The role of the CC chemokine, RANTES, in acute lung allograft rejection

Screening gene signatures for clinical response subtypes of lung transplantation

Lung is the most important organ in the human respiratory system, whose normal functions are quite essential for human beings. Under certain pathological conditions, the normal lung functions could no longer be maintained in patients, and lung transplantation is generally applied to ease patients' breathing and prolong their lives. However, several risk factors exist during and after lung transplantation, including bleeding, infection, and transplant rejections. In particular, transplant rejections are difficult to predict or prevent, leading to the most dangerous complications and severe status in patients undergoing lung transplantation. Given that most common monitoring and validation methods for lung transplantation rejections may take quite a long time and have low reproducibility, new technologies and methods are required to improve the efficacy and accuracy of rejection monitoring after lung transplantation. Recently, one previous study set up the gene expression profiles of patients who underwent lung transplantation. However, it did not provide a tool to predict lung transplantation responses. Here, a further deep investigation was conducted on such profiling data. A computational framework, incorporating several machine learning algorithms, such as feature selection methods and classification algorithms, was built to establish an effective prediction model distinguishing patient into different clinical subgroups, corresponding to different rejection responses after lung transplantation. Furthermore, the framework also screened essential genes with functional enrichments and create quantitative rules for the distinction of patients with different rejection responses to lung transplantation. The outcome of this contribution could provide guidelines for clinical treatment of each rejection subtype and contribute to the revealing of complicated rejection mechanisms of lung transplantation.

Chronic Lung Allograft Dysfunction: Evolving Concepts and Therapies

The primary factor that limits long-term survival after lung transplantation is chronic lung allograft dysfunction (CLAD). CLAD also impairs quality of life and increases the costs of medical care. Our understanding of CLAD continues to evolve. Consensus definitions of CLAD and the major CLAD phenotypes were recently updated and clarified, but it remains to be seen whether the current definitions will lead to advances in management or impact care. Understanding the potential differences in pathogenesis for each CLAD phenotype may lead to novel therapeutic strategies, including precision medicine. Recognition of CLAD risk factors may lead to earlier interventions to mitigate risk, or to avoid risk factors all together, to prevent the development of CLAD. Unfortunately, currently available therapies for CLAD are usually not effective. However, novel therapeutics aimed at both prevention and treatment are currently under investigation. We provide an overview of the updates to CLAD-related terminology, clinical phenotypes and their diagnosis, natural history, pathogenesis, and potential strategies to treat and prevent CLAD.

Screening and identification of key regulatory connections and immune cell infiltration characteristics for lung transplant rejection using mucosal biopsies

This study aimed to explore key regulatory connections underlying lung transplant rejection. The differentially expressed genes (DEGs) between rejection and stable lung transplantation (LTx) samples were screened using R package limma, followed by functional enrichment analysis and protein-protein interaction network construction. Subsequently, a global triple network, including miRNAs, mRNAs, and transcription factors (TFs), was constructed. Furthermore, immune cell infiltration characteristics were analyzed to investigate the molecular immunology of lung transplant rejection. Finally, potential drug-target interactions were generated. In brief, 739 DEGs were found between rejection and stable LTx samples. PTPRC, IL-6, ITGAM, CD86, TLR8, TYROBP, CXCL10, ITGB2, and CCR5 were defined as hub genes. Eight TFs, including STAT1, SPIB, NFKB1, SPI1, STAT5A, RUNX1, VENTX, and BATF, and five miRNAs, including miR-335-5p, miR-26b-5p, miR-124-3p, miR-1-3p, and miR-155-5p, were involved in regulating hub genes. The immune cell infiltration analysis revealed higher proportions of activated memory CD4 T cells, follicular helper T cells, γδ T cells, monocytes, M1 and M2 macrophages, and eosinophils in rejection samples, besides lower proportions of resting memory CD4 T cells, regulatory T cells, activated NK cells, M0 macrophages, and resting mast cells. This study provided a comprehensive perspective of the molecular co-regulatory network underlying lung transplant rejection.

CCR4 expression on host T cells is a driver for alloreactive responses and lung rejection

Despite current immunosuppressive strategies, long-term lung transplant outcomes remain poor due to rapid allogenic responses. Using a stringent mouse model of allo-airway transplantation, we identify the CCR4-ligand axis as a central node driving secondary lymphoid tissue homing and activation of the allogeneic T cells that prevent long-term allograft survival. CCR4 deficiency on transplant recipient T cells diminishes allograft injury and when combined with CTLA4-Ig leads to an unprecedented long-term lung allograft accommodation. Thus, we identify CCR4-ligand interactions as a central mechanism driving allogeneic transplant rejection and suggest it as a potential target to enhance long-term lung transplant survival.

Host-Pathogen Interactions and Chronic Lung Allograft Dysfunction

Lung transplantation is now considered to be a therapeutic option for patients with advanced-stage lung diseases. Unfortunately, due to post-transplant complications, both infectious and noninfectious, it is only a treatment and not a cure. Infections (e.g., bacterial, viral, and fungal) in the immunosuppressed lung transplant recipient are a common cause of mortality post transplant. Infections have more recently been explored as factors contributing to the risk of chronic lung allograft dysfunction (CLAD). Each major class of infection-(1) bacterial (Staphylococcus aureus and Pseudomonas aeruginosa); (2) viral (cytomegalovirus and community-acquired respiratory viruses); and (3) fungal (Aspergillus)-has been associated with the development of CLAD. Mechanistically, the microbe seems to be interacting with the allograft cells, stimulating the induction of chemokines, which recruit recipient leukocytes to the graft. The recipient leukocyte interactions with the microbe further up-regulate chemokines, amplifying the influx of allograft-infiltrating mononuclear cells. These events can promote recipient leukocytes to interact with the allograft, triggering an alloresponse and graft dysfunction. Overall, interactions between the microbe-allograft-host immune system alters chemokine production, which, in part, plays a role in the pathobiology of CLAD and mortality due to CLAD.

Impact of Allograft Injury Time of Onset on the Development of Chronic Lung Allograft Dysfunction After Lung Transplantation

The impact of allograft injury time of onset on the risk of chronic lung allograft dysfunction (CLAD) remains unknown. We hypothesized that episodes of late-onset (≥6 months) allograft injury would produce an augmented CXCR3/ligand immune response, leading to increased CLAD. In a retrospective single-center study, 1894 transbronchial biopsy samples from 441 lung transplant recipients were reviewed for the presence of acute rejection (AR), lymphocytic bronchiolitis (LB), diffuse alveolar damage (DAD), and organizing pneumonia (OP). The association between the time of onset of each injury pattern and CLAD was assessed by using multivariable Cox models with time-dependent covariates. Bronchoalveolar lavage (BAL) CXCR3 ligand concentrations were compared between early- and late-onset injury patterns using linear mixed-effects models. Late-onset DAD and OP were strongly associated with CLAD: adjusted hazard ratio 2.8 (95% confidence interval 1.5-5.3) and 2.0 (1.1-3.4), respectively. The early-onset form of these injury patterns did not increase CLAD risk. Late-onset LB and acute rejection (AR) predicted CLAD in univariable models but lost significance after multivariable adjustment for late DAD and OP. AR was the only early-onset injury pattern associated with CLAD development. Elevated BAL CXCR3 ligand concentrations during late-onset allograft injury parallel the increase in CLAD risk and support our hypothesis that late allograft injuries result in a more profound CXCR3/ligand immune response.

Gene Expression Profiling of Bronchoalveolar Lavage Cells Preceding a Clinical Diagnosis of Chronic Lung Allograft Dysfunction

Background

Chronic Lung Allograft Dysfunction (CLAD) is the main limitation to long-term survival after lung transplantation. Although CLAD is usually not responsive to treatment, earlier identification may improve treatment prospects.

Methods

In a nested case control study, 1-year post transplant surveillance bronchoalveolar lavage (BAL) fluid samples were obtained from incipient CLAD (n = 9) and CLAD free (n = 8) lung transplant recipients. Incipient CLAD cases were diagnosed with CLAD within 2 years, while controls were free from CLAD for at least 4 years following bronchoscopy. Transcription profiles in the BAL cell pellets were assayed with the HG-U133 Plus 2.0 microarray (Affymetrix). Differential gene expression analysis, based on an absolute fold change (incipient CLAD vs no CLAD) >2.0 and an unadjusted p-value ≤0.05, generated a candidate list containing 55 differentially expressed probe sets (51 up-regulated, 4 down-regulated).

Results

The cell pellets in incipient CLAD cases were skewed toward immune response pathways, dominated by genes related to recruitment, retention, activation and proliferation of cytotoxic lymphocytes (CD8⁺ T-cells and natural killer cells). Both hierarchical clustering and a supervised machine learning tool were able to correctly categorize most samples (82.3% and 94.1% respectively) into incipient CLAD and CLAD-free categories.

Conclusions

These findings suggest that a pathobiology, similar to AR, precedes a clinical diagnosis of CLAD. A larger prospective investigation of the BAL cell pellet transcriptome as a biomarker for CLAD risk stratification is warranted.

Gene transfer of the S24F regulated on activation normal T-cell expressed and secreted-chemokine ligand 5 variant attenuates cardiac allograft rejection

BACKGROUND

Regulated on activation normal T-cell expressed and secreted (RANTES)-chemokine ligand 5 plays a key role in mediating heart transplant rejection. Suppression of RANTES-mediated signals can reduce leukocyte recruitment and mitigate transplant rejection severity. The present study describes the construction of an adenovirus overexpression vector encoding a natural S24F RANTES variant as a means of reducing leukocyte recruitment, resulting in the prevention of allograft rejection.

METHODS

The in vitro transendothelial chemotaxis assay was used to compare RANTES-induced transmigration of peripheral blood mononuclear cells across human umbilical vein endothelial cells cultured on the upper Transwell chamber. Intracoronary delivery of Ad-S24F, Ad-Null, or phosphate-buffered saline was performed in BALB/c donor hearts that were transplanted into the abdominal cavity of C57BL/6 recipients as a measure of allograft survival. Intragraft inflammatory cell infiltrates and associated proinflammatory cytokine expression profiles were detected by immunohistochemistry and quantitative real-time polymerase chain reaction on day 6 after transplantation, respectively.

RESULTS

Regulated on activation normal T-cell expressed and secreted-induced peripheral blood mononuclear cell transendothelial chemotaxis is inhibited by S24F (Ad-S24F, 9.2%±0.02%; Ad-Null, 17.7%±0.02%; medium control, 15.1%±0.01%; P<0.05). Cardiac allograft survival was prolonged after delivery of 1×10 plaque-forming units of Ad-S24F (13.00±0.33 days compared with 9.38±0.60 and 9.00±0.38 days after Ad-Null or phosphate-buffered saline treatment, respectively, P<0.05). S24F gene transfer reduced the number of intragraft CD8 T lymphocytes, monocyte-macrophages, and T-cell receptor αβ cell infiltrates (P<0.05) and decreased transcripts for RANTES and interferon-γ (P<0.05).

CONCLUSION

S24F is an important component of the chemokine network involved in regulating the biologic activity of RANTES, and its expression can be used in the prevention and treatment of cardiac allograft rejection.

Biomarkers of pulmonary rejection

Immunologic complications after lung transplantation (LT) include acute cellular rejection (ACR), antibody-mediated rejection (AMR), and most forms of chronic allograft dysfunction (CAD). ACR is an inflammatory process in which the reaction is mediated by the T-cell population. Most episodes of ACR fully recover with treatment, but repeated bouts are considered to be a risk factor for CAD. Biomarker cytokines interleukin (IL)-10, IL-15, IL-6, CCL5, CCR2 and IFNγ may play significant roles in this complication. Formerly bronchiolitis obliterans syndrome (BOS) or chronic rejection or most forms of CAD were considered to be immunologic complications not amenable therapeutic measures. CAD, the main limitation for long-term survival in LT, is characterized histologically by airway epithelial cell apoptosis and luminal fibrosis in the respiratory bronchioles causing airflow obstruction and, in some cases, lung parenchymal affectations causing restrictive lung disease. Several biomarkers have been studied in CAD, IL-6, IL-8, IL-17, IL-23, IL-13, IFN γ, and TGF β cytokines, pH, bile acid, and tripsine of gastroesophageal reflux and toll-like receptors of innate immunity. Herein we have reviewed the literature of biomarkers involved in lung rejection.

Array-based methods for diagnosis and prevention of transplant rejection

DNA microarray is a microhybridization-based assay that is used to simultaneously study the expression of thousands of genes, thus providing a global view of gene expression in a tissue sample. This powerful technique has been adopted by many biomedical disciplines and will likely have a profound impact on the diagnosis, treatment and prognosis of human diseases. This review article presents an overview of the application of microarray technology to the field of solid-organ transplantation.

Bronchiolitis obliterans syndrome: the Achilles' heel of lung transplantation

Lung transplantation is a therapeutic option for patients with end-stage pulmonary disorders. Unfortunately, chronic lung allograft dysfunction (CLAD), most commonly manifest as bronchiolitis obliterans syndrome (BOS), continues to be highly prevalent and is the major limitation to long-term survival. The pathogenesis of BOS is complex and involves alloimmune and nonalloimmune pathways. Clinically, BOS manifests as airway obstruction and dyspnea that are classically progressive and ultimately fatal; however, the course is highly variable, and distinguishable phenotypes may exist. There are few controlled studies assessing treatment efficacy, but only a minority of patients respond to current treatment modalities. Ultimately, preventive strategies may prove more effective at prolonging survival after lung transplantation, but their remains considerable debate and little data regarding the best strategies to prevent BOS. A better understanding of the risk factors and their relationship to the pathological mechanisms of chronic lung allograft rejection should lead to better pharmacological targets to prevent or treat this syndrome.

Mechanisms and mediators of inflammation: potential models for skin rejection and targeted therapy in vascularized composite allotransplantation

Vascularized composite allotransplantation (VCA) is an effective treatment option for patients suffering from limb loss or severe disfigurement. However, postoperative courses of VCA recipients have been complicated by skin rejection, and long-term immunosuppression remains a necessity for allograft survival. To widen the scope of this quality-of-life improving procedure minimization of immunosuppression in order to limit risks and side effects is needed. In some aspects, the molecular mechanisms and dynamics of skin allograft rejection seem similar to inflammatory skin conditions. T cells are key players in skin rejection and are recruited to the skin via activation of adhesion molecules, cytokines, and chemokines. Blocking these molecules has not only shown success in the treatment of inflammatory dermatoses, but also prolonged graft survival in various models of solid organ transplantation. In addition to T cell recruitment, ectopic lymphoid structures within the allograft associated with chronic rejection in solid organ transplantation might contribute to the strong alloimmune response towards the skin. Selectively targeting the molecules involved offers exciting novel therapeutic options in the prevention and treatment of skin rejection after VCA.

Role of cold shock Y-box protein-1 in inflammation, atherosclerosis and organ transplant rejection

Chemokines (chemoattractant cytokines) are crucial regulators of immune cell extravasation from the bloodstream into inflamed tissue. Dysfunctional regulation and perpetuated chemokine gene expression are linked to progressive chronic inflammatory diseases and, in respect to transplanted organs, may trigger graft rejection. RANTES (regulated upon activation, normal T cell expressed and secreted (also known as CCL5)) is a model chemokine with relevance in numerous inflammatory diseases where the innate immune response predominates. Transcription factor Y-box binding protein-1 (YB-1) serves as a trans-regulator of CCL5 gene transcription in vascular smooth muscle cells and leucocytes. This review provides an update on YB-1 as a mediator of inflammatory processes and focuses on the role of YB-1 in CCL5 expression in diseases with monocytic cell infiltrates, albeit acute or chronic. Paradigms of such diseases encompass atherosclerosis and transplant rejection where cold shock protein YB-1 takes a dominant role in transcriptional regulation.

Green tea epigallo-catechin-galleate ameliorates the development of obliterative airway disease

Lung transplantation has the worst outcome compared to all solid organ transplants due to chronic rejection known as obliterative bronchiolitis (OB). Pathogenesis of OB is a complex interplay of alloimmune-dependent and -independent factors, which leads to the development of inflammation, fibrosis, and airway obliteration that have been resistant to therapy. The alloimmune-independent inflammatory pathway has been the recent focus in the pathogenesis of rejection, suggesting that targeting this may offer therapeutic benefits. As a potent anti-inflammatory agent, epigallo-catechin-galleate (EGCG), a green tea catechin, has been very effective in ameliorating inflammation in a variety of diseases, providing the rationale for its use in this study in a murine heterotopic tracheal allograft model of OB. Mice treated with EGCG had reduced inflammation, with significantly less neutrophil and macrophage infiltration and significantly reduced fibrosis. On further investigation into the mechanisms, inflammatory cytokines keratinocyte (KC), interleukin-17 (IL-17), and tumor necrosis factor-α (TNF-α), involved in neutrophil recruitment, were reduced in the EGCG-treated mice. In addition, monocyte chemokine monocyte chemoattractant protein-1 (MCP-1) was significantly reduced by EGCG treatment. Antifibrotic cytokine interferon-γ-inducible protein-10 (IP-10) was increased and profibrotic cytokine transforming growth factor-β (TGF-β) was reduced, further characterizing the antifibrotic effects of EGCG. These findings suggest that EGCG has great potential in ameliorating the development of obliterative airway disease.

Immune response CC chemokines CCL2 and CCL5 are associated with pulmonary sarcoidosis

Background

Pulmonary sarcoidosis involves an intense leukocyte infiltration of the lung with the formation of non-necrotizing granulomas. CC chemokines (chemokine (C-C motif) ligand 2 (CCL2)-CCL5) are chemoattractants of mononuclear cells and act through seven transmembrane G-coupled receptors. Previous studies have demonstrated conflicting results with regard to the associations of these chemokines with sarcoidosis. In an effort to clarify previous discrepancies, we performed the largest observational study to date of CC chemokines in bronchoalveolar lavage fluid (BALF) from patients with pulmonary sarcoidosis.

Results

BALF chemokine levels from 72 patients affected by pulmonary sarcoidosis were analyzed by enzyme-linked immunosorbent assay (ELISA) and compared to 8 healthy volunteers. BALF CCL3 and CCL4 levels from pulmonary sarcoidosis patients were not increased compared to controls. However, CCL2 and CCL5 levels were elevated, and subgroup analysis showed higher levels of both chemokines in all stages of pulmonary sarcoidosis. CCL2, CCL5, CC chemokine receptor type 1 (CCR1), CCR2 and CCR3 were expressed from mononuclear cells forming the lung granulomas, while CCR5 was only found on mast cells.

Conclusions

These data suggest that CCL2 and CCL5 are important mediators in recruiting CCR1, CCR2, and CCR3 expressing mononuclear cells as well as CCR5-expressing mast cells during all stages of pulmonary sarcoidosis.

V(alpha)14iNKT cells promote liver pathology during adenovirus infection by inducing CCL5 production: implications for gene therapy

Replication-defective recombinant adenoviruses are the most widely studied replication-defective vectors for the potential treatment of inherited human diseases. However, broad clinical application of replication-defective adenoviruses in gene therapy is being hindered by the induction of vigorous innate and adaptive immune responses against the vector that cause deleterious effects in the liver. V(alpha)14 invariant natural killer T cells (V(alpha)14iNKT cells) are thymus-derived innate T cells at the interface between the two arms of the immune response and provide full engagement of host defense. The pathophysiological role of intrahepatic V(alpha)14iNKT cells during replication-defective adenovirus infection is not known and is the main focus of our study. Our data showed that intrahepatic V(alpha)14iNKT cells were activated in response to adenovirus infection to induce significant levels of hepatic chemokine (C-C motif) ligand 5 (CCL5) and subsequent liver toxicity. Moreover, intrahepatic CCL5 production was selectively reduced by V(alpha)14iNKT cell deficiency. In vivo studies utilizing CCL5-deficient mice or V(alpha)14iNKT cell-deficient mice demonstrated that CCL5 deficiency or V(alpha)14iNKT cell deficiency was associated with reduced liver pathology. Similar results were seen after blocking the biological effects of the CCL5 receptors. In conclusion, we have identified an important proinflammatory role for activated intrahepatic V(alpha)14iNKT cells in positively influencing hepatic CCL5 production to promote acute liver inflammation and injury. Therefore, our findings highlight the blockade of CCL5 interaction with a cognate receptor(s) as an important potential strategy to alleviate liver pathology associated with replication-defective adenovirus infection.

Chemokine Receptor-5Delta32 Mutation is No Risk Factor for Ischemic-Type Biliary Lesion in Liver Transplantation

It has been shown that certain chemokine receptor polymorphisms may correspond to certain complications after organ transplantation. Ischemic-type biliary lesion (ITBL) encounters for major morbidity and mortality in liver transplant recipients. So far, the exact cause for ITBL remains unclear. Certain risk factors for the development of ITBL like donor age and cold ischemic time are well described. In a previous study, a 32-nucleotide deletion of the chemokine receptor-5Δ32 (CCR-5Δ32) was strongly associated with the incidence of ITBL in adult liver transplantation. This study re-evaluates the association of CCR-5Δ32 gene polymorphism and the incidence of ITBL. 169 patients were included into this retrospective analysis. 134 patients were homozygous for wild-type CCR-5, 33 patients heterozygous, and 2 patients were homozygous for CCR-5Δ32 mutation. There were no major differences in donor or recipients demographics. No association was found between CCR-5Δ32 mutation and the development of ITBL. We conclude that CCR-5Δ32 is no risk factor for the development of ITBL in our patient cohort.

Copy number variation in the CCL4L gene is associated with susceptibility to acute rejection in lung transplantation

Lung transplantation (LT) has become an accepted therapy for selected patients with advanced lung disease. One of the main limitations to successful LT is rejection of the transplanted organ where chemokines are pivotal mediators. Here, we test the relationship between copy number variation (CNV) in the CCL4L chemokine gene and rejection risk in LT patients (n=161). Patients with no acute rejection showed a significantly lower mean number of CCL4L copies than patients that showed acute rejection (1.66 vs 1.96, P=0.014), with an even greater number of gene copies seen in patients with more than one episode of acute rejection (1.66 vs 2.30, P=0.001). Additionally, patients with > or =2 CCL4L copies had a significantly higher risk of acute rejection compared with patients that had 0-1 CCL4L copies (odds ratio 2.65; 95% confidence interval, 1.33-5.28; P=0.0046). A combined analysis of CCL4L CNV and the rs4796195 CCL4L single nucleotide polymorphism demonstrated that the effect of CCL4L copy number in acute rejection is mainly because of the number of copies of the CCL4L1 allelic variant. This finding constitutes the first report of CNV as a correlate factor in allograft rejection.

Analysis of the CC chemokine receptor 5Delta32 polymorphism in pediatric liver transplant recipients

In adult liver graft recipients, it has been shown that certain chemokine polymorphisms (CCR5Delta32) may correspond to ischemic type biliary lesions leading to chronic graft dysfunction. The aim of our present study was to assess the importance of CCR5Delta32 polymorphism in a cohort of pediatric liver graft recipients with regard to acute or chronic graft dysfunction. A total of 137 children post-liver transplantation have been included for genetic analysis (CCR5Delta32 polymorphism), and the incidence of acute and chronic graft dysfunction was analyzed. The most common diagnosis leading to LTx was biliary atresia (56.2%), the median age was 14 months, and 33.5% of the patients received a living-related graft. In all, 110 of the subjects were found to have the CCR5 wild type, 25 children were heterozygous for CCR5Delta32, and two patients were homozygous. Of 137, 44 (32.1%) developed acute graft rejection, nine out of 137 (6.6%) chronic graft dysfunction (vanishing bile duct syndrome), and 84 (61.3%) children had neither acute nor chronic graft rejection. There was no significant correlation between acute graft rejection or chronic graft dysfunction and the CCR5Delta32 allele in the study population. We conclude that CCR5Delta32 polymorphism may not play a role in acute or chronic liver graft dysfunction in children.

Chemokines and transplant vasculopathy

Transplant vasculopathy (TV) remains the leading cause of late death among heart transplant recipients. Transplant vasculopathy is characterized by progressive neointimal proliferation, leading to ischemic failure of the allograft. Multiple experimental and clinical studies have shown that injury to the graft at various stages of transplantation can be a risk factor for development of transplant vasculopathy. The hallmark of cardiac allograft injury is the infiltration of leukocytes. Recruitment of leukocytes requires intercellular communication between infiltrating cells, endothelium, parenchymal cells, and components of extracellular matrix. These events are mediated via the generation of adhesion molecules, cytokines, and chemokines. The chemokines, by virtue of their specific cell receptor expression, can selectively mediate the local recruitment/activation of distinct leukocytes/cells, allowing for migration across the endothelium and beyond the vascular compartment. This report provides a comprehensive review of the chemokines that participate in the development of transplant vasculopathy.

What differentiates normal lung repair and fibrosis? Inflammation, resolution of repair, and fibrosis

There has been ongoing controversy related to what differentiates normal lung repair and fibrosis. For example, the current prevailing concept has been that idiopathic forms of pulmonary fibrosis are due only to epithelial injury in response to some unknown cause that results in persistent evolving fibrosis without preceding inflammation. This concept would suggest that the lung responds to injury in a different manner than other organs, such as the liver, kidney, and heart. However, that would seem to contradict known established pathological concepts. To address this controversy, concepts were presented as follows: (1) loss of basement membrane integrity is critical in determining the "point of no return," and contributes to the inability to reestablish normal lung architecture with promotion of fibrosis; (2) loss of epithelial cells, endothelial cells, and basement membrane integrity in usual interstitial pneumonia associated with idiopathic pulmonary fibrosis leads to destroyed lung architecture and perpetual fibrosis; (3) transforming growth factor-beta is necessary, but not entirely sufficient, to promote permanent fibrosis; (4) persistent injury/antigen/irritant is critical for the propagation of fibrosis; (5) idiopathic pulmonary fibrosis is an example of a process related to the persistence of an "antigen(s)," chronic inflammation, and fibrosis; and (6) unique cells are critical cellular players in the regulation of fibrosis. In keeping with the theme of the Aspen Lung Conference, it is hoped that more questions are raised than answered in this presentation, in support of the continued need for research in this area to address these important concepts.

Pulmonary hypertension associated with lung transplantation obliterative bronchiolitis and vascular remodeling of the allograft

Pathologic obliterative bronchiolitis (OB)/Bronchiolitis obliterans syndrome (pathologic OB/BOS) is the major obstacle to long-term survival post-lung transplantation (LT). Our group has demonstrated that pulmonary hypertension (PH) complicates the course of chronic inflammatory lung diseases that have similarities to pathologic OB/BOS and that vascular remodeling of the bronchial circulation occurs during BOS. Consequently, we hypothesized that PH is associated with pathologic OB/BOS and may result from a vasculopathy of the allograft pulmonary circulation. We conducted a single-center, retrospective study and examined the presence of PH and vasculopathy in patients with pathologic OB/BOS. Fifty-two pathologic specimens post-LT were recovered from January 10, 1997 to January 5, 2007 and divided into two groups, those with and without pathologic OB/BOS.PH was defined as a mean pulmonary artery pressure (mPAP) > 25 mmHg by right heart catheterization (RHC) or right ventricular systolic pressure (RVSP) > or = 45 mmHg by transthoracic echocardiogram (TTE). PH was more prevalent in those LT recipients with pathologic OB/BOS (72% vs. 0%, p = 0.003). Furthermore, pulmonary arteriopathy and venopathy were more prevalent in patients with pathologic OB/BOS (84% vs. 4%, p < 0.0001, and 77% vs. 35%, p = 0.004, respectively). PH is common in LT recipients with pathologic OB/BOS and is associated with a vasculopathy of the allograft pulmonary circulation.

Altered levels of CC chemokines during pulmonary CMV predict BOS and mortality post-lung transplantation

Pulmonary CMV infection (CMVI) and disease (CMVD) is associated with reduced long-term survival post-lung transplantation, however, the specific biologic mechanisms remain unclear. We have demonstrated a role of CC chemokines during lung allograft dysfunction. Based on these findings, we hypothesized that pulmonary CMV upregulates the expression of multiple CC chemokines that leads to allograft dysfunction and decreased long-term survival. We performed a nested case control study in lung transplant recipients to investigate alterations in CC chemokine biology during pulmonary CMV. Levels of CC chemokines were measured in bronchoalveolar lavage fluid (BALF) from recipients with CMVI (n = 33), CMVD (n = 6), and in healthy lung transplant controls (n = 33). We found a trend toward increased levels of MIP-1alpha/CCL3 during pulmonary CMVI. Levels of MCP-1/CCL2 and RANTES/CCL5 were significantly elevated during pulmonary CMV. Interestingly, elevated levels of CCL3 in BALF were protective with regards to survival. Importantly, elevated levels of CCL2 in BALF predicted the development of BOS, while elevated levels of CCL5 in BALF predicted an increase in mortality post-lung transplant. Altered levels of specific CC chemokines during pulmonary CMV are associated with future clinical outcomes. These results suggest a possible utility of BALF CC chemokines as biomarkers for guiding risk assessment during pulmonary CMV post-lung transplantation.

Chemokines as therapeutic targets in renal cell carcinoma

Targeting novel pathways associated with tumor angiogenesis, invasion and immunity, may lead to improvement in patient outcomes for renal cell carcinoma. Chemokines potentiate tumor growth, metastasis, angiogenesis and immune evasion through interactions with stromal cells and neoplastic cells. Further understanding of the mechanisms involved in chemokine-mediated angiogenesis and metastasis may lead to improved therapeutic strategies in this disease. Interactions between chemokine expression and signaling, and the VEGF and hypoxia-inducible factor pathways offer important opportunities to intervene in the process of renal cell carcinoma proliferation, angiogenesis and invasion. Modulation of the CXCR3/CXCR3-ligand or the CXCR4/CXCL12 biologic axis may be potential therapeutic targets for the treatment of renal cell carcinoma. Furthermore, combination treatment with agents targeting chemokine signaling with therapies directed at angiogenesis and tumor immunity may lead to improved outcomes in this disease.

Alloimmune lung injury induced by local innate immune activation through inhaled lipopolysaccharide

BACKGROUND

Alloimmune lung injury, characterized by perivascular lymphocytic inflammation, lymphocytic bronchiolitis (LB), and obliterative bronchiolitis (OB), causes substantial morbidity and mortality after lung transplantation and bone marrow transplantation (BMT), but little is known regarding its pathogenesis. We have developed and pursued the hypothesis that local activation of pulmonary innate immunity through toll-like receptor (TLR)-4 is critical to the development of posttransplant alloimmune lung injury.

METHODS

We developed a fully major histocompatibility complex-mismatched murine BMT model without systemic graft-versus-host disease, and challenged mice with aerosolized lipopolysaccharide (LPS), a prototypic TLR4 agonist, to determine the effect upon pulmonary alloimmune lung injury.

RESULTS

LPS-exposed allogeneic BMT recipient mice developed histological and biological features of LB and OB, which were not observed in non-LPS-exposed allogeneic controls or syngeneic LPS-exposed mice. LPS-induced lymphocytic lung inflammation was dependent upon intact TLR4 signaling in donor-derived hematopoietic cells but not recipient structural lung cells, demonstrating a distinct function for TLR4 on hematopoietic cells in mediating alloimmunity.

CONCLUSIONS

We demonstrate a critical role for localized, environmentally induced innate immune activation in promoting alloimmune lung injury. Local inhibition of TLR4 signaling in pulmonary resident hematopoietic cells represents a novel and potentially important therapeutic target to prevent posttransplant rejection.

CCR1/CCL5 (RANTES) receptor-ligand interactions modulate allogeneic T-cell responses and graft-versus-host disease following stem-cell transplantation

Acute graft-versus-host disease (GVHD) and leukemic relapse are serious complications of allogeneic stem-cell transplantation (SCT). Recruitment of activated T cells to host target tissues or sites of leukemic infiltration (graft-versus-leukemia [GVL]) is likely mediated by chemokine receptor-ligand interactions. We examined the contribution of donor cell CCR1 expression to the development of GVHD and GVL using a well-established murine SCT model (B6 --> B6D2F1) and CCR1-deficient mice (CCR1(-/-)). Allo-SCT with CCR1(-/-) donor cells significantly reduced systemic and target organ GVHD severity, and CCR1 expression on both T cells and accessory cells contributed to GVHD mortality. Significant GVL activity was preserved following CCR1(-/-) SCT, but the survival advantage diminished with increasing tumor burden. We then explored the effects of CCR1 expression on allo-specific T-cell responses. Although cytolytic effector function was maintained on a per-cell basis, T-cell proliferation and IFNgamma secretion were significantly reduced both in vivo and in vitro. T-cell function was partially dependent on interactions between CCR1 and CCL5. Collectively, these data demonstrate that CCR1 expression on donor cells contributes to the development of both GVHD and GVL, and suggest that CCR1/CCL5 receptor-ligand interactions modulate allo-specific T-cell responses occurring in this context.

Expression of CXCR3 on Mononuclear Cells and CXCR3 Ligands in Patients With Metastatic Renal Cell Carcinoma in Response to Systemic IL-2 Therapy

Chemokines play an important role in regulating tumor-mediated immunity, angiogenesis, and tumor cell metastasis. The chemokine receptor, CXCR3, is expressed in various human tumors, including renal cell carcinoma (RCC). CXCR3 is also associated with antiangiogenic effects in multiple tumors, and we hypothesized that interleukin-2 (IL-2) treatment of patients with metastatic clear cell RCC could augment CXCR3 levels on circulating mononuclear cells and correlate to outcome. The kinetics of CXCR3 expression on circulating mononuclear cells and its ligands (CXCL9, CXCL10, and CXCL11) in plasma were evaluated in 20 patients with metastatic clear cell RCC during cycles 1 and 2 of high dose IL-2 therapy. Subpopulations of peripheral blood mononuclear cells (PBMCs) were studied by dual color flow cytometry. Angiogenic ligands were measured and an "angiogenic ratio" was calculated prehigh and posthigh dose IL-2. CXCR3 expression on PBMC at baseline was similar in patients with metastatic RCC and normal controls. PBMC CXCR3 expression increased during treatment, and peaked during cycle 2. Plasma from RCC patients displayed similar baseline levels of CXCR3 ligands to normal controls. However, the angiogenic ratio was significantly increased in patients with metastatic RCC at baseline. Plasma levels of CXCR3 ligands increased during treatment, resulting in a reversal in the angiogenic ratio to favor angiostatic chemokines. The CXCR3/CXCR3 ligand biologic axis and angiogenic ratio may be important biomarkers in clear cell RCC patients who are undergoing high dose IL-2 therapy.

Elevation of interleukin-15 protein expression in bronchoalveolar fluid in acute lung allograft rejection

BACKGROUND

Acute rejection remains a major source of morbidity in lung transplantation. Although interleukin (IL)-2 has been the principal T-cell growth factor implicated in acute rejection, IL-2 blockade does not prevent acute rejection completely. Recently, IL-15, a stromal cell-derived cytokine, has been found to share a similar biological function with IL-2. We hypothesized that IL-15 levels may be elevated in acute lung rejection in the presence of IL-2 blockade.

METHODS

Acute allograft rejection developed in 21 of 42 lung transplant recipients. BAL fluid (BALF) was analyzed for IL-2 and IL-15 protein expression by standard enzyme-linked immunosorbent assay.

RESULTS

The average (+/- SD) BALF IL-15 level was higher in lung transplant recipients with acute rejection compared to those without rejection (25 +/- 25 pg/mL vs 4.5 +/- 1.5 pg/mL, respectively; p < 0.0001). In addition, there appeared to be a bimodal distribution of BALF IL-15 levels in lung transplant recipients with acute rejection. BALF IL-2 levels were not associated with acute rejection. BALF IL-15 levels were not associated with bacterial, fungal, or cytomegalovirus infection.

CONCLUSION

These data show that BALF IL-15 levels are elevated in acute lung allograft rejection in the presence of IL-2 receptor blockade and may be an important mediator for acute rejection in lung transplantation.

Human and murine obliterative bronchiolitis in transplant

Obliterative bronchiolitis is a devastating illness that limits the long-term success of lung transplantation. Its high prevalence and overall poor response to current therapeutic measures demands further research to elucidate pathogenic mechanisms. Toward this goal, there is a role for animal models to study the mechanisms of obliterative bronchiolitis, such as the murine heterotopic tracheal allograft model. This review compares the tracheal allograft model to human obliterative bronchiolitis pathology and highlights the important mechanisms of airway rejection described using this model. Although certain limitations exist, the pursuit of proof-of-concept studies in this model, as well as other animal models, can provide the basis for genetic and cellular translational human studies directed toward post-transplant obliterative bronchiolitis pathogenesis. To meet these challenges, we call for the establishment of a National Institutes of Health-supported Lung Transplant Network to better orchestrate translational research efforts in obliterative bronchiolitis pathogenesis and treatment, and to advance the field of lung transplantation.

IL-13 is pivotal in the fibro-obliterative process of bronchiolitis obliterans syndrome

Acute allograft rejection is considered to be a predominately type 1 immune mediated response to the donor alloantigen. However, the type 2 immune mediated response has been implicated in multiple fibroproliferative diseases. Based on the fibro-obliterative lesion found during bronchiolitis obliterans syndrome (BOS), we hypothesized that the type 2 immune mediated response is involved in chronic lung allograft rejection. Specifically, whereas acute rejection is, in part, a type 1 immune response, chronic rejection is, in part, a type 2 immune response. We found the type 2 cytokine, IL-13, to be elevated and biologically active in human bronchoalveolar lavage fluid during BOS. Translational studies using a murine model of BOS demonstrated increased expression of IL-13 and its receptors that paralleled fibro-obliteration. In addition, in vivo neutralization of IL-13 reduced airway allograft matrix deposition and murine BOS, by a mechanism that was independent of IL-4. Furthermore, using IL-13Ralpha2(-/-) mice, we found increased fibro-obliteration. Moreover, anti-IL-13 therapy in combination with cyclosporin A had profound effects on reducing murine BOS. This supports the notion that IL-13 biological axis plays an important role during the pathogenesis of BOS independent of the IL-4 biological axis.

Angiotensin II Receptor Expression Following Intestinal Transplantation in Mice

BACKGROUND

To further improve the success rate of intestinal transplantation there is a need to find early appearing indicators of rejection. The specific aim of this study was to compare Angiotensin (Ang) II type 1 receptor and Ang II type 2 receptor expression in relation to histological signs of rejection.

METHODS

Mice of the C57BL6 strain with syngeneic intestinal grafts were compared to mice subjected to allogeneic intestinal transplantation with BalbC strain as donors. Local expression of Ang II type 1 and 2 receptor was evaluated using rt-PCR and Western blot and compared to histological picture in grafts and native intestine.

RESULTS

The Ang II type 2 receptor protein expression was markedly up-regulated in the allogeneically transplanted graft from day 1 postoperatively. Histological signs of rejection were not seen until day 6.

CONCLUSION

Intestinal allograft transplantation in mice is associated with a marked up-regulation of the Ang II type 2 receptor. However, the detailed role of the renin-angiotensin system in the immune rejection following intestinal transplantation remains to be clarified.

CXCR3 and its ligands in a murine model of obliterative bronchiolitis: regulation and function

Lung transplantation remains the only effective therapy for patients with end-stage lung disease, but survival is limited by the development of obliterative bronchiolitis (OB). The chemokine receptor CXCR3 and two of its ligands, CXCL9 and CXCL10, have been identified as important mediators of OB. However, the relative contribution of CXCL9 and CXCL10 to the development of OB and the mechanism of regulation of these chemokines has not been well defined. In this study, we demonstrate that CXCL9 and CXCL10 are up-regulated in unique patterns following tracheal transplantation in mice. In these experiments, CXCL9 expression peaked 7 days posttransplant, while CXCL10 expression peaked at 1 day and then again 7 days posttransplant. Expression of CXCL10 was also up-regulated in a novel murine model of lung ischemia, and in bronchoalveolar lavage fluid taken from human lungs 24 h after lung transplantation. In further analysis, we found that 3 h after transplantation CXCL10 is donor tissue derived and not dependent on IFN-gamma or STAT1, while 24 h after transplantation CXCL10 is from recipient tissue and regulated by IFN-gamma and STAT1. Expression of both CXCL9 and CXCL10 7 days posttransplant is regulated by IFN-gamma and STAT1. Finally, we demonstrate that deletion of CXCR3 in recipients reduces airway obliteration. However, deletion of either CXCL9 or CXCL10 did not affect airway obliteration. These data show that in this murine model of obliterative bronchiolitis, these chemokines are differentially regulated following transplantation, and that deletion of either chemokine alone does not affect the development of airway obliteration.

CCR5, RANTES and CX3CR1 polymorphisms: possible genetic links with acute heart rejection

BACKGROUND

The inflammation response is modulated by the elaborated chemokine-chemokine receptor system, which also plays an important role in the development of acute rejection (AR). In this study, we hypothesized that functional genetic variants of some of these modulatory proteins might influence the outcome of AR.

METHODS

In a retrospective analysis of a cohort of heart transplanted patients (n=158), we examined eight polymorphisms in four genes implicated in this inflammatory process: RANTES, CCR5, CCR2 and CX3CR1. On the basis of timing occurrence, AR episodes (grade>or= 3A) were classified in "early" (0-3 months posttransplantation; EAR) or "late" outcomes (4-12 months posttransplantation; LAR).

RESULTS

The incidences of EAR and LAR were 57.6% and 41%, respectively. Number of LAR episodes was significantly higher in subjects that have already experienced one or more EAR episodes, as compared to subjects that had no EAR (median [25%-75%]: 4 () vs. 1 [1-2.5] respectively; P<0.0001). Statistical univariate analysis showed that none of the mentioned polymorphisms were correlated with EAR or LAR. However, allele-allele association analysis showed that subjects carrying both the CX3CR1 249I allele and CCR5 No-E haplotypes were significantly at lower risk of experiencing EAR (OR=0.2 [95%-CI=0.1-0.5], P=0.001). In contrast subjects carrying both the CCR5 E haplotype and the RANTES -403A allele were significantly at higher risk to develop LAR (OR=8.1 [95%-CI=2.3-28.7], P=0.002).

CONCLUSIONS

This exploratory study in heart transplantation suggests that the outcomes of EAR and LAR episodes may be influenced by genetic variant interactions such as "CX3CR1 249I*CCR5 No-E" and "CCR5 E*RANTES -403A."

Lentiviral Gene Transfer of the Chemokine Antagonist RANTES 9-68 Prolongs Heart Graft Survival

BACKGROUND

Allograft tolerance might be achieved by expressing immunomodulatory proteins through gene therapy. We have evaluated the possibility of promoting significantly allograft survival in a vascularized cardiac allograft model by performing ex vivo gene transfer. We used a lentiviral vector encoding the chemokine antagonist RANTES 9-68 that is capable of competing with native RANTES.

METHODS

The Fisher donor/Lewis recipient rat strain combinations were used and all animals received for the first 5 days posttransplantation a subtherapeutic dose of cyclosporine A (1.5 mg/kg). Ex vivo gene transfer into heart allograft was performed by multiple injections of the SIN.cPPT lentiviral vector, which corresponds to the multiply attenuated, self-inactivating lentivector derived from the human immunodeficiency virus (HIV)-1.

RESULTS

About 6% of the cardiac tissue had integrated lentiviral vector, which closely matches the mean in vivo RANTES antagonist expression of 5% obtained by immunohistochemistry. In vivo RANTES 9-68 expression has significantly prolonged graft survival (median [25%-75%]: 20 [17-26] days), compared to the control 15 ([14-15] days; P=0.0007). Furthermore, hearts transduced with RANTES 9-68 showed a significant (P<0.05) reduction in cell infiltration and intragraft expression of TNF-alpha, IFN-gamma, endogenous RANTES, and TGF-beta.

CONCLUSION

Lentiviral gene transfer of RANTES 9-68 antagonist attenuates significantly the inflammatory response and delays allograft rejection, despite low levels of transduction. Future improvement of heart transduction by lentiviral vectors, as it has been achieved with other vectors, might become an attractive alternative therapy for treating allografts that require sustained gene expression for better organ preservation.

CXCR2/CXCR2 Ligand Biology during Lung Transplant Ischemia-Reperfusion Injury

Lung transplantation is a therapeutic option for a number of end-stage pulmonary disorders. Early lung allograft dysfunction (ischemia-reperfusion injury) continues to be the most common cause of early mortality after lung transplantation and a significant risk factor for the development of bronchiolitis obliterans syndrome. Ischemia-reperfusion injury is characterized histopathologically by lung edema and a neutrophil predominate leukocyte extravasation. The specific mechanism(s) that recruit leukocytes to the lung during post-lung transplantation ischemia-reperfusion injury have not been fully elucidated. Because the ELR+ CXC chemokines are potent neutrophil chemoattractants, we investigated their role during post-lung transplantation ischemic-reperfusion injury. We found elevated levels of multiple ELR+ CXC chemokines in human bronchoalveolar lavage fluid from patients with ischemia-reperfusion injury. Proof of concept studies using a rat orthotopic lung transplantation model of "cold" ischemic-reperfusion injury demonstrated an increase in lung graft neutrophil sequestration and injury. In addition, lung expression of CXCL1, CXCL2/3, and their shared receptor CXCR2 paralleled lung neutrophil infiltration and injury. Importantly, inhibition of CXCR2/CXCR2 ligand interactions in vivo led to a marked reduction in lung neutrophil sequestration and graft injury. Taken together these experiments support the notion that increased expression of ELR+ CXC chemokines and their interaction with CXCR2 plays an important role in the pathogenesis of post-lung transplantation cold ischemia-reperfusion injury.

CXCR2/CXCR2 ligand biological axis impairs alveologenesis during dsRNA-induced lung inflammation in mice

The histologic phenotype of bronchopulmonary dysplasia (BPD) is characterized by decreased alveolization and is preceded by infiltration of activated neutrophils into the lung that can lead to sustained lung injury and potential interruption of normal lung development. Potential pathogens triggering early neutrophil influx include either prenatal or postnatal exposure to bacteria or viruses. Specific mechanisms recruiting neutrophils to the lung and subsequently decreasing alveolization during virus-induced lung inflammation and injury have not been fully elucidated. Because CXC chemokines, such as CXCL1 and CXCL2/3 acting through their putative receptor, CXCR2, are potent neutrophil chemoattractants, the authors investigated their role in dsRNA-induced lung injury and decreased alveolization, in which dsRNA (poly IC) is a well-described synthetic agent mimicking acute viral infection. Intratracheal dsRNA led to significant increases in neutrophil infiltration and lung injury at 72 hours and to decreased alveolization at 5 days after dsRNA exposure in newborn (10 days old) BALB/c mice, when compared with controls treated and not treated with ssRNA (poly C). Expression of CXCL1 and CXCR2 paralleled neutrophil recruitment to the lung and preceded the decrease in alveolization. Inhibition of CXCR2/CXCR2 ligand interaction by pretreating dsRNA-exposed mice with an anti-CXCR2 neutralizing antibody significantly attenuated neutrophil sequestration and lung injury, and preserved normal alveolization. These findings demonstrate that the CXCR2/CXCR2 ligand biologic axis plays an important role during the pathogenesis of dsRNA-induced lung injury and decreased alveolization and may be relevant to the pathogenesis of BPD.

CCR1 antagonists in clinical development

Chemokines (chemotactic cytokines) are a family of low-molecular-weight proteins that direct the cellular migration of leukocytes by binding to and activating the G protein-coupled receptors displayed on the leukocyte cell surface. The inadvertent or excessive generation of chemokines has been associated with the inflammatory component of several disease processes, and consequently, considerable efforts have been made to characterise chemokine/chemokine receptor interactions with the ultimate aim of therapeutic intervention. This review focuses on the biology of CC chemokine receptor 1, which together with its ligands is thought to recruit leukocytes during the progression of rheumatoid arthritis, multiple sclerosis and organ transplant rejection. The developments made in antagonising this receptor and efficacies of these compounds in the clinical setting are also highlighted.

Lung transplantation: opportunities for research and clinical advancement

Lung transplantation is the only definitive therapy for many forms of end-stage lung diseases. However, the success of lung transplantation is limited by many factors: (1) Too few lungs available for transplantation due to limited donors or injury to the donor lung; (2) current methods of preservation of excised lungs do not allow extended periods of time between procurement and implantation; (3) acute graft failure is more common with lungs than other solid organs, thus contributing to poorer short-term survival after lung transplant compared with that for recipients of other organs; (4) lung transplant recipients are particularly vulnerable to pulmonary infections; and (5) chronic allograft dysfunction, manifest by bronchiolitis obliterans syndrome, is frequent and limits long-term survival. Scientific advances may provide significant improvements in the outcome of lung transplantation. The National Heart, Lung, and Blood Institute convened a working group of investigators on June 14-15, 2004, in Bethesda, Maryland, to identify opportunities for scientific advancement in lung transplantation, including basic and clinical research. This workshop provides a framework to identify critical issues related to clinical lung transplantation, and to delineate important areas for productive scientific investigation.

Role of CXCR2/CXCR2 ligands in vascular remodeling during bronchiolitis obliterans syndrome

Angiogenesis and vascular remodeling support fibroproliferative processes; however, no study has addressed the importance of angiogenesis during fibro-obliteration of the allograft airway during bronchiolitis obliterans syndrome (BOS) that occurs after lung transplantation. The ELR(+) CXC chemokines both mediate neutrophil recruitment and promote angiogenesis. Their shared endothelial cell receptor is the G-coupled protein receptor CXC chemokine receptor 2 (CXCR2). We found that elevated levels of multiple ELR(+) CXC chemokines correlated with the presence of BOS. Proof-of-concept studies using a murine model of BOS not only demonstrated an early neutrophil infiltration but also marked vascular remodeling in the tracheal allografts. In addition, tracheal allograft ELR(+) CXC chemokines were persistently expressed even in the absence of significant neutrophil infiltration and were temporally associated with vascular remodeling during fibro-obliteration of the tracheal allograft. Furthermore, in neutralizing studies, treatment with anti-CXCR2 Abs inhibited early neutrophil infiltration and later vascular remodeling, which resulted in the attenuation of murine BOS. A more profound attenuation of fibro-obliteration was seen when CXCR2(-/-) mice received cyclosporin A. This supports the notion that the CXCR2/CXCR2 ligand biological axis has a bimodal function during the course of BOS: early, it is important for neutrophil recruitment and later, during fibro-obliteration, it is important for vascular remodeling independent of neutrophil recruitment.

Community acquired respiratory viral infections after lung transplantation: clinical features and long-term consequences

Community acquired respiratory viruses (CARVs) are increasingly recognized as serious threats to lung transplant recipients. While CARVs such as respiratory syncytial virus, parainfluenza, influenza, and adenovirus usually cause self-limited illnesses in immunocompetent subjects, infections in the transplant recipient can be dramatic. As transplant recipients live longer and diagnostic methods improve, the burden of CARVs will undoubtedly increase. Because of limited therapeutic options, some patients may succumb to CARV infections, while many survivors develop chronic allograft dysfunction. Recognition of this latter phenomenon has implicated CARVs in the pathogenesis of bronchiolitis obliterans.

CXCR2 is critical for dsRNA-induced lung injury: relevance to viral lung infection

BACKGROUND: Respiratory viral infections are characterized by the infiltration of leukocytes, including activated neutrophils into the lung that can lead to sustained lung injury and potentially contribute to chronic lung disease. Specific mechanisms recruiting neutrophils to the lung during virus-induced lung inflammation and injury have not been fully elucidated. Since CXCL1 and CXCL2/3, acting through CXCR2, are potent neutrophil chemoattractants, we investigated their role in dsRNA-induced lung injury, where dsRNA (Poly IC) is a well-described synthetic agent mimicking acute viral infection. METHODS: We used 6-8 week old female BALB/c mice to intratracheally inject either single-stranded (ssRNA) or double-stranded RNA (dsRNA) into the airways. The lungs were then harvested at designated timepoints to characterize the elicited chemokine response and resultant lung injury following dsRNA exposure as demonstrated qualititatively by histopathologic analysis, and quantitatively by FACS, protein, and mRNA analysis of BAL fluid and tissue samples. We then repeated the experiments by first pretreating mice with an anti-PMN or corresponding control antibody, and then subsequently pretreating a separate cohort of mice with an anti-CXCR2 or corresponding control antibody prior to dsRNA exposure. RESULTS: Intratracheal dsRNA led to significant increases in neutrophil infiltration and lung injury in BALB/c mice at 72 h following dsRNA, but not in response to ssRNA (Poly C; control) treatment. Expression of CXCR2 ligands and CXCR2 paralleled neutrophil recruitment to the lung. Neutrophil depletion studies significantly reduced neutrophil infiltration and lung injury in response to dsRNA when mice were pretreated with an anti-PMN monoclonal Ab. Furthermore, inhibition of CXCR2 ligands/CXCR2 interaction by pretreating dsRNA-exposed mice with an anti-CXCR2 neutralizing Ab also significantly attenuated neutrophil sequestration and lung injury. CONCLUSION: These findings demonstrate that CXC chemokine ligand/CXCR2 biological axis is critical during the pathogenesis of dsRNA-induced lung injury relevant to acute viral infections.

Absence of Recipient CCR5 Promotes Early and Increased Allospecific Antibody Responses to Cardiac Allografts

Acute rejection is mediated by T cell infiltration of allografts, but mechanisms mediating the delayed rejection of allografts in chemokine receptor-deficient recipients remain unclear. The rejection of vascularized, MHC-mismatched cardiac allografts by CCR5(-/-) recipients was investigated. Heart grafts from A/J (H-2(a)) donors were rejected by wild-type C57BL/6 (H-2(b)) recipients on day 8-10 posttransplant vs day 8-11 by CCR5(-/-) recipients. When compared with grafts from wild-type recipients, however, significant decreases in CD4(+) and CD8(+) T cells and macrophages were observed in rejecting allografts from CCR5-deficient recipients. These decreases were accompanied by significantly lower numbers of alloreactive T cells developing to IFN-gamma-, but not IL-4-producing cells in the CCR5(-/-) recipients, suggesting suboptimal priming of T cells in the knockout recipients. CCR5 was more prominently expressed on activated CD4(+) than CD8(+) T cells in the spleens of allograft wild-type recipients and on CD4(+) T cells infiltrating the cardiac allografts. Rejecting cardiac allografts from wild-type recipients had low level deposition of C3d that was restricted to the graft vessels. Rejecting allografts from CCR5(-/-) recipients had intense C3d deposition in the vessels as well as on capillaries throughout the graft parenchyma similar to that observed during rejection in donor-sensitized recipients. Titers of donor-reactive Abs in the serum of CCR5(-/-) recipients were almost 20-fold higher than those induced in wild-type recipients, and the high titers appeared as early as day 6 posttransplant. These results suggest dysregulation of alloreactive Ab responses and Ab-mediated cardiac allograft rejection in the absence of recipient CCR5.

Impact of MHC class II incompatibility on localization of mononuclear cell infiltrates to the bronchiolar compartment of orthotopic lung allografts

Chronic pathological changes in transplanted lungs are unique because they center on the airways. We examined the relative role of MHC class I and II antigens in causing bronchial pathology in orthotopic lung transplants to rats maintained on cyclosporin A (CsA). Transplants mismatched for MHC class II antigens had significantly more peri-bronchiolar infiltrates than MHC class I incompatible transplants. No significant increase in infiltrates was found in lung transplants incompatible for MHC class I plus II antigens compared to MHC class II antigens alone. Immunohistochemistry demonstrated that MHC class II antigen expression was confined to macrophages in MHC class I incompatible transplants, but was upregulated on bronchial epithelium in transplants with MHC class II incompatibilities. Vascular endothelium was notably devoid of MHC class II antigen expression in all transplants. However, both peri-bronchial and peri-vascular infiltrates were frequently cuffed by alveolar macrophages and type II pneumocytes that expressed MHC class II antigens. PCR analysis demonstrated that IFN-gamma and regulated on activation, normal T cells expressed and secreted (RANTES) were upregulated in MHC class II incompatible transplants. Thus, MHC class II incompatible orthotopic lung transplants in rats maintained on CsA immunosuppression undergo a bronchiolcentric upregulation of alloantigens.

Immunomonitoring of Renal Transplant Recipients in the Early Posttransplant Period by Sequential Analysis of Chemokine and Chemokine Receptor Gene Expression in Peripheral Blood Mononuclear Cells

INTRODUCTION

We sought to determine whether sequential changes in chemokine ligand/receptor gene expression in the early posttransplant period of human renal allografts can be detected in peripheral blood mononuclear cells (PBMCs) and whether any such changes are predictive of clinical events.

METHODS

Blood samples from 106 renal transplant recipients and 29 donor nephrectomy patients were taken preoperatively and daily for 14 days. Within the study period 22 patients had biopsy-proven acute rejection. From each blood sample PBMCs were separated and gene expression levels for chemokines CCL3, CCL4, CCL5, CXCL10, and their receptors CCR1, CCR5, and CXCR3, were determined using real-time quantitative PCR.

RESULTS

Different gene expression patterns were seen between the rejector and nonrejector groups with decreases in CCL4 and CCR5 expression on days 6 to 8 and increases in CCR1 expression on days 9 and 10 posttransplant. With CXCL10, decreases in expression were seen in the nonrejector group but increases were seen in the rejector group posttransplant. With data aligned to time of rejection diagnosis, statistically significant increases, that preceded the clinical detection of acute rejection were seen in CCR1 and CXCL10 expression. Both their expression levels returned to pretransplant baseline values after successful antirejection therapy.

CONCLUSION

We have demonstrated that changes in chemokine receptor/ligand gene expression by sequential monitoring in PBMCs can be detected in the early posttransplant period. In particular, CCR1 and CXCL10, which showed increased expression prior to rejection and returned to baseline levels with antirejection therapy, may have potential use in immunomonitoring and as predictive factors of rejection prior to its clinical manifestation.

Participation of RANTES and T-Cell Apoptosis in Human Renal Allograft

The aim of this study was to evaluate the serum RANTES (Regulated upon Activation of Normal T cell Expressed and Secreted) levels and the expression of CCR5, as well as the percentage of apoptotic cells, in peripheral T lymphocytes from renal transplanted patients with acute rejection (AR), chronic rejection (CR) or stable evolution (SE). RANTES serum levels were determined by enzyme-linked immunoadsorbent assay and CCR5 expression, as well as the percentage of apoptotic lymphocytes, on a FACScan flow cytometer. After staining with different antibodies, the cells were subjected to three-colour flow cytometric analysis. Data analysis was performed using winmdi 2.5 software. The serum RANTES level and percentages of CCR5/CD4 and CCR5/CD8 T lymphocytes in CR, AR and SE were lower than that in the control group (P <0.05). The level of CD4 and CD8 T lymphocytes in early apoptosis was higher in AR patients than in CR, SE or C groups (P <0.05). In the case of late apoptosis, the percentage of apoptotic/necrotic cells was higher in the CR than AR, SE or C groups (P <0.05). The RANTES serum levels and the percentage of peripheral CCR5 T lymphocytes would not indicate the renal allograft state. The increase of early apoptotic T lymphocytes could be a marker of AR process and could also indicate the initial step in reducing the cytotoxic T lymphocytes, thus favouring the graft evolution.