Prevention of cytomegalovirus infection-enhanced experimental obliterative bronchiolitis by antiviral prophylaxis or immunosuppression in rat tracheal allografts

The role of innate immunity in the long-term outcome of lung transplantation

Long-term survival after lung transplantation remains suboptimal due to chronic lung allograft dysfunction (CLAD), a progressive scarring process affecting the graft. Although anti-donor alloimmunity is central to the pathogenesis of CLAD, its underlying mechanisms are not fully elucidated and it is neither preventable nor treatable using currently available immunosuppression. Recent evidence has shown that innate immune stimuli are fundamental to the development of CLAD. Here, we examine long-standing assumptions and new concepts linking innate immune activation to late lung allograft fibrosis.

The Role of Infections in BOS

Background: Infectious agents, particularly cytomegalovirus (CMV), have long been considered to be potential triggers for BOS, although the exact magnitude of the role of infections and the mechanisms thereof remain an area of active research. Methods: This chapter will review previous literature and newer results concerning the possible roles of CMV, other herpesviruses, community-acquired respiratory viruses, bacteria (including Pseudomonas, other gram-negative, gram-positive, and atypical organisms), and fungi, including colonization as well as invasive infection. Results: The text reviews and evaluates the body of literature supporting a role for these infectious agents as risk factors for BOS and time to BOS. Changing patterns of infection over time are taken into account, and studies that have shown an association between BOS (or lack thereof) and CMV are reviewed. Strategies for prevention or early treatment of infections are discussed as potential means of preserving allograft function long term. Immunizations, stringent infection-control practices, and antimicrobial treatment including newer therapies will be discussed. Conclusion: In addition to the classic literature that has focused on CMV, an expanding spectrum of infectious organisms has been implicated as possible risk factors for BOS. Increasing knowledge of the impact of long-term antiviral suppression, prophylaxis, and outcomes of early therapy will help guide future recipient management.

Relevance of maintenance triple-drug immunosuppression to bridle the amplification of rat cytomegalovirus infection after experimental lung transplantation

Immunosuppressive therapy required to treat rejection after lung transplantation (LTx) contributes significantly to the pathogenesis of cytomegalovirus (CMV) infection and disease. In a weak allogeneic left LTx model in the rat (Fisher 344 [F344] to Wistar Kyoto [WKY] rats) we analyzed the influence of acute CMV infection on postoperative day (POD) 3, with application of standard triple-drug immunosuppression (TD-IS) (cyclosporin A, azathioprine, prednisolone) on late outcome after LTx. Native right lungs and syngeneic grafts (WKY to WKY) served as controls. Rats were sacrificed on POD 15, 30, 60, and 100. TD-IS completely prevented acute and chronic rejection in non-infected rats. Allografts of CMV-infected rats treated with TD-IS showed only mild perivascular infiltrations in 6/10 rats (POD 15 and 30), which persisted up to POD 100 in 4/10 rats. In the long-term course, mild isolated interstitial and alveolar changes were found in 40% of these animals. In conclusion, rat CMV infection partially neutralized the immunosuppressive effect of TD-IS. However, an amplification of CMV infection under TD-IS can be controlled and does not result in fatal outcome.

Subclinical viremia increases risk for chronic allograft injury in pediatric renal transplantation

The impact of subclinical viral infection on chronic allograft injury in the pediatric renal transplant population is not well defined. We prospectively assessed cytomegalovirus (CMV) and Epstein-Barr virus (EBV) DNAemia by monthly PCR in 55 pediatric renal transplant recipients for the first 2 years after transplantation. Subclinical CMV and EBV infection occurred in 22 and 36%, respectively. Multivariable linear regression analysis suggested that both subclinical CMV and EBV infection independently associate with significant declines in GFR during the first 2 years after transplantation. CMV seronegativity associated with a significantly greater decline in GFR than seropositivity (P < 0.01). Subclinical CMV infection and subclinical EBV infection each associated with approximately fourfold greater odds of histologic evidence of chronic allograft injury (odds ratio 4.61 [95% confidence interval 1.18 to 18.07] and odds ratio 4.33 [95% confidence interval 1.34 to 14.00], respectively). An increase in viral load of CMV or EBV also associated with increased risk for moderate to severe chronic allograft injury. Taken together, these results demonstrate an association between subclinical CMV and EBV infections, which occur despite standard antiviral prophylaxis, and chronic allograft injury in pediatric renal transplant recipients.

Mechanisms of cytomegalovirus-accelerated vascular disease: induction of paracrine factors that promote angiogenesis and wound healing

Human cytomegalovirus (HCMV) is associated with the acceleration of a number of vascular diseases such as atherosclerosis, restenosis, and transplant vascular sclerosis (TVS). All of these diseases are the result of either mechanical or immune-mediated injury followed by inflammation and subsequent smooth muscle cell (SMC) migration from the vessel media to the intima and proliferation that culminates in vessel narrowing. A number of epidemiological and animal studies have demonstrated that CMV significantly accelerates TVS and chronic rejection (CR) in solid organ allografts. In addition, treatment of human recipients and animals alike with the antiviral drug ganciclovir results in prolonged survival of the allograft, indicating that CMV replication is a requirement for acceleration of disease. However, although virus persists in the allograft throughout the course of disease, the number of directly infected cells does not account for the global effects that the virus has on the acceleration of TVS and CR. Recent investigations of up- and downregulated cellular genes in infected allografts in comparison to native heart has demonstrated that rat CMV (RCMV) upregulates genes involved in wound healing (WH) and angiogenesis (AG). Consistent with this result, we have found that supernatants from HCMV-infected cells (HCMV secretome) induce WH and AG using in vitro models. Taken together, these findings suggest that one mechanism for HCMV acceleration of TVS is mediated through induction of secreted cytokines and growth factors from virus-infected cells that promote WH and AG in the allograft, resulting in the acceleration of TVS. We review here the ability of CMV infection to alter the local environment by producing cellular factors that act in a paracrine fashion to enhance WH and AG processes associated with the development of vascular disease, which accelerates chronic allograft rejection.

Human cytomegalovirus secretome contains factors that induce angiogenesis and wound healing

Human cytomegalovirus (HCMV) is implicated in the acceleration of a number of vascular diseases including transplant vascular sclerosis (TVS), the lesion associated with chronic rejection (CR) of solid organ transplants. Although the virus persists in the allograft throughout the course of disease, few cells are directly infected by CMV. This observation is in contrast to the global effects that CMV has on the acceleration of TVS/CR, suggesting that CMV infection indirectly promotes the vascular disease process. Recent transcriptome analysis of CMV-infected heart allografts indicates that the virus induces cytokines and growth factors associated with angiogenesis (AG) and wound healing (WH), suggesting that CMV may accelerate TVS/CR through the induction and secretion of AG/WH factors from infected cells. We analyzed virus-free supernatants from HCMV-infected cells (HCMV secretomes) for growth factors, by mass spectrometry and immunoassays, and found that the HCMV secretome contains over 1,000 cellular proteins, many of which are involved in AG/WH. Importantly, functional assays demonstrated that CMV but not herpes simplex virus secretomes not only induce AG/WH but also promote neovessel stabilization and endothelial cell survival for 2 weeks. These findings suggest that CMV acceleration of TVS occurs through virus-induced growth factors and cytokines in the CMV secretome.

Ganciclovir for cytomegalovirus: a call for indefinite prophylaxis in lung transplantation

BACKGROUND

Universal ganciclovir (GCV) prophylaxis is a strategy aimed at reducing cytomegalovirus (CMV) infection and delaying the development of bronchiolitis obliterans syndrome (BOS). However, the optimal duration of GCV prophylaxis remains unclear. We report our experience with GCV prophylaxis administered indefinitely and its effect on CMV pneumonitis, BOS and survival after lung transplantation (LT).

METHODS

One hundred fifty-one patients surviving >100 days after LT were analyzed. GCV was given to 130 CMV donor- or recipient-seropositive patients. Data from 90 patients who received indefinite GCV prophylaxis (IND) and 40 patients who discontinued their GCV prophylaxis (STOP) were compared.

RESULTS

CMV pneumonitis occurred in 16%, 8%, 17% and 19% of patients in the D+R+, D-R+, D+R- and D-R- groups, respectively. In the STOP cohort, 15 of 40 patients developed CMV pneumonitis (median time 79 days) after GCV was stopped. Ten of these 15 patients developed BOS (median time 116 days) after discontinuing GCV. The risk of CMV pneumonitis in the STOP cohort was significantly higher when GCV prophylaxis was discontinued within the first year. Cumulative incidence of CMV pneumonitis in the IND and STOP groups at 5 years was 2% and 57%, respectively (p < 0.001). BOS-free survival and survival were similar across both groups.

CONCLUSIONS

Indefinite GCV prophylaxis prevents CMV pneumonitis in 98% of LT recipients. Thirty-eight percent of patients discontinuing prophylaxis developed CMV pneumonitis, 50% of whom progressed to BOS within 1 year. Continuing ganciclovir prophylaxis indefinitely after lung transplantation should be considered.

[Infection in lung transplantation]

Actualmente, el trasplante de pulmón se considera un tratamiento válido para un buen número de pacientes con insuficiencia respiratoria grave. De todas formas, las complicaciones son muy frecuentes y pueden llevar a fracaso del injerto a medio y largo plazo y menor supervivencia. De acuerdo con el registro de la International Society for Heart and Lung Transplantation, las tasas de supervivencia al primer, segundo y quinto año fueron, en 2006, del 74, 65 y 47%, respectivamente. El principal obstáculo para el éxito a largo plazo del trasplante de pulmón es el rechazo crónico, caracterizado histológicamente como bronquiolitis obliterante, que acontece en cerca de dos terceras partes de los pacientes. Uno de los factores más importantes para el desarrollo de bronquiolitis obliterante, además del número de rechazos agudos, es la infección y la enfermedad por citomegalovirus (CMV). Recientemente, se ha destacado el papel de la infección por diferentes virus respiratorios como factores de riesgo para el desarrollo de rechazo crónico en receptores de un trasplante de pulmón. Las complicaciones infecciosas son una causa frecuente de morbimortalidad en este tipo de pacientes, y la causa de muerte de cerca de la mitad de ellos. La infección bacteriana es la complicación más frecuente de un receptor de un trasplante de pulmón. Del total, el 35-66% son bacterianas y el 50-85% de los pacientes presentan como mínimo un episodio de infección bacteriana. La segunda causa más frecuente de infección, después de la bacteriana, es la infección por CMV. A pesar de utilizar diferentes estrategias de prevención, la incidencia sigue siendo elevada, y se sitúa alrededor del 7% el primer año postrasplante. Es el único tipo de trasplante de órgano sólido en el cual la etiología más frecuente de la infección fúngica es Aspergillus spp., a diferencia del resto, en que típicamente se deben a Candida spp. La incidencia de aspergilosis invasora se cifra en alrededor del 4%.

CMV increases tubular apoptosis through the TNF-alpha-TNF-R1 pathway in a rat model of chronic renal allograft rejection

INTRODUCTION

Destruction of transplanted kidneys through chronic allograft nephropathy [CAN], also known as chronic rejection, is the greatest obstacle in successful kidney transplantation. Causes behind CAN are many, from pre-transplant causes to infections. Viral infections, especially CMV, are a risk factor for chronic rejection. We have previously developed a rat kidney transplant model, in which CMV enhances the development of chronic rejection under triple drug treatment. In this model we have now further studied the routes of apoptosis in virus induced early CAN vs. the routes of apoptosis in a later developing non-infectious CAN.

MATERIALS AND METHODS

Renal transplantations were performed in a strain combination of DA/BN under immunosuppression. One group of animals was infected with RCMV and the other was left uninfected. The grafts were harvested on days 3-40 after transplantation. Apoptotic cells were visualised by in situ terminal transferase mediated dUTP nick end labelling [TUNEL] from paraffin embedded, formalin fixed kidney grafts. Cytokines were labelled imunohistochemically from frozen sections, among them tumour necrosis factor alpha [TNF-alpha] and its receptor-protein 1 [TNF-R1] as well as CD 95 [FAS], caspase 3 and CD14. The results were semi-quantitatively scored from 0 to 3+ over various tissues structures separately.

RESULTS

In the CMV infected grafts, we could demonstrate a more intense TUNEL reaction in tubular epithelium [2.0+/-1.0 vs. 0.8+/-0.5 at day 14, P<0.05] as well as an earlier increase in the expression TNF-alpha in the vascular endothelium [2.0+1.0 vs. 0.0+0.0 at days 3-5, P<0.05] than in the non-infected group. There was also an earlier increase in the tubular TNF-R1 expression [2.2+0.8 vs. 1.0+0.0 at days 5-7, P<0.05]. There was no difference in the expression of CD14, caspase 3 or FAS between the groups.

CONCLUSIONS

CMV enhanced development of CAN was associated with tubular apoptosis and concomitant increase of TNF-alpha-TNF-R1, rather than the FAS-FAS-ligand activation.

Vascular Endothelial Growth Factor Plays a Major Role in Development of Experimental Obliterative Bronchiolitis

Obliterative bronchiolitis (OB) is the major limitation for long-term survival of lung allograft recipients. The exact molecular and cellular mechanisms contributing to obliterative lesion formation are unknown. Pathological characteristics of OB are epithelial damage, peribronchial inflammation, and increasing obliteration of bronchioli. Vascular endothelial growth factor (VEGF) is an angiogenic growth factor that exerts proinflammatory effects by increasing endothelial permeability and inducing expression of endothelial adhesion molecules. We investigated the role of VEGF in the development of OB in rat tracheal allografts and the role of VEGF receptors (VEGFR)-1 and -2 in the development of OB in mouse tracheal allografts. In nontreated allografts, with increasing loss of epithelium and airway occlusion, VEGF messenger RNA (mRNA) and protein expression vanished in the epithelium and increased in smooth muscle cells and mononuclear inflammatory cells compared with syngeneic grafts. Intragraft VEGF overexpression by adenoviral transfer of a mouse VEGF164 gene led to a decrease in epithelial necrosis but increased luminal occlusion by >50% compared with AdLacZ-treated rat tracheal allografts. When compared with the control immunoglobulin (Ig)G group, simultaneous treatment with antibodies against VEGFR-1 and -2 significantly lowered the degree of luminal occlusion of mouse tracheal allografts.

Acute rejection and cardiac allograft vascular disease is reduced by suppression of subclinical cytomegalovirus infection

BACKGROUND

Anticytomegalovirus (CMV) prophylaxis prevents the acute disease but its impact on subclinical infection and allograft outcome is unknown. We sought to determine whether CMV prophylaxis administered for three months after heart transplant would improve patient outcomes.

METHODS

This prospective cohort study of 66 heart transplant recipients compared aggressive CMV prophylaxis (n = 21, CMV hyperimmune globulin [CMVIG] plus four weeks of intravenous ganciclovir followed by two months of valganciclovir); with standard prophylaxis (n = 45, intravenous ganciclovir for four weeks). Prophylaxis was based on pretransplant donor (D) and recipient (R) CMV serology: R-/D+ received aggressive prophylaxis; R+ received standard prophylaxis. Outcome measures were: CMV infection assessed by DNA-polymerase chain reaction on peripheral blood polymorphonuclear leukocytes, acute rejection, and cardiac allograft vascular disease (CAV) assessed by intravascular ultrasound. All patients completed one year of follow-up. RESULTS.: CMV infection was subclinical in all but four patients (two in each group). Aggressively treated patients had a lower incidence of CMV infection (73 +/- 10% vs. 94 +/- 4%; P = 0.038), and an independent reduced relative risk for acute rejection graded > or =3A (relative risk [95% CI] = 0.55 [0.26-0.96]; P = 0.03), as compared with the standard prophylaxis group. Aggressively prophylaxed patients also showed a slower progression of CAV, in terms of coronary artery lumen loss (lumen volume change=-21 +/- 13% vs. -10+/-14%; P = 0.05); and vessel shrinkage (vessel volume change = -15 +/- 11% vs. -3 +/- 18%; P = 0.03).

CONCLUSIONS

Prolonged (val)ganciclovir plus CMVIG reduces viral levels, acute rejection, and allograft vascular disease, suggesting a role for chronic subclinical infection in the pathophysiology of the most common diseases affecting heart transplant recipients.

Role of platelet-derived growth factor and vascular endothelial growth factor in obliterative airway disease

RATIONALE

Platelet-derived growth factor (PDGF) is an important smooth muscle cell mitogen, and vascular endothelial growth factor (VEGF) is a known angiogenic and proinflammatory growth factor. We hypothesized that specific therapy aimed at these growth factors might inhibit the development of experimental obliterative airway disease (OAD).

METHODS

In fully mismatched rat tracheal allografts, we used imatinib and PTK/ZK, either alone or in combination, to block PDGF and VEGF receptor protein tyrosine kinase (RTK) action, respectively. Prophylaxis was initiated at the time of transplantation. Early treatment was commenced on Day 7 during the inflammatory phase and late treatment on Day 14 during the fibroproliferative phase of OAD. No immunosuppression was administered.

MEASUREMENTS AND MAIN RESULTS

Prophylaxis with either PTK/ZK or imatinib alone significantly reduced OAD, and combined prophylaxis completely prevented its development. Early treatment with PTK/ZK and imatinib also effectively reduced the development of OAD. Late treatment failed to show significant efficacy. Blocking VEGF RTK action with PTK/ZK reduced the activation of allograft blood vessels and the number of lymph vessels in the allograft airway wall, and significantly diminished allograft inflammation, whereas PDGF blockade with imatinib inhibited the growth of smooth muscle cells in the proliferating lesion.

CONCLUSIONS

Combined prophylactic PDGF and VEGF RTK blockade completely prevents the development of OAD. Also, when early treatment with PTK/ZK and imatinib is commenced during the inflammatory phase of OAD development, it significantly attenuates the development of tracheal occlusion, suggesting that these drugs could potentially be used to treat bronchiolitis obliterans syndrome in its early phase.

Combined CMV Prophylaxis Improves Outcome and Reduces the Risk for Bronchiolitis Obliterans Syndrome (BOS) after Lung Transplantation

BACKGROUND

The benefit of cytomegalovirus (CMV) hyperimmune globuline in preventing CMV infection after lung transplantation still remains unclear. The aim of this study was to investigate the effect of combined prophylaxis using ganciclovir (GAN) and CMV hyperimmune globulin (CMV-IG) on CMV infection, CMV disease, survival and its role in preventing Bronchiolitis obliterans syndrome (BOS).

METHODS

A consecutive series of 68 CMV high-risk lung transplant recipients (D+/R-, D+/R+), who had a minimum follow-up of 1 year posttransplant were analyzed. Thirty patients (44.1%) received single GAN prophylaxis for 3 months (control group) and 38 recipients (55.9%) received GAN together with CMV-IG 7 times during the first postoperative month (study group). Median follow-up was 16.5 months in the control and 23.8 months in the study group (P = 0.54).

RESULTS

Five CMV-related deaths (16.7%) occurred in the control group (P = 0.014). Fifteen recipients suffered from CMV pneumonitis and three patients had CMV syndrome. In the control group, 13 recipients (43.3%) suffered from clinically manifested CMV disease compared to 5 (13.2%) in the study group (P = 0.007). Additionally, recipient survival was significantly better in the study group (P = 0.01). One year freedom from CMV affection was 52.1% in the control and 71.5% in the study group (P = 0.027). Three-year freedom from BOS was significantly higher in the study group (54.3% vs. 82%, P = 0.024).

CONCLUSIONS

In CMV high risk patients, additional CMV-IG administration seems to be effective to reduce CMV-related morbidity and to avoid CMV-related mortality. Reduced incidence of BOS may result from improved CMV prevention, although randomized trials are warranted.

CMV-specific CD8 T-cell dynamics in the blood and the lung allograft reflect viral reactivation following lung transplantation

Despite the potentially high burden of cytomegalovirus (CMV)-related disease following lung transplantation, the role of the cytotoxic T-lymphocyte (CTL) response to CMV in this patient group is ill-defined. We assessed the CMV-specific T-cell response in the blood and lung allograft of immunosuppressed lung transplant recipients receiving antiviral prophylaxis and following their withdrawal. While the proportion of CMV-specific CTL varied between patients, in the absence of CMV reactivation the level of CMV-specific CD8+ T cells in the blood remained stable over time. In the majority of patients CMV-specific cells could be detected in the lung allograft, often in the absence of viral DNA. Additionally, following primary CMV lung infection, CMV-specific CD8+ T cells were detected no earlier than 100 days post-transplantation but still prior to the detection of viral DNA in the lung allograft. Together these findings suggest that very low levels of CMV replication are sufficient to both prime and recruit CMV-specific CD8+ T cells to the MHC-mismatched lung allograft. The direct detection of CMV-specific T cells with an effector phenotype in the lung allograft suggests a protective antiviral function. This study provides a framework upon which the association between CMV and chronic allograft rejection can be further studied.

Lung transplantation for cystic fibrosis: 6-year follow-up

Lung transplantation is currently the most effective means of improving survival and quality of life in patients with end-stage cystic fibrosis. In reviewing our 6-year experience we sought to evaluate complications and survival after sequential bilateral lung transplantation. Between October 1996 and October 2002, 114 patients with cystic fibrosis were referred to us from 15 Italian regional centers and 2 support centers for cystic fibrosis as possible candidates for lung transplantation. Of these 114 patients, 99 were included in the waiting list and 15 were refused. The mean time spent on the waiting list was 6.8+/-5.2 months (range 1 day-21 months) for those patients receiving lung transplantation, and 5.4+/-4.5 months (range 10 days-18 months) for those 35 patients who died while on the waiting list. A total 55 patients (6 children and 49 adults), mean age 25.6+/-6.6 years (range 9-52 years), 29 males, underwent bilateral sequential lung transplantation. One patient had a second transplantation 14 months after the first. The most frequent medical non-infective complications after transplantation were chronic renal failure (n=27 patients), diabetes (n=31), osteoporosis (n=17), arterial hypertension (n=14), seizures (n=4), transient cerebral ischaemia (n=1), and transient bilateral blindness (n=1). Bacterial lower airways respiratory infections with the organisms that colonized patients' airways before lung transplantation developed in 42 patients; cytomegalovirus (CMV) infection in 41; and opportunistic infections of the lung with Pneumocystis carinii in 3 patients. Cultures of sputum or bronchoalveolar lavage fluid grew Aspergillus fumigatus in nine patients; aspergillosis of right bronchial anastomosis developed in one patient and a lung infection in another. Another patient had a pulmonary infection secondary to Aspergillus niger. An average of 1.3 episodes of acute rejection developed per patient in the first 6 months after lung transplantation. Freedom from bronchiolitis obliterans syndrome was 95% at 1 year, 82.5% at 2 years, 70% at 3 years, and 65% at 4, 5 and 6 years. Actuarial survival rates were 80% at 1 month, 79% at 1 year, 74% at 2 years, 70% at 3 years and 58% at 4, 5 and 6 years. Ten patients (17.8%) died in the early postoperative period (1-30 days) for the following reasons: primary graft failure (n=4), multiorgan failure (n=3), Burkholderia cepacia sepsis (n=1), myocardial infarction (n=1), and pulmonary embolism (n=1). Mortality was accounted for by 9 patients (16%) who died from 9 to 43 months after lung transplantation, for the following reasons: P. carinii infection (n=2), bronchiolitis obliterans syndrome (n=4), A. fumigatus pulmonary infection (n=1), unknown cause (n=1) and suicide (n=1). In conclusion, the leading causes of morbidity after lung transplantation for cystic fibrosis are pulmonary bacterial infection and opportunistic infections. Bronchiolitis obliterans develops in more than half of lung transplant recipients who survive for more than 3 years and is an important cause of death in the late post transplantation period.

Rat cytomegalovirus and Listeria monocytogenes infection enhance chronic rejection after allogenic rat lung transplantation

The role of infection in the pathomechanism of obliterative bronchiolitis (OB) after human lung transplantation is controversial. In a rat lung transplantation model, we analyzed the effect of viral [rat cytomegalovirus (RCMV)] and bacterial infection [Listeria monocytogenes (LM)] on the development of chronic allograft rejection. Fisher rats underwent single left lung transplantation with allografts from Lewis rats. Postoperatively, animals were infected with either RCMV or LM, or served as noninfected controls. Animals were killed on day 120 and both lungs were evaluated histopathologically for chronic airway and chronic vascular rejection. Infection with RCMV produced a significant increase in the incidence of chronic airway rejection (66.7% vs. 20%), compared with noninfected long-term surviving animals. In rats with bacterial infection (LM) a similar increase of chronic airway changes as in viral infection (50% vs. 20%) was observed. Chronic rejection of allografts infected with either RCMV or LM was associated with significantly enhanced expression of intercellular adhesion molecule-1 (ICAM-1) on the endothelium. More infiltrating leukocytes (CD18, CD11a, CD44) and ED1-positive macrophages were found in allografts of infected animals. In this experimental model of chronic airway rejection in long-term surviving rats, not only viral but also bacterial infection resulted in enhanced development of chronic airway and vascular rejection. These results support our hypothesis that infectious complications have a substantial influence on the development of OB in human lung allografts.

Dual Role of Vascular Endothelial Growth Factor in Experimental Obliterative Bronchiolitis

Obliterative bronchiolitis (OB) is the major limitation for long-term survival of lung allograft recipients. We investigated the role of vascular endothelial growth factor (VEGF) in the development of OB in rat tracheal allografts. In nonimmunosuppressed allografts, VEGF mRNA and protein expression vanished in the epithelium and increased in smooth muscle cells and mononuclear inflammatory cells with progressive loss of epithelium and airway occlusion compared with syngeneic grafts. Intragraft VEGF overexpression by adenoviral transfer of a mouse VEGF(164) gene increased early epithelial cell proliferation and regeneration but increased microvascular remodeling and lymphangiogenesis and luminal occlusion by more than 50% compared with AdlacZ-treated allografts. Although VEGF receptor inhibition decreased early epithelial regeneration in noninfected allografts, it reduced microvascular remodeling, lymphangiogenesis, intragraft traffic of CD4(+) and CD8(+) T cells, and the degree of luminal occlusion. Simultaneous VEGF gene transfer and platelet-derived growth factor receptor inhibition with imatinib preserved respiratory epithelium and totally prevented luminal occlusion. In conclusion, our findings indicate that VEGF has a dual role in transplant OB. Our results suggest that VEGF may protect epithelial integrity. On the other hand, VEGF may enhance luminal occlusion by increasing the recruitment of mononuclear inflammatory cells with platelet-derived growth factor acting as a final effector molecule in this process.

Treated Cytomegalovirus Pneumonia Is Not Associated with Bronchiolitis Obliterans Syndrome

The association of cytomegalovirus (CMV) infection with the development of bronchiolitis obliterans syndrome (BOS) is unclear. We studied 341 lung transplant recipients to assess whether histopathologically diagnosed CMV pneumonia treated with ganciclovir was a risk factor for development of BOS and patient survival. We also analyzed the relationship between CMV donor/recipient serologic status and BOS plus the temporal association between acute rejection and CMV pneumonia. Freedom from BOS for patients with (n = 151) and without (n = 190) CMV pneumonia was 83 and 90% (1 year), 52 and 56% (3 years), and 29 and 38% (5 years), respectively (p = 0.2660). Cumulative survival of patients with and without CMV pneumonia was 90 and 93% (1 year), 70 and 74% (3 years), and 58 and 63% (5 years), respectively (p = 0.1811). There were no significant differences in either development of BOS or patient survival with any combination of donor/recipient serostatus for CMV. Acute rejection occurred in the month preceding CMV pneumonia in 62 of 193 (32%) cases. Histopathologically confirmed CMV pneumonia treated with ganciclovir is not a risk factor for BOS or patient survival, nor is any particular CMV serologic donor/recipient group. CMV pneumonia often follows acute rejection, perhaps as a result of augmented immunosuppression.

Deferred versus prophylactic therapy with gancyclovir for cytomegalovirus in allograft liver transplantation

OBJECTIVE

The aim of this study was to assess the efficacy of deferred versus prophylactic therapy with gancyclovir to prevent cytomegalovirus (CMV) infection or disease in liver transplantation recipients, and to alter the timing of infection or the incidences of acute rejection, chronic rejection, or death.

METHODS

We retrospectively studied 89 consecutive liver transplant recipients with a minimum of 1 year follow-up. CMV early antigen detection (pp65) was performed weekly for the first 2 months and thereafter monthly for an additional 10 months. Forty-one recipients were administered prophylactic treatment and (48 recipients) deferred therapy for positive antigenemia.

RESULTS

During the first year after transplantation, CMV infection or disease developed in 61% or 12.2% of those treated with prophylactic therapy and 54.1% or 31.3% of those treated with deferred therapy (P = 0.51 or P = 0.032, respectively). The mean time to CMV disease in the prophylactic group was 161 +/- 33 days compared with 82 +/- 27 days for the deferred therapy arm (P < 0.001). Subgroup analysis based on CMV serological status also showed prophylactic treatment significantly diminished CMV disease in the CMV IgG antibody negative group. No patients died in the prophylactic group, and one died in the deferred group (P = 0.54). The incidence of acute rejection episodes was 34% in the prophylactic and 46% in the deferred group (P = 0.26). Chronic rejection was observed in two recipients in the prophylactic group versus one recipient in the deferred arm (P = 0.35).

CONCLUSION

Compared with deferred therapy prophylactic therapy with gancyclovir decreased CMV disease and delayed the onset of CMV disease after liver transplantation.

Role of endogenous endothelin-1 in transplant obliterative airway disease in the rat

Endothelin-1 (ET-1) expression is increased after lung transplantation in association with ischemia reperfusion injury and acute rejection. However, little is known of the role of ET-1 during the development of obliterative bronchiolitis. In this study, we investigated the biological significance of ET-1 in obliterative airway disease development using a rat tracheal allograft model. Immunoreactivity of ET-1 and its receptors ET-RA and ET-RB was increased four-fold in allografts compared with syngrafts and localized to mononuclear cells and smooth muscle cells of the myofibroproliferative lesion and airway wall, indicating that ET-1 may mediate its effects in both a paracrine and autocrine manner in smooth muscle cells. Inhibition of ET-1 action by a nonselective ET-1 receptor antagonist, bosentan, significantly decreased tracheal occlusion, which was linked to delayed epithelial necrosis, suppressed smooth muscle cell proliferation, and a marked reduction in the number of interleukin-1beta and interleukin-2 immunoreactive cells. Our findings show that endogenous ET-1 activation is associated with obliteration of the airway wall, and blocking signaling downstream of ET-1 receptors leads to attenuation of obliterative airway disease. The results suggest that ET-1 has a proproliferative and proinflammatory role in the development of obliterative bronchiolitis.

[Bronchiolitis with airflow obstruction in adults]

PURPOSE

The purpose of this paper is twofold: to describe the clinical and anatomical characteristics of bronchiolitis associated with airflow obstruction in adults; to present through a clinical approach, a classification of the main aetiologies or pathological frames associated with that entity.

KEY POINTS

The constrictive bronchiolitis type is the most frequently encountered. On clinical grounds, cough, crackles, and a progressive dyspnea develop usually within a few weeks. Radiological signs of bronchiolar abnormalities are best visualized on high resolution expiratory CT scan. The decrease in maximal airflows and oxygen tension is of limited amplitude and poorly reversible with bronchodilators. Diagnosis is easily performed when a causative event, or the clinical context, can be delineated: inhalation of toxic fumes, diffuse bronchiectasis, rheumatoid arthritis, lung or bone marrow transplantation. Delayed formation of bronchiectasis in the central airways is common. The treatment is not standardized; corticosteroids are usually prescribed as a first line therapy; the benefit of the addition of, or substitution with immunosuppressive drugs has not been adequately evaluated, but is, on the mean, of limited amplitude.

PERSPECTIVES

Recent advances in the identification of inhaled agents toxic for the distal airways help in establishing appropriate measures of prevention. When the aetiology of the bronchiolitis cannot be suspected, extensive search of a causative agent should be performed, including microbial and mineral analysis of bronchoalveolar products. Negative results should lead to perform a surgical lung biopsy. The study of chronic rejection processes in animal models of lung transplantation, the identification of inhibitory factors of bronchiolar fibrogenesis, and the efficacy of some anti-cytokines on inflammatory processes could result in new therapeutic approaches.

Platelet-derived growth factor regulates cytomegalovirus infection-enhanced obliterative bronchiolitis in rat tracheal allografts

BACKGROUND

Cytomegalovirus (CMV) infection is a risk factor for the development of obliterative bronchiolitis (OB) after lung transplantation.

METHODS

In the rat tracheal allograft model, rat CMV (RCMV) infection is associated with accelerated OB through enhanced alloimmune activation and increased smooth muscle cell (SMC) proliferation. Using this model, we investigated the role of platelet-derived growth factor (PDGF) in RCMV infection-enhanced OB.

RESULTS

Immunohistochemistry and in situ hybridization revealed that RCMV infection significantly up-regulates PDGF ligand and receptor expression in inflammatory and SMC-like cells in tracheal allografts. Selective inhibition of PDGF receptor tyrosine kinase activity by CGP 53716 prevents the development of OB in RCMV-infected allograft recipients.

CONCLUSION

The results of this study emphasize the key regulatory role of PDGF in the pathogenesis of RCMV infection-enhanced OB, suggesting a novel strategy for the prevention of this fibroproliferative disorder.

Reduced risk for extensive chronic graft-versus-host disease in patients receiving transplants with human leukocyte antigen-identical sibling donors given polymerase chain reaction-based preemptive therapy against cytomegalovirus

BACKGROUND

The aim of this study was to investigate the relationship between cytomegalovirus (CMV) and extensive chronic graft-versus-host disease (GvHD) after allogeneic stem-cell transplantation (SCT).

METHODS

Two hundred sixty-two consecutive patients undergoing conventional SCT with human leukocyte antigen-identical sibling donors, given cyclosporine A and methotrexate as GvHD prophylaxis and surviving more than 3 months after SCT, were retrospectively analyzed. Most patients received transplants because of a hematologic malignancy (n=226), but 36 patients with nonmalignant disorders were included in the analysis. Ninety-nine patients were monitored for CMV infection with rapid virus isolation and 163 patients by either a pp65 antigenemia test (n=5) or a qualitative polymerase chain reaction (PCR) assay for CMV-DNA (n=158).

RESULTS

One hundred thirty (50%) of the patients developed chronic GvHD, of whom 17 (6.5%) developed extensive chronic GvHD. Risk factors for development of extensive chronic GvHD were determined by multivariate logistic regression. The strategy of PCR-based monitoring for CMV-DNA, giving preemptive antiviral therapy on demand, significantly decreased the risk for developing extensive chronic GvHD (odds ratio=0.32, P =0.03). No other factors tested, including recipient and donor age and sex, source of graft, cell dose, and acute GvHD, had any significant effect on the development of extensive chronic GvHD.

CONCLUSIONS

We conclude that the risk for extensive chronic GvHD in this homogenous group of patients was reduced by the use of PCR-based preemptive therapy.

Increased matrix metalloproteinase-2 and membrane type 1 matrix metalloproteinase activity and expression in heterotopically transplanted murine tracheas

BACKGROUND

Bronchiolitis obliterans syndrome (BOS) is the most common long-term cause of morbidity and mortality after heart-lung or lung transplantation. One pathologic feature of BOS is infiltration of fibroblasts and connective tissue products into the airway lumen, which form a fibrous, collagen-rich occlusion. Heterotopically transplanted allogeneic murine tracheal stenosis resemble BOS in the development of obliterans airway disease. Matrix metalloproteinases (MMPs) are key enzymes involved in tissue remodeling and, clinically, have several roles in pulmonary diseases. Among the MMP family, type IV collagenases, MMP-2 and MMP-9, have high gelatinolytic activity and are thought to play a role in several pulmonary diseases. Membrane type 1 MMP (MT1-MMP) activates the zymogen of MMP-2 (proMMP-2, 72 kd), and activated MMP-2 (active MMP-2, 62 kd) degrades type IV collagen and plays an important role in clinical pulmonary disease. In this study, we examine the expression of MMP-2, its activator MT1-MMP and MMP-9 in BOS using murine trachea transplantation models.

METHODS

Rats were divided into 5 experimental groups (n = 10 in each group). Group I was a control group with intact tracheas. Animals with tracheal grafts underwent heterotopically syngeneic (Groups II and III) or allogeneic (Groups IV and V) transplantation. The recipient rats were killed 7 days (Groups II and IV) or 28 days (Groups III and V) after transplantation. The harvested tracheal grafts were examined histologically. MMP activity was assessed using gelatin zymography analysis, and MMP-2 and MT1-MMP gene expression was examined by quantitative real-time polymerase chain reaction analysis. Distribution of gelatinolytic activity was studied using in situ zymography.

RESULTS

There was little histologic change in the intact trachea (Group I) and in all isografts (Groups II and III). Fibrotic tissues in Group V significantly occluded the tracheal lumen, and there was severe lymphocyte infiltration in Group IV. According to gelatin zymography, proMMP-9 was faint at 7 days, but activated MMP-9 was not present in all groups. The MMP-2 gelatinolytic bands were predominant; the activation in Group V was significantly greater than that in Group IV, and in Group III it was significantly greater than that in Group II. Gene expression of both MMP-2 and MT1-MMP were significantly higher in Group V than in the other groups (p < 0.01), and MMP-2 was clearly activated. Gelatinolytic activity was localized in the fibrotic tissues or lymphocytes of thickening lumen after destruction of the epithelium by stenosis.

CONCLUSIONS

These results demonstrate that MMP-2, together with its activator MT1-MMP, may have an important role in the development of BOS, which is associated with destruction of the tracheal epithelium, leading to fibrosis.