Periodontopathogen- and host-derived immune response in acute coronary syndrome.

Owing to molecular mimicry, periodontal pathogen carriage may result in a systemic cross-reactive immune response with the host. The analyses were performed to investigate if serum antibody levels to human heat shock protein 60 (HSP60) are associated with the antibody levels and salivary carriage of two periodontal pathogens, Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis, as well as with the dental status in patients with acute coronary syndrome (ACS). ACS patients (n = 141) were monitored at baseline when entering to hospital, and after 1 week, 3 months and 1 year. Periodontal status was recorded by dental radiographs, and A. actinomycetemcomitans and P. gingivalis were detected by PCR from saliva at baseline. Serum IgG and IgA antibody levels were determined at all time points. All antibody levels remained quite stable during the follow-up. Serum IgG-class antibody levels to A. actinomycetemcomitans and HSP60 had a strong positive correlation with each other at all time points (r∼0.4, P < 0.05). Mean serum IgG antibody levels to HSP60 were significantly higher in the A. actinomycetemcomitans IgG- and IgA-seropositive than in the seronegative patients, but did not differ between the pathogen carriers compared to the non-carriers. HSP60 antibody levels did not differ significantly between the edentulous, non-periodontitis and periodontitis patients. Despite the observed cross-reactivity in the systemic IgG-class antibody response to HSP60 and A. actinomycetemcomitans, the pathogen carriage in saliva or the periodontal status did not affect the HSP60 antibody levels in ACS patients.

The association of body mass index, waist and hip circumference, and waist-hip ratio with Chlamydia pneumoniae IgG antibodies and high-sensitive C-reactive protein at 31 years of age in Northern Finland Birth Cohort 1966.

BACKGROUND: Viruses and bacteria like Chlamydia pneumoniae and Helicobacter pylori have been suggested to have a role in pathogenesis of overweight and obesity. OBJECTIVE: We studied whether C. pneumoniae-specific IgG antibodies are associated with elevated body mass index (BMI), waist and hip circumference, and/or waist-hip ratio (WHR), and whether the risk is more pronounced in the simultaneous presence of an ongoing inflammation as measured by elevated high-sensitive C-reactive protein (hsCRP) levels. SUBJECTS AND METHODS: Our study population was derived from the Northern Finland Birth Cohort 1966 (NFBC1966), a general population sample of 12,058 live-born children. This cross-sectional study consisted of 5044 persons at 31 years of age. Serum C. pneumoniae IgG titers were measured by microimmunofluorescence test, and hsCRP levels by immunoenzymometric assay. RESULTS: C. pneumoniae IgG positivity (titer ≥ 32), both alone and jointly with elevated hsCRP (≥ 1.64 mg l(-1), an upper quartile), was found to significantly associate with elevated BMI in the whole study population and with elevated hip and waist circumference in women, yet no association with WHR was seen. The analyses were adjusted for sex (when appropriate), smoking, socioeconomic position, glucose, insulin, high- and low-density lipoprotein cholesterols, triglycerides, leukocytes and pulse pressure. CONCLUSION: These findings suggest that especially in women, persistent C. pneumoniae infection may be associated with overweight/obesity, independently of more traditional risk factors.

Interleukin-6-174 G/C promoter polymorphism is associated with persistence of Chlamydia pneumoniae antibodies in young men.

A promoter polymorphism -174 G/C in the inflammatory cytokine interleukin-6 (IL-6) gene has been associated with differences in serum IL-6 levels and a risk for inflammatory conditions, such as cardiovascular diseases. We investigated whether this polymorphism is associated with Chlamydia pneumoniae, a common causative agent of respiratory infection with tendency for persistent infections, in 867 Finnish military recruits. IgG seropositivity in arrival and departure serum samples during 6-12 months of military service was considered as persistence of antibodies and a possible prolonged or chronic infection. The -174C allele was significantly associated with IgG seropositivity (P = 0.0002) and the persistence of IgG antibodies (P = 0.0002) as well as with slightly elevated C-reactive protein (CRP) levels (P = 0.003). In addition, the association was stronger when persistent C. pneumoniae antibodies were present together with elevated CRP than when either of them was positive alone (OR; 95% CI: 3.45; 2.00-5.98 and 1.41; 1.00-1.99, respectively). Our data suggest that IL-6 -174 G/C polymorphism is associated with persistence of C. pneumoniae antibodies and may be linked to the chronic or prolonged infection with systemic low-grade inflammation.

Elevated MMP-8 and decreased myeloperoxidase concentrations associate significantly with the risk for peripheral atherosclerosis disease and abdominal aortic aneurysm.

Matrix metalloproteinases are responsible for degradation and remodelling of extracellular matrix and exert important roles in initiation and progression of inflammatory diseases. We aimed to examine the role of Matrix metalloproteinases (MMPs) and their regulators in degenerative arterial diseases. Serum samples were collected from patients with arterial disease (n = 126), who underwent surgery because of symptomatic aorto-occlusive disease (AOD, n = 18), carotid artery stenosis (n = 67) or abdominal arotic aneurysm (n = 41). Serum MMP-1, MMP-8, MMP-13, TIMP-1, myeloperoxidase (MPO) and neutrophil elastase (HNE) concentrations were determined by ELISA, and the molar ratio of MMP-8 and TIMP-1 was calculated. To get reference values, the determinations were done on samples of healthy blood donors (n = 100). In univariate analyses, the patients had higher MMP-8 (P < 0.001), TIMP-1 (P = 0.045), and MMP-8/TIMP-1 (P < 0.001), and lower MPO (P < 0.001) when compared with the blood donors. All three subgroups had higher MMP-8 (P < 0.001) and MMP-8/TIMP-1 (P < 0.001), and lower MPO (P < 0.01, except AOD) levels when compared with the references. In multiple logistic regression analyses, the male gender (P < 0.01), age (P < 0.001), elevated MMP-8 (P < 0.001) and decreased MPO (P < 0.001) concentrations associated significantly with the risk for arterial disease, and provided an area under curve (AUC) of 0.97 in the Receiver operating characteristics analyses. In multiple linear regression analyses, HNE correlated with both MMP-8 (P < 0.001) and MPO (P = 0.008) concentrations. Combination of high MMP-8 and low MPO level in serum eventually reflecting selectively modified neutrophil degranulation may indicate increased risk for arterial disease.

Chlamydia pneumoniae infection is associated with elevated body mass index in young men.

Chlamydia pneumoniae infection is said to be associated with obesity. We studied the association between C. pneumoniae infection and inflammation and increased BMI in 891 Finnish military recruits. IgG seropositivity in arrival and departure serum samples during 6-12 months of military service was considered as persistence of antibodies and a possible indication of chronic infection. Persistently high C-reactive protein (CRP) level (elevated on arrival and departure) (OR 2.2, 95% CI 1.3-3.9), and persistent C. pneumoniae antibodies (OR 2.1, 95% CI 1.5-2.8) were significant risk factors for overweight (BMI 25 kg/m2). In addition, those who had persistent antibodies and persistently elevated CRP levels, or those who had either of them, had a significantly higher BMI (kg/m2) compared to those who had neither of them (25.8 vs. 24.6 vs. 23.5, respectively; P<0.001). These results provide new information about the association between possible chronic C. pneumoniae infection and obesity in young men.

Effects of CD14, TLR2, TLR4, LPB, and IL-6 gene polymorphisms on Chlamydia pneumoniae growth in human macrophages in vitro.

Chlamydia pneumoniae is an obligate intracellular gram-negative bacterium, which causes respiratory infections in humans. It can infect various cell types, e.g. vascular endothelial cells, smooth muscle cells and monocyte-derived macrophages in vitro. The susceptibility of macrophages from healthy individuals to C. pneumoniae infection is highly variable. In this study, we evaluated the effects of innate immunity genes CD14 -260 C>T, TLR2 Arg753Gln, TLR4 Asp299Gly, LBP Phe436Leu and IL6 -174 G>C polymorphisms on C. pneumoniae growth in human macrophages in vitro. The growth of C. pneumoniae was highest in CD14 -260 C>T TT genotype cells and the difference to CC and CT genotypes was statistically significant (P = 0.032 and 0.022 respectively). The G-allele of the IL6 -174 G>C polymorphism had a positive influence on chlamydial growth; the difference was statistically significant only between CC and GC genotypes (P = 0.018). TLR2 Arg 753Gln, TLR4 Asp299Gly, LBP Phe436Leu polymorphisms showed no effect on chlamydial growth.

Susceptibility of human monocyte-macrophages to Chlamydia pneumoniae infection in vitro is highly variable and associated with levels of soluble CD14 and C. pneumoniae IgA and human HSP-IgG antibodies in serum.

Chlamydia pneumoniae, an intracellular microbe, causes respiratory infections and may participate in the development of atherosclerosis. It is able to survive and multiply in macrophages. The susceptibility of monocyte-macrophages from healthy individuals to C. pneumoniae infection in vitro was studied. Intracellular growth of C. pneumoniae, as an indicator of susceptibility to infection, was compared to serum levels of C-reactive protein, soluble CD14 (sCD14), human heat shock protein (HSP)-IgG, human HSP-IgA, C. pneumoniae IgG and IgA antibodies. The production of C. pneumoniae in infected macrophages was highly variable, ranging from 0 to 638 chlamydial genomes per human genome. Chlamydia pneumoniae production associated positively with serum C. pneumoniae IgA (titre: > or =10) and hHSP-IgG and negatively with sCD14 concentration. The association between sCD14 concentration, C. pneumoniae IgA and human HSP-IgG antibodies and C. pneumoniae production was statistically significant only among males. Age and gender did not correlate with the production. We hypothesize that persons whose macrophages cannot restrict the growth of C. pneumoniae are more prone to chronic infection by this agent.

Acute Chlamydia pneumoniae infections in asthmatic and non-asthmatic military conscripts during a non-epidemic period.

Chlamydia pneumoniae respiratory tract infections were studied in 512 male military conscripts (123 asthmatic and 389 non-asthmatic) taking part in 180-day service between July 2004 and July 2005 in Kajaani, Finland. Respiratory tract infections requiring a medical consultation were analysed prospectively. At baseline, at end of service, and during each episode of respiratory infection, blood samples were obtained for measurement of C. pneumoniae antibodies. Data concerning the clinical features of each infection episode were collected. Serological evidence of acute C. pneumoniae infection was found in 34 of the 512 conscripts with antibody data available, including 9.8% of the asthmatic subjects and 5.7% of the non-asthmatic subjects (p 0.111). A serological diagnosis could be made for 25 clinical episodes in 24 conscripts. The spectrum of respiratory tract infections included 13 episodes of mild upper respiratory tract infection and seven episodes of sinusitis, with five episodes involving asthma exacerbation. Two of three pneumonias were primary infections. Primary infections were diagnosed in five subjects, and re-infection/reactivation in 19 subjects, with the latter comprising 12 non-asthmatic subjects and seven asthmatic subjects (p 0.180). Prolonged infections were present in six asthmatic subjects and one non-asthmatic subject (p 0.001). A wide variety of respiratory tract infections, ranging from common cold to pneumonia, were associated with serologically confirmed C. pneumoniae infections. Infections were often mild, with common cold and sinusitis being the most common manifestations. Acute, rapidly resolved C. pneumoniae infections were equally common among asthmatic subjects and non-asthmatic subjects, whereas prolonged infections were more common among subjects with asthma.

Pathogenic bacteria and viruses in induced sputum or pharyngeal secretions of adults with stable asthma.

BACKGROUND: Respiratory infections are well known triggers of asthma exacerbations, but their role in stable adult asthma remains unclear. METHODS: 103 asthmatics and 30 control subjects were enrolled in the study. Sputum was induced by inhalation of 3% NaCl solution. Oropharyngeal swab specimens were obtained from the posterior wall of the oropharynx. Respiratory specimens were analysed by RT-PCR for rhinovirus, enterovirus and respiratory syncytial virus and by PCR for adenovirus, Chlamydia pneumoniae, Mycoplasma pneumoniae and Bordetella pertussis. RESULTS: Sputum samples from two of the 30 healthy controls (6.7%), five of 53 patients with mild asthma (9.4%), and eight of 50 with moderate asthma (16.0%) were positive for rhinovirus. Rhinovirus positive asthmatic subjects had more asthma symptoms and lower forced expiratory volume in 1 second (FEV(1)) (79% predicted) than rhinovirus negative cases (93.5% predicted; p = 0.020). Chlamydia pneumoniae PCR was positive in 11 healthy controls (36.6%), 11 mild asthmatics (20.8%), and 11 moderate asthmatics (22%), and PCR positive asthmatics had lower FEV(1)/FVC than negative cases (78.2% v 80.8%, p = 0.023). Bordetella pertussis PCR was positive in 30 cases: five healthy controls (16.7%), 15 mild asthmatics (28.3%), and 10 moderate asthmatics (20%). Bordetella pertussis positive individuals had lower FEV(1)/FVC (77.1% v 80.7%, p = 0.012) and more asthma symptoms than B pertussis negative cases. CONCLUSIONS: Rhinovirus, C pneumoniae, and B pertussis are found in the sputum or pharyngeal swab specimens of asthmatic subjects without concurrent symptoms of infection or asthma exacerbation, as well as in some healthy controls. Positivity is associated with lower lung function and more frequent asthma symptoms.

Inhibitory effect of dietary phenolic compounds on Chlamydia pneumoniae in cell cultures.

Chlamydial infections are very common worldwide. All chlamydial species have a tendency to cause persistent infections, which have been associated to several chronic diseases including blinding trachoma, infertility and coronary heart disease (CHD). At present, no efficient treatment for the eradication of chronic chlamydial infections exists and, thus, new antichlamydial compounds are urgently needed. This study was designed to screen antichlamydial activity of natural flavonoids and other natural and structurally similar synthetic compounds against Chlamydia pneumoniae in human cell line (HL). HL cells were infected with C. pneumoniae and incubated 72 h with studied compounds. Reduction in the number of inclusions was determined with immunofluorescence staining. In vitro minimum inhibitory concentration was also determined for some of the most active compounds. Thirty seven percentage of the studied compounds (57 in total) were highly active against C. pneumoniae and all the studied compounds were non-toxic to the host cells at studied concentrations. Our study revealed direct antichlamydial effect for selected polyphenolic compounds against C. pneumoniae, in vitro. We also demonstrated the ability of some of the investigated compounds to accumulate inside cells or into cell membranes and cause inhibition, even when present only prior to infection.

Prevalence and persistence of antibodies to herpes viruses, Chlamydia pneumoniae and Helicobacter pylori in Alaskan Eskimos: the GOCADAN Study.

The prevalence and persistence of antibodies against cytomegalovirus (CMV), herpes simplex virus types 1 (HSV1) and 2 (HSV2), Helicobacter pylori and Chlamydia pneumoniae were determined in Alaskan Eskimos. The study included 610 individuals (mean age 43 +/- 15 years; 45% males) participating in the Genetics of Coronary Artery Disease in Alaska Natives (GOCADAN) study. Archived serum samples and those collected during the GOCADAN study were analysed for antibodies against the above pathogens by ELISA. The current prevalence of antibody seropositivity was 94% to CMV, 90% to HSV1, 38% to HSV2, 80% to H. pylori, and 42% to C. pneumoniae. The persistence of antibodies (in both archived and current samples) against CMV, HSV1 and H. pylori was high (83%, 84% and 67%, respectively) compared with those against HSV2 (26%) and C. pneumoniae (29%). Moreover, the seroconversion rates to these organisms were low. Most individuals acquired CMV, HSV1 and H. pylori antibodies by the age of 24 years (94%, 90% and 72%, respectively), and >50% carried HSV2 and C. pneumoniae antibodies by the age of 45 years. There were gender differences in antibody seropositivity rates. Over 70% of individuals had antibodies to at least three of the five pathogens tested. The study demonstrated the high prevalence and lifelong persistence of multiple antibodies, suggesting chronic infections among Alaskan Eskimos.

Heat shock protein 60 autoimmunity and early lipid lesions in cholesterol-fed C57BL/6JBom mice during Chlamydia pneumoniae infection.

Chronic Chlamydia pneumoniae infection and autoimmunity to heat shock protein 60 (Hsp60) have both been documented to be associated with atherosclerosis. Herein, we studied the effects of C. pneumoniae infection and a diet with a low-cholesterol supplement on the development of autoantibodies to mouse Hsp60 and early lipid lesions in the aortic valve of C57BL/6JBom mice. In addition, pulmonary infection was investigated. C57BL/6JBom mice were given one to three C. pneumoniae inoculations and fed either a regular diet or a diet enriched with 0.2% cholesterol. Autoantibody responses against mouse Hsp60 developed in both diet groups when the mice were infected with C. pneumoniae and in uninfected mice fed a cholesterol-enriched diet. C. pneumoniae infections increased subendothelial foam cell accumulation in mice on a 0.2% cholesterol-enriched diet (p = 0.022), without apparent hypercholesterolemia. These in vivo data suggest that autoantibodies against mouse Hsp60 develop as a consequence of cholesterol feeding and repeated C. pneumoniae infections. Further, infectious burden increased early lipid lesions in C57BL/6JBom mice fed a cholesterol-enriched diet.

Antibodies to Chlamydia trachomatis heat shock proteins Hsp60 and Hsp10 and subfertility in general population at age 31.

PROBLEM: To assess the association between antibodies to Chlamydia trachomatis heat shock proteins 60 and 10 (Hsp60 and Hsp10) and subfertility in a general population sample. METHOD OF STUDY: A nested case (n = 146)-control (n = 278) study in a population-based birth cohort. Serum immunoglobulin (Ig)G and IgA antibodies against C. trachomatis Hsp60 and Hsp10, explanatory factors, were measured by enzyme immunoassay, using recombinant proteins as antigens. The main outcome variable was subfertility (time to pregnancy > or =12 months). RESULTS: The prevalence and medians of serum IgA antibodies to Hsp60 and Hsp10 were significantly higher in the female partners of subfertile couple than in their fertile controls. On the contrary, among male partners of subfertile couple, especially among smokers serum antibody levels to Hsp antigens were lower than in the controls. CONCLUSION: The results indicate a serological association of antibodies to chlamydial Hsp antigens with female subfertility in a population-based sample.

Association between Chlamydia trachomatis antibodies and subfertility in the Northern Finland Birth Cohort 1966 (NFBC 1966), at the age of 31 years.

The objective of this study was to assess the serological association between previous Chlamydia trachomatis infection and subfertility in a general population sample. A nested case (n = 493)-control (n = 986) study in a population-based birth cohort consisting of 12,058 live births from the year 1966 was conducted. The analysis was restricted to those 6007 cohort members who replied to a postal inquiry and participated in a health examination including blood samples at the age of 31 years. The presence of C. trachomatis-specific serum IgG antibodies was screened by a synthetic peptide-based enzyme-linked immunosorbent assay. All the positive sera were further tested by the microimmunofluorescence method using immunotype pools and individual immunotypes of C. trachomatis as antigens. An association was found between the detection of immunotype-specific C. trachomatis antibodies and subfertility both in men and women. The results of the present study confirm the serological association between past C. trachomatis infections and subfertility in male or female partners of the couple in the population-based sample.

Treatment of acute Chlamydia pneumoniae infection with telithromycin in C57BL/6J mice.

OBJECTIVES: The efficacy of telithromycin, a new ketolide antibiotic, was investigated in the treatment of acute Chlamydia pneumoniae infection in a mouse model. METHODS: C57BL/6J mice were inoculated intranasally, and the effects of three different doses of telithromycin (25, 50 and 100 mg/kg) were assessed after 5 and 10 days of treatment. Lungs for culture, PCR, histopathology, and blood for serum samples were collected immediately after each treatment period and at 3 weeks post-inoculation. C. pneumoniae-specific antibodies were analysed, and the effect of treatment was assessed by culture, detection of C. pneumoniae DNA and determination of histopathological inflammatory changes in mouse lungs. RESULTS: Culture negativity in the lungs was achieved with the higher doses, 50 and 100 mg/kg, after 10 days of treatment. C. pneumoniae DNA was not totally eradicated with the treatments, but the groups treated with 50 and 100 mg/kg doses for 10 days had the lowest DNA positivity rates (10%) 3 weeks after the inoculation. In lung histopathology, the efficacy of telithromycin on inflammatory changes was also dose-dependent: higher doses were more effective in reducing the inflammatory reaction. Overall, the 25 mg/kg dose had a weaker effect compared with the others. CONCLUSIONS: Telithromycin had both time- and dose-dependent effects on the eradication of chlamydia and on reducing infection-induced inflammatory changes in mouse lungs.

Joint effects of different human papillomaviruses and Chlamydia trachomatis infections on risk of squamous cell carcinoma of the cervix uteri.

This case-control study based in Nordic serum banks evaluated the joint effects of infections with genital human papillomavirus (HPV) types, and Chlamydia trachomatis in the aetiology of cervical squamous cell carcinoma. Through a linkage with the cancer registries, 144 cases were identified and 420 controls matched to them. Exposure to past infections was defined by the presence of specific IgG antibodies. The odds ratio (OR) for the second-order interaction of HPV16, HPV6/11 and C. trachomatis was small (1.0) compared to the expected multiplicative OR, 57, and the additive OR, 11. The interactions were not materially different among HPV16 DNA-positive squamous cell carcinomas. When HPV16 was replaced with HPV18/33 in the analysis of second-order interactions with HPV6/11 and C. trachomatis, there was no evidence of interaction, the joint effect being close to the expected additive OR. Possible explanations for the observed antagonism include misclassification, selection bias or a true biological phenomenon with HPV6/11 and C. trachomatis exposures antagonizing the carcinogenic effects of HPV16.

Chlamydia pneumoniae infection and inflammation in adults with asthma.

BACKGROUND: Chlamydia pneumoniae infection and immune response to the C. pneumoniae heat shock protein 60 (CpHsp60) have been suggested to be associated with asthma. OBJECTIVES: To study whether a slightly elevated C-reactive protein (CRP) level as a marker of low-grade systemic inflammation has a role in this association, we collected serum and sputum samples from 103 asthma patients with disease severity ranging from mild to moderate and from 30 healthy volunteers. METHODS: IgA and IgG antibodies to C. pneumoniae elementary bodies (CpEB) and CpHsp60 were measured by enzyme immunoassay. Serum CRP levels were measured with a rapid two-site ultra-sensitive assay based on time-resolved immunofluorometry. RESULTS: The asthma patients, especially those with moderate asthma, had higher serum IgA antibody levels to CpHsp60 than the healthy controls (test for trend, p = 0.05), whereas antibody levels to CpEB antigen did not differ between the study groups. CRP levels were higher in both asthma groups compared to the control group and moreover, the patients with moderate asthma had higher CRP levels than those with mild asthma (test for trend, p < 0.01). The subjects with a slightly elevated CRP level, defined as > or =1.8 mg/l, had higher CpEB IgA (p = 0.001), CpEB IgG (p = 0.008) and CpHsp60 IgA (p = 0.023) antibody levels in serum compared to the subjects with lower CRP levels. CONCLUSIONS: Slightly elevated CRP levels as a marker of low-grade systemic inflammation may be associated with C. pneumoniae infection in asthma patients.

Chlamydia pneumoniae together with collagenase-2 (MMP-8) in periodontal lesions.

OBJECTIVE: Dental infections may be associated with subsequent atherosclerosis. In this regard we wanted to study if traces of Chlamydia pneumoniae can be found from deep periodontal pockets characterized with elevated collagenase-2 [matrix metalloproteinase (MMP)-8] levels in gingival crevicular fluid (GCF). Chlamydia pneumoniae has not previously been found to infect the oral cavity. SUBJECTS AND METHODS: Subgingival samples of dental plaque were collected from 31 teeth in 12 adult periodontitis patients by means of sterile curettes and examined for C. pneumoniae using a quantitative PCR technique. GCF samples were also collected and assayed by an immunofluorometric assay (IFMA) for MMP-8. RESULTS: Chlamydia pneumoniae RNA was demonstrated in a sample from one of the patients studied. Periodontal treatment eliminated the C. pneumoniae from the patient's subgingival dental plaque as well as reduced GCF MMP-8 level. CONCLUSIONS: Our findings suggest that C. pneumoniae, which is not normally thought to be involved in periodontitis, can be found in dental plaque.

Lipoprotein(a), Chlamydia pneumoniae, leptin and tissue plasminogen activator as risk markers for valvular aortic stenosis.

AIMS: The aim of the present study was to identify risk markers for the development of valvular aortic stenosis (AS). Lipoprotein(a) (Lp(a)) and Chlamydia pneumoniae IgG antibody titres in plasma and in circulating immune complexes as well as leptin and tissue plasminogen activator (t-PA) in plasma were studied. METHODS AND RESULTS: One hundred and one patients (41 women and 60 men, mean age 71+/-8 years) with significant AS and 101 age- and sex-matched controls were included in this study. All patients underwent aortic valve replacement at the University Hospital in Umeå, Sweden. The controls had no symptoms of cardiovascular disease and they were examined echocardiographically. An Lp(a) level >or=480 mg x l(-1), a C. pneumoniae-specific IgG titre >or=1/128, a high leptin level and a high t-PA mass concentration in plasma were identified as risk markers for AS. A strong synergism between Lp(a) and C. pneumoniae IgG antibodies in circulating immune complexes was found. CONCLUSION: Our data indicate that a chronic C. pneumoniae infection and a high plasma Lp(a) level might influence and aggravate aortic heart valve sclerosis via the formation of circulating immune complexes. The present study also strongly suggests an association between high plasma leptin, t-PA mass concentration and AS.