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Parmjeet S Randhawa

Publications and source records attributed to Parmjeet S Randhawa.

13 recordsLinked to original sources
PubMed2006

Detection of CD8+ T cells sensitized to BK virus large T antigen in healthy volunteers and kidney transplant recipients.

BK virus (BKV) infections after renal transplantation are increasingly recognized. Development of immune monitoring strategies against BKV requires definition of antigenic epitopes. Hence, T cells from HLA-A02-positive healthy subjects and kidney transplant recipients were stimulated by BKV lysate pulsed on mature autologous dendritic cells and screened against four different T antigen peptides or against BKV lysate. IFN-gamma production was measured by ELISPOT assays. The peptide BKV362-371 (MLTERFNHIL) was naturally processed and recognized by five of six healthy subjects (39 +/- 11 IFN-gamma spots/100,000 cells) and five of seven kidney transplant recipients (21 +/- 12 IFN-gamma spots). Less frequent and weaker CD8+ T-cell responses were detected against three other peptides. Thus, BKV large T antigen is a target for CD8+ T-cell immunity. T-antigen-specific T-cytotoxic cells circulate in healthy blood donors, implying that transient expression of T antigen presumably occurs at sites of viral latency and helps maintain a constant pool of circulating CD8+ T memory cells.

Adult↗
PubMed2006

Diagnosis and treatment of BK virus-associated transplant nephropathy.

The incidence of polyoma virus infection, particularly that of BK virus (BKV) in kidney transplant recipients has been increasing steadily since early 1990s. The diagnosis is generally made by a renal allograft biopsy. However the diagnosis can sometimes be difficult because of the pathological similarities between BKV associated nephropathy (BKVAN) and acute cellular rejection. In addition to the difficulties in making a diagnosis, the treatment of BKVAN can also be very complex. Reduction in immunosuppression is generally advocated as the initial therapeutic option for the management of BKVAN. Despite reduced immunosuppression, BKV can persist in the renal allograft and lead to gradual loss of kidney function. Hence, new therapeutic options are being evaluated for treatment of BKVAN. Cidofovir, an anti-viral agent with known nephrotoxic effects, has been successfully used in very low doses to treat patients with BKVAN, with serial measurement of the blood and urine BKV load with PCR assays. More recently several other agents have also been utilized to treat BKVAN, with variable success. This chapter summarizes the current diagnostic modalities and therapeutic options for BKVAN.

BK Virus↗
PubMed2006

Immunoglobulin G, A, and M responses to BK virus in renal transplantation.

Immunoglobulin G (IgG), IgA, and IgM antibodies were measured in serum samples from 71 organ donors, 81 kidney transplant recipients at transplantation, and 67 patients during the posttransplant period by using a virus-like particle-based enzyme-linked immunosorbent assay (ELISA). BK virus (BKV) and JC virus DNA were detected in urine and plasma by real-time PCR. IgG antibodies to BKV were demonstrated in the majority (80.3 to 100%) of patients irrespective of clinical category, but titers were highest in patients with active viral replication. IgA antibodies were present with greater frequency (72.7 to 81.3% versus 0 to 23.6%; P < 0.001) and higher titer (mean optical density, 0.11 to 0.15 versus 0.05 to 0.08; P < 0.001) in patients who were BKV DNA positive than those who were BKV DNA negative. IgM antibodies showed a similar pattern of reactivity but lower frequency in the setting of active viral replication (9.1 to 43.7% versus 0 to 1.4%; P < 0.001). A rise in IgG level of >0.577 optical density (OD) units or a rise in IgA or IgM level of >0.041 OD units was strongly associated with active viral replication. Urine viral load showed a positive correlation with IgM titer (r = 0.22) but a negative correlation with IgG titer (r = -0.28) and IgA titer (r = -0.1). Chronic dialysis patients typically did not have serologic or virologic evidence of active BKV infection. Anti-BKV titers did not rise in patients with JC viruria. In conclusion, measurement of anti-BKV antibody titer and class response can be used to detect the onset of viral replication. ELISAs can be quite specific despite considerable sequence homology between BK virus and JC virus.

Adolescent↗
PubMed2004

Retransplantation in patients with graft loss caused by polyoma virus nephropathy.

The characteristics and outcome in 10 patients who underwent retransplantation after losing their renal grafts to BK virus-associated nephropathy (BKAN) are described. The patients underwent retransplantation at a mean of 13.3 months after failure of the first graft. Nephroureterectomy of the first graft was performed in seven patients. Maintenance immunosuppression regimens after the first and second grafts were similar, consisting of a combination of a calcineurin inhibitor, mycophenolate mofetil, and prednisone. BKAN recurred in one patient 8 months after retransplantation, but stabilization of graft function was achieved with a decrease in immunosuppression and treatment with low-dose cidofovir. After a mean follow-up of 34.6 months, all patients were found to have good graft function with a mean creatinine of 1.5 mg/dL. From this collective experience from five transplant centers (although the follow-up after retransplantation was not extensive), it can be concluded that patients with graft loss caused by BKAN can safely undergo retransplantation. The risk of recurrence does not seem to be increased in comparison with the first graft.

Adult↗
PubMed2004

Glomerular changes in BK virus nephropathy.

This study seeks to define the glomerular changes that are associated with human BK virus nephropathy (BKVN). It is based on histopathologic review of 124 biopsies showing light-microscopic changes of viral nephropathy. The diagnosis of BKVN was confirmed by immunohistochemistry or by in situ hybridization. Histological lesions were scored by the Banff 97 criteria for renal allograft pathology and were correlated with clinical parameters. Viral cytopathic effect in the parietal Bowman's capsular epithelium was seen in 21/124 (17%) biopsies. Immunohistochemistry showed infection of Bowman's capsular epithelium in an additional 15/124 (12%) biopsies. Crescents were found in 15/124 (12%) samples. Glomerulitis exceeding grade Banff g1 was only occasionally shown (4/124=3% biopsies). Other pathologic lesions documented include mild increase in mesangial matrix in 23% biopsies, aneurysmal dilatation of glomerular capillaries in 28%, ischemic glomerulopathy in 62%, and chronic transplant glomerulopathy graded as mild (cg1) in 62% of biopsies and as moderate (cg2) in 2/124 (1.9%) biopsies. These findings show that infection of the glomerular epithelium cells can occur in a subset of patients with BKVN, most often in biopsies with high viral load in the tubular epithelium. Isolated crescents can occur in BKVN biopsies, but rapidly progressive glomerulonephritis is not observed. Two biopsies showed electron-dense deposits on ultrastructural examination, but a cause and effect relationship to BK virus infection could not be established.

Adolescent↗
PubMed2003

Polyomavirus allograft nephropathy: sequential assessment of histologic viral load, tubulitis, and graft function following changes in immunosuppression.

Our initial cases of polyoma virus allograft nephropathy (PVAN) received pulse steroids due to anxiety about concomitant acute rejection triggered by the presence of tubulitis. However, our current policy is to reduce immunosuppression in all cases. The aim of this study was to determine whether clinical follow-up in these patient categories shows any differences in: (a) histologic viral load, (b) grade of tubulitis, and (c) graft function. Reduced viral load assessed within 8 weeks was seen in 4/20 (20.0%) biopsies treated initially by increased immunosuppression, compared to 15/19 (83.3%) biopsies treated with reduced immunosuppression (p = 0.001, Fisher's exact test). Yet, >70% reversal of the rise in serum creatinine occurred in only 3/19 (15.8%) and 1/19 (5.3%) patients, respectively, in these two groups. Improved tubulitis was seen in 11/20 (55%) of biopsies treated with steroids, despite the lack of beneficial effect on serum creatinine in 12/19 (63.1%) instances. In biopsies not treated with any change in immunosuppression, the serum creatinine remained stable in 1/5 (20%) and worsened in 4/5 (80%) biopsies. These data demonstrate that in biopsies with PVAN and tubulitis, reduced immunosuppression is more effective in lowering viral load than steroid therapy. Lack of parallelism between viral load, tubulitis grade, and serum creatinine illustrates a complex interplay of viral and alloimmune factors leading to graft injury.

Adult↗
PubMed2003

Minimal evidence of transdifferentiation from recipient bone marrow to parenchymal cells in regenerating and long-surviving human allografts.

Liver, small intestine, and heart allografts in residence for 4 days to 16 years were analyzed by simultaneous XY fluorescent in situ hybridization to search for evidence of the recently described process of transdifferentiation of recipient bone marrow stem cells to allograft parenchymal cells. These studies were carried out in an effort to find conditions associated with maximal levels of engraftment or expansion of the recipient parenchymal cells. Despite prolonged survival up to 16 years, regeneration after severe preservation injury or use of split livers, only rare, isolated and tentatively identified recipient hepatocytes were detected in liver allografts. In intestinal allografts, despite survival of up to 8 years and extensive mucosal regeneration because of severe damage from acute rejection, there was no crypt replacement by recipient epithelial cells. In cardiac allografts, no recipient myocytes were detected despite recipient survival for 2-3 days and 3-4 weeks after myocardial infarcts at 5 and 8 years after transplantation. Parenchymal cell transdifferentiation from recipient bone marrow stem cells was rare to nonexistent in severely injured, regenerating, and long-surviving allografts. The rare isolated recipient parenchymal cells tentatively identified did not appear to behave as stem cells: they did not form clusters and did not increase with time after transplantation. Because of the extremely low frequency, interpretation was difficult. Regardless of these results, a more vigorous search for conditions that promote transdifferentiation is warranted.

Adolescent↗
PubMed2003

Occurrence of urinary tract infection in patients with renal allograft biopsies showing neutrophilic tubulitis.

Lymphocytic tubulitis is a well-accepted criterion for acute cellular rejection in renal allograft biopsies. Neutrophilic tubulitis has been used as a surrogate marker for urinary tract infection, but it is not clear how reliably this lesion can be used to make this diagnosis. Biopsy findings were correlated with clinical features in 26 renal allograft biopsies with interstitial polymorphonuclear infiltrates associated with neutrophilic tubulitis. The grade of neutrophilic tubulitis exceeded the grade of lymphocytic tubulitis in 7 (44%) of 16 patients with, but in only 0 patients without, a positive urine culture. Culture confirmed urinary tract infection in 16 (62%) of 26 patients. It is possible that prior antibiotic therapy led to a false-negative culture and masked the diagnosis in two additional patients. Lymphocytic tubulitis made it difficult to exclude concurrent acute cellular rejection in all biopsies studied. In 6 (23%) of 26 patients, negative cultures and response to steroid treatment confirmed that neutrophilic tubulitis can occur in biopsies without urinary tract infection. The relative contributions of infection and rejection could not be determined in patients treated with both steroids and antibiotics. Neutrophilic tubulitis in a renal allograft biopsy should alert the clinician to the possibility of urinary tract infection, even if concurrent lymphocytic tubulitis is present. Confirmation by urine culture is needed because biopsies with ischemic injury and acute cellular or antibody-mediated rejection can show overlapping histology.

Adult↗
PubMed2003

Kidney transplantation under a tolerogenic regimen of recipient pretreatment and low-dose postoperative immunosuppression with subsequent weaning.

OBJECTIVE: The purpose of this work was to perform kidney transplantation under a regimen of immunosuppression that facilitates rather than interferes with the recently defined mechanisms of alloengraftment and acquired tolerance. SUMMARY BACKGROUND DATA: In almost all centers, multiple immunosuppressive agents are given in large doses after kidney transplantation in an attempt to reduce the incidence of acute rejection to near zero. With the elucidation of the mechanisms of alloengraftment and acquired tolerance, it was realized that such heavy prophylactic immunosuppression could systematically subvert the clonal exhaustion-deletion that is the seminal mechanism of tolerance. In addition, it has been established that the rejection response can be made more readily treatable by pretransplant immunosuppression. Consequently, we conducted kidney transplantation in compliance with 2 therapeutic principles: recipient pretreatment and the least possible use of posttransplant immunosuppression. METHODS: One-hundred fifty unselected renal transplant recipients with a mean age of 51 +/- 15 years and multiple risk factors had pretreatment with approximately 5 mg/kg of rabbit antithymocyte globulin (Thymoglobulin) in the hours before transplantation, under covering bolus doses of prednisone to prevent cytokine reactions. Minimal posttransplant immunosuppression was with tacrolimus monotherapy to which steroids or other agents were added only for the treatment of rejection. At or after 4 months after transplant, spaced-dose weaning from tacrolimus monotherapy was begun in patients who had exhibited a satisfactory course. RESULTS: One-year actuarial patient and graft survival was 97% and 92%, respectively. Although the incidence of early acute rejection was 37%, only 7% required prolonged treatment with any agent other than tacrolimus. After a follow-up of 6 to 21 months, the mean serum creatinine in patients with functioning grafts is 1.8 +/- 1.0 mg/dL. Seventy-three percent of the patients met the criteria for spaced weaning. Although rejection episodes occasionally required restoration of daily treatment, 94 (63%) of the 150 patients currently receive tacrolimus in spaced doses ranging from every other day to once a week. CONCLUSIONS: With this approach to immunosuppression, it has been possible to avoid early posttransplant overimmunosuppression and thereby to promote the evolution of a degree of partial tolerance sufficient to undertake substantial dose reduction. The strategy, which is applicable for all organ grafts, constitutes a paradigm shift in transplant management at our center.

Adult↗
PubMed2002

Quantitation of viral DNA in renal allograft tissue from patients with BK virus nephropathy.

BACKGROUND: BK virus (BKV) allograft nephropathy (BKVAN) is a complication in renal transplantation recipients. Histopathology is the gold standard for diagnosis. Quantitative polymerase chain reaction (PCR) assay for renal biopsy has not been evaluated as a diagnostic test. Determination of renal BKV load may identify patients at risk for disease before histologic nephropathy. METHODS: Quantitative PCR assay for BKV DNA was performed in 28 biopsies of patients with BKVAN; 50 biopsies were performed before a diagnosis of BKVAN, and 126 control biopsies were from patients without a history of BKVAN. RESULTS: BKV DNA was present in 19 of 50 (38%) biopsies performed 1 to 164 weeks before diagnosis of BKVAN. The viral load (mean 216 copies/cell) was lower than in biopsies of patients with BKVAN (mean 6063 viral copies/cell, <0.05). In 10 of 127 (7.8%) control biopsies, a low level of BKV DNA (mean 3.8 copies/cell) was found in three biopsies from chronic allograft nephropathy patients; two biopsies with acute rejection; four biopsies with borderline change; and one biopsy with cytomegalovirus nephritis. CONCLUSION: BKV load exceeding 59 copies per cell identified all cases of BKVAN. The diagnostic sensitivity, specificity, positive predictive value, and negative predictive value of quantitative PCR were 100%, 92.1%, 73.6%, and 100%, respectively. Lower levels of BKV DNA were identified in biopsies performed before viral nephropathy development. Future research will determine if earlier recognition of at-risk patients allows application of antiviral strategies to improve graft outcome.

BK Virus↗
PubMed2002

DNA sequencing of viral capsid protein VP-1 region in patients with BK virus interstitial nephritis.

BACKGROUND: Mutations in the viral capsid protein VP-1 region are associated with increased pathogenicity of polyomavirus in experimental systems. This study sought to determine whether analogous viral genetic changes occur in human BK virus (BKV) interstitial nephritis (ISN). METHODS: PCR was used to amplify a 94-bp nucleotide sequence of the viral capsid protein VP-1 region (positions 1740-1833, Dun numbering) in 49 biopsies obtained from 24 patients with BKV-ISN. DNA sequencing was performed by the dideoxy method. RESULT: The VP-1 region was highly polymorphic and 22 "hot spots" of sequence variability were noted. Genotypes I, II, and IV were assigned to 13, 1, and 5 cases, respectively, but 5 cases could not be unambiguously classified due to sequence heterogeneity at sites used to discriminate between genotypes. Even in cases where genotypes could be assigned, only 5 biopsies showed complete sequence identity with published genotype sequences. Sequential biopsies showed temporal changes in one or more nucleotides in all patients with multiple samples. In one patient, the initial biopsy showed viral genotype 1, although subsequent biopsies showed complex genetic patterns, including a biopsy consistent with viral genotype IV. CONCLUSIONS: Many viral strains associated with BKV-ISN are difficult to classify and possibly distinct from those described in kidney transplant recipients without BKV-ISN. VP-1 sequences undergo continual modification as patients are followed in time. This genetic instability could conceivably have implications for evasion of host immunity and development of resistance to antiviral drugs.

BK Virus↗