Blockade of complement inhibits obliterative bronchiolitis in rat tracheal allografts.

The role of complement activation in the development of obliterative bronchiolitis, a manifestation of chronic lung allograft rejection, was investigated in the heterotopic rat tracheal allograft model. An increase in intragraft complement components C3 and C5b-9 (membrane attack complex) as well as IgM and IgG deposits were demonstrated during the progressive loss of respiratory epithelium and airway occlusion in nontreated allografts compared with syngeneic grafts. A 7-d treatment with recombinant human soluble complement receptor type 1 (sCR1; 20 mg/kg/d, intraperitoneal), an inhibitor of both the classic and alternative complement pathways, significantly decreased epithelial necrosis and intragraft neutrophil infiltration, and reduced obliterative changes by 40%. Immunohistochemical analysis of the grafts showed that sCR1 treatment significantly decreased early C5b-9 and IgG deposits, neutrophil chemoattractant IL-8 immunoreactivity, and ICAM-1 expression. Treatment with sCR1 was associated with increased staining for Th2 cytokines, in particular IL-10, with concomitant downregulation of IL-2 and TNF-alpha immunoreactivity. In contrast, sCR1 treatment did not affect the number of graft-infiltrating CD4(+) and CD8(+) T cells, CD45(+) B cells, ED1(+) and ED3(+) macrophages, or immune activation with expression of IL-2Ralpha or MHC class II. In conclusion, this is the first study to demonstrate that blockade of complement activation attenuates the development of OB and suggests that in addition to T cell-driven responses, humoral and antigen-independent immune responses also operate in the disease process. A blockade of complement activation renders the chemokine milieu unattractive to neutrophils and also modulates the alloimmune response toward Th2 cytokines, which may have an antiproliferative role in fibroproliferative disorders.

Enhanced intimal proliferation upon injury to pre-existing neointima and resistance of neointimal cells to cell death.

Recent evidence supports a role for cell death and inflammation as etiologic factors in neointimal formation and restenosis after angioplasty. This study was undertaken to examine the pattern and intensity of the proliferative response, cell death, and activation of inflammatory, endothelial and smooth muscle cells (SMC) in a model of intimal reinjury. Two ballooning injuries were performed to rat aorta, the second one 14 days after the first injury. Our results demonstrate that ballooning injury to pre-existing neointima differs clearly from an injury to a normal aorta. First, ballooning injury to pre-existing neointima doubled the proliferative response of SMC and intimal thickening, but proliferation of SMC occurred only in the intima, and did not extend into the media. Second, within four hours after the first injury, the number of TUNEL-positive SMC in the media increased from 3% to 23%, but no such increase was found in the pre-existing neointima after the second injury. Third, the prompt proliferative response of intimal SMC after the second injury was linked with a significant increase in endothelial P-selectin and neointimal VCAM-1 immunoreactivity, compared to the first injury at corresponding time points, followed by high numbers of activated ED3+ macrophages and CD4+ T cells in the developing neointima. A balance in injury-induced cell death and proliferation obviously maintains stable cell numbers observed in the media, whereas in the neointima, the resistance of SMC to injury-induced cell death may contribute to a rapid lesion formation in restenosis.

The Banff 97 working classification of renal allograft pathology.

BACKGROUND: Standardization of renal allograft biopsy interpretation is necessary to guide therapy and to establish an objective end point for clinical trials. This manuscript describes a classification, Banff 97, developed by investigators using the Banff Schema and the Collaborative Clinical Trials in Transplantation (CCTT) modification for diagnosis of renal allograft pathology. METHODS: Banff 97 grew from an international consensus discussion begun at Banff and continued via the Internet. This schema developed from (a) analysis of data using the Banff classification, (b) publication of and experience with the CCTT modification, (c) international conferences, and (d) data from recent studies on impact of vasculitis on transplant outcome. RESULTS: Semiquantitative lesion scoring continues to focus on tubulitis and arteritis but includes a minimum threshold for interstitial inflammation. Banff 97 defines "types" of acute/active rejection. Type I is tubulointerstitial rejection without arteritis. Type II is vascular rejection with intimal arteritis, and type III is severe rejection with transmural arterial changes. Biopsies with only mild inflammation are graded as "borderline/suspicious for rejection." Chronic/sclerosing allograft changes are graded based on severity of tubular atrophy and interstitial fibrosis. Antibody-mediated rejection, hyperacute or accelerated acute in presentation, is also categorized, as are other significant allograft findings. CONCLUSIONS: The Banff 97 working classification refines earlier schemas and represents input from two classifications most widely used in clinical rejection trials and in clinical practice worldwide. Major changes include the following: rejection with vasculitis is separated from tubulointerstitial rejection; severe rejection requires transmural changes in arteries; "borderline" rejection can only be interpreted in a clinical context; antibody-mediated rejection is further defined, and lesion scoring focuses on most severely involved structures. Criteria for specimen adequacy have also been modified. Banff 97 represents a significant refinement of allograft assessment, developed via international consensus discussions.

Cytomegalovirus infection and cardiac allograft vasculopathy.

There is a wealth of clinical and experimental evidence indicating the interaction of cytomegalovirus (CMV) infection and rejection in cardiac and other solid organ allografts. A plausible explanation for this association comes from data showing that therapy with biologicals, sepsis, and rejection, all lead to the release of TNF-alpha which, upon binding to its receptor, activates NF-kB. TNF-alpha is also able to stimulate the activity of the CMV-IE enhancer/promoter region. CMV infection of several cell lines leads to NF-kB activation. NF-kB binding sites are present in regulatory regions of various cellular and viral genes, including the IE enhancer region of CMV. In a reciprocal situation, CMV infection, most likely via gamma-interferon, leads to upregulation of MHC antigens in the transplant and, thereby, to increased transplant immunogenicity. Thus, a vicious circle is induced. We have investigated in detail the pathobiology of CMV and allograft vasculopathy (chronic rejection) in experimental animals, using aortic and cardiac allografts as well as a trachea model. The results may be summarized as follows: Infection of the recipient with rat CMV results in an early inflammatory response in the aortic and cardiac allograft vascular adventitia and intima (endothelialitis) and in the airway wall of tracheal allografts. This early inflammatory response leads to enhanced intimal thickness in aortic and cardiac allografts and enhanced luminal occlusion of tracheal allografts. Timewise, this coincides with early activation of intragraft inflammatory leukocytes and increased mRNA of various growth factors and cytokines. When the recipients receive gancyclovir, the enhanced intimal response in aortic and cardiac allografts and luminal occlusion in tracheal allografts is entirely abolished. Gancyclovir treatment dramatically reduces the inflammatory response in the allograft, and thereby growth factor synthesis in response to injury. However, gancyclovir does not prevent the expression of IE antigen of CMV, suggested to inactivate tumor suppressor protein p53 predisposing smooth muscle cells to increased growth. Taken together, the effect of CMV infection on cardiac allograft dysfunction is bidirectional and biphasic. The bidirectional nature emerges from the observations that acute CMV infection may accelerate acute rejection, and, on the other hand, acute alloimmune response-associated cytokine response may activate latent CMV infection. The biphasic effect of CMV on allograft dysfunction refers to its early and late detrimental effects, i.e. during the time of acute and chronic rejection. These two effects of CMV on allograft dysfunction emphasize the need for precise diagnosis of CMV infection in transplant recipients and pre-emptive or prophylactic anti-viral therapy. The benefits of this strategy may not be evident during the early post-transplant period, but 5-10 years after transplantation they manifest as better graft survival.

A vitamin D analog, MC1288, inhibits adventitial inflammation and suppresses intimal lesions in rat aortic allografts.

Certain analogs of vitamin D have been shown to prevent autoimmune diseases and prolong cardiac allograft survival. We transplanted aortic allografts from DA rats to WF rats to investigate the effect of a synthetic vitamin D analog, MC1288, and cyclosporine (CsA), alone or in combination, on acute and chronic rejection (allograft arteriosclerosis) and the mechanism of action of MC1288. The histological changes in the vascular wall were quantitated as point score units (psu). Adventitial inflammation linked with acute rejection at 1 month after transplantation decreased from 10.0+/-0.9 psu to 4.1+/-1.0 psu (P<0.01) when MC1288, 0.1 microg/kg/every other day, and CsA, 5 mg/kg/day, were combined. Intimal thickening decreased from 2.5+/-0.3 psu to 1.1+/-0.4 psu (P<0.05) at 3 months after transplantation. Proliferation of the adventitial lymphoid cells, detected by bromodeoxyuridine labeling, decreased from 140+/-36 to 20+/-19 labeled cells/cross-section. MC1288 alone suppressed interleukin 2 receptor-expressing cells from 156 to 90 positive cells/cross-section. Taken together, MC1288 with CsA effectively suppress T cell proliferation and activation and decrease intimal thickening.

Cytomegalovirus infection-enhanced chronic kidney allograft rejection is linked with intercellular adhesion molecule-1 expression.

In human kidney allografts, association of acute rejection and glomerulopathy with cytomegalovirus (CMV) infection has been demonstrated. To investigate the effect of CMV infection on the development of experimental chronic kidney allograft rejection, heterotopic kidney allografts from DA (Ag-B4, RT1a1) rat donors to WF (Ag-B2, RT1u) rat recipients were used. The animals received cyclosporine A (CsA) 5 mg/kg/day s.c. either for 1 or 12 weeks. Two groups of recipients were infected with 10(5) plaque-forming units of rat CMV (RCMV) and two other groups were left noninfected and used as controls. The grafts were removed 12 weeks after transplantation for histology and immunohistochemistry. RCMV infection significantly enhanced the development of chronic kidney allograft rejection in rats on continuous CsA the intensity of interstitial inflammation (P < 0.025), particularly the degree of pyroninophilic cells in the inflammatory infiltrate (P < 0.025), the glomerular mesangial matrix increase (P < 0.05) and capillary basement membrane thickening (P < 0.01), the extent of endothelial cell swelling (P < 0.025) and intimal proliferation (P < 0.025) in the graft vasculature, and the extent of tubular epithelial atrophy (P < 0.025). Chronic allograft damage index (CADI) was significantly increased to 4.3 +/- 0.8 in RCMV-infected allografts, compared to 0.8 +/- 0.4 in noninfected (P < 0.02). In addition, RCMV infection significantly increased the number of acute rejection episodes (serum creatinine > 200 mumol/liter, P < 0.05) and almost doubled the end-stage serum creatinine. RCMV infection significantly increased ICAM-1 expression on the vascular endothelium (P < 0.05) and tubular epithelial cells (P < 0.01), and was linked with enhanced interstitial, glomerular, and tubular inflammation. In 80% of allografts on continuous CsA, RCMV antigens could be observed in sporadic inflammatory cells one week after infection and in tubular epithelial cells at 12 weeks. In heavily inflamed allografts where the CsA treatment was discontinued at one week, enhancement of RCMV infection on the histological changes attributable to chronic kidney allograft rejection could not be demonstrated. Our results show that during CsA immunosuppression, RCMV infection enhances chronic kidney allograft rejection associated with increased interstitial inflammation as well as vascular endothelial and tubular epithelial ICAM-1 expression.

Triple drug immunosuppression significantly reduces aortic allograft arteriosclerosis in the rat.

We evaluated the effect of triple drug immunosuppression (cyclosporine A 10 mg . kg(-1) . d(-1), methylprednisolone 0.5 mg . kg(-1) . d(-1) on the development of allograft arteriosclerosis (chronic rejection). The recipients of rat aortic allografts from the DA (AG-B4,RT1a) to the WF (AG-B2,RT1u) strain were either treated with triple drug immunosuppression (n=23) or left untreated (n=23) and used as controls. The grafts were removed 7, 14, 30, 90, and 180 days after transplantation, and vascular wall changes were evaluated by quantitative histology, [3H]thymidine autoradiography, and immunohistochemistry. Nonimmunosuppressed aortic allografts developed progressive arteriosclerotic alterations 1 to 6 months after transplantation that were virtually identical to those observed during chronic rejection in human cardiac allografts. Linear regression analysis revealed that triple drug immunosuppression with clinically relevant dosages of drugs significantly reduced intimal thickening (r=.69 versus r=.88, P<.05). Concomitantly, there was a marked reduction in the number of inflammatory cells (P<.01) and their rate of proliferation (P<.025) in the allograft adventitia during the period of acute inflammation (30 days after transplantation). Immunohistochemistry revealed that the number of helper T cells (W3/25) and monocyte/macrophages (OX42) but not cytotoxic T cells (OX8) or natural killer cells (3.2.3) was significantly (P<.05) reduced. The number of adventitial cells expressing interleukin-2 receptor (CD25) (P<.05), MHC class II (OX6) (P<.05) and leukocyte function-associated antigen-1 alpha-chain (CD11a) (P<.025) was also significantly reduced at 30 days. Triple drug immunosuppression downregulated the induction of MHC class II and intercellular adhesion molecule-1 on the graft endothelium but had no significant effect on the number of subendothelial inflammatory cells. In addition, [3H]thymidine autoradiography demonstrated that triple drug immunosuppression significantly reduced the rate of cell proliferation in the media, composed of smooth-muscle cells, 30 and 90 days after transplantation. Thus, triple drug immunosuppression efficiently reduced the development of allograft arteriosclerosis by down-regulating the inflammatory response and the level of immune++ activation in the allograft adventitia during the acute rejection period, resulting in diminished intimal thickening of the graft in the long run. These results support the concept that allograft arteriosclerosis is due to or at least initiated by immune injury of the graft.

Rat cytomegalovirus infection and chronic kidney allograft rejection.

To investigate the effect of cytomegalovirus (CMV) infection on the development of experimental chronic kidney allograft rejection, orthotopic kidney allografts from DA donors (Ag-B4, RT1a1) to WF (Ag-B2, RT1u) recipients were used. The rats received cyclosporine A (CsA) for 12 weeks. A group of recipients was infected with 10(5) plaque-forming units of rat CMV (RCMV), and another group was left non-infected and used as controls. The grafts were removed 12 weeks after transplantation. RCMV infection significantly enhanced the development of chronic kidney allograft rejection as follows: the intensity of interstitial inflammation (P < 0.025), particularly the degree of pyroninophilic cells in the inflammatory infiltrate (P < 0.025); the glomeruli mesangial matrix increase (P < 0.05) and capillary basement membrane thickening (P < 0.01); the extent of endothelial cell swelling (P < 0.025) and intimal proliferation (P < 0.025) in the graft vasculature; and the extent of tubular epithelial atrophy (P < 0.025). The chronic allograft damage index (CADI) was significantly increased to 4.2 +/- 0.9 in RCMV-infected allografts, compared with 0.8 +/- 0.4 in non-infected (P < 0.02). At the molecular level, RCMV infection significantly increased vascular endothelial (P < 0.05) and tubular epithelial (P < 0.01) ICAM-1 expression. Viral antigens were detected in tubular epithelial cells and in some inflammatory cells.

How cyclosporine modifies histological and molecular events in the vascular wall during chronic rejection of rat cardiac allografts.

Accelerated allograft arteriosclerosis (chronic rejection) has emerged as a major factor affecting long-term survival of human cardiac allografts. The underlying mechanism of this disorder remains unclear. The purpose of this study was to investigate the effect of cyclosporine on the development of cardiac allograft arteriosclerosis at the cellular and molecular level. Heterotopic rat cardiac allografts from DA donors to WF recipients, with a strong genetic disparity in major histocompatibility complex and non-major histocompatibility complex loci, were used. The allograft recipients received triple-drug immunosuppression consisting of methylprednisolone (0.5 mg/kg/day), azathioprine (2 mg/kg/day), and three different doses of cyclosporine A (CsA; 5, 10, and 20 mg/kg/day). The grafts were removed 3 months after transplantation and processed for histology and immunohistochemistry. Low dose CsA (5 mg/kg/day) was associated with a severe form of intimal cell accumulation and intimal thickening in epicardial arteries and in smaller intramyocardial arterioles with nearly occluded vessel lumens 3 months after transplantation. The intermediate dose CsA (10 mg/kg/day) significantly inhibited arterial intimal thickening but was not efficient in reducing intimal cell accumulation. Instead, high dose CsA (20 mg/kg/day) significantly inhibited all arteriosclerotic vascular wall changes in the allografts. Immunohistochemistry revealed that the occluded epicardial arteries of cardiac allografts with low dose CsA expressed VCAM-1 on the endothelium. Higher CsA doses significantly reduced the expression of endothelial VCAM-1. Neither ICAM-1 nor major histocompatibility complex class II were expressed. Perivascular arterial infiltrates consisting of T helper cells and monocytes/macrophages were a characteristic finding in the allograft with low dose CsA. In the allografts treated with higher doses of CsA, arterial perivascular infiltrates were seldom seen. Our results conclusively demonstrate that sufficient immunosuppression with CsA inhibits intimal thickening and intimal cell accumulation of long-surviving rat cardiac allografts in a dose-dependent fashion. Arteriosclerotic alterations associated with increased expression of arterial endothelial VCAM-1 were totally down-regulated by high doses of CsA.

Cytomegalovirus infection enhances mRNA expression of platelet-derived growth factor-BB and transforming growth factor-beta 1 in rat aortic allografts. Possible mechanism for cytomegalovirus-enhanced graft arteriosclerosis.

We have recently demonstrated that rat cytomegalovirus (RCMV) infection induces an early inflammatory response in the adventitia (perivasculitis) and in the subendothelial space (endothelialitis) as well as doubles smooth muscle cell (SMC) proliferation and intimal thickening of rat aortic allografts performed from the DA (AG-B4, RT1a) to the WF (AG-B2, RT1v) strain. In this study, the impact of RCMV infection on the structure of inflammation in the allograft adventitia and on the expression of SMC growth factors in the allograft vascular wall was investigated. The recipient rats were inoculated with 10(5) plaque-forming U of RCMV Maastricht strain or left noninfected and used as controls. The allografts were removed at 7 days and 1 and 3 months after transplantation and processed for morphometry and immunohistochemistry. RNA was isolated for reverse transcriptase polymerase chain reaction (RT-PCR). RCMV infection was associated with significantly upregulated presence (P < .05) of T helper (W3/25), T cytotoxic (OX8), and natural killer (3.2.3) cells in the allograft adventitia 7 days after transplantation but not thereafter. More monocyte/macrophages (OX42) were also present in RCMV-infected allografts, but the difference was not significant. Concomitantly, RCMV infection significantly enhanced (P < .05) the expression of major histocompatibility complex class II (OX6) and almost doubled (P = NS) the expression of interleukin-2R (CD25), intercellular adhesion molecule-1 (CD54;1A29), and lymphocyte function-associated antigen-1 alpha-chain (CD11a; WT.1) in the adventitial inflammatory infiltrate. RCMV infection was linked with an early, prominent expression of both PDGF-BB mRNA at 7 days (P < .05) and at 1 month (P < .025) and of transforming growth factor-beta 1 mRNA at 7 days (P < .025) and at 1 month (P < .025) after transplantation. A less-prominent mRNA upregulation of acidic fibroblast growth factor (P < .05) was associated with RCMV infection at 7 days and at 1 month, as well as of epidermal growth factor at 1 month after transplantation, when compared with noninfected allografts, although the mRNA expression in both groups was below the levels of nontransplanted DA aortas. RCMV infection almost doubled basic fibroblast growth factor mRNA expression (P = NS) in the allograft vascular wall at 7 days and at 1 month. RCMV infection had no additional impact on insulin-like growth factor-1 mRNA expression when compared with noninfected allografts.(ABSTRACT TRUNCATED AT 400 WORDS)

Direct induction of class II molecules by cytomegalovirus in rat heart microvascular endothelial cells is inhibited by ganciclovir (DHPG).

It has been demonstrated both in vivo and in vitro that cytomegalovirus regulates not only MHC class I but also class II antigen expression on vascular endothelial cells. The CMV-linked MHC induction is believed to be involved in acute rejection mechanisms and chronic vasculopathy after transplantation. In this study, we have investigated the effect of 9-(1,3-dihydroxy-2-propoxymethyl) guanine (DHPG; ganciclovir) on CMV-induced class II expression in cultured rat heart microvascular endothelial cells. Two sets of cultured endothelial cells were infected with rat CMV. One of the sets was treated with various concentrations of DHPG and the other set was left untreated. MHC class II antigen expression on the cells was demonstrated by mAbs, by immunoperoxidase (IP) technique, and by FACS. Class II expression was maximal on CMV-infected cells 4-7 days after infection when 77.5 +/- 14.5% of the endothelial cells expressed class II in IP staining. DHPG inhibited the induction of class II, but the inhibitory effect was dependent upon the drug concentration. With increasing concentrations of DHPG (0, 1, 10, 100, and 1000 micrograms/ml), as demonstrated by IP staining (surface and intracellular expression), the frequency of class II-positive cells decreased from 77.5 +/- 14.5% to 58.0 +/- 15.0%, 36.0 +/- 23.0%, 3.0 +/- 3.0%, and 0 +/- 0%, respectively. By FACS (surface expression), the number of class II-positive cells remained somewhat lower, but decreased similarly with increasing concentrations of DHPG (from 37.8 +/- 1.1% to 6.2 +/- 3.1%) (surface expression). Also, the intensity of expression decreased concomitantly. These results suggest that DHPG inhibits CMV-induced class II expression via inhibition of CMV DNA polymerase.

Cytomegalovirus infection-enhanced allograft arteriosclerosis is prevented by DHPG prophylaxis in the rat.

BACKGROUND: Major risk factors for accelerated allograft arteriosclerosis include humoral and cellular immune response, hyperlipidemia, and viral infections. We demonstrated earlier that rat cytomegalovirus (RCMV) infection doubles smooth muscle cell proliferation and intimal thickening of rat aortic allografts. In this study, the effects of 9-(1,3-dihydroxy-2-propoxymethyl)guanine (DHPG) on RCMV-enhanced rat allograft arteriosclerosis are investigated. METHODS AND RESULTS: Aortic allografts from the DA to the WF rat strain were used. The recipients were inoculated with 10(5) plaque-forming units of RCMV 1 day after transplantation. Two groups of RCMV-infected rats were treated with DHPG with an initial dose of 20 mg/kg IP and a maintenance dose of 10 mg/kg IP twice a day for a period of 14 days. In the DHPG prophylaxis group (n = 22), the drug administration started 1 day before infection, and in the DHPG treatment group (n = 17), 7 days after infection. One group of infected rats was left untreated (n = 21). The grafts were removed 7 and 14 days and 1, 3, and 6 months after transplantation. In the DHPG prophylaxis group, no virus could be recovered by plaque assays. In the treatment group, 50% of rats were virus-positive at 1 month and 40% at 3 months. DHPG prophylaxis prevented the infiltration of inflammatory cells and their proliferation in the adventitia of RCMV-infected recipients (P < .01), with a 60% reduction in the interleukin-2 receptor expression (P < .05) and a 30% decrease in major histocompatibility complex class II expression (P = NS). DHPG prophylaxis did not significantly alter the levels of insulin-like growth factor-1, epidermal growth factor, platelet-derived growth factor-BB, transforming growth factor-beta 1, acidic fibroblast growth factor, and basic fibroblast growth factor messages in the allograft vascular wall. Early media necrosis was reduced. Arteriosclerotic alterations and proliferation of smooth muscle cells were both reduced 50% to 70% by DHPG prophylaxis (P < .05 at 3 months). The responses in the DHPG treatment group were quite similar but less impressive and statistically nonsignificant. CONCLUSIONS: We consider it likely that DHPG inhibits arteriosclerotic alterations primarily by reducing the infectious virus and thereby the inflammatory response in the allograft vascular wall; another possibility is a direct antiproliferative effect on smooth muscle cell replication. A dose-dependent inhibitory effect of DHPG on smooth muscle cell replication was recorded in an in vitro study.

Triple drug immunosuppression significantly reduces immune activation and allograft arteriosclerosis in cytomegalovirus-infected rat aortic allografts and induces early latency of viral infection.

The effect of triple drug immunosuppression (cyclosporine A 10 mg/kg/day+methylprednisolone 0.5 mg/kg/day+azathioprine 2 mg/kg/day) on rat cytomegalovirus (RCMV)-enhanced allograft arteriosclerosis was investigated applying WF (AG-B2, RT1v) recipients of DA (AG-B4, RT1a) aortic allografts. The recipients were inoculated intraperitoneally with 10(5) plaque-forming units of RCMV 1 day after transplantation or left noninfected. The grafts were removed on 7 and 14 days, and at 1, 3, and 6 months after transplantation. The presence of viral infection was demonstrated by plaque assays, cell proliferation by [3H]thymidine autoradiography, and vascular wall alterations by quantitative histology and immunohistochemistry. Triple drug immunosuppression reduced the presence of infectious virus in plaque assays and induced early latency of viral infection. It significantly reduced the peak adventitial inflammatory response (P < 0.05) and reduced and delayed intimal nuclear intensity and intimal thickening (P < 0.05) in RCMV-infected allografts. The proliferative response of smooth muscle cells was reduced by triple drug immunosuppression to 50% of that observed in nonimmunosuppressed RCMV-infected allografts, but still the proliferative peak response was seen at 1 month. Only low level immune activation, ie, the expression of interleukin-2 receptor (P < 0.05) and MHC class II, was observed under triple drug immunosuppression in the adventitia of RCMV-infected allografts, whereas there was no substantial change in the phenotypic distribution of inflammatory cells. In conclusion, although RCMV infection significantly enhances allograft arteriosclerosis also in immunosuppressed allografts, triple drug immunosuppression has no additional detrimental effect but rather a protective one on vascular wall histology. These results further suggest that RCMV-enhanced allograft arteriosclerosis may be an immunopathological condition linked to the host immune response toward the graft and/or the virus rather than a direct virus-induced phenomenon.

Cytomegalovirus infection-associated generalized immune activation in heart allograft recipients: a study of cellular events in peripheral blood and endomyocardial biopsy specimens.

An association between cytomegalovirus (CMV) infection, heart allograft rejection, and arteriosclerosis has been reported. To investigate the mechanisms of this association, the cellular immune response in peripheral blood and the inflammation in heart allografts during antigenemia were studied. CMV antigenemia occurred in 13 recipients. In recipients with severe CMV infection, a significantly weaker immune response was recorded in peripheral blood: fewer lymphoid blast cells (max. 2.4% +/- 0.4%) and large granular lymphocytes (LGL; max. 9.3% +/- 1.4%) were seen than in patients with mild or asymptomatic CMV infection (lymphoid blast cells max. 6.5% +/- 0.8% P < 0.01 and LGLs max. 20% +/- 2.3%, P < 0.05). Thus, a strong immune response with lymphoid activation was associated with clinically good outcome of CMV infection. In heart allograft histology, subendothelial inflammation of small intramyocardial vessels was a characteristic finding during CMV antigenemia compared to CMV-free recipients (at the peak P < 0.01). However, no difference in this mild and short-lived inflammatory response was observed between clinically mild or severe CMV infection. The CMV-linked generalized immune activation and inflammation of the vascular structures might contribute to the initiation of allograft vasculopathy and to the pathogenesis of chronic heart allograft rejection.

Vascular cell adhesion molecule-1 (VCAM-1) is induced during cytomegalovirus infection in vascular structures of heart allografts.

This study was designed to investigate the expression of vascular cell adhesion molecule-1 (VCAM-1) and the counter-ligand VLA-4 (CD 49d) in frozen sections of endomyocardial biopsies (EMBs) of heart allografts in relation to the onset of cytomegalovirus (CMV) infection diagnosed by CMV antigenemia. Altogether, 105 EMBs were obtained from 21 heart transplant recipients. Serial EMBs from nine patients with CMV infection, from five patients with rejection, and from seven patients with a noncomplicated postoperative course were analyzed. Associated with CMV infection, capillary expression of VCAM-1 was significantly induced when compared to control biopsies (P < 0.0001). A striking difference in the expression of VCAM-1 during rejection and CMV infection was observed: in most rejecting biopsies only a few capillaries stained faintly for VCAM-1, whereas during CMV infection, multifocal intense staining was found (P < 0.0001).

Effect of ganciclovir prophylaxis on cytomegalovirus-enhanced allograft arteriosclerosis.

Clinical and experimental studies have established the accelerating role of cytomegalovirus (CMV) infection on cardiac allograft arteriosclerosis, i.e. chronic rejection. In this study, we investigated the effect of ganciclovir prophylaxis on the development of CMV-enhanced allograft arteriosclerosis. Rat aortic allografts were done from DA donors to WF recipients and either infected with 10(5) plaque-forming units of rat CMV (RCMV) 1 day after transplantation or left uninfected. RCMV-infected allografts received ganciclovir at an initial dose of 20 mg/kg and a maintenance dose of 10 mg/kg twice a day for 14 days. Grafts were removed at 7, 14 days, and 1 and 3 months after transplantation and processed for morphometry and autoradiography. The results of this study demonstrated that ganciclovir prophylaxis significantly delays and reduces RCMV-enhanced allograft arteriosclerosis in the rat.

Cytomegalovirus infection and accelerated cardiac allograft vasculopathy in human cardiac allografts.

Cardiac allograft vasculopathy is a major limiting factor of the long-term survival of heart transplant patients. An association of cytomegalovirus infection and cardiac allograft vasculopathy has been described. We analyzed 104 endomyocardial biopsy specimens obtained from 53 heart transplant recipients and correlated the histologic findings with 115 angiograms obtained from the same patients during 4 postoperative years. The frequency of vascular changes in endomyocardial biopsy specimens was significantly higher than in angiograms during the first 3 posttransplantation years (P < 0.001, P < 0.005, P < 0.03, respectively). Also, in patients with angiographically documented cardiac allograft vasculopathy, significantly higher scores of capillary and arteriolar endothelial cell accumulation and arteriolar intimal thickness were recorded when compared with the recipients with normal angiograms (P < 0.02, P < 0.05, P < 0.005, respectively). Altogether, 29 of 53 recipients underwent cytomegalovirus infection during the first posttransplant year. Cytomegalovirus infection was associated with arteriolar endothelial cell accumulation and with increased intimal thickness of intramyocardial vessels of 1-year endomyocardial biopsy specimens when compared with cytomegalovirus-free recipients (P < 0.02 and P < 0.005, respectively). After the second year, the cytomegalovirus-associated endothelial cell response subsided, but the thickness of intima had increased when compared with cytomegalovirus-free patients (P < 0.05). Thereafter, the cytomegalovirus-associated histologic changes reached a plateau. In coronary angiography, the cardiac allograft vasculopathy changes were detected in a slower pace. Thus only after 2 posttransplantation years, cytomegalovirus-associated acceleration of cardiac allograft vasculopathy was observed, compared with cytomegalovirus-free patients (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Cytomegalovirus infection enhances smooth muscle cell proliferation and intimal thickening of rat aortic allografts.

Inbred DA (AG-B4, RT1a) and WF (AG-B2, RT1v) rats were used as donors and recipients of aortic allografts. The recipient rats were inoculated i.p. either on day 1 (early infection) or on day 60 (late infection) with 10(5) plaque-forming units of rat cytomegalovirus (RCMV). The control rats were left noninfected. The presence of viral infection was demonstrated by plaque assays from biopsies of the salivary glands, liver, and spleen at sacrifice. The rats received 300 microCi[3H]thymidine by i.v. injection 3 h before sacrifice, and the grafts were removed at various time points for histology, immunohistochemistry, and autoradiography. RCMV infection significantly enhanced the generation of allograft arteriosclerosis. Infection at the time of transplantation had two important effects. First, the infection was associated with an early, prominent inflammatory episode and proliferation of inflammatory cells in the allograft adventitia. Second, the viral infection doubled the proliferation rate of smooth muscle cells and the arteriosclerotic alterations in the intima. In late infection the impact of RCMV infection on the allograft histology was nearly nonexistent. RCMV infection showed no effect in syngeneic grafts. These results suggest that early infection is more important to the generation of accelerated allograft arteriosclerosis than late infection, and that an acute alloimmune response must be associated with virus infection, to induce accelerated allograft arteriosclerosis. RCMV-infected aortic allografts, as described here, provide the first experimental model to investigate the interaction between the virus and the vascular wall of the transplant.

Cytomegalovirus induces class II expression in rat heart endothelial cells.

An association between cytomegalovirus infection, cardiac allograft rejection, and atherosclerosis has been described. It has been suggested that cytomegalovirus induces major histocompatibility complex antigen expression in the graft and may trigger rejection. The induction of major histocompatibility complex antigens is thought to be mediated by interferon-gamma produced by activated T cells during the infection. To study whether cytomegalovirus infection induces major histocompatibility complex class II antigen expression in heart endothelium, cultured rat heart endothelial cells were infected with rat cytomegalovirus. The infection was shown by cytopathic effect and immunofluorescence using monoclonal cytomegalovirus-specific antibodies. Major histocompatibility complex class II antigen expression was analyzed before and during cytomegalovirus infection by two different methods, by a fluorescence-activated cell sorter and immunoperoxidase techniques using monoclonal antibodies. Uninfected endothelial cell cultures were treated with interferon-gamma and used as positive controls of class II induction. Induction of class II antigens was recorded in cytomegalovirus-infected endothelial cell cultures, and during the course of infection the class II expression increased toward the appearance of cytopathic effect. In uninfected cells, class II was induced by interferon-gamma, but this induction could be inhibited by adding antiinterferon-gamma antibody to the cultures. However, anti-interferon-gamma did not inhibit the induction of class II caused by cytomegalovirus. In conclusion, cytomegalovirus induced major histocompatibility complex class II antigen expression in rat heart endothelial cells in vitro. This induction of class II was independent of interferon-gamma and was caused by the virus itself. Direct induction of class II antigens by cytomegalovirus in heart endothelium may also be involved in rejection mechanisms in vivo.

Quantitation of cytomegalovirus infection-associated histologic findings in endomyocardial biopsies of heart allografts.

To investigate whether histologic changes in heart allografts may be associated with cytomegalovirus infection, 46 heart transplant recipients were monitored for cytomegalovirus. Altogether, 762 endomyocardial biopsy specimens were analyzed. The histologic changes were semiquantitatively scored from mild to severe, and special attention was paid to inflammatory infiltrates and vascular changes. Cytomegalovirus infection occurred in 27 of 46 patients, shown by cytomegalovirus-antigenemia test. The endomyocardial biopsy findings were investigated in relation to cytomegalovirus-antigenemia. In the acute phase of cytomegalovirus infection during antigenemia, an inflammatory infiltrate, subendothelial lymphocytosis, was a characteristic finding in the endomyocardial biopsy specimens. An intense arteriolar endothelial cell proliferation and thickening of intima occurred. Long-term histologic findings with two years follow-up revealed a cytomegalovirus-associated enhanced vascular intimal thickening that narrowed the lumen of small intramyocardial arterioles. Acute rejection episodes were diagnosed in 15 of 27 patients with cytomegalovirus and in 9 of 19 patients free of cytomegalovirus. The inflammatory infiltrate of acute rejection was more peripheral to the vessels and did not obscure the findings characteristic to cytomegalovirus infection. The arteriolar endothelial proliferation and intimal thickening were significantly more prominent in cytomegalovirus infection than in biopsy specimens from patients with rejection only. In long-term follow-up, arteriolar endothelial proliferation declined, but the intimal thickness persisted and increased. The increase was significantly higher in patients with cytomegalovirus than in patients with rejection. In conclusion, an inflammatory response in vessel walls with alterations of small intramyocardial arterioles leading to narrowing of the vascular lumen of the graft was associated with cytomegalovirus infection in heart transplant patients.