throat swabs from six (1.1%), and from seven (1.3%) patients, respectively, of 557 patients consulting a general practitioner for complaints suggestive for a virus infection during the 1994/1995 respiratory infections season. Two patients remained C. pneumoniae PCR-positive for at least 4 weeks. All others were negative within 3 weeks. Double infections of C. pneumoniae and influenza virus (3/6), and of M. pneumoniae and respiratory syncytial virus (1/7) or rhinovirus (1/7) were diagnosed. During the 1992/1993 season, attempts to isolate C. pneumoniae in cell culture or to detect C. pneumoniae DNA by PCR using throat swabs were all negative for 80 patients with a sore throat, although serological data suggested a C. pneumoniae infection in 13 (16%) patients. A specimen from another patient of this group was M. pneumoniae PCR-positive and the corresponding serum specimens showed a persistent high antibody titre. In summary, the prevalence of acute C. pneumoniae and M. pneumoniae infections was less than 2% in patients consulting a general practitioner.

Chlamydia pneumoniae in abdominal aortic aneurysms: abundance of membrane components in the absence of heat shock protein 60 and DNA

In this article, we describe the results of a comparative study for the detection of Chlamydia pneumoniae in abdominal aortic aneurysm specimens of 19 patients through the use of immunocytochemistry (ICC), in situ hybridization (ISH), and polymerase chain reaction (PCR), along with the detection of cytomegalovirus (CMV) and herpes simplex virus (HSV) by ICC and PCR. C pneumoniae-specific membrane protein was detected in specimens of all 19 (100%; 95% confidence interval [CI] 82% to 100%) and of 15 (79%; 95% CI 54% to 94%) patients with monoclonal antibodies RR-402 and TT-401, respectively. Chlamydial lipopolysaccharide was detected in specimens of 15 (79%; 95% CI 54% to 94%) patients when the results of 4 different monoclonal antibodies were combined. Surprisingly, chlamydial heat shock protein 60 was not detected in any of the specimens by ICC. Furthermore, C pneumoniae DNA was not detected by ISH when a C pneumoniae major outer membrane protein gene fragment was used as probe, nor was it reproducibly detected by PCR on extracted DNA. These results may be explained either by different kinetics of degradation of the different components of C pneumoniae after infection of the vessel wall or by the involvement of other Chlamydia-like microorganisms. Coexistence of C pneumoniae antigens and HSV antigens but not CMV antigens was observed in specimens from 10 of 18 (56%; 95% CI 31% to 78%) patients by ICC. CMV and HSV DNAs were not detected by PCR. In conclusion, we have demonstrated the presence of antigens of C pneumoniae in the absence of specific DNA in abdominal aortic aneurysms, suggesting persistence of the antigens rather than a persistent infection.

Coronary angioplasty induces rise in Chlamydia pneumoniae-specific antibodies

Chlamydia pneumoniae is frequently found in atherosclerotic lesions, and high titers of specific antibodies are associated with increased risk for acute myocardial infarction. However, a causative relation has not been established yet. We performed a prospective study of 93 patients undergoing percutaneous transluminal coronary angioplasty (PTCA) to investigate whether angioplasty influences Chlamydia-specific antibody titers and whether there is an association with restenosis. Blood samples were obtained before and 1 and 6 months after angioplasty. Antibodies against chlamydial lipopolysaccharide and against purified C. pneumoniae elementary bodies were measured by enzyme-linked immunosorbent assay (ELISA). After angioplasty, the prevalence of antibodies to lipopolysaccharide rose from 20 to 26% for immunoglobulin A (IgA), from 53 to 64% for IgG, and from 2 to 7% for IgM (P = 0.021, 0.004, and 0.046, respectively). There was a rapid increase of mean antibody titers of all antibody classes within 1 month of PTCA. During the following 5 months, antibody titers decreased slightly but were still higher than baseline values. Results of the C. pneumoniae-specific ELISA were essentially the same. The rise of anti-Chlamydia antibodies was not caused by unspecific reactivation of the immune system, as levels of antibodies against cytomegalovirus did not change. Neither seropositivity nor antibody titers were related to restenosis. However, increases in mean IgA and IgM titers were restricted to patients who had suffered from myocardial infarction earlier in their lives. In conclusion, we show that PTCA induces a stimulation of the humoral immune response against C. pneumoniae. These data support the idea that plaque disruption during angioplasty might make hidden chlamydial antigens accessible to the immune system.

The species specificity of the microimmunofluorescence antibody test and comparisons with a time resolved fluoroscopic immunoassay for measuring IgG antibodies against Chlamydia pneumoniae

AIMS

To examine the species specificity of the microimmunofluorescence test (MIF) and assess a time resolved fluoroscopic immunoassay (TRIA) for measuring IgG antibodies to C pneumoniae.

METHODS

Sera from 1020 subjects were tested by MIF for IgG, IgM, and IgA antibodies to C pneumoniae, C trachomatis, and C psittaci; 501 serum samples were also tested by TRIA for IgG antibodies to C pneumoniae.

RESULTS

C pneumoniae antibody titres as measured by MIF were correlated with those for C psittaci and trachomatis. It was estimated that on average, one third of the twofold dilution steps that make up the final C pneumoniae antibody titre may be due to cross reacting genus specific antibody. The results of TRIA correlated well with those of MIF. In 75% of cases, the TRIA result predicted a three titre range within which the actual MIF result would fall.

CONCLUSIONS

MIF does not appear to be as species specific as claimed. TRIA is unlikely to be as specific but as it is completely objective, easier to perform, amenable to automation, and gives reproducible results, it is a rapid and useful method for comparing populations.

Reactions of polyclonal and neutralizing anti-p54 monoclonal antibodies with an isolated, species-specific 54-kilodalton protein of Chlamydia pneumoniae

A recently described 54-kDa protein has been detected in six type strains and three patient isolates of Chlamydia pneumoniae by immunoblotting with sera from patients positive for antibodies to C. pneumoniae by the microimmunofluorescence test. This protein was not found in either C. trachomatis E or C. psittaci Z 432 as an antigen, confirming its species specificity. The 54-kDa protein was isolated by continuous-elution electrophoresis and immunoglobulin G monoclonal antibodies (MAbs) against the isolated antigen were produced. MAb 8B11E6 reacted only with the 54-kDa band of C. pneumoniae and not with C. trachomatis E or C. psittaci in a Western immunoblot assay. This antibody was purified and tested for neutralizing activity together with three additional anti-p54-active MAbs (8B11E6, 8B11B4, and 10F1C1). In Buffalo green monkey cells, all of the MAbs significantly reduced the infectivity of C. pneumoniae elementary bodies, whereas no neutralizing activity could be observed with C. trachomatis E or C. psittaci Z 432. These results not only confirm the species specificity of the 54-kDa protein but also indicate that this protein might play an important role in the pathogenesis of C. pneumoniae infection. Furthermore, the results suggest a possible protective role of anti-p54 antibodies in an adaptive immune response.

Cardiovascular disease risk from prior Chlamydia pneumoniae infection can be related to certain antigens recognized in the immunoblot profile

Chlamydia pneumoniae infection has been described as a risk factor for atherosclerosis on the basis of raised seroreactivity against complete elementary bodies among cardiovascular disease (CVD) patients. In order to identify antigens of possible pathogenetic relevance, C. pneumoniae IgG and IgA immunoblot profiles were compared for CVD patients (IgG: n = 159; IgA: n = 72) and for controls (IgG: n = 158; IgA: n = 115), all with prior C. pneumoniae infection. IgG and IgA recognition patterns were very similar, and a broad range of antigens was commonly recognized. However, statistical analysis demonstrated IgG seroresponses to 40, 54, 60, 75, and 98 kDa antigens to be more frequent among patients and resulting in odds ratios between 2.3 (98 kDa) and 29.4 (40 kDa) for development of CVD. This relation remained evident after adjustment for age and sex. Cardiovascular risk from prior chlamydial infection can thus be linked to certain antigens. Thus, for the first time potential atherogenetic virulence factors of C. pneumoniae are described. Though causal relation of chlamydial and atherosclerotic disease cannot be proven yet, evidence is growing that chlamydial structures play a part in the multifactorial pathogenesis of one of the most prevalent health hazards world-wide.

Detection of serum antibodies against Chlamydia pneumoniae by in vitro neutralization and microimmunofluorescence assays

Antibodies to Chlamydia pneumoniae (IOL-207) were studied by the microimmunofluorescence (MIF) assay and in vitro neutralization in serum samples from 230 healthy adults and 332 patients at risk of C. pneumoniae infection. In the MIF test, the prevalence of immunoglobulin G (IgG) antibody was 53.9% among healthy subjects and 40.7% in the patients. An MIF antibody titre of > or = 1 : 512, consistent with acute infection by C. pneumoniae was documented in 23 out of 332 patients, and in none of the healthy adults. C. pneumoniae complement-dependent neutralizing antibody was detected in 25.8% and 31.2%, respectively of MIF-positive sera from healthy subjects and patients. The neutralizing antibody detection rate was 52.2% among the 23 patients with MIF titres of > or = 1 : 512. Complement-independent neutralization was observed in only 5 sera from healthy subjects and in 3 sera from patients. The complement-dependent neutralizing ability of sera significantly (p < 0.001) correlated with MIF titres.

Chlamydia pneumoniae (TWAR)

Chlamydia pneumoniae (TWAR) is a recently recognized third species of the genus Chlamydia that causes acute respiratory disease. It is distinct from the other two chlamydial species that infect humans, C. trachomatis and C. psittaci, in elementary body morphology and shares less than 10% of the DNA homology with those species. The organism has a global distribution, with infection most common among children between the ages of 5 and 14 years. In children, TWAR infection is usually mild or asymptomatic, but it may be more severe in adults. Pneumonia and bronchitis are the most common clinical manifestations of infection, and TWAR is responsible for approximately 10% of cases of pneumonia and 5% of cases of bronchitis in the United States. The microimmunofluorescence serologic assay is specific for TWAR and can distinguish between recent and past infections. The organism can be isolated in cell culture; however, PCR techniques have recently facilitated its detection in tissues and clinical specimens.

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.

Isolation and characterization of a gene encoding a Chlamydia pneumoniae 76-kilodalton protein containing a species-specific epitope

Chlamydia pneumoniae is a human respiratory pathogen. Unlike the other two Chlamydia species, no species-specific antigen has been defined for C. pneumoniae. An immunoreactive clone containing a 0.8-kb fragment was isolated from a C. pneumoniae (AR-39) genomic library by using anti-C. pneumoniae rabbit immune serum. By Southern hybridization analysis of chromosomal digests of the different Chlamydia spp., the 0.8-kb fragment was shown to react specifically with C. pneumoniae. Subcloning of this fragment into the pGEX-1 lambda T expression vector resulted in the expression of a 62-kDa fusion protein. This fusion protein as well as the cleaved C. pneumoniae peptide were recognized by anti-C. pneumoniae rabbit immune serum, while the glutathione S-transferase moiety was not recognized. The fusion protein was used to produce monospecific rabbit antiserum. This antiserum was shown to react with a 76-kDa protein in all C. pneumoniae isolates tested, specifically recognize C. pneumoniae inclusions in tissue culture, and neutralize infectivity of C. pneumoniae in cell culture. No reactivity was observed with Chlamydia trachomatis or Chlamydia psittaci. To isolate the entire coding sequence of the 76-kDa protein, two partially overlapping fragments of C. pneumoniae DNA, a 3.2-kb HindIII fragment and a 1.2-kb PvuII fragment, were isolated, cloned, and sequenced. No significant sequence similarity was found with any previously reported nucleotide or amino acid sequence of the other Chlamydia species. This C. pneumoniae protein containing a species-specific epitope could play a role in pathogenesis and may be useful as a diagnostic tool.

Characterization of Chlamydia pneumoniae species-specific proteins immunodominant in humans

Proteins of Chlamydia pneumoniae immunodominant in humans were characterized with the sera of 13 patients who were not likely to have been exposed to C. trachomatis or C. psittaci. The serological responses among these patients were similar on a qualitative basis, but some differences were found quantitatively. However, the serological responses of the patients who were infected with C. pneumoniae differed markedly from those of two patients who were infected with C. trachomatis and two who were infected with C. psittaci and those of mice that were transtracheally infected with C. pneumoniae. Among proteins immunodominant in the patients who were infected with C. pneumoniae, a 40-kDa major outer membrane protein was genus specific and 53-, 46-, and 43-kDa proteins were species specific in their reactions with the majority of the human sera used. A few sera reacted strongly with a 73-kDa protein genus specifically. Some proteins with weak immunogenicity exhibited species specificity. An antigenic analysis with human sera and murine monoclonal antibodies against the 53-kDa protein showed that hte antigenicities were strictly conserved among the seven strains of C. pneumoniae tested. The genus-specific 73-kDa protein was solubilized with octylglucoside. All of the species-specific immunodominant proteins were solubilized with sodium dodecyl sulfate, but the genus-specific major outer membrane protein was not. These results suggest that a serological diagnosis of C. pneumoniae infection could be achieved species specifically by comparison of the serum responses to sodium dodecyl sulfate- and octylglucoside-soluble fractions.

Prevalence of Chlamydia pneumoniae antibodies in patients with acute respiratory infections in Israel

AIMS

To evaluate the prevalence of antibodies to Chlamydia pneumoniae (TWAR) in relation to other aetiological agents of acute respiratory infections in Israeli patients.

METHOD

Serum samples from 604 patients (183 children and 421 adults) were collected over three years. Antibodies to C pneumoniae, C trachomatis, and Legionella sp were evaluated using the microimmunofluorescence (MIF) assay. Antibodies to Mycoplasma pneumoniae were detected using the Serodia Myco II test.

RESULTS

Antibodies to TWAR were detected in 319 (51.3%) sera. Twenty one patients had MIF results indicative of recent infection. TWAR prevalence and antibody titres in children (aged 1-10 years) were low, gradually increased in teenagers (11-18 years), and were highest in adults and elderly patients. In contrast to the consistently noted TWAR antibody prevalence and serological evidence of recent infection during the study period, a significant decrease in those variables was recorded for C trachomatis. Six patients had serological evidence of recent infection with both C pneumoniae and C trachomatis. The presence of antibodies to Mycoplasma pneumoniae and Legionella sp was tested in 473 of the patients; 29 had antibodies to M pneumoniae and 23 to Legionella sp. Six patients (including five children) had serological evidence of recent infection with M pneumoniae and four with Legionella sp.

CONCLUSION

C pneumoniae should be considered in patients with acute respiratory diseases. MIF is the preferred method for monitoring the presence of antibodies to this organism.

Identification of Chlamydia pneumoniae-specific protein antigens in immunoblots

The immunoblot patterns of 248 sera, all examined previously by the microimmunofluorescence test (MIF) for species-specific Chlamydia antibodies, were analyzed. Predominant specific antibody activity was directed to the 54 kDa protein of Chlamydia pneumoniae, which was recognized by 93% of sera positive for Chlamydia pneumoniae by MIF but by only 2% of sera positive for Chlamydia trachomatis and negative for Chlamydia pneumoniae and by 3% of sera negative for both Chlamydia pneumoniae and Chlamydia trachomatis. This antigen appears to be specific for Chlamydia pneumoniae. Other Chlamydia pneumoniae-specific protein antigens were recognized far less frequently. Absorption analysis indicated that the 54 kDa protein is located on the surface of the Chlamydia pneumoniae elementary bodies.

Distinguishing Chlamydia species by restriction analysis of the major outer membrane protein gene

Clinical isolates of Chlamydia pneumoniae from diverse geographic locations and strains of other Chlamydia species were typed by polymerase chain reaction (PCR) amplification of the major outer membrane protein (MOMP) gene followed by restriction fragment length polymorphism analysis of the product. Use of synthetic primers corresponding to highly conserved regions of the MOMP gene resulted in amplification of a 1070 bp product in laboratory strains and clinical isolates of C. pneumoniae, C. trachomatis and C. psittaci. PCR products were digested with restriction enzymes Alu I and Mbo I and separated by polyacrylamide gel electrophoresis. Restriction fragment patterns varied in length from 8-12 bands of 30-400 bp in size in Alu I digests, and 6-7 bands of 50-400 bp in size in Mbo I digests. Strains representing different chlamydia species were easily distinguishable by this method, as were different serovars of C. trachomatis. Strains of C. pneumoniae tested include laboratory strain TW-183 and recent clinical isolates from Atlanta, Brooklyn, Wisconsin and Norway. One combination of primers reacted with C. psittaci strains and C. pneumoniae strain TW-183, but not with other strains of C. pneumoniae tested regardless of the concentration of DNA in the sample. With use of a pan-reactive primer combination, however, restriction patterns were similar in all strains of C. pneumoniae tested. This gene typing technique can be valuable for distinguishing the three chlamydial species and potentially strains of C. pneumoniae in clinical and epidemiologic studies.

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.

Antigenic variation among strains of Chlamydia pneumoniae

The antigenic profiles of six strains of Chlamydia pneumoniae were analyzed by the microimmunofluorescence test (MIF) and immunoblotting with human serum and murine monoclonal antibody. MIF-derived antibody titers in serum samples from culture-positive patients were four- to eightfold higher against autologous isolate antigen than they were against the prototype antigen strain TW-183. Sera of patients with respiratory illness that were culture negative and complement fixation positive for Chlamydia spp. produced higher titers by MIF against a strain of C. pneumoniae isolated in the area than they did against TW-183. For two of five cases, the criteria for establishing the diagnosis of acute infection were met only with use of the antigen from the local strain; TW-183 was inadequate for this purpose. Immunoblot profiles revealed antigenic differences between strains that varied with the human serologic response; i.e., unique antigens were recognized by the sera of some individuals and not by the sera of others. Using the reactivity of a genus-specific monoclonal antibody against a major outer membrane protein, we found that strain CWL-011, isolated in Atlanta, Ga., may possess a major outer membrane protein with a molecular mass between those of C. trachomatis L2 and other C. pneumoniae strains. These data provide evidence of several new and unique serotypes of C. pneumoniae and suggest that the serologic diagnosis of C. pneumoniae infection may require the use of antigens from more than one strain of this species.

Serological response to Chlamydia pneumoniae infection

The human serological response was analyzed by using sera from patients who were serologically positive but isolation negative for Chlamydia pneumoniae and from patients with proven C. pneumoniae infection based on serology and isolation. To assess whether seroreactivity to C. pneumoniae proteins had potential diagnostic value, the cross-reactivities of these sera to other Chlamydia species and of sera from patients infected with C. trachomatis and C. psittaci to C. pneumoniae proteins were determined. In all serum samples from patients with proven C. pneumoniae infections, reactivities were seen with 98-, 68-, 60-, 39.5-, and 30-kilodalton proteins. Similar patterns were seen in sera from patients who were serologically positive and isolation negative. The onset of seropositivity for C. pneumoniae was accompanied by reactivities against presumably shared chlamydial antigens and a C. pneumoniae-specific 98-kilodalton protein.