Published online before print July 26, 2007, doi: 10.1161/ATVBAHA.107.141846
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
© 2007 American Heart Association, Inc.
Atherosclerosis and Lipoproteins |
Chronic Immune Reactivity Against Persisting Microbial Antigen in the Vasculature Exacerbates Atherosclerotic Lesion Formation
From the Research Department, Kantonal Hospital St Gallen, St Gallen, Switzerland.
Correspondence to Burkhard Ludewig, Research Department, Kantonsspital St Gallen, Rorschacherstrasse 95, CH-9007 St Gallen, Switzerland. E-mail burkhard.ludewig{at}kssg.ch
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Objective— The purpose of this study was to examine the relative contribution of different immunopathological mechanisms during murine cytomegalovirus (MCMV)-mediated acceleration of atheroma formation in apolipoprotein E–deficient (apoE–/–) mice.
Methods and Results— To distinguish between the effects of systemic activation and cognate immune reactivity against a pathogen-derived persisting antigen in the vasculature, we used hypercholesterolemic transgenic mice constitutively expressing the β-galactosidase (β-gal) transgene in the cardiovascular system (apoE–/–xSM-LacZ). After infection with β-gal–recombinant MCMV-LacZ, apoE–/–, and apoE–/–xSM-LacZ mice mounted comparable cellular immune responses against the virus. β-gal–specific CD8+ T cells expanded rapidly and remained detectable for at least 100 days in both mouse strains. However, compared with apoE–/– mice, apoE–/–xSM-LacZ mice developed drastically accelerated atherosclerosis. Moreover, atherosclerotic lesions in MCMV-LacZ–infected apoE–/–xSM-LacZ but not apoE–/– mice were associated with pronounced inflammatory infiltrates.
Conclusions— Taken together, our data indicate that chronic immune reactivity against pathogen-derived antigens persisting in the vasculature significantly exacerbates atherogenesis.
This study demonstrates that T cell responses directed against persisting microbial antigen within the vasculature favor the development of an inflammatory environment that is important for the acceleration of atherosclerotic lesion development.
Key Words: cytomegalovirus • atherosclerosis • inflammation • immunopathology • coronary heart disease
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Chronic inflammatory processes in the vascular wall are crucial for initiation and perpetuation of atherosclerotic lesions.1 It appears that it is the "infectious burden", ie, the overall impact of repeated or chronic infections with multiple pathogens,2 that determines the extent of atherosclerosis and clinical prognosis.3,4 Epidemiological and experimental evidence indicates that herpesviruses represent important viral pathogens that elicit arterial inflammation and may thereby exacerbate atherosclerotic disease. Seroepidemiological studies have shown a link between human cytomegalovirus (HCMV) infection and atherosclerosis.5,6 Furthermore, detection of HCMV DNA in atherosclerotic lesions of patients with coronary artery disease7,8 suggests that HCMV infection may impair vascular functions. HCMV infection of cells in the vascular wall may directly contribute to neointima formation through the viral US28 gene product which functions as a chemokine receptor and enhances the migration of smooth muscle cells in response to inflammatory chemokines.9 Likewise, the chemokine receptor M33 of the murine CMV (MCMV) is essential for MCMV-induced migration of vascular smooth muscle cells10 indicating that vascular integrity can be altered through virus-intrinsic factors.
In addition, various infection-associated immunopathological mechanisms impinge on the atherosclerotic process.11 Molecular similarities ("mimicry") between microbial and host proteins, as found in the structurally related human and chlamydial heat shock proteins (HSP60/65), precipitate inflammatory reactions in atherosclerotic lesions.12 General immune activation with systemic ("bystander") effects on the vascular wall can be triggered by a MCMV infection-associated increase in IFN
serum levels leading to the secretion of proinflammatory cytokines such as monocyte chemoattractant protein-1 (MCP-1) by endothelial cells.13 It is possible that such processes foster the recruitment of monocytes/macrophages and T cells to atherosclerotic lesions.14 It has been argued that the transient induction of bystander cytokines during the first 2 weeks after MCMV infection of apoE–/– mice may be crucial for MCMV-mediated acceleration of atherosclerosis.15,16 However, systemic immune activation by generalized herpesvirus simplex virus 1 infection seems not to be sufficient to aggravate lesion formation in hypercholesterolemic apoE–/– mice.17 It appears that it is rather the specific tropism of herpesviruses for cells of the vascular wall that determines the enhancement of atherogenesis in apoE–/– mice after herpesvirus infection.17,18 Therefore, an issue central to the role of murine and human cytomegaloviruses in atherogenesis is the relative contribution of the different immunopathological mechanisms ("bystander activation" versus "reactivity against persisting antigens") during the development of atherosclerotic lesions.
In the present study we used a well-defined mouse model of cardiovascular immunopathology19 to distinguish between MCMV infection-associated systemic immune activation and specific immune reactivity directed against a persisting viral antigen in the vasculature. In SM-LacZ mice, the β-galactosidase (β-gal) antigen is expressed in arterial smooth muscle cells.20 The peripherally expressed antigen is ignored by T cells unless the antigen is efficiently presented in secondary lymphoid organs.21 During infection with β-gal recombinant MCMV (MCMV-LacZ) the vascular β-gal transgene in SM-LacZ mice functions therefore as a pathogen-derived antigen that persists in the arterial wall. Infection of hypercholesterolemic apoE–/–x SM-LacZ mice with MCMV-LacZ revealed that virus-induced T cell responses directed against the transgenic β-gal antigen within the vasculature favor the development of an inflammatory environment that is important for the acceleration of atherosclerotic lesion development.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Isolation of Arterial Smooth Muscle Cells
Aortas from C57BL/6, SM-lacZ, and Fas-KO mice were cut into small pieces and digested with collagenase type II (2 mg/mL, dissolved in DMEM; Sigma). After incubation for 45 minutes at 37°C, single cell suspensions were prepared by passing through a syringe with a 21G needle. Cells were washed twice with DMEM 10% FCS and plated onto 6-well plates (cell suspension from 1 aorta into 2 wells). After 4-hour incubation at 37°C, nonadherent cells were removed by washing with medium and the remaining cells were cultured further for 10 days. More than 90% of the cells stained positive for smooth muscle actin (not shown).
Immunohistology
Freshly removed organs were immersed in HBSS and snap-frozen in liquid nitrogen (LN2). Frozen tissue sections were cut in a cryostat and fixed in acetone for 10 minutes. Sections were incubated with antibodies against β-gal (MP Biomedicals,), CD8 (clone YTS169.4.2), CD4 (YTS191.1.2), or F4/80 (Biomedicals AG, clone BM8) followed by goat anti-rat Ig (Caltag Labs) and alkaline phosphatase-labeled donkey anti-goat Ig (Jackson ImmunoResearch Labs). Alkaline phophatase was visualized by using AS-BI phosphate/New Fuchsin, and sections were counterstained with hemalum. For the quantitative evaluation of atherosclerotic lesions, 5 to 10 serial cross-sections through the aortic origin, beginning with the appearance of all 3 valve cusps, were stained with Sudan Red, counterstained with hemalum, and measured by using a Leica DM R microscope, Leica DC300 FX camera and Leica IM1000 (version 1.20) computer-aided morphometry software. The average lesion size for each mouse was calculated.
For semiquantitative assessment of inflammatory alterations in atherosclerotic lesions, sections were evaluated in a blinded fashion by 2 observers using the following criteria: grade 0, no infiltration; grade 1, confined minor infiltration (foci of <20 cells) in the perivascular space; grade 2, confined major infiltration (foci of >20 cells) in the perivascular space and/or within the intimal lesion; grade 3, multiple clusters of inflammatory cells (>100 cells) in the perivascular space; grade 4:, multiple clusters of inflammatory cells (>100 cells) in the perivascular space and within the intimal lesion. Average severity has been calculated for MCMV-LacZ–infected hypercholesterolemic mice. Infiltration with CD8+ T cells was enumerated on 3 sections per mouse covering the area of the coronary artery bifurcations.
For β-gal staining in whole tissue mounts, aortic arches were prepared from C57BL/6 and SM-lacZ mice and immersed in PBS 2 mmol/L MgCl2. After fixation in PBS containing 0.5% glutaraldehyde and 2 mmol/L MgCL2 for 1 hour, tissues were rinsed in PBS. β-gal activity was revealed by incubation for 2 to 4 hour at 37°C in X-Gal buffer (5 mmol/L potassium ferrocyanide, 5 mmol/L potassium ferricyanide, 2 mmol/L MgCl2 and 1 mg/mL X-Gal in PBS).
Please see supplemental materials, available online at http://atvb.ahajournals.org, for additional Materials and Methods.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
CD8+ T Cell Reactivity in the Course of MCMV Infection
In a first set of experiments, we determined whether MCMV-induced CTL can recognize β-gal epitopes presented by aortic SMC from SM-LacZ mice. SM-LacZ mice constitutively express the β-gal transgene in aortic SMC (Figure 1A). Interestingly, β-gal expressing SMC from SM-LacZ could only be recognized and lysed by β-gal497–504 specific CTL after preincubation with IFN
(Figure 1B). Recognition of SMC by MCMV-induced CTL could be enhanced by exogenous pulsing with β-gal497–504 peptide. Furthermore, SMC lacking the Fas death receptor and Fas-competent C57BL/6 SMC could only be lysed by perforin-competent CTL (Figure 1C). These data indicate that (1) SMC expressing a protein shared by a cytomegalovirus can be lysed by virus-specific CTL, and (2) that CTL-mediated death of SMC is mainly mediated via perforin-dependent lysis.
|
The adaptive immune response against MCMV is dominated by CD8+ T cells that are required for the termination of the productive infection and the establishment of latency.22 MCMV-specific memory CTL responses may show differences in their expansion and contraction patterns, eg, a rapid expansion can be followed by a pronounced contraction phase or by the continuous increase of IFN producing memory CTL.23,24 We therefore tested in a first set of experiments, the CTL responses directed against the β-gal497–504 epitope and the immunodominant MCMV M45985–993 epitope of MCMV. Analysis with MHC class I tetramers on days 6, 50 and 100 post infection revealed that both β-gal497–504- and M45985–993-specific CD8+ T cells followed a similar pattern in normo- and hypercholesterolemic mice with maximal expansion during the acute response, a pronounced contraction and subsequent establishment of a stable long-term memory cell population (Figure 2A).
|
3). C, For ELISPOT analysis, 5x104 MACS-purified CD8+ splenocytes were incubated with unpulsed, β-gal–, or M45-peptide pulsed dendritic cells, respectively, and numbers of IFN
Based on the finding that IFN permits recognition of aortic SMC by MCMV-induced CTL (Figure 1B) and because IFN accelerates atherosclerotic lesion development,25 we determined the ability of virus-specific CD8+ T cells to produce IFN using intracellular cytokine staining (Figure 2B) and ELISPOT assays (Figure 2C and 2D). The ELISPOT assays were used for measurement of IFN-secreting cells in the memory phase because this assay provides a better resolution and accuracy at lower T cell frequencies. These analyses revealed that neither hypercholesterolemia nor the presence of the β-gal-transgene had a significant impact on the peak expansion of β-gal497–504- and M45985–993-specific IFN-secreting CD8+ T cells (Figure 2B). Furthermore, both β-gal497–504- and M45985–993-specific memory CTL were able to secrete IFN following in vitro restimulation (Figure 2C and 2D). Again, the activity of anti-MCMV CD8+ T cells was not significantly different between hypercholesterolemic and normocholesterolemic mice, and there was no indication that the β-gal transgene in the vasculature had an influence on MCMV-induced CTL responses (Figure 2C and 2D). Taken together, the presented transgenic model provides the means to quantify and to phenotypically characterize virus-specific CD8+ T cells which recognize a persisting vascular antigen both under normo- and hypercholesterolemic conditions.
Virus Replication and Lipid Metabolism
It has been described previously that hypercholesterolemia may negatively influence immune reactivity and consequently alters the host-pathogen interaction with delayed clearance of viruses,26 bacteria,27 or fungi.28 We therefore assessed whether hypercholesterolemia in apoE–/– and apoE–/–xSM-LacZ mice influences initial replication and distribution of MCMV in comparison to normocholesterolemic C57BL/6 and SM-LacZ mice. Polymerase chain reaction (PCR)-based quantification of MCMV genome equivalents revealed that spleens and salivary glands were equally well infected in the four mouse strains (Figure 3A). Furthermore and in contrast to previous studies in mice,29 we could not observe a modulation of cholesterol levels in the course of MCMV infection in normo- or hypercholesterolemic mice (Figure 3B). Of particular importance for this study is that apoE–/– and apoE–/–xSM-LacZ mice are only distinguishable by constitutive β-gal expression in the cardiovascular system, all other MCMV infection-associated parameters such as T cell responses, viral distribution, and total cholesterol values were comparable.
|
Accelerated Atherogenesis in MCMV-Infected ApoE–/–xSM-LacZ Mice
The impact of infection with β-gal recombinant MCMV-LacZ on atherosclerotic lesion development was assessed in the aortic sinus. The most striking observation was the nearly 200% increase of atherosclerotic lesion formation in apoE–/–xSM-LacZ versus apoE–/– control mice on day 50 after infection (Figure 4A and 4B). The acceleration of atherogenesis attributable to chronic virus-driven immune reactivity against the vascular β-gal antigen was less pronounced on day 100 after infection (Figure 4A and 4B). However, in accordance with a previous report from Epstein and colleagues,30 we found only a mild enhancement of atherosclerosis through infection of apoE–/– mice with MCMV on day 100 after infection (Figure 4B). These data indicate that it is mainly the chronic immune reactivity against the persisting MCMV antigen in the vasculature that exacerbates atherosclerotic lesion formation.
|
In addition to the accelerated lesion formation, MCMV-LacZ–infected apoE–/–xSM-LacZ mice showed significant mononuclear infiltrations both in the neointima (Figure 4A, asterisks) and in the perivascular tissue underlying the atherosclerotic lesions (Figure 4A, arrow heads). Immunohistological characterization of the vascular inflammatory infiltrates revealed the presence of macrophages and T cells, with a predominance of CD8+ T cells (Figure 5). Semiquantitative in situ analysis revealed that MCMV-LacZ–infected apoE–/–xSM-LacZ showed significantly stronger inflammatory infiltration compared with apoE–/– mice, both on day 50 (1.8±0.5 versus 0.6±0.2; P<0.05) and on day 100 (2.1±0.3 versus 1.1±0.3; P<0.05) after infection. Furthermore, enumeration of CD8 T cells infiltrating neointima and perivascular space revealed that MCMV-LacZ infection of apoE–/–xSM-LacZ mice elicited a more pronounced recruitment of these cells compared with infected apoE–/– mice; both on day 50 (CD8 T cells per slide: 20.9±8.1 (n=13) versus 6.4±1.6 (n=9); P<0.05) and on day 100 (40.1±6.6 (n=8) versus 12.9±4.7 (n=11); P<0.01) after infection. It is thus conceivable that the abundant CD8+ T cells in and around the atherosclerotic lesions in apoE–/–xSM-LacZ mice were recruited to this location as a consequence of the ongoing immune activation during the persistent MCMV infection.
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The inflammatory nature of atherosclerosis is mediated by various factors. The major pathological mechanisms underlying the onset and perpetuation of the chronic immune activation within the vascular wall include hemodynamic shear stress leading to the expression of proinflammatory genes,31 accumulation of dendritic cells at predisposed sites,32 and systemic immune activation via toll-like receptor (TLR) ligands.33 Understanding and ranking the contribution of the different immunopathological mechanisms mediating disease initiation and progression is thus essential for the development and evaluation of treatment strategies. General immune activation in the course of systemic virus infection may elicit high levels of cytokines in the circulation. In the context of cytomegalovirus infection, IFN
can be produced by virus-specific NK and Th cells.34 It is possible that IFN that is generated in the course of virus infection, either systemically or locally within the inflamed tissue, could promote CTL-mediated SMC lysis by virus-specific CTL through upregulation of MHC I molecules. In human SMC, for example, cytomegalovirus infection can lead to an increased MHC class I expression in smooth muscle cells, hence modulating their immunogenicity.35 Nevertheless, the results of this investigation demonstrate that chronic immune reactivity against a persisting microbial antigen in the arterial wall is a dominant immunopathological factor during MCMV-accelerated atherosclerosis in hypercholesterolemic apoE–/– mice.
Evidence from experimental and natural infections with herpesviruses supports the notion that general immune activation by a viral infection is less important for the inflammatory processes in the vascular wall. For example, -herpesvirus infection of large arteries is associated with an acute lymphoid panarteritis and chronic obliterating arteriosclerosis in chicken36 and cattle.37 Furthermore, murine -herpesvirus 68 (HV68) exhibits a prominent tropism for medial smooth muscle cells of great elastic arteries38 and, consequently, enhances atherogenesis in apoE–/– mice.17,18 In MCMV infection, viral antigens have been reported to be expressed in endothelial and smooth muscle cells of the aorta.29 However, the presence of MCMV in the aorta is limited to a few weeks after infection15; a condition under which MCMV only mildly aggravates atherosclerosis in apoE–/– mice. Thus, accumulation of inflammatory cells in the perivascular space and increased development of atherosclerotic lesions heavily infiltrated with inflammatory cells, depends probably on prolonged antigen presentation within the vessel wall, as it is the case in apoE–/–xSM-LacZ mice. Likewise, factors that favor MCMV persistence in the vasculature lead to increased vascular inflammation39 and atherosclerosis.29
Activated T cells are a major fraction of the cellular components in human atherosclerotic plaques.40 Immunohistological analysis revealed that in advanced plaques of apoE–/– mice, CD4+ T cells are prominent in the fibrous cap and subendothelially, whereas CD8+ T cells are sparse.41 The importance of CD4+ T cells in the amplification of atherogenesis has been demonstrated in adoptive transfer studies where CD4+ T cells from apoE–/– transferred to immunodeficient apoE–/–xscid/scid mice accelerated lesion formation.42 CD4 T cells are activated during MCMV infection and help to maintain long-term control of MCMV in certain cell types within salivary gland tissues.43 It is likely that not only CD8+ but also CD4+ MCMV-specific T cells have contributed to the observed amplification of atherosclerotic lesions in apoE–/–xSM-LacZ mice. Furthermore, it may well be that the recently described dendritic cell network present in atherosclerosis-prone sites of the aorta32 locally presents viral antigens to both CD4+ and CD8+ T cells.
Infections are an important risk factor in atherosclerosis-related diseases such as coronary artery disease or stroke. It is striking that in particular those infectious agents which possess a pronounced tropism for cells of the vascular wall (HCMV or Chlamydia pneumoniae) are the most prominent in the list of infectious agents that contribute to the "infectious burden".4,44,45 Taken together with the data presented in this study, it is most likely that long-lasting immune reactivity against antigens of vascular-tropic infectious agents significantly amplifies inflammatory reactions within atherosclerotic lesions. Thus, treatment strategies against atherosclerosis should aim at reducing exaggerated immune reactivity within the atherosclerotic lesion without impairing general immune defense mechanisms against the persisting pathogen.
|
Acknowledgments |
|---|
We thank Silvia Behnke and Andre Fitsche for help with immunohistochemistry.
Sources of Funding
The project received support from the Swiss National Science Foundation, the Fritz Thyssen Stiftung, the Novartis Foundation for Biomedical Research and the Jubiläumsstiftung Rentenanstalt.
Disclosures
None.
|
Footnotes |
|---|
Original received August 21, 2006; final version accepted July 10, 2007.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
1. Wick G, Knoflach M, Xu Q. Autoimmune and inflammatory mechanisms in atherosclerosis. Annu Rev Immunol. 2004; 22: 361–403.[CrossRef][Medline] [Order article via Infotrieve]
2. Epstein SE, Zhu J, Burnett MS, Zhou YF, Vercellotti G, Hajjar D. Infection and atherosclerosis: potential roles of pathogen burden and molecular mimicry. Arterioscler Thromb Vasc Biol. 2000; 20: 1417–1420.
3. Espinola-Klein C, Rupprecht HJ, Blankenberg S, Bickel C, Kopp H, Victor A, Hafner G, Prellwitz W, Schlumberger W, Meyer J. Impact of infectious burden on progression of carotid atherosclerosis. Stroke. 2002; 33: 2581–2586.
4. Espinola-Klein C, Rupprecht HJ, Blankenberg S, Bickel C, Kopp H, Rippin G, Victor A, Hafner G, Schlumberger W, Meyer J. Impact of infectious burden on extent and long-term prognosis of atherosclerosis. Circulation. 2002; 105: 15–21.
5. Zhou YF, Leon MB, Waclawiw MA, Popma JJ, Yu ZX, Finkel T, Epstein SE. Association between prior cytomegalovirus infection and the risk of restenosis after coronary atherectomy. N Engl J Med. 1996; 335: 624–630.
6. Gattone M, Iacoviello L, Colombo M, Castelnuovo AD, Soffiantino F, Gramoni A, Picco D, Benedetta M, Giannuzzi P. Chlamydia pneumoniae and cytomegalovirus seropositivity, inflammatory markers, and the risk of myocardial infarction at a young age. Am Heart J. 2001; 142: 633–640.[CrossRef][Medline] [Order article via Infotrieve]
7. Hendrix MG, Salimans MM, van Boven CP, Bruggeman CA. High prevalence of latently present cytomegalovirus in arterial walls of patients suffering from grade III atherosclerosis. Am J Pathol. 1990; 136: 23–28.[Abstract]
8. Chiu B, Viira E, Tucker W, Fong IW. Chlamydia pneumoniae, cytomegalovirus, and herpes simplex virus in atherosclerosis of the carotid artery. Circulation. 1997; 96: 2144–2148.
9. Streblow DN, Soderberg-Naucler C, Vieira J, Smith P, Wakabayashi E, Ruchti F, Mattison K, Altschuler Y, Nelson JA. The human cytomegalovirus chemokine receptor US28 mediates vascular smooth muscle cell migration. Cell. 1999; 99: 511–520.[CrossRef][Medline] [Order article via Infotrieve]
10. Melnychuk RM, Smith P, Kreklywich CN, Ruchti F, Vomaske J, Hall L, Loh L, Nelson JA, Orloff SL, Streblow DN. Mouse cytomegalovirus M33 is necessary and sufficient in virus-induced vascular smooth muscle cell migration. J Virol. 2005; 79: 10788–10795.
11. Ludewig B, Krebs P, Scandella E. Immunopathogenesis of atherosclerosis. J Leukoc Biol. 2004; 76: 300–306.
12. George J, Afek A, Gilburd B, Shoenfeld Y, Harats D. Cellular and humoral immune responses to heat shock protein 65 are both involved in promoting fatty-streak formation in LDL-receptor deficient mice. J Am Coll Cardiol. 2001; 38: 900–905.
13. Rott D, Zhu J, Burnett MS, Zhou YF, Wasserman A, Walker J, Epstein SE. Serum of cytomegalovirus-infected mice induces monocyte chemoattractant protein-1 expression by endothelial cells. J Infect Dis. 2001; 184: 1109–1113.[CrossRef][Medline] [Order article via Infotrieve]
14. Froberg MK, Adams A, Seacotte N, Parker-Thornburg J, Kolattukudy P. Cytomegalovirus infection accelerates inflammation in vascular tissue overexpressing monocyte chemoattractant protein-1. Circ Res. 2001; 89: 1224–1230.
15. Vliegen I, Duijvestijn A, Grauls G, Herngreen S, Bruggeman C, Stassen F. Cytomegalovirus infection aggravates atherogenesis in apoE knockout mice by both local and systemic immune activation. Microbes Infect. 2004; 6: 17–24.[Medline] [Order article via Infotrieve]
16. Vliegen I, Herngreen SB, Grauls GE, Bruggeman CA, Stassen FR. Mouse cytomegalovirus antigenic immune stimulation is sufficient to aggravate atherosclerosis in hypercholesterolemic mice. Atherosclerosis. 2005; 181: 39–44.[CrossRef][Medline] [Order article via Infotrieve]
17. Alber DG, Vallance P, Powell KL. Enhanced atherogenesis is not an obligatory response to systemic herpesvirus infection in the apoE-deficient mouse: comparison of murine gamma-herpesvirus-68 and herpes simplex virus-1. Arterioscler Thromb Vasc Biol. 2002; 22: 793–798.
18. Alber DG, Powell KL, Vallance P, Goodwin DA, Grahame-Clarke C. Herpesvirus infection accelerates atherosclerosis in the apolipoprotein E-deficient mouse. Circulation. 2000; 102: 779–785.
19. Ludewig B, Freigang S, Jaggi M, Kurrer MO, Pei YC, Vlk L, Odermatt B, Zinkernagel RM, Hengartner H. Linking immune-mediated arterial inflammation and cholesterol-induced atherosclerosis in a transgenic mouse model. Proc Natl Acad Sci U S A. 2000; 97: 12752–12757.
20. Moessler H, Mericskay M, Li Z, Nagl S, Paulin D, Small JV. The SM 22 promotor directs tissue-specific expression in arterial but not in venous or visceral smooth muscle cells in transgenic mice. Development. 1996; 122: 2415–2425.[Abstract]
21. Ludewig B, Ochsenbein AF, Odermatt B, Paulin D, Hengartner H, Zinkernagel RM. Immunotherapy with dendritic cells directed against tumor antigens shared with normal host cells results in severe autoimmune disease. J Exp Med. 2000; 191: 795–804.
22. Reddehase MJ. Antigens and immunoevasins: opponents in cytomegalovirus immune surveillance. Nat Rev Immunol. 2002; 2: 831–844.[CrossRef][Medline] [Order article via Infotrieve]
23. Karrer U, Sierro S, Wagner M, Oxenius A, Hengel H, Koszinowski UH, Phillips RE, Klenerman P. Memory inflation: continuous accumulation of antiviral CD8+ T cells over time. J Immunol. 2003; 170: 2022–2029.
24. Munks MW, Cho KS, Pinto AK, Sierro S, Klenerman P, Hill AB. Four distinct patterns of memory CD8 T cell responses to chronic murine cytomegalovirus infection. J Immunol. 2006; 177: 450–458.
25. Gupta S, Pablo AM, Jiang Xc, Wang N, Tall AR, Schindler C. IFN-gamma potentiates atherosclerosis in ApoE knock-out mice. J Clin Invest. 1997; 99: 2752–2761.[Medline] [Order article via Infotrieve]
26. Ludewig B, Jaggi M, Dumrese T, Brduscha-Riem K, Odermatt B, Hengartner H, Zinkernagel RM. Hypercholesterolemia exacerbates virus-induced immunopathologic liver disease via suppression of antiviral cytotoxic T cell responses. J Immunol. 2001; 166: 3369–3376.
27. Roselaar SE, Daugherty A. Apolipoprotein E-deficient mice have impaired innate immune responses to Listeria monocytogenes in vivo. J Lipid Res. 1998; 39: 1740–1743.
28. Netea MG, Demacker PN, de Bont N, Boerman OC, Stalenhoef AF, van der Meer JW, Kullberg BJ. Hyperlipoproteinemia enhances susceptibility to acute disseminated Candida albicans infection in low-density-lipoprotein-receptor-deficient mice. Infect Immun. 1997; 65: 2663–2667.[Abstract]
29. Berencsi K, Endresz V, Klurfeld D, Kari L, Kritchevsky D, Gonczol E. Early atherosclerotic plaques in the aorta following cytomegalovirus infection of mice. Cell Adhes Commun. 1998; 5: 39–47.[Medline] [Order article via Infotrieve]
30. Hsich E, Zhou YF, Paigen B, Johnson TM, Burnett MS, Epstein SE. Cytomegalovirus infection increases development of atherosclerosis in Apolipoprotein-E knockout mice. Atherosclerosis. 2001; 156: 23–28.[CrossRef][Medline] [Order article via Infotrieve]
31. Hajra L, Evans AI, Chen M, Hyduk SJ, Collins T, Cybulsky MI. The NF-kappa B signal transduction pathway in aortic endothelial cells is primed for activation in regions predisposed to atherosclerotic lesion formation. Proc Natl Acad Sci U S A. 2000; 97: 9052–9057.
32. Jongstra-Bilen J, Haidari M, Zhu SN, Chen M, Guha D, Cybulsky MI. Low-grade chronic inflammation in regions of the normal mouse arterial intima predisposed to atherosclerosis. J Exp Med. 2006.
33. Mullick AE, Tobias PS, Curtiss LK. Modulation of atherosclerosis in mice by Toll-like receptor 2. J Clin Invest. 2005; 115: 3149–3156.[CrossRef][Medline] [Order article via Infotrieve]
34. Hengel H, Koszinowski UH, Conzelmann KK. Viruses know it all: new insights into IFN networks. Trends Immunol. 2005; 26: 396–401.[CrossRef][Medline] [Order article via Infotrieve]
35. Hosenpud JD, Chou SW, Wagner CR. Cytomegalovirus-induced regulation of major histocompatibility complex class I antigen expression in human aortic smooth muscle cells. Transplantation. 1991; 52: 896–903.[Medline] [Order article via Infotrieve]
36. Fabricant CG, Fabricant J, Litrenta MM, Minick CR. Virus-induced atherosclerosis. J Exp Med. 1978; 148: 335–340.
37. O’Toole D, Li H, Roberts S, Rovnak J, DeMartini J, Cavender J, Williams B, Crawford T. Chronic generalized obliterative arteriopathy in cattle: a sequel to sheep-associated malignant catarrhal fever. J Vet Diagn Invest. 1995; 7: 108–121.
38. Dal Canto AJ, Swanson PE, O’Guin AK, Speck SH, Virgin HW. IFN-gamma action in the media of the great elastic arteries, a novel immunoprivileged site. J Clin Invest. 2001; 107: R15–R22.[Medline] [Order article via Infotrieve]
39. Presti RM, Pollock JL, Dal Canto AJ, O’Guin AK, Virgin HW4. Interferon gamma regulates acute and latent murine cytomegalovirus infection and chronic disease of the great vessels. J Exp Med. 1998; 188: 577–588.
40. Hansson GK, Holm J, Jonasson L. Detection of activated T lymphocytes in the human atherosclerotic plaque. Am J Pathol. 1989; 135: 169–175.[Abstract]
41. Zhou X, Stemme S, Hansson G. Evidence for a local immune response in atherosclerosis. CD4+ T cells infiltrate lesions of apolipoprotein-E-deficient mice. Am J Pathol. 1996; 149: 359–366.[Abstract]
42. Zhou X, Nicoletti A, Elhage R, Hansson GK. Transfer of CD4(+) T cells aggravates atherosclerosis in immunodeficient apolipoprotein E knockout mice. Circulation. 2000; 102: 2919–2922.
43. Jonjic S, Mutter W, Weiland F, Reddehase MJ, Koszinowski UH. Site-restricted persistent cytomegalovirus infection after selective long-term depletion of CD4+ T lymphocytes. J Exp Med. 1989; 169: 1199–1212.
44. Blankenberg S, Rupprecht HJ, Bickel C, Espinola-Klein C, Rippin G, Hafner G, Ossendorf M, Steinhagen K, Meyer J. Cytomegalovirus infection with interleukin-6 response predicts cardiac mortality in patients with coronary artery disease. Circulation. 2001; 103: 2915–2921.
45. Corrado E, Rizzo M, Tantillo R, Muratori I, Bonura F, Vitale G, Novo S. Markers of inflammation and infection influence the outcome of patients with baseline asymptomatic carotid lesions: a 5-year follow-up study. Stroke. 2006; 37: 482–486.
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||