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Biomedical subjects

Shane M Meehan

Publications and source records attributed to Shane M Meehan.

11 recordsLinked to original sources
PubMed2006

Nephron segment localization of polyoma virus large T antigen in renal allografts.

This study uses CD10 and epithelial membrane antigen (EMA) as respective proximal and distal tubular segment markers to localize polyoma virus replicative activity, as determined by large T antigen (TAg) expression, in allograft polyoma virus nephropathy (PVN). Sixteen biopsies and 2 nephrectomy specimens with PVN had serial 2-mum paraffin sections stained using monoclonal antibodies to polyoma virus TAg by immunoperoxidase with diaminobenzidine as chromogen. A second immunolabeling step used CD10 as a proximal nephron marker or EMA as a distal tubular marker, and alkaline phosphatase with fast red as chromogen. BK viral DNA was detected in blood in 16 of 18 tested. Fourteen of 16 had cortex and medulla, and 2 had cortex only in the biopsy sample. Fourteen (100%) of 14 had double-positive EMA and TAg expression (EMA+TAg+) in medullary collecting ducts. T antigen was evident in loops of Henle in nephrectomies. Thirteen (81.3%) of 16 had EMA+TAg+, and 10 (62.5%) of 16 had CD10+TAg+ cortical tubular segments. CD10+TAg+ cells were observed in the parietal epithelium of Bowman's capsule in 3 biopsies (18.75%). T antigen was observed in 5.1% of CD10+ tubular profiles compared with 21% of EMA+ profiles in renal cortex (P < .0001). Polyoma virus TAg was observed in medullary collecting ducts, in distal and proximal cortical tubules, and in Bowman's capsule, in decreasing order of frequency. Loops of Henle also had TAg. This distribution suggests potential for an ascending route of infection of allograft tubules in PVN.

Adult↗
PubMed2005

Implications of immunohistochemical detection of C4d along peritubular capillaries in late acute renal allograft rejection.

BACKGROUND: Immunohistochemical detection of the C4d complement product along peritubular capillaries (PC) may indicate humoral rejection of renal allografts. We examined the frequency of PC C4d expression in renal-allograft biopsies with acute rejection (AR) arising more than 6 months after transplantation and the impact of this finding. METHODS: C4d was detected by immunoperoxidase in 2-micron paraffin sections of consecutive biopsies obtained over a 3-year period. The extent was classified as diffuse (> or =50% PC C4d+), focal (<50% C4d+), and negative (C4d-). Clinical data were obtained by retrospective chart review. Fifty-five AR episodes with Banff 97 types 1A (n = 13), 1B (n = 26), 2A (n = 11), 2B (n = 3), and 3 (n = 2) met inclusion criteria. RESULTS: PC C4d expression was diffuse in 23 (42%), focal in 9 (16%), and negative in 23 (42%) biopsies. AR episodes with focal and diffuse C4d expression had higher proportionate elevation of serum creatinine at biopsy and 4 weeks after diagnosis (P< or =0.05). Biopsies with diffuse PC C4d had interstitial hemorrhage (56.5%) and plasmacytic infiltrates (52%) more frequently than C4d- biopsies (22% and 16%), P = 0.02, but had no other distinctive histologic features. Graft loss was greater in diffuse (65%) compared with focal C4d+ (33%) and C4d- (33%) groups 1 year after diagnosis, P = 0.03. Other clinical and pathologic parameters did not differ significantly, including treatment received for AR. CONCLUSION: Evidence of acute cellular with occult humoral rejection is identified in more than 40% of late AR episodes. Late acute humoral rejection may be associated with interstitial hemorrhage and plasma cells and contributes significantly to graft loss.

Biopsy↗
PubMed2005

Polyoma virus infection of renal allografts: relationships of the distribution of viral infection, tubulointerstitial inflammation, and fibrosis suggesting viral interstitial nephritis in untreated disease.

Whether polyoma virus (PV) infection of renal allografts induces an antiviral or antigraft immune reaction is unclear. By examination of the relationships of tubular PV to graft inflammation and scarring, this study sought histological evidence of viral interstitial nephritis in allograft biopsies with untreated PV infection and compared the inflammatory indices to controls with acute rejection (AR). Morphological features including viral cytopathic changes (VCCs) and modified Banff 97 histological indices were evaluated in sections of 28 diagnostic biopsies from a group of patients receiving prednisone, tacrolimus, and mycophenolate mofetil at constant dosage before biopsy. Two-micrometer paraffin sections were stained for PV large T antigen (TAg) and for C4d, by immunohistochemistry. Tubular profiles with 1 or more nuclei expressing TAg per x200 field were scored using an interval scale (0-10; none to 91-100%) by 2 observers. Controls with AR (n = 38, TAg negative) were matched for time after transplantation and severity of Banff 97 interstitial inflammation (i) and tubulitis (t) scores. Median t scores for tubules with VCC or TAg or both exceeded scores for tubules without VCC or TAg (3 versus 0, P = .001). Tubular TAg score correlated with i score (r = 0.58, P < .01) and sum ct + ci score (r = 0.61, P < .001). Atrophic tubules in scars had persistent VCC and/or TAg. Interstitial plasma cells (75% versus 21%) and neutrophils (32% versus 0%) were more frequent, and interstitial fibrosis was more severe (ci >1 in 54% versus 21%) in polyoma virus nephropathy (PVN) than in the group with AR (P < .01). Intimal arteritis (0% versus 35.7%), peritubular capillary C4d (0% versus 47.4%), and interstitial hemorrhage (4% versus 37%) were almost exclusively found in AR (P < .01). Tubular inflammation in untreated PVN involves infected tubular profiles with greater severity than those without evidence of infection. The extent of tubular PV infection is proportional to interstitial inflammation and scarring. Tubulointerstitial inflammation in PV infection has significant qualitative differences from AR. Observations in these examples of untreated PVN suggest that the allograft inflammatory reaction may exhibit features of viral tubulointerstitial nephritis distinct from AR.

Biopsy↗
PubMed2004

Fabry disease: renal involvement limited to podocyte pathology and proteinuria in a septuagenarian cardiac variant. Pathologic and therapeutic implications.

In men with classical Fabry disease (alpha-galactosidase A [alpha-Gal A] deficiency), kidney failure occurs as early as the second decade of life. In contrast, men with the mild "cardiac variant" have late-onset cardiac involvement and proteinuria but usually do not have renal failure. To investigate the nature of renal involvement in the cardiac variant of Fabry disease, the renal function and morphology were assessed in a 75-year-old affected man. He had mild congestive heart failure, a reduced left ventricular ejection fraction, and hypercholesterolemia but lacked the classical Fabry disease manifestations, including angiokeratoma, acroparesthesias, corneal and lenticular opacities, and hypohidrosis. At age 75 years, he had significant proteinuria, and mildly decreased renal function (serum creatinine, 1.8 mg/dL [159 micromol/L]), presumably secondary to hypertensive arteriosclerosis. He had about 4% residual alpha-Gal A activity in leukocytes, and mutation analysis identified the N215S missense mutation, the common lesion in cardiac variants. Histologic and ultrastructural studies of kidney tissue showed that lysosomal glycosphingolipid deposition was extensive in podocytes, rare in tubular epithelial cells, and absent in mesangial, interstitial, and vascular endothelial and smooth muscle cells. This cardiac variant serves as an "experiment of nature" showing that the residual alpha-Gal A activity precludes glycosphingolipid deposition in the renal endothelial and other cells that lead to early renal failure in classically affected men, whereas marked podocyte accumulation is associated with proteinuria and possibly late-onset renal dysfunction. These findings have important implications for the renal effectiveness of enzyme replacement therapy in classically affected patients and for the aggressive treatment of proteinuria in Fabry disease.

Aged↗
PubMed2003

Platelets and capillary injury in acute humoral rejection of renal allografts.

Platelet accumulation in glomerular capillaries (GC) and peritubular capillaries (PC) has pathogenetic importance in antibody-mediated hyperacute renal allograft rejection. CD61 is expressed constitutively by platelets, by platelet microparticles arising from platelet activation, and is readily detectable by immunohistochemistry. This study examined the immunohistochemical localization of CD61 in acute humoral rejection (AHR) of renal allografts to explore the relationship of platelet accumulation to antibody-mediated rejection. Two observers graded the extent of CD61 staining in PC and GC from 0 (none) to 2+ (>50%) in 15 renal allograft biopsy specimens with AHR and compared these with tissues from allografts with acute cellular rejection (ACR) (n = 23); acute calcineurin inhibitor toxicity (ACIT) (n = 21) with thrombotic microangiopathy (TMA) (n = 11) and tubular toxicity only (n = 10); acute tubular necrosis (ATN) (n = 16); acute renal vein thrombosis (RVT) (n = 4); and histologically unremarkable native kidneys (n = 26). Selected tissues were examined by electron microscopy and stained for CD34 by immunohistochemistry. Histologically unremarkable native kidney tissues had CD61 only in scattered small lumenal granules in GC and PC. Mural and occlusive lumenal CD61 deposits (>0.5+) were observed in 13 of 13 (100%) allograft tissues with GC thrombi due to AHR (1) and ACIT TMA (9) and RVT (3). Twenty-seven of 66 allografts (40.9%) without glomerular thrombi had >0.5+ GC CD61 in AHR (60%), ACR (26%), tubular ACIT (60%), and ATN (44%). More than trace (>0.5+) PC mural and lumenal CD61 deposits were seen only in AHR (53.3%) and ACR (30%). PC CD61 correlated with interstitial hemorrhage (r = 0.64), neutrophilic capillaritis (r = 0.47), and interstitial inflammation (r = 0.47) (P <0.001 for each). PC CD61 was observed in 11 of 11 foci of necrosis due to AHR, RVT, and ischemia. In AHR, capillaries with CD61 deposits had few platelets, numerous microvesicles and membrane fragments, severe endothelial injury seen on electron microscopy, and reduced capillary CD34 expression. CD61 detection by immunohistochemistry revealed products of capillary platelet activation in allograft biopsy specimens without light microscopic thrombi. Observations in this study suggest that intracapillary platelet activation occurs in response to graft capillary injury from many causes and may not be specific for antibody-mediated rejection.

Acute Disease↗
PubMed2003

Treatment of refractory BK virus-associated nephropathy with cidofovir.

BK virus-associated nephropathy (BKVN) has become recognized as an important cause of allograft dysfunction in renal transplant recipients and despite reduction in immunosuppression, 30-40% of recipients ultimately progress to allograft loss. Cidofovir is an antiviral agent that demonstrates in vitro activity against murine polyomavirus and has been proposed for treatment of BKVN in renal allograft recipients. We describe the clinical course, renal function, serial renal histology and urine and blood viral load measurements in two consecutive patients with refractory BKVN who were treated with low-dose cidofovir (0.25 mg/kg IV). In each case, renal dysfunction and BK viral load progressed despite reduced immunosuppression, and persistent BK virus infection was documented in serial renal allograft biopsy specimens. Administration of low-dose cidofovir was associated with clearance of BK virus DNA from blood and allograft, and stabilization of renal function in both patients, without significant toxicity. These preliminary data suggest that low-dose cidofovir may be tolerated, even among renal transplant recipients with significant renal dysfunction due to BKVN. Prospective, controlled trials are warranted to further define the optimal dose, toxicity and potential role of cidofovir in renal transplant recipients with BK virus nephropathy.

Adult↗
PubMed2002

Successful retransplantation after renal allograft loss to polyoma virus interstitial nephritis.

BACKGROUND: Although polyoma virus infection is being increasingly recognized as a cause of renal allograft dysfunction and failure, the risk of polyoma recurrence in a subsequent transplant is unknown. We present the first reported case of successful retransplantation after polyoma virus-induced renal allograft loss. CASE REPORT: A 40-year-old Caucasian woman received a cadaveric kidney transplant. Baseline immunosuppression included corticosteroids, mycophenolate mofetil, and tacrolimus. Her post-transplant clinical course was complicated by an early acute rejection episode on posttransplant day (PTD) 6, that warranted treatment with OKT3. A biopsy performed on PTD 154 to evaluate a rise in creatinine revealed polyoma virus interstitial nephritis. Despite reduction in immunosuppression, the renal function progressively worsened and dialysis was initiated by PTD 160, followed by transplant nephrectomy on PTD 184. Four months later, she received a living related kidney from her sister. Immunosuppression was initiated with prednisone, azathioprine, and tacrolimus. She had immediate graft function with a decrease in serum creatinine from 12.8 to 1.1 mg/dl. Three and one-half years after her second renal transplant, her allograft functions well, with a serum creatinine of 1 mg/dl. Both quantitative and qualitative assays of blood and urine (by PCR) remain negative for BK virus, indicating the absence of virus reactivation. CONCLUSION: Judicious retransplantation should be considered as a therapeutic option in the management of polyoma virus induced graft failure. Previous graft loss secondary to polyoma virus infection is not a contraindication to retransplantation.

Adult↗
PubMed2000

Acceptance reaction: intragraft events associated with tolerance to renal allografts in miniature swine.

Inbred miniature swine that are treated for 12 d with a high dose of cyclosporin A develop tolerance to MHC class II matched, class I-mismatched renal allografts. The aim of this study was to clarify the intrarenal allograft events associated with the development of tolerance in this protocol. Morphologic and immunologic studies were performed in serial biopsies from accepting grafts after 12 d of cyclosporin A treatment (n = 4) and were compared with those from untreated control rejecting grafts (n = 4). In accepting grafts with stable function, a transient interstitial infiltrate developed. The cellular infiltrate had many similarities to that in rejecting grafts; both had T cells and macrophages, similar proportions of T-cell subsets, and a similar frequency of in situ nick end labeling (TUNEL)+ apoptotic infiltrating cells. However, the cellular infiltrate in the acceptance reaction was distinguished by less T-cell activation (interleukin-2 receptor+), less proliferation (proliferating cell nuclear antigen+) of infiltrating cells, and less graft cell apoptosis in arteries, tubules, glomeruli, and peritubular capillaries. Thereafter, the infiltrate in the accepting grafts progressively resolved with decreased cell proliferation, activation, and apoptotic graft parenchymal cell injury, but the high frequency of apoptosis persisted in graft-infiltrating cells. In parallel to the intragraft events, donor-specific unresponsiveness developed as assessed by cell-mediated cytotoxicity by blood mononuclear cells in vitro. In conclusion, the acceptance reaction in transplanted grafts is characterized by progressive resolution of T-cell proliferation and activation and of cell-mediated graft injury, as well as prolonged T-cell apoptosis. These intragraft events suggest that both T-cell anergy and T-cell deletion occur in the graft during the development of tolerance. Some of the described immunopathologic findings (activation, proliferation, apoptosis) may be useful in distinguishing acceptance from rejection, as well as in predicting later graft acceptance in tolerance induction protocols.

Animals↗