The XIIIth Banff Conference on Allograft Pathology: The Banff 2015 Heart Meeting Report: Improving Antibody-Mediated Rejection Diagnostics: Strengths, Unmet Needs, and Future Directions.

The 13th Banff Conference on Allograft Pathology was held in Vancouver, British Columbia, Canada from October 5 to 10, 2015. The cardiac session was devoted to current diagnostic issues in heart transplantation with a focus on antibody-mediated rejection (AMR) and small vessel arteriopathy. Specific topics included the strengths and limitations of the current rejection grading system, the central role of microvascular injury in AMR and approaches to semiquantitative assessment of histopathologic and immunophenotypic indicators, the role of AMR in the development of cardiac allograft vasculopathy, the important role of serologic antibody detection in the management of transplant recipients, and the potential application of new molecular approaches to the elucidation of the pathophysiology of AMR and potential for improving the current diagnostic system. Herein we summarize the key points from the presentations, the comprehensive, open and wide-ranging multidisciplinary discussion that was generated, and considerations for future endeavors.

Zinc-mediated reduction of apoptosis in cardiac allografts.

BACKGROUND: Apoptosis is thought to occur during immune-mediated acute rejection of cardiac allografts. In vitro studies have shown that zinc inhibits the activity of the proapoptotic enzyme caspase-3. We hypothesized that ZnCl(2) would reduce acute cardiac rejection in vivo via the blockade of caspase-3-dependent apoptosis. (99m)Tc-labeled annexin V was used to measure apoptosis in cardiac allografts through nuclear imaging. Annexin V binds to phosphatidylserines, which are externalized to the outer membrane of apoptotic cells. METHODS AND RESULTS: Twenty-seven PVG rat hearts were transplanted heterotopically into the abdomen of untreated ACI rats as controls (group 1). Fifteen were scanned and euthanized on postoperative day 4, and 12 were assessed for graft survival. Group 2 and 3 rats (n=15 each) received 1 and 5 mg/kg ZnCl(2) BID IP, respectively. Nine of each of these groups were scanned and euthanized on postoperative day 4, and 6 were studied for allograft survival. Group 4 rats (n=3) received isografts. Region-of-interest analysis demonstrated a dose-dependent reduction in (99m)Tc annexin uptake in ZnCl(2)-treated allografts: 2.43+/-0.37% for group 1, 1. 97+/-0.41% for group 2, 1.21+/-0.47% for group 3, and 0.55+/-0.19% for group 4 (ANOVA, P:=0.001). Graft survival times of 6.4+/-1.7, 9. 3+/-3.0, and 11.5+/-3.4 days for groups 1, 2, and 3, respectively, were also observed (ANOVA, P:=0.001). Caspase-3 activity in the allografts showed a 3.7-fold reduction in group 3 animals compared with group 1 animals (P:=0.004). CONCLUSIONS: Apoptosis that occurs in acute cardiac allograft rejection is reduced with ZnCl(2) in a dose-dependent manner via caspase-3 inhibition.

Feasibility of in vivo intravascular ultrasound tissue characterization in the detection of early vascular transplant rejection.

BACKGROUND: Unprocessed ultrasound radiofrequency (RF) signal analysis has been shown to distinguish different tissue structures more reliably than gray-scale interpretation of conventional ultrasound images. METHODS AND RESULTS: The objective of this study was to test the feasibility of in vivo intravascular ultrasound (IVUS) RF signal analysis in an animal model of allograft rejection. Six cynomolgus monkeys underwent transplantation of 3-cm aortic allograft segments distal to the renal arteries from immunologically mismatched donors. IVUS imaging with a 30-MHz system was performed 84 to 105 days after the operation. RF signals were acquired from cross sections of the recipient and the allograft aortas in real time with a digitizer at 500 MHz with 8-bit resolution. Sixty-five cross sections and 68 regions of interest (31 in host aorta and 37 in allograft) were analyzed in the adventitial layer with a total number of 8568 vectors processed. For each region of interest, a weighted-average attenuation was calculated on the basis of the attenuation and length for each individual vector. Histological examination was performed at every cross section imaged by IVUS. When the gray-scale images of conventional IVUS scored by an independent observer were compared, no distinction between adventitia of the native aorta and allograft was possible. Analysis of the average RF backscatter power also showed no significant difference (70.32+/-3.55 versus 70.72+/-3.38 dB). However, the average attenuation of allografts was significantly lower than that of the host aortas (2.64+/-1.38 versus 4.02+/-1.16 dB/mm, P<0.001). Histology demonstrated a marked adventitial inflammatory response in all allografts, with no inflammation observed in the host aortas. CONCLUSIONS: In vivo IVUS tissue characterization can be performed during routine imaging. In this model of transplant vasculopathy, RF attenuation measurements were more sensitive than visual or quantitative gray-scale analysis.

Tissue characterization of atherosclerotic plaques by intravascular ultrasound radiofrequency signal analysis: an in vitro study of human coronary arteries.

BACKGROUND: Conventional gray-scale images of intravascular ultrasound (IVUS) cannot accurately differentiate histologic subtypes of sonolucent coronary plaques with or without a lipid core. METHODS: We analyzed radiofrequency signals obtained in vitro from 24 regions of interest (ROI) of noncalcified (sonolucent) plaques in 10 atherosclerotic coronary artery specimens pressure-fixed by formalin. Radiofrequency signals were sampled with a 30-MHz IVUS catheter and digitized at 500 MHz in 8-bit resolution. The ROIs were histologically categorized into 12 plaques with a lipid core and 12 plaques without it. Integrated backscatter and statistical parameters of the radiofrequency envelope (mean/SD ratio [MSR], skewness, and kurtosis) within the ROI were calculated offline, and their ability to detect a lipid core was compared with visual analysis of the IVUS video images. In the group with lipid cores, percent area of a lipid core in each ROI was measured in a digitized histologic image by a computerized planimeter. RESULTS: Sensitivity and specificity of MSR, skewness, and kurtosis for lipid core detection were substantially greater than visual video image analysis (83.3% and 91.7%, 100% and 91.7%, 100% and 91.7% vs 53.3% and 71.7%). Furthermore, the parameters of integrated backscatter, MSR, skewness, and kurtosis were significantly correlated to percent of core area (r = -0.64, -0.73, 0.78, and 0.63, respectively; P<.05). CONCLUSIONS: Compared with IVUS video images, the parameters of radiofrequency signal analysis may be used to aid in more accurate detection and quantitative evaluation of a lipid core, which is one of the major factors of a vulnerable coronary plaque.

Infectious mononucleosis. Diagnosis by in situ hybridization in two cases with atypical features.

Two cases of infectious mononucleosis are reported in which in situ hybridization studies were of use to distinguish this disorder from non-Hodgkin's lymphoma. One patient was an 80-year-old man with a tonsillar mass that histologically resembled non-Hodgkin's lymphoma and, on fixed tissue immunohistochemistry, appeared to contain a population of cells anomalously coexpressing the B-cell marker L26 and the T-cell marker Leu-22, suggesting diffuse large-cell non-Hodgkin's lymphoma. The second patient was a 43-year-old woman with inguinal lymphadenopathy that, on histologic examination, also mimicked diffuse large-cell lymphoma. In situ hybridization studies for Epstein-Barr virus revealed both cases to possess EBV DNA in a pattern characteristic of infectious mononucleosis. In addition, in situ hybridization studies for immunoglobulin light-chain mRNA demonstrated a polyclonal pattern of kappa and lambda mRNA expression. This report demonstrates the utility of the in situ hybridization technique as an adjunct to routine diagnosis.

Spindle cell neoplasms of lymph nodes of probable reticulum cell lineage. True reticulum cell sarcoma?

Primary spindle cell neoplasms involving hematolymphoid organs are extremely rare. We present four cases of spindle cell neoplasms of unusual phenotype arising within lymph nodes. Two of the four cases showed morphologic and immunophenotypic features suggestive of interdigitating reticulum cell lineage; these cases expressed several macrophage antigens and S-100 protein but not CD1. The other two cases showed evidence suggestive of dendritic reticulum cell lineage. Both cases expressed HLA-DR, several macrophage antigens, complement receptors C3b and C3d; one case expressed R4/23; both showed the presence of desmosomes on ultrastructural examination. A germline configuration for the immunoglobulin heavy chain and beta-T--cell receptor genes was detected in all four cases. Of the two patients in the first group, one had local recurrence of tumor; the other died of widespread metastases. Of the two patients in the second group, both are alive and well at 12 and 27 months follow-up, respectively.

The role of respiratory epithelium in a rat model of obliterative airway disease.

BACKGROUND: The etiology and pathogenesis of obliterative bronchiolitis after lung transplantation remain to be fully elucidated. Using a rat model of heterotopically transplanted trachea grafts, we have examined the role airway epithelium plays in obliterative airway disease (OAD). METHODS: Rat trachea isografts were denuded of epithelium by protease digestion. Grafts were inoculated either with or without native airway epithelial cells and transplanted into the omentum of recipient animals. RESULTS: Airway epithelium removal resulted in OAD in denuded isogeneic trachea grafts. Reseeding of the denuded grafts with epithelial cells significantly reduced airway obliteration from 78% to 22% luminal occlusion. CONCLUSIONS: Non-immune-mediated injury will cause OAD, and epithelial cell replacement in denuded isografts can significantly reduce the fibrotic progression of the disease.

Viral serine proteinase inhibitor (SERP-1) effectively decreases the incidence of graft vasculopathy in heterotopic heart allografts.

BACKGROUND: Graft vascular disease (GVD) is the most common cause of late graft failure in solid organ transplantation. Recent studies have shown good efficacy of a novel nontoxic viral-derived serine proteinase inhibitor (SERP-1) in preventing postangioplasty restenosis. The current study was designed to test whether short-term treatment with SERP-1 was effective in reducing the incidence of GVD in a solid organ transplant. METHODS: Piebald-Virol-Glaxo (PVG) donor hearts were transplanted into August-Copenhagen-Irish (ACI) recipients and observed for 90 days. All recipients (n=60) were treated with microemulsion cyclosporine (CsA) 7.5 mg/kg per gavage from day 0 to day 9 and randomized into 4 groups. SERP-1 was given intravenously. Group I received CsA monotherapy; group II, CsA+SERP-1 1 ng/g (postoperative days 0-9); group III, CsA+SERP-1 10 ng/g (postoperative days 0-9); and group IV, CsA+SERP-1 10 ng/g (postoperative days 0-9, 30, and 60). Graft viability was monitored by palpation, and GVD was assessed by morphometry. RESULTS: Two animals in group I rejected their allografts on postoperative days 7 and 14, 1 animal in group II rejected the allograft (postoperative day 31), and none in group III and IV rejected the allografts. At 90 days postoperative, 23.8% of all coronary vessels showed evidence of GVD in group I, 18.4% in group II, 12.9% in group III, and 11.8% in group IV. The difference in incidence of GVD was significant between groups I and III (P<0.05) and groups I and IV (P<0.05). Treatment with SERP-1 was well tolerated, and all animals regained weight quickly postsurgery. CONCLUSIONS: Treatment of allograft recipients with SERP-1 in combination with CsA early after transplantation significantly decreases the incidence of GVD when compared to grafts treated with only CsA. These results demonstrate the clinical potential for this novel serine protease inhibitor to prevent GVD in solid organ transplantation.

Prolonged inhibition of obliterative airway disease in murine tracheal allografts by brief treatment with anti-leukocyte function-associated antigen-1 (CD11a) monoclonal antibody.

BACKGROUND: We have previously shown that anti-leukocyte function-associated antigen (LFA)-1 (CD11a) monoclonal antibody (mAb) prevents acute rejection and produces donor-specific unresponsiveness in murine recipients of heterotopic heart allografts. Here, we investigate the ability of this mAb to prevent the development of obliterative airway disease (OAD) in murine recipients of tracheal allografts. METHODS AND RESULTS: BALB/c tracheae were heterotopically transplanted into C3H mice. OAD developed by day 28 after transplantation and was characterized histologically by a loss of epithelial cell coverage and luminal obliteration of the tracheal allograft with a proliferation of fibrogenic mesenchymal cells, which is a lesion comparable to obliterative bronchiolitis in human lung transplant recipients. Monotherapy with anti-LFA-1 mAb preserved graft epithelium, prevented the development of OAD, and maintained unresponsiveness to donor antigen for more than 42 days after the final mAb administration. CONCLUSION: These findings suggest the potential for anti-LFA-1 mAb therapy to suppress both acute and chronic rejection in clinical lung transplantation.

Rapamycin inhibits development of obliterative airway disease in a murine heterotopic airway transplant model.

Obliterative bronchiolitis is the major cause of long-term morbidity and mortality in heart-lung and lung transplant recipients. There is presently no completely effective therapy for the treatment of obliterative bronchiolitis. We have examined the effects of rapamycin (RPM) on the development of obliterative airway disease in murine recipients of heterotopically transplanted allograft tracheas. In this model, an untreated allograft develops almost complete occlusion of the airway lumen with fibroblastic tissue and collagen scar by day 28 after transplantation. RPM administered intraperitoneally at the time of transplantation or even as late as day 14 after transplantation markedly inhibited obliteration of the airway lumen by fibroblastic tissue. Also, RPM significantly inhibited infiltration of the graft by macrophages. In the RPM-treated animals, the airway was reconstituted with an attenuated squamous epithelium rather than a normal pseudostratified epithelium. No adverse side effects were observed with RPM doses up to 12 mg/kg/ day. These findings suggest a potential role for RPM, perhaps in combination with cyclosporine, in preventing and treating obliterative bronchiolitis in heart-lung and lung allograft recipients.

Immunosuppressive therapies for the prevention and treatment of obliterative airway disease in heterotopic rat trachea allografts.

BACKGROUND: Obliterative bronchiolitis remains a major long-term complication after lung transplantation. Using a reproducible model of heterotopically transplanted rat tracheas, this study examined the role of several novel immunosuppresive compounds to prevent and reverse obliterative airway disease in these animals. METHODS: Brown Norway rat trachea were transplanted into the greater omentum of Lewis (allografts) or Brown Norway (isografts) animals. Recipient animals were treated with rapamycin, cyclosporine, 15-deoxyspergulin, mycophenolate mofetil, or leflunomide from day 0, 7, or 14 until day of graft removal, either day 28 or 50. Trachea segments were evaluated for degree of lumenal occlusion, as well as percent and type of lumen epithelial cell coverage. RESULTS: All untreated allografted tracheas obliterated completely, although isografts appeared patent with normal respiratory epithelium when they were removed. Leflunomide, rapamycin, and cyclosporine effectively prevented obliteration when treatment was initiated at day 0, with rapamycin showing continued efficacy when initiated as late as day 7. 15-deoxyspergulin and mycophenolate mofetil failed to consistently inhibit obliteration with any treatment schedule. An inverse correlation was found between epithelial coverage and degree of obliteration, and was especially pronounced in grafts from cyclosporine-treated animals. CONCLUSIONS: Immunosuppressive drug therapy will inhibit airway obliteration, but efficacy sharply diminishes if initiation of treatment is delayed. Efficacy also varies among immunosuppressive compounds, and results indicate those drugs that enable epithelial regrowth most effectively inhibit airway graft obliteration.

Epithelial re-growth is associated with inhibition of obliterative airway disease in orthotopic tracheal allografts in non-immunosuppressed rats.

BACKGROUND: Because epithelial cells are targets of alloimmune injury leading ultimately to airway obliteration, we tested whether epithelial re-growth could prevent obliterative airway disease (OAD) in orthotopic tracheal allografts. METHODS: Brown Norway tracheal segments were orthotopically transplanted into nonimmunosuppressed Lewis rats. Allografts were removed on days 2-10 (n=13), 30 (n=4), and 60 (n=5) for histology, computerized morphometry (obliteration), and immunohistochemical detection of mononuclear cells, smooth muscle alpha-actin, and tissue phenotype. Normal tracheas, host tracheas, and heterotopically transplanted allografts served as controls. RESULTS: Orthotopic allografts removed on days 2-10 exhibited epithelial damage and re-growth and mononuclear cell infiltration. On days 30 and 60, partially ciliated cuboidal or attenuated epithelium completely covered the lumen. Although mononuclear cells declined, numerous T cells with a high CD4/CD8 ratio were found in the epithelium till day 60. Orthotopic allograft epithelium expressed donor phenotype on day 7, but recipient phenotype on days 30 and 60. Despite subepithelial alpha-actin positive myofibroblast proliferation, obliteration did not progress from day 7 to 30 and 60 (35, 30, and 33%, respectively). Although more than in normal or host tracheas, the obliteration in orthotopic allografts on days 30 and 60 was significantly less (P<0.001) than in heterotopic allografts. CONCLUSIONS: We describe, for the first time, longterm patency of fully histoincompatible orthotopic tracheal allografts in nonimmunosuppressed rats. Despite acute alloimmune injury and induction of myofibroblast proliferation, epithelial re-growth from the host limited the progression of OAD, thus emphasizing the role of epithelium in the control of airway obliteration.

Potentiation of immunosuppressive efficacy by combining the novel leflunomide analog, HMR 279, with microemulsion cyclosporine in a rat lung transplant model.

BACKGROUND: The novel leflunomide (LFM) analog, HMR 279, potentiates the immunosuppressive efficacy of microemulsion cyclosporine (Neoral) in rodent heart transplantation. The present study was designed to evaluate the immunosuppressive efficacy of this combination in comparison to the combination of Neoral and LFM in a stringent allogeneic rodent lung transplant model. METHODS: Donor lungs from Brown Norway rats were implanted into Lewis recipients and were followed for 21 days. Postoperative monitoring included daily weight assessment, chest radiographs, drug trough levels measured by high-performance liquid chromatography (LFM/HMR 279) and high-performance liquid chromatography/mass spectrometry (Neoral), and blinded histology assessment of the transplanted lung on the day of death based on the International Society for Heart and Lung Transplantation working formulation. Untreated lung recipients served as controls (group I, n=5). Rats were assigned to the following treatment groups: II, 7.5 mg/kg/day Neoral (n=6); III, 10 mg/kg/day LFM (n=6); IV, 10 mg/kg/day HMR 279 (n=6); V, 10 mg/kg/day LFM plus 7.5 mg/kg/day Neoral given simultaneously (n=13); and VI, 10 mg/kg/day HMR 279 plus 7.5 mg/kg/day Neoral given simultaneously (n=6). Drugs were given daily by oral gavage. RESULTS: All rats except for one in the HMR 279 monotherapy group survived the follow-up period. The chest radiographs in the control, LFM, and HMR 279 monotherapy groups showed moderate to complete opacification of the left chest by postoperative day 7 (controls) and day 14 (LFM, 279). At postoperative day 21, the Neoral monotherapy and the combination groups showed no signs of opacification in the radiographs. Combination therapies of Neoral plus HMR 279 or Neoral plus LFM were most successful in preventing histologic allograft rejection. Combining Neoral and HMR 279 resulted in a significant decrease in the cyclosporine trough levels. Co-administration of LFM plus Neoral resulted in significantly higher LFM trough levels when compared to LFM monotherapy. Of all treatments studied, the combination of HMR 279 plus Neoral was tolerated best as assessed by percentage of weight change. CONCLUSIONS: This study showed for the first time in a stringent rodent lung transplant model that combined treatment of LFM or HMR 279 plus Neoral potentiates the immunosuppressive efficacies of these drugs and successfully prevents allograft rejection.

Prevention of acute allograft rejection in nonhuman primate lung transplant recipients: induction with chimeric anti-interleukin-2 receptor monoclonal antibody improves the tolerability and potentiates the immunosuppressive activity of a regimen using low doses of both microemulsion cyclosporine and 40-O-(2-hydroxyethyl)-rapamycin.

BACKGROUND: In previous studies of cynomolgus monkey lung allograft recipients, we demonstrated significant immunosuppressive efficacy but reduced tolerability after combined treatment with high doses of microemulsion cyclosporine (CsA) and SDZ RAD (40-O-(2-hydroxyethyl)-rapamycin). The current study was designed to compare efficacy and tolerability of a combination of low-dose CsA and high-dose SDZ RAD (CTL group) to triple therapy using the chimeric anti-interleukin-2 (IL-2) receptor (CD25) monoclonal antibody (mAb) basiliximab (anti-IL-2 receptor mAb) for induction therapy (basiliximab: 5 mg intravenously on days 0 and 4) plus low-dose CsA and low-dose SDZ RAD for maintenance immunosuppression (CD25 group). CsA and anti-IL-2 receptor mAb are drugs that reduce cytokine synthesis and block IL-2-mediated lymphocyte stimulation, respectively. SDZ RAD blocks lymphocyte stimulation by other cytokines (e.g., IL-15) that are not inhibited by anti-IL-2 receptor mAb. METHODS: Twelve unilateral lung transplants were performed. Recipients were observed for 49 days by daily weight assessment, hemograms, blood chemistries, radiographs, and lung biopsies. Monkeys were euthanized before day 49 in the event of excessive weight loss (>25%) or organ failure. Target CsA trough levels were 100-200 ng/ml. Target SDZ RAD trough levels in the CTL group (no mAb) were 20-40 ng/ml, and 10-20 ng/ml in the CD25 group. RESULTS: None of the monkeys in the CD25 group needed to be euthanized early due to signs of drug toxicity. In contrast, four monkeys in the CTL group were sacrificed on days 28-35 as a result of excessive weight loss (n=3) and renal functional impairment (n=1). Three recipients in the CD25 group were euthanized on days 36, 38, and 46 as a result of persistent high fever associated with severe rejection. The median animal survival in the CTL group was 32 vs. 46 days in the CD25 group (P<0.04). The only two long-term survivors in the CTL group showed moderate rejection at day 49. The median rejection scores at day 14 (A0) and day 28 (A2) were identical in the two groups, despite the fact that the mean SDZ RAD trough level was significantly lower in the CD25 group (CTL: 38+/-3 ng/ml, CD25: 18+/-2 ng/ml, P<0.0001). After basiliximab levels fell below the minimum therapeutic level (1 mg/ml) on day 28, the median rejection score at day 49 increased to A4 in the CD25 group. CONCLUSION: This is the first study to combine an anti-IL-2 receptor mAb with a drug from the rapamycin class plus CsA. Our study shows that induction therapy with basiliximab enabled SDZ RAD blood levels to be significantly reduced, which led to improved tolerability without the penalty of increased rejection.

Sirolimus (rapamycin) halts and reverses progression of allograft vascular disease in non-human primates.

BACKGROUND: Current immunosuppressive protocols fail to prevent chronic rejection often manifested as graft vascular disease (GVD) in solid organ transplant recipients. Several new immunosuppressants including sirolimus, a dual function growth factor antagonist, have been discovered, but studies of drug efficacy have been hampered by the lack of a model of GVD in primates, as a prelude to clinical trials. As described earlier, we have developed a novel non-human primate model of GVD where progression of GVD is quantified by intravascular ultrasound (IVUS). METHODS: Twelve cynomolgus monkeys underwent aortic transplantation from blood group compatible but mixed lymphocyte reaction-mismatched donors. To allow the development of GVD in the allograft, no treatment was administered for the first 6 weeks. Six monkeys were treated orally with sirolimus from day 45 after transplantation to day 105. RESULTS: Progression of GVD measured as change in intimal area from day 42 to 105 was halted in sirolimus-treated monkeys compared to untreated monkeys (P<0.001, general linear model). On day 105, the intimal area +/- SEM was 3.7+/-1.0 and 6.4+/-0.5 mm2, respectively (P<0.05, t test). The magnitude of allograft intimal area on day 105 correlated inversely with sirolimus trough levels (R2=0.67, P<0.05). Regression of the intimal area was seen in four of six sirolimus-treated monkeys, which was significantly different from the untreated monkeys (P<0.05). CONCLUSIONS: Our results in the first non-human primate model of GVD showed that treatment with sirolimus not only halted the progression of preexisting GVD but also was associated with partial regression. Sirolimus trough blood levels were correlated with efficacy. Therefore, sirolimus has the potential to control clinical chronic allograft rejection.

Obliterative airway disease after heterotopic tracheal xenotransplantation: pathogenesis and prevention using new immunosuppressive agents.

BACKGROUND: The purpose of this study was to investigate whether obliterative bronchiolitis might occur after xenogenic pulmonary transplantation. A model for obliterative airway disease (OAD) after tracheal allograft transplantation in the rat undergoes tracheal obliteration with histologic features characteristic of obliterative bronchiolitis in human lung transplant recipients. Using this model, the pathogenesis of OAD and its prevention with immunosuppressive drugs was studied in rat recipients of hamster tracheal grafts. METHODS: Tracheae from 30 hamsters (xenografts) or 23 Brown-Norway rats (allografts) were implanted and wrapped in the greater omentum of untreated Lewis rats. The grafts were removed on day 1, 3, 7, 14, 21, or 28 after transplantation and stained with hematoxylin and eosin and Masson's trichrome and by immunohistochemistry and immunofluorescence (IFL) techniques. In addition, 25 recipients were treated with cyclosporine (CsA, 10 mg/kg p.o.), leflunomide (LFM, 20 mg/kg p.o.), or rapamycin (RPM, 6 mg/kg i.p.) for 14 or 21 days (5 animals per treatment group). Visual and morphometric analyses were used to evaluate the extent of airway obliteration, luminal coverage by respiratory or flattened cuboidal epithelium, and extent and density of peritracheal cellular inflammation. RESULTS: In all xenografts, a neutrophilic infiltration of the mucosa and submucosa was observed from day 1 until day 14 and was associated with complete loss of tracheal epithelium by day 14. A marked peritracheal mononuclear cellular infiltrate mixed with plasma cells and eosinophils was seen on days 7 and 14. Both the extent of peritracheal inflammation and the density of the mononuclear cell infiltrate were significantly increased in xenograft tracheae when compared with the allografts. Tracheal obliteration began on day 14 and reached a maximum of 43% on day 21 with evidence of intraluminal fibrosis. In contrast to IFL of allografts, IFL of xenografts demonstrated marked deposition of rat immunoglobulin in the peritracheal tissue on days 7 and 14. The effects of treatment with immunosuppressive drugs on tracheal graft narrowing and protection of respiratory epithelium were as follows: After 14 days of treatment, the percentage of tracheal graft narrowing was 12%, 23%, and 19% in the no treatment, CsA, and LFM groups, respectively; the percentage of respiratory epithelium at 14 days was 0%, 21%, and 95%. After 21 days of treatment, the percentage of tracheal graft narrowing was 43%, 49%, 12%, and 5% for the no treatment, CsA, LFM, and RPM groups, respectively; the percentage of respiratory epithelium at 21 days was 0%, 39%, 86%, and 0%. Using computerized morphometry, the extent and densities of the peritracheal cellular infiltrates were significantly reduced in LFM- and CsA-treated groups when compared with untreated xenograft controls. LFM and RPM, but not CsA, significantly reduced the degree of luminal obliteration compared with no treatment (P<0.05). LFM and, to a lesser extent, CsA were able to prevent the loss of normal respiratory epithelium. Analysis by IFL revealed a marked decrease in rat immunoglobulin deposition in xenografts from LFM- and RPM-treated groups compared with xenografts from CsA-treated or untreated rats. CONCLUSIONS: (1) OAD occurs not only after tracheal allotransplantation but also after xenotransplantation. (2) Subepithelial infiltration of neutrophils and the appearance of plasma cells and eosinophils in the peritracheal infiltrates distinguished the histology of rejected xenografts from allografts. (3) Antibody deposition was detected by IFL only in xenografts. (4) Treatment with LFM or RPM significantly decreased the severity of luminal obliteration. Importantly, LFM also prevented the loss of respiratory epithelium.

Coadministration of neoral and the novel rapamycin analog, SDZ RAD, to rat lung allograft recipients: potentiation of immunosuppressive efficacy and improvement of tolerability of staggered versus simultaneous treatment.

BACKGROUND: Neoral and rapamycin derivative (RAD) have complementary mechanisms for inhibition of lymphocyte activation and are substrates for the same pathways of drug metabolism. Therefore, we investigated treatment regimens designed to minimize pharmacokinetic interactions and to potentiate immunosuppressive efficacy in a highly stringent rat lung allograft model. METHODS: Lewis recipients of Brown Norway lungs received the following daily oral doses: (A) RAD at 2.5 mg/kg (n=9); (B) Neoral at 7.5 mg/kg (n=8); (C) RAD at 2.5 mg/kg + Neoral at 7.5 mg/kg simultaneously (n=8); or (D) RAD at 2.5 mg/kg + Neoral at 7.5 mg/kg (n=6) staggered 6 hr apart. Rats were assessed by daily weights, chest radiographs, drug trough levels (high-performance liquid chromatography/mass spectrometry), and blinded scoring of graft histology at death (day 21). RESULTS: Radiographs were completely opacified in all grafts of control and RAD monotherapy groups on days 7 and 14, respectively. Grafts were mildly opacified (Neoral monotherapy) and completely clear (both RAD + Neoral groups) on day 21. Simultaneous or staggered combined treatment dramatically reduced histologic rejection compared with treatment with either drug alone. Simultaneous treatment caused poor tolerability (poor grooming, lethargy) and significantly higher day-14 RAD and cyclosporine (CsA) trough levels (49+/-5 and 638+/-106 ng/ml; P<0.04) than in the staggered group (28+/-3 and 318+/-25 ng/ml) in which all animals were clinically normal. RAD and CsA day-14 trough levels in the staggered group were the same or lower than trough levels in animals treated with either drug alone (RAD 27+/-3/Neoral 815+/-67 ng/ml). CONCLUSIONS: (1) Administration of RAD + Neoral suppressed lung rejection more effectively than treatment with either drug alone. (2) Trough levels did not differ between monotherapy and staggered combination therapy for RAD but were lower for CsA. These results suggested that pharmacological, rather than pharmacokinetic, interactions between the parent drugs were responsible for the potentiation of immunosuppression when these drugs were coadministered. 3) Staggered administration of RAD+Neoral avoided the pharmacokinetic interactions that caused the elevated drug blood levels and poor tolerability caused by simultaneous administration. Thus, we could potentiate efficacy and improve tolerability by staggering administration of RAD and Neoral.

Combined immunosuppression with cyclosporine (neoral) and SDZ RAD in non-human primate lung transplantation: systematic pharmacokinetic-based trials to improve efficacy and tolerability.

BACKGROUND: We studied the efficacy and tolerability of combined immunosuppressive therapy with cyclosporine A microemulsion (Neoral) plus the macrolide SDZ RAD 40-0 (2-hydroxyethyl) rapamycin (RAD) in a stringent cynomolgus monkey lung graft model in comparison with cyclosporine or SDZ RAD monotherapy. METHODS: Thirty-nine cynomolgus monkeys received mixed lymphocyte reaction (MLR) mismatched unilateral lung transplants. Immunosuppressants were administered orally as single daily doses. The observation period was 28 days and follow-up included serial trough blood drug concentrations measured by high performance liquid chromatography/mass spectrometry, blood analyses, chest radiographs, open lung biopsies, as well as tissue drug concentrations and graft histology at necropsy. RESULTS: Graft biopsies in monkeys treated with vehicle (n=4), Neoral (day 1-7: 150 mg/kg/day; day 8-28: 100 mg/kg/day; n=6; mean +/- SE trough level (MTL): 292+/-17 ng/ml) or SDZ RAD monotherapy (1.5 mg/kg/day; n=6; MTL: 15+/-1 ng/ml) showed severe rejection. Coadministration in two transplant monkeys of Neoral (150/100 mg/kg/day) and SDZ RAD (1.5 mg/kg/day) caused their early death. In both animals, SDZ RAD blood levels were more than 5-fold higher than under monotherapy (MTL: 82+/-18 ng/ml). Simultaneous administration (n=6) of Neoral (150/100 mg/kg/day; MTL: 217+/-16 ng/ml) and SDZ RAD (0.3 mg/kg/day; MTL: 24+/-2 ng/ml) improved graft outcome (mild rejection). Side effects included renal failure (n=2) and seizures (n=1). Three monkeys survived to day 28. In this group the MTL for cyclosporin was 143+/-13 and for RAD 38+/-3. Staggered treatment completely prevented rejection in four of six grafts. However, five of six monkeys had moderate to severe diarrhea. In a concentration-controlled trial of simultaneously administered Neoral and SDZ RAD in transplant monkeys (target SDZ RAD MTL: 20-40 ng/ml; cyclosporine MTL: 100-200 ng/ml) all six monkeys survived with improved drug tolerability and an average biopsy score of mild rejection. CONCLUSION: Combination of orally administered SDZ RAD and Neoral showed excellent immunosuppressive efficacy in a stringent lung transplant model. The drug interaction and the narrow therapeutic index of this drug combination required careful dose adjustments to optimize tolerability and efficacy.

Pseudomalignant ulcerative change of the gastrointestinal tract.

The occurrence of pseudomalignant ulcerative change in seven specimens from the colon and rectum of six patients is described. In all cases, there was surface ulceration of a polypoid lesion which contained granulation tissue and acute and chronic inflammation. There was an underlying inflammatory pseudopolyp in four lesions, a juvenile polyp in one lesion, an adenomatous polyp in one lesion, and a benign retention polyp in one lesion. Within the stroma of all cases were numerous atypical cells that mimicked a malignant neoplasm. The atypical cells expressed vimentin in immunohistochemical studies; no expression of keratins, leukocyte common antigen, factor VIII, Ulex europaeus, carcinoembryonic antigen, actin, or desmin was found. Recognition of this lesion is important, as confusion with carcinoma, lymphoma, sarcoma, or a viral infection may easily occur.

Infantile histiocytoid cardiomyopathy--myocardial or conduction system hamartoma: what is the cell type involved?

Primary myocardial diseases in the pediatric age group encompass a variety of metabolic, infectious, congenital, and acquired disorders, one of which is "histiocytoid cardiomyopathy." We describe clinical and pathologic features in two infants. Autopsy findings in the first case were consistent with sudden cardiac death. The second infant has survived for 2 years on antiarrhythmic therapy with amiodarone. Microscopically, cells with vacuolated to granular cytoplasm were grouped in fascicles, imparting a pseudonodular appearance, but following a distribution reminiscent of conduction fibers. Ultrastructurally, the cells lack a T-tubule system, possess scattered lipid droplets and desmosomes rather than side-to-side junctions, and contain leptomeric fibrils that predominantly marginate to the cell periphery without sarcomeres. Immunostaining of paraffin-embedded tissue reveals perimembranous immunoreactivity for muscle-specific actin, but not for the histiocytic markers CD68 (KP1) and lysozyme. Immunohistochemistry may be a practical alternative when tissue is not saved for electron microscopy. The clinical and pathologic features of this disorder in light of the current literature suggest that it may be hamartoma, possibly of conduction system origin.