Abstract
The immune system may interplay between Chlamydia pneumoniae infection and coronary artery disease (CAD). Major histocompatibility complex genes regulate innate and adaptive immunity. Patients with CAD (n = 100) and controls (n = 74) were enrolled. Human leukocyte antigens (HLA-A, HLA-B, and HLA-DRB1), four lymphotoxin alpha single-nucleotide polymorphisms, and complement C4A and C4B allotypes were typed, and their haplotypes were inferred. The presence of serum C. pneumoniae immunoglobulin A (IgA) (titer, ≥40) or IgG (titer, ≥128) antibodies or immune complex (IC)-bound IgG antibodies (titer, ≥2) was considered to be a serological marker suggesting chronic C. pneumoniae infection. C. pneumoniae IgA antibodies were found more frequently in patients than in controls (P = 0.04). Among the patients, multiple logistic regression analysis showed the HLA-B*35 allele to be the strongest-risk gene for C. pneumoniae infection (odds ratio, 7.88; 95% confidence interval, 2.44 to 25.43; P = 0.0006). Markers of C. pneumoniae infection were found more frequently in patients with the HLA-A*03-B*35 haplotype than in those without the haplotype (P = 0.007 for IgA; P = 0.008 for IgG; P = 0.002 for IC). Smokers with HLA-B*35 or HLA-A*03-B*35 had markers of C. pneumoniae infection that appeared more often than in smokers without these genes (P = 0.003 and P = 0.001, respectively). No associations were found in controls. In conclusion, HLA-B*35 may be the link between chronic C. pneumoniae infection and CAD.
Atherosclerosis is a chronic inflammatory process (11) in which infections, especially those caused by Chlamydia pneumoniae (24, 35), have been suggested to play a role. C. pneumoniae is a common cause of respiratory tract infections. Like all chlamydial species, it has a tendency to cause chronic infections. This may lead to severe sequelae such as chronic obstructive pulmonary disease (42) and cardiovascular diseases (24). Most likely, all individuals get infected with C. pneumoniae during their lifetimes, but many of them are capable of resolving the infection, and only some become chronically infected. It is assumed that in order to maintain a persistent infection and to evade host defense mechanisms, chlamydiae have developed specific strategies (9), e.g., by being an obligatory intracellular organism and by having a unique and complicated life cycle (21). An aberrant and persistent form of C. pneumoniae can be induced by gamma interferon (31), antibiotics (7), and tobacco smoke (44) in in vitro cell cultures. In vivo, however, immunogenetic factors (22) of the host also contribute to the infection outcome.
The major histocompatibility complex (MHC) region takes part in innate and adaptive immunity (28). MHC molecules present microbial peptides to the appropriate subsets of T cells. Patients with specific HLA genes are susceptible or resistant to certain viral and nonviral pathogens (12, 32). Immunoglobulin A (IgA) and IgG antibodies against C. pneumoniae (35) and immune complexes (ICs) (23, 25) have frequently been found to be present in sera of patients with coronary artery disease (CAD). Recently, we showed that HLA-B*35- and DRB1*01-related haplotypes are found more frequently in patients with CAD than in healthy age- and sex-matched controls. Also, smokers who had a complement component C4B null allele together with HLA-DRB1*01 were shown to be prone to cardiovascular disease (30). Therefore, in this study, we assessed MHC genes associated with serological markers of C. pneumoniae infection, elevated specific IgA and IgG antibody levels and the presence of specific circulating ICs, in patients with CAD.
MATERIALS AND METHODS
Study subjects.
Patients with CAD (n = 148) were recruited from nine different central hospitals in Finland between September 1998 and December 2000, as described previously (39). The inclusion criteria for the patients were as follows. Patients had to have clear symptoms of angina with electrocardiographic evidence of myocardial ischemia. Patients who met the anginal pain inclusion criteria but none of the electrocardiographic criteria were eligible to enter the trial if their cardiac enzymes were consistent with the occurrence of myocardial infarction. Patients with prolonged chest pain with electrocardiogram changes indicating either unstable angina (n = 43) or non-Q-wave myocardial infarction (n = 105) were enrolled. No differences in the C. pneumoniae infection markers between the patients with unstable angina and non-Q myocardial infarction were found (data not shown). The original study was a placebo-controlled study on clarithromycin treatment of patients with acute coronary syndrome (ACS) (39). For the MHC gene study, we randomly selected 100 of the patients. No differences in the C. pneumoniae infection markers studied were found between the patients receiving study medication and placebo (data not shown). Blood samples from patients were taken at the time of hospitalization (visit 1) and 1 week (visit 2), 3 months (visit 3), and 1 year (visit 4) after hospital admission. Consecutive age- and sex-matched healthy blood donors (n = 74) served as controls and donated a blood sample once. The criteria for blood donation are available at http://www.veripalvelu.redcross.fi/.
Baseline characteristics of the patients and controls are shown in Table 1. All patients and controls gave written informed consent. Study protocols were approved by local ethics committees.
TABLE 1.
Characteristics of patients with ACS and controls
| Characteristic | Value for patient groupa
|
|
|---|---|---|
| ACS (n = 100) | Control (n = 74) | |
| Mean age (yr) ± SD | 63.2 ± 9.6 | 63.9 ± 1.6 |
| Mean body mass index (kg/m2) ± SD | 27.3 ± 3.8 | NA |
| No. of patients (%) | ||
| Female | 30 (30) | 25 (33.8) |
| Hypertension | 44 (44) | NAb |
| Diabetes | 21 (21) | NAb |
| Hypercholesterolemia | 74 (74) | NAb |
| Smoking status | ||
| Current smoker | 33 (33) | 8 (10.8)c |
| Ex-smoker | 26 (26) | NAb |
| Never smoker | 41 (41) | NAb |
| HLA statusd | ||
| HLA-A*03 | 52 (52) | 32 (43.2) |
| HLA-B*35 | 35 (35) | 14 (18.9) |
| HLA-DRB1*01 | 38 (38) | 13 (17.6) |
| HLA-A*03-B*35 | 25 (25) | 11 (14.9) |
| LTA+724C | 86 (86) | 64 (86.5) |
| HLA-A*03-B*35-LTA+724C | 21 (21) | 11 (14.9) |
NA, not available; n, number of patients.
Controls filled the questionnaire formatted by the Blood Transfusion Service before blood donation. Any of these clinical conditions are severe enough for the need of medication, and they would have been a contraindication for blood donation.
Current smokers in the control group were detected with cotinine measurement (see the text for details).
Number of patients positive for the MHC allele or haplotype. Differences between ACS patients and controls had a P value of <0.05 for HLA-B*35 and a P value of <0.01 for HLA-DRB1*01; the rest of them were not significant, as described previously (30).
Laboratory procedures.
Genomic HLA-A, HLA-B, and HLA-DRB1 tissue typing, four lymphotoxin alpha (LTA) single-nucleotide polymorphisms (positions +253 [a/g], +496 [C/T], +633 [c/g], and +724 [C/A]), and complement C4A and C4B allotyping were performed (lowercase indicates intronic and uppercase indicates exonic variation). MHC haplotypes of the subjects were inferred using all these markers (30).
Sera were tested for C. pneumoniae-specific IgA and IgG antibodies by the microimmunofluorescence method using elementary bodies of Kajaani 6 as antigens (43). Fourfold serum dilutions were used, starting from 1/32 for IgG and 1/10 for IgA, as described previously (13, 14). Isolation of C. pneumoniae-specific ICs was performed by polyethylene glycol precipitation, and IgG antibodies against C. pneumoniae were measured from dissociated ICs by microimmunofluorescence at twofold dilutions starting from a dilution of 1/2, as described previously (13, 25).
Due to the lack of information on controls’ smoking statuses, we measured plasma cotinine levels by use of a gas chromatograph equipped with a nitrogen phosphorous detector. The cutoff point for the classification of active smoking was set at 10 ng/ml (1), revealing subjects who had smoked tobacco within a week.
Statistical analysis.
For this study, elevated levels of antichlamydial IgA (titer, ≥40) or IgG (titer, ≥128) or the presence of IC-bound antichlamydial IgG antibodies (titer, ≥2) at any visit was considered to be a marker of C. pneumoniae infection, suggesting persistent infection (14). Positivity with any of these three titers was considered to be positivity for C. pneumoniae infection. The correlation between C. pneumoniae infection and CAD was examined by comparing C. pneumoniae infection markers in patients and controls. The potential association between MHC genes and C. pneumoniae infection markers was examined as follows.
Forward stepwise multiple-logistic regression analysis was used to study the association between alleles (HLA-A, HLA-B, LTA+253a/g, LTA+496C/T, LTA+633c/g, LTA+724C/A, C4A, C4B, and HLA-DRB1) and any of the markers of C. pneumoniae infection. Categorical data were compared by the chi-square or Fisher's exact test to study whether the frequencies of C. pneumoniae infection markers differed in patients with and those without the MHC alleles.
Data were analyzed using SPSS 12.0.1 (SPSS Inc., Chicago, IL). For all statistical tests, a P value of <0.05 was considered to be statistically significant.
RESULTS
Baseline characteristics of patients with ACS (n = 100) and controls (n = 74) are shown in Table 1. C. pneumoniae titers for both patients and controls ranged between 5 and 640 for IgA, 16 and 2,048 for IgG, and 1 and 32 for IC. Patients were C. pneumoniae seropositive more often than controls (Table 2).
TABLE 2.
C. pneumoniae markers, gender, and smoking status in patients with ACS (n = 100) and controls (n = 74)a
| Risk factor | No. (%) of subjects in group:
|
P value | |
|---|---|---|---|
| ACS | Control | ||
| IgA titer ≥40 | 37 (37.4) | 17 (23.0) | 0.04 |
| IgA GMT | 14.6 | 9.4 | 0.05 |
| IgG titer ≥128 | 24 (24.2) | 14 (18.9) | NS |
| IgG GMT | 34.1 | 32.3 | NS |
| IC titer ≥2 (%) | 31 (31.3) | 14 (18.9) | NS |
| Marker positivityb | 51 (51.5) | 27 (36.5) | 0.05 |
| Gender | |||
| Male | 38/69 (55.1) | 20/49 (40.8) | NS |
| Female | 13/30 (43.3) | 7/25 (28.0) | NS |
| Smoking status | |||
| Never smoked | 19/40 (47.5) | NA | — |
| Ever smokedc | 32/59 (54.2) | NA | — |
| Current smoker | 19/33 (57.6) | 4/8 (50.0)d | NS |
| Ex-smoker | 13/26 (50.0) | NA | — |
Data are number of subjects (percentage) or number of subjects/total number of subjects studied (percentage). Numbers of subjects indicate the subjects who were positive for C. pneumoniae infection markers. For gender and smoking status, the number of subjects indicates the subjects who were positive for the any of the markers of C. pneumoniae infection. GMT, geometric mean titer; NA, not available; NS, not significant; —, not calculated. The value for C. pneumoniae-specific IgA, IgG, and IC was missing in one patient with ACS.
Positive with any of the three markers of C. pneumoniae infection: IgA titer of ≥40, IgG titer of ≥128, or IC titer of ≥2.
Current smokers and ex-smokers.
Current smokers (n = 8) in controls were detected with cotinine measurement (see the text for details), and four of them were positive with any of the markers of C. pneumoniae infection.
In univariate analyses, any single marker (IgA titer of ≥40, IgG titer of ≥128, or IC titer of ≥2) of C. pneumoniae infection was found more frequently in the patients with the haplotypes HLA-A*03-B*35 and HLA-A*03-B*35-LTA+724C than in patients without these haplotypes (Table 3). Also, any of the markers of C. pneumoniae infection were found significantly more frequently in patients with the HLA-A*03-B*35 or the HLA-A*03-B*35-LTA+724C haplotype than in patients with the HLA-DRB1*01 allele (P = 0.044 and P = 0.048, respectively). In subgroup analyses, when gender and smoking were also considered, any of the markers of C. pneumoniae infection were significantly associated with males having the HLA-A*03-B*35 (P = 0.008) or HLA-A*03-B*35-LTA+724C (P = 0.02) haplotype as well as with current smokers with these haplotypes or the HLA-B*35 allele alone (P = 0.001, P = 0.009, and P = 0.003, respectively) (Table 4). Among the controls, no associations between C. pneumoniae markers and MHC genes (Table 3), smoking status, or gender were found.
TABLE 3.
Significant association of MHC genes and haplotypes with a single marker of C. pneumoniae infections in patients with ACSa
| Patient group, gene(s), and infection marker | No. (%) of patients with genea:
|
OR (95% CI) | P value | |
|---|---|---|---|---|
| Present | Absent | |||
| Diseased | ||||
| HLA*03-B*35 | ||||
| IgA | 15 (60) | 22 (29.7) | 3.55 (1.38-9.10) | 0.007 |
| IgG | 11 (44) | 13 (17.6) | 3.69 (1.37-9.93) | 0.008 |
| IC | 14 (56) | 17 (23) | 4.27 (1.64-11.12) | 0.002 |
| LTA+724C | ||||
| IgA | 35 (41.2) | 2 (14.3) | 4.20 (0.88-19.95) | 0.054 |
| IgG | 23 (27.1) | 1 (7.1) | NS | |
| IC | 31 (36.5) | 0 (0.0) | Undefined | 0.004 |
| HLA-A*03-B*35-LTA+724C | ||||
| IgA | 12 (57.1) | 25 (32.1) | 2.83 (1.05-7.58) | 0.03 |
| IgG | 8 (38.1) | 16 (20.5) | NS | |
| IC | 11 (52.4) | 20 (25.6) | 3.19 (1.18-8.64) | 0.02 |
| HLA-B*35 | ||||
| IgA | 17 (48.6) | 20 (31.3) | NS | |
| IgG | 12 (34.3) | 12 (18.8) | NS | |
| IC | 16 (45.7) | 15 (23.4) | 2.75 (1.14-6.64), 0.02 | 0.02 |
| Controls | ||||
| HLA*03-B*35 | ||||
| IgA | 4 (36.4) | 13 (20.6) | NS | |
| IgG | 4 (36.4) | 10 (15.9) | NS | |
| IC | 3 (27.3) | 11 (17.5) | NS | |
| LTA+724C | ||||
| IgA | 14 (21.9) | 3 (30.0) | NS | |
| IgG | 13 (20.3) | 1 (10.0) | NS | |
| IC | 14 (21.9) | 0 (0.0) | NS | |
| HLA-A*03-B*35-LTA+724C | ||||
| IgA | 4 (36.4) | 13 (20.6) | NS | |
| IgG | 4 (36.4) | 10 (15.9) | NS | |
| IC | 3 (27.3) | 11 (17.5) | NS | |
| HLA-B*35 | ||||
| IgA | 4 (28.6) | 13 (21.7) | NS | |
| IgG | 5 (35.7) | 9 (15.0) | NS | |
| IC | 3 (21.4) | 11 (18.3) | NS | |
Value for C. pneumoniae-specific IgA, IgG, and IC were missing (n = 1). Analyses were at the univariate level. NS, not significant. The total numbers of subjects who had HLA*03-B*35 in the diseased and control groups were 25 and 11, respectively (74 and 63 subjects did not have the allele, respectively); the total numbers of subjects who had LTA+724C in the diseased and control groups were 85 and 64, respectively (14 and 10 subjects did not have the allele, respectively); the total numbers of subjects who had HLA-A*03-B*35-LTA+724C in the diseased and control groups were 21 and 11, respectively (78 and 63 subjects did not have the allele, respectively); and the total numbers of subjects who had HLA-B*35 in the diseased and control groups were 35 and 14, respectively (64 and 60 subjects did not have the allele, respectively).
TABLE 4.
Significant correlations between any of the markers of C. pneumoniae infection and the known risk factors for C. pneumoniae infection in patients with ACSa
| MHC gene | Risk factor | No. of subjects/total no. of subjects studied (%) with combined markers of C. pneumoniaeb:
|
P value | |
|---|---|---|---|---|
| Present | Absent | |||
| HLA-A*03-B*35 | Male | 16/20 (80.0) | 22/49 (44.9) | 0.008 |
| Current smoker | 12/13 (92.3) | 7/20 (35.0) | 0.001 | |
| Ever smokedc | 16/19 (84.2) | 16/40 (40.0) | 0.001 | |
| HLA-A*03-B*35- | Male | 13/16 (81.3) | 25/53 (47.2) | 0.02 |
| LTA+724C | Current smoker | 10/11 (90.9) | 9/22 (40.9) | 0.009 |
| Ever smoked | 14/16 (87.5) | 18/43 (41.9) | 0.002 | |
| HLA-B*35 | Male | 18/28 (64.3) | 20/41 (48.8) | NS |
| Current smoker | 14/17 (82.4) | 5/16 (31.3) | 0.003 | |
| Ever smoked | 18/25 (72.0) | 14/34 (41.2) | 0.02 | |
| HLA-A*03 | Male | 24/40 (60.0) | 14/29 (48.3) | NS |
| Current smoker | 15/18 (83.3) | 4/15 (26.7) | 0.001 | |
| Ever smoked | 22/33 (66.7) | 10/26 (38.5) | 0.03 | |
| LTA+724C | Male | 36/59 (61.0) | 2/10 (20.0) | 0.03 |
| Current smoker | 19/30 (63.3) | 0/3 (0.0) | NS | |
| Ever smoked | 30/50 (60.0) | 2/9 (22.2) | NS | |
Analyses were at the univariate level. NS, not significant.
Positive with any of the three markers of C. pneumoniae infection: IgA titer of ≥40, IgG titer of ≥128, or IC titer of ≥2. Values for C. pneumoniae-specific IgA, IgG, and IC were missing (n = 1).
Current smokers and ex-smokers.
In multiple-logistic regression analysis, any of the markers of C. pneumoniae infection were associated with HLA-B*35 (odds ratio [OR], 7.88; 95% confidence interval [CI], 2.44 to 25.43; P = 0.0006) as well as with HLA-A*02 (OR, 4.15; 95% CI, 1.42 to 12.10; P = 0.009) and C4B2 (OR, 3.60; 95% CI, 1.19 to 10.86; P = 0.02). However, the latter two did not associate in univariate analyses.
DISCUSSION
This study shows for the first time that markers of C. pneumoniae infection are associated with HLA-B*35-related haplotypes in patients with ACS. Furthermore, among these patients, the prevalence of C. pneumoniae infection markers was more pronounced in smokers and males. In the controls, HLA-B*35 was not associated with C. pneumoniae infection. HLA-B*35 alone or together with the other functionally important genes on the A*03-B*35-LTA+724C haplotype may provide one possible link between CAD and C. pneumoniae infection.
C. pneumoniae infection has been linked to CAD by several methodological approaches, e.g., by seroepidemiological studies and by demonstrating the presence of C. pneumoniae in atherosclerotic lesions by culture, immunocytochemistry, PCR, and electron microscopy. In the present study, we used elevated antichlamydial IgA, IgG, and ICs as markers of chronic C. pneumoniae infection. Thus, antibodies are only indirect evidence of chronic Chlamydia infection; however, IC and IgA levels will not stay high without a continuous infection (25, 36). The prevalence of these markers was lower than that reported previously (35) but significantly higher in patients than in controls. Smoking and male gender are established risk factors for CAD and also predispose one to C. pneumoniae infection (19, 22). Also, in this study, male gender and smoking, when related to HLA-B*35, were definite risk factors for C. pneumoniae infection in patients with CAD. When HLA-B*35 was absent, any of the markers of C. pneumoniae infection were almost threefold lower in current smokers. No such relation was found in controls. Thus, suggested chronic C. pneumoniae infection in patients with CAD seems to be the result of multiple factors, and among them, the HLA-B*35-positive haplotype may play an important role.
Associations between immunity and genes regulating inflammation with CAD and C. pneumoniae infection have been studied only occasionally (29, 34). Dahlén et al. (5) previously studied class II HLA genes and showed that C. pneumoniae antibodies and high Lp(a) levels were associated with HLA-DRB1*03 and HLA-DRB1*13, but the association was not later confirmed by the same group (5, 15). We have recently shown an association between CAD and HLA-B*35, DRB1*01-related haplotypes. The results in this study may indicate that the elevated markers of C. pneumoniae infection associate especially with the presence of the HLA-B*35 allele on the haplotype HLA-A*03-B*35-LTA+724C. Eighty- one percent of HLA-A*03-B*35 and HLA-A*03-B*35-LTA+724C haplotype-positive patients had any of the markers of C. pneumoniae infection, while on the contrary, 55% of HLA-DRB1*01-positive patients had any of the markers of C. pneumoniae infection.
Both the incidence of CAD (16, 17) and the prevalence of C. pneumoniae markers (18) are elevated in the eastern part of Finland. The HLA-B*35 allele is one of the most frequently isolated HLA alleles in the Finnish population and has an even higher prevalence in the eastern parts (40), suggesting an accessible association between CAD, C. pneumoniae, and the HLA-B*35 allele.
In addition to C. pneumoniae, an infectious etiology of atherosclerosis and CAD has been implicated with regard to Helicobacter pylori, herpes simplex virus, and cytomegalovirus (27). Several case control studies suggested that vaccination against influenza virus may reduce the risk of myocardial infarction (8, 26). One of the preferred alleles in the influenza A virus-specific cytotoxic-T-lymphocyte response is HLA-B*3501; preferential HLA usage is dependent on the type of the virus and determines differential cytokine expression (2, 3). The HLA-B*35 allele has also been associated with chronic hepatitis B virus, hepatitis C virus, and herpes simplex virus infections; Epstein-Barr virus seropositivity; and cytotoxic responses against Aspergillus and Mycobacterium tuberculosis (10, 20, 33, 45). In human immunodeficiency virus infection, the rapid progression of the disease has been correlated to the interaction of a virus peptide with B*35 (4). Recently, it has been shown that C. pneumoniae-infected host cells can induce genes involved in apoptosis (6), while HLA-B35 influences the apoptosis rate (37).
The results of our study indicate that HLA-B35 presents C. pneumoniae peptides and may further provide an environment that predetermines the establishment of persistent C. pneumoniae infection. The HLA-B*35 allele has been shown to confer a significant proapoptotic influence to different kind of cells. It may promote pathological cell activation and proliferation and gene transcription through the control of the intracellular cation concentration (38). C. pneumoniae-infected monocyte cells are shown to up-regulate many genes including the vasoconstrictor endothelin 1 (41). HLA-B*35 influences the upregulation of endothelin 1, providing an explanation for the epidemiological association existing between isolated pulmonary hypertension and HLA-B*35 (38).
In conclusion, our results show that the HLA-B*35-positive haplotypes confer a C. pneumoniae-related risk for CAD.
Acknowledgments
This study was funded by the University of Helsinki Foundation, Finnish-Norwegian Medical Foundation, Aarne Koskelo Foundation, Finnish Foundation for Cardiovascular Research, Special Governmental Subsidy for Health Sciences Research (EVO), Medical Research Fund of the Finnish Red Cross Blood Transfusion Service, and the Päivikki and Sakari Sohlberg Foundation.
M.-L.L. is employed by the Haartman Institute, University of Helsinki, and consults at HaartBio, a company owned by the University of Helsinki and which offers MHC typing services. No conflicts are reported for all other authors.
Footnotes
Published ahead of print on 7 November 2007.
REFERENCES
- 1.Benowitz, N. L., F. Kuyt, P. Jacob III, R. T. Jones, and A. L. Osman. 1983. Cotinine disposition and effects. Clin. Pharmacol. Ther. 34:604-611. [DOI] [PubMed] [Google Scholar]
- 2.Boon, A. C., G. De Mutsert, R. A. Fouchier, K. Sintnicolaas, A. D. Osterhaus, and G. F. Rimmelzwaan. 2004. Preferential HLA usage in the influenza virus-specific CTL response. J. Immunol. 172:4435-4443. [DOI] [PubMed] [Google Scholar]
- 3.Boon, A. C., G. de Mutsert, Y. M. Graus, R. A. Fouchier, K. Sintnicolaas, A. D. Osterhaus, and G. F. Rimmelzwaan. 2002. Sequence variation in a newly identified HLA-B35-restricted epitope in the influenza A virus nucleoprotein associated with escape from cytotoxic T lymphocytes. J. Virol. 76:2567-2572. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Carrington, M., and S. J. O'Brien. 2003. The influence of HLA genotype on AIDS. Annu. Rev. Med. 54:535-551. [DOI] [PubMed] [Google Scholar]
- 5.Dahlén, G. H., J. Boman, L. S. Birgander, and B. Lindblom. 1995. Lp(a) lipoprotein, IgG, IgA and IgM antibodies to Chlamydia pneumoniae and HLA class II genotype in early coronary artery disease. Atherosclerosis 114:165-174. [DOI] [PubMed] [Google Scholar]
- 6.Eickhoff, M., J. Thalmann, S. Hess, M. Martin, T. Laue, J. Kruppa, G. Brandes, and A. Klos. 2007. Host cell responses to Chlamydia pneumoniae in gamma interferon-induced persistence overlap those of productive infection and are linked to genes involved in apoptosis, cell cycle, and metabolism. Infect. Immun. 75:2853-2863. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Gieffers, J., J. Rupp, A. Gebert, W. Solbach, and M. Klinger. 2004. First-choice antibiotics at subinhibitory concentrations induce persistence of Chlamydia pneumoniae. Antimicrob. Agents Chemother. 48:1402-1405. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8.Gurfinkel, E. P., R. Leon de la Fuente, O. Mendiz, and B. Mautner. 2004. Flu vaccination in acute coronary syndromes and planned percutaneous coronary interventions (FLUVACS) study. Eur. Heart. J. 25:25-31. [DOI] [PubMed] [Google Scholar]
- 9.Hackstadt, T. 2000. Redirection of host vesicle trafficking pathways by intracellular parasites. Traffic 1:93-99. [DOI] [PubMed] [Google Scholar]
- 10.Hammond, A. S., M. R. Klein, T. Corrah, A. Fox, A. Jaye, K. P. McAdam, and R. H. Brookes. 2005. Mycobacterium tuberculosis genome-wide screen exposes multiple CD8 T cell epitopes. Clin. Exp. Immunol. 140:109-116. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11.Hansson, G. K. 2005. Inflammation, atherosclerosis, and coronary artery disease. N. Engl. J. Med. 352:1685-1695. [DOI] [PubMed] [Google Scholar]
- 12.Hill, A. V. 1998. The immunogenetics of human infectious diseases. Annu. Rev. Immunol. 16:593-617. [DOI] [PubMed] [Google Scholar]
- 13.Huittinen, T., D. Hahn, T. Anttila, E. Wahlström, P. Saikku, and M. Leinonen. 2001. Host immune response to Chlamydia pneumoniae heat shock protein 60 is associated with asthma. Eur. Respir. J. 17:1078-1082. [DOI] [PubMed] [Google Scholar]
- 14.Huittinen, T., M. Leinonen, L. Tenkanen, H. Virkkunen, M. Manttari, T. Palosuo, V. Manninen, and P. Saikku. 2003. Synergistic effect of persistent Chlamydia pneumoniae infection, autoimmunity, and inflammation on coronary risk. Circulation 107:2566-2570. [DOI] [PubMed] [Google Scholar]
- 15.Jonasson, L., T. Eriksson, G. H. Dahlén, and B. Lindblom. 1997. Lipoprotein (a) and HLA-DRB1 and -DQB1 genes in coronary artery disease. Atherosclerosis 133:111-114. [DOI] [PubMed] [Google Scholar]
- 16.Jousilahti, P., E. Vartiainen, J. Pekkanen, J. Tuomilehto, J. Sundvall, and P. Puska. 1998. Serum cholesterol distribution and coronary heart disease risk: observations and predictions among middle-aged population in eastern Finland. Circulation 97:1087-1094. [DOI] [PubMed] [Google Scholar]
- 17.Jousilahti, P., E. Vartiainen, J. Tuomilehto, J. Pekkanen, and P. Puska. 1998. Role of known risk factors in explaining the difference in the risk of coronary heart disease between eastern and southwestern Finland. Ann. Med. 30:481-487. [DOI] [PubMed] [Google Scholar]
- 18.Karvonen, M., J. Tuomilehto, J. Pitkäniemi, A. Naukkarinen, and P. Saikku. 1994. Chlamydia pneumoniae IgG antibody prevalence in south-western and eastern Finland in 1982 and 1987. Int. J. Epidemiol. 23:176-184. [DOI] [PubMed] [Google Scholar]
- 19.Karvonen, M., J. Tuomilehto, J. Pitkäniemi, A. Naukkarinen, and P. Saikku. 1994. Importance of smoking for Chlamydia pneumoniae seropositivity. Int. J. Epidemiol. 23:1315-1321. [DOI] [PubMed] [Google Scholar]
- 20.Kim, J. H., C. W. Pyo, D. K. Koh, J. K. Hur, J. H. Kang, and T. G. Kim. 2006. Alteration of the influences of HLA classes I and II alleles on the perinatal hepatitis B virus infection after immunoprophylaxis in Korean children. Hepatol. Res. 35:118-126. [DOI] [PubMed] [Google Scholar]
- 21.Kuo, C. C., L. A. Jackson, L. A. Campbell, and J. T. Grayston. 1995. Chlamydia pneumoniae (TWAR). Clin. Microbiol. Rev. 8:451-461. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 22.Leinonen, M. 2000. Chlamydia pneumoniae and other risk factors for atherosclerosis. J. Infect. Dis. 181(Suppl. 3):S414-S416. [DOI] [PubMed] [Google Scholar]
- 23.Leinonen, M., E. Linnanmaki, K. Mattila, M. S. Nieminen, V. Valtonen, M. Leirisalo-Repo, and P. Saikku. 1990. Circulating immune complexes containing chlamydial lipopolysaccharide in acute myocardial infarction. Microb. Pathog. 9:67-73. [DOI] [PubMed] [Google Scholar]
- 24.Leinonen, M., and P. Saikku. 2002. Evidence for infectious agents in cardiovascular disease and atherosclerosis. Lancet Infect. Dis. 2:11-17. [DOI] [PubMed] [Google Scholar]
- 25.Linnanmäki, E., M. Leinonen, K. Mattila, M. S. Nieminen, V. Valtonen, and P. Saikku. 1993. Chlamydia pneumoniae-specific circulating immune complexes in patients with chronic coronary heart disease. Circulation 87:1130-1134. [DOI] [PubMed] [Google Scholar]
- 26.Madjid, M., M. Naghavi, S. Litovsky, and S. W. Casscells. 2003. Influenza and cardiovascular disease: a new opportunity for prevention and the need for further studies. Circulation 108:2730-2736. [DOI] [PubMed] [Google Scholar]
- 27.Mehta, J. L., T. G. Saldeen, and K. Rand. 1998. Interactive role of infection, inflammation and traditional risk factors in atherosclerosis and coronary artery disease. J. Am. Coll. Cardiol. 31:1217-1225. [DOI] [PubMed] [Google Scholar]
- 28.MHC Sequencing Consortium. 1999. Complete sequence and gene map of a human major histocompatibility complex. Nature 401:921-923. [DOI] [PubMed] [Google Scholar]
- 29.Momiyama, Y., R. Hirano, H. Taniguchi, H. Nakamura, and F. Ohsuzu. 2001. Effects of interleukin-1 gene polymorphisms on the development of coronary artery disease associated with Chlamydia pneumoniae infection. J. Am. Coll. Cardiol. 38:712-717. [DOI] [PubMed] [Google Scholar]
- 30.Palikhe, A., J. Sinisalo, M. Seppänen, V. Valtonen, M. S. Nieminen, and M. L. Lokki. 2007. Human MHC region harbors both susceptibility and protective haplotypes for coronary artery disease. Tissue Antigens 69:47-55. [DOI] [PubMed] [Google Scholar]
- 31.Pantoja, L. G., R. D. Miller, J. A. Ramirez, R. E. Molestina, and J. T. Summersgill. 2001. Characterization of Chlamydia pneumoniae persistence in HEp-2 cells treated with gamma interferon. Infect. Immun. 69:7927-7932. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 32.Petzl-Erler, M. L. 1999. Genetics of the immune responses and disease susceptibility. Ciência Cultura 51:1999-2011. [Google Scholar]
- 33.Ramadan, G., B. Davies, V. P. Kurup, and C. A. Keever-Taylor. 2005. Generation of cytotoxic T cell responses directed to human leucocyte antigen class I restricted epitopes from the Aspergillus f16 allergen. Clin. Exp. Immunol. 140:81-91. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 34.Rugonfalvi-Kiss, S., V. Endresz, H. O. Madsen, K. Burian, J. Duba, Z. Prohaszka, I. Karadi, L. Romics, E. Gonczol, G. Fust, and P. Garred. 2002. Association of Chlamydia pneumoniae with coronary artery disease and its progression is dependent on the modifying effect of mannose-binding lectin. Circulation 106:1071-1076. [DOI] [PubMed] [Google Scholar]
- 35.Saikku, P., M. Leinonen, K. Mattila, M. R. Ekman, M. S. Nieminen, P. H. Makela, J. K. Huttunen, and V. Valtonen. 1988. Serological evidence of an association of a novel Chlamydia, TWAR, with chronic coronary heart disease and acute myocardial infarction. Lancet ii:983-986. [DOI] [PubMed] [Google Scholar]
- 36.Saikku, P., M. Leinonen, L. Tenkanen, E. Linnanmaki, M. R. Ekman, V. Manninen, M. Manttari, M. H. Frick, and J. K. Huttunen. 1992. Chronic Chlamydia pneumoniae infection as a risk factor for coronary heart disease in the Helsinki Heart Study. Ann. Intern. Med. 116:273-278. [DOI] [PubMed] [Google Scholar]
- 37.Salazar, G., G. Colombo, S. Lenna, R. Antonioli, L. Beretta, A. Santaniello, and R. Scorza. 2007. HLA-B35 influences the apoptosis rate in human peripheral blood mononucleated cells and HLA-transfected cells. Hum. Immunol. 68:181-191. [DOI] [PubMed] [Google Scholar]
- 38.Santaniello, A., G. Salazar, S. Lenna, R. Antonioli, G. Colombo, L. Beretta, and R. Scorza. 2006. HLA-B35 upregulates the production of endothelin-1 in HLA-transfected cells: a possible pathogenetic role in pulmonary hypertension. Tissue Antigens 68:239-244. [DOI] [PubMed] [Google Scholar]
- 39.Sinisalo, J., K. Mattila, V. Valtonen, O. Anttonen, J. Juvonen, J. Melin, H. Vuorinen-Markkola, and M. S. Nieminen. 2002. Effect of 3 months of antimicrobial treatment with clarithromycin in acute non-Q-wave coronary syndrome. Circulation 105:1555-1560. [DOI] [PubMed] [Google Scholar]
- 40.Siren, M. K., H. Sareneva, M. L. Lokki, and S. Koskimies. 1996. Unique HLA antigen frequencies in the Finnish population. Tissue Antigens 48:703-707. [DOI] [PubMed] [Google Scholar]
- 41.Virok, D., A. Loboda, L. Kari, M. Nebozhyn, C. Chang, C. Nichols, V. Endresz, E. Gonczol, K. Berencsi, M. K. Showe, and L. C. Showe. 2003. Infection of U937 monocytic cells with Chlamydia pneumoniae induces extensive changes in host cell gene expression. J. Infect. Dis. 188:1310-1321. [DOI] [PubMed] [Google Scholar]
- 42.von Hertzen, L., H. Alakarppa, R. Koskinen, K. Liippo, H. M. Surcel, M. Leinonen, and P. Saikku. 1997. Chlamydia pneumoniae infection in patients with chronic obstructive pulmonary disease. Epidemiol. Infect. 118:155-164. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 43.Wang, S. P., and J. T. Grayston. 1970. Immunologic relationship between genital TRIC lymphogranuloma venerum, and related organisms in a new microtiter indirect immunofluorescence method. Am. J. Ophthalmol. 70:367-374. [DOI] [PubMed] [Google Scholar]
- 44.Wiedeman, J. A., R. Kaul, L. S. Heuer, N. N. Thao, K. E. Pinerton, and W. M. Wenman. 2005. Tobacco smoke induces a persistent, but recoverable state in Chlamydia pneumoniae infection of human endothelial cells. Microb. Pathog. 39:197-204. [DOI] [PubMed] [Google Scholar]
- 45.Yoon, S. K., J. Y. Han, C. W. Pyo, J. M. Yang, J. W. Jang, C. W. Kim, U. I. Chang, S. H. Bae, J. Y. Choi, K. W. Chung, H. S. Sun, H. B. Choi, and T. G. Kim. 2005. Association between human leukocytes antigen alleles and chronic hepatitis C virus infection in the Korean population. Liver Int. 25:1122-1127. [DOI] [PubMed] [Google Scholar]