The impact of terminal complement blockade on the efficacy of induction with polyclonal rabbit antithymocyte globulin in living donor renal allografts.

BACKGROUND: Eculizumab, a potent inhibitor of terminal complement activation, appears promising in reducing early antibody-mediated rejection in positive crossmatch kidney transplantation. However, its concomitant use with polyclonal rabbit antithymocyte globulin (rATG) might reduce the efficacy of rATG. This study aimed to evaluate the effect of eculizumab on the efficacy of rATG in vivo and determine the role of complement in rATG-induced lymphocyte cell depletion. PATIENTS AND METHODS: Thirty-six kidney transplant recipients were classified into 3 groups according to induction regime: anti-IL-2 receptor antibody alone induction group (basiliximab, n=8); rATG induction (n=20), and rATG+eculizumab induction group (n=8). Peripheral blood T-cell subsets and NK cells were measured 3-4 days after transplant (after 3 doses of rATG). RESULTS: Compared to anti-IL-2 receptor antibody induction group, both groups treated with rATG demonstrated significant depletion of all T-cell subsets (CD3-positive cells) (P<0.0001 for rATG vs. anti-IL-2 receptor antibody induction group; P<0.001 for rATG+eculizumab vs. anti-IL-2 receptor antibody group). However, while T-cell counts were low in all rATG-treated patients, eculizumab treatment resulted in higher peripheral blood T-cell counts in rATG treated patients (P=0.005). Before induction, median total lymphocyte counts were normal for the three study groups. By 1, 4 months and 1 year, median the total lymphocyte count was normal for the anti-IL-2 receptor antibody group but was below normal range or at the lower edge of normality for rATG and rATG+eculizumab groups. CONCLUSIONS: This small-sample size study suggests that peripheral T cells are depleted by rATG in the presence of terminal complement inhibition. However, eculizumab appears to have a mild inhibitory effect on peripheral blood T-cell depletion by rATG in kidney transplant recipients.

MR elastography in renal transplant patients and correlation with renal allograft biopsy: a feasibility study.

RATIONALE AND OBJECTIVES: Magnetic resonance elastography (MRE) images the propagation of mechanical shear waves in tissue and uses that information to generate quantitative measures of tissue stiffness. Hepatic MRE has been successfully performed in thousands of patients, with good correlation between histologic grade of fibrosis and tissue stiffness. There has been no prior investigation of the utility of MRE for the assessment of kidney transplants. The aims of this study were to prospectively evaluate the feasibility of MRE in a small group of kidney transplant recipients and to correlate the measured magnetic resonance elastographic stiffness values with biopsy-proven histopathologic fibrosis. MATERIALS AND METHODS: MRE of renal transplants was performed in 11 patients returning for protocol allograft biopsies. Calculated tissue stiffness values were compared to histologic degree of fibrosis in nine of the 11 patients. RESULTS: The mean stiffness of two patients with moderate interstitial fibrosis was higher than the mean of six patients with mild interstitial fibrosis, but not significantly so (90 Hz, P = .12; 120 Hz, P = .17; 150 Hz, P = .26). The mean stiffness of the two patients with moderate interstitial fibrosis was slightly greater than the mean of one patient with no significant interstitial fibrosis at 90 Hz (P = .78) and slightly less at 120 and 150 Hz (P = .88 and P = .76). The mean stiffness of the six patients with mild interstitial fibrosis did not differ significantly from that of the one patient with no interstitial fibrosis (90 Hz, P = .35; 120 Hz, P = .22; 150 Hz, P = .16). CONCLUSIONS: Preliminary results demonstrate feasibility and support known multifactorial influences on renal stiffness.

The impact of proteasome inhibition on alloantibody-producing plasma cells in vivo.

BACKGROUND: Donor specific alloantibody producing plasma cells (DSA-PCs) appear resistant to conventional immunosuppressive agents. This study aimed to determine the impact of pretransplant monotherapy with the proteasome inhibitor bortezomib on DSA-PCs in sensitized renal allograft candidates and to assess if DSA-PC depletion would enhance the efficacy of DSA removal using plasma exchange (PE). METHODS: Only patients with DSA levels considered too high to successfully undergo transplantation with PE alone were included in this study: i.e. those with a baseline B flow cytometric crossmatch (BFXM) >450 against a potential living donor.Four sensitized patients received 4 doses (1.3 mg/m/dose) of bortezomib and 4 received 16 doses. The number of DSA-PCs was determined pre and post-treatment using an ELISPOT assay. Five of these patients underwent post-treatment PE and their response was compared to 8 highly-sensitized patients (BFXM >450) who underwent PE alone. RESULTS: When considering all 8 patients as one group, bortezomib treatment decreased DSA-PCs in the marrow (mean±SD=16.7±14.5 DSA-PCs/ml pre-treatment vs. 6.2±3.6 DSA-PCs/ml after treatment, P=0.048). In the time frame of the study, bortezomib alone did not decrease serum DSA levels. However, five bortezomib treated patients underwent PE and showed a greater decease in DSA compared to the historical control group of 8 sensitized patients who underwent PE alone (mean decrease in BFXM channel shift=272.6±92.1 with bortezomib vs 95.4±72.2 in PE alone P=0.008). CONCLUSIONS: Bortezomib depletes DSA-PCs and appears to potentiate DSA removal by PE in sensitized renal transplant recipients.

The utility of comprehensive assessment of donor specific anti-HLA antibodies in the clinical management of pediatric kidney transplant recipients.

Advances in anti-HLA antibody characterization have had a major impact on kidney transplantation. Comprehensive characterization of DSA has improved protocols for allosensitized transplant candidates, increasing access to acceptable donors. Sensitive and specific solid phase antibody detection assays have given important insight into the clinical characteristics of antibody-mediated allograft injury, resulting in the development of a classification system for acute AMR. In addition, important insights into the nature of chronic antibody-mediated allograft rejection have been achieved as a result of improvements in DSA characterization. Finally, assays initially developed as tools to detect DSA in the clinical setting have been employed in innovative research protocols, allowing the investigation of new therapeutic approaches.

A novel mutation of LAMB2 in a multigenerational mennonite family reveals a new phenotypic variant of Pierson syndrome.

PURPOSE: To describe a novel laminin ß-2 (LAMB2) mutation associated with nephrotic syndrome and severe retinal disease without microcoria in a large, multigenerational family with Pierson syndrome. DESIGN: Retrospective chart review and prospective family examination. PARTICIPANTS: An extended consanguineous family of 52 members. METHODS: The eyes, urine, and serum DNA were evaluated in all family members after discovering 2 patients, both younger than 10 years, with bilateral retinal detachments and concurrent renal dysfunction. Linkage analysis was performed in the 9 living affected individuals, 7 using the Illumina Human Hap370 Duo Bead Array (Illumina, San Diego, CA) and 2 using GeneChip 10K (Affymetrix, Santa Clara, CA) mapping arrays. MAIN OUTCOME MEASURES: The prevalence and severity of ocular and kidney involvement and genetic findings. RESULTS: Eleven affected family members were identified (9 living), all manifesting chronic kidney disease and bilateral chorioretinal pigmentary changes, with or without retinal detachments, but without microcoria or neurodevelopmental deficits, segregating in an autosomal recessive pattern. The causative gene was localized to a 9-Mb region on chromosome 3. Comprehensive gene sequencing revealed a novel LAMB2 variant (c.440A → G; His147R) that was homozygous in the 9 living, affected family members, observed at a frequency of 2.1% in the Old Order Mennonite population, and absent in 91 non-Mennonite controls. The mutation is located in a highly conserved site in the N-terminal domain VI of LAMB2. CONCLUSIONS: This study describes a novel mutation of LAMB2 and further expands the spectrum of eye and renal manifestations associated with defects in the laminin ß-2 chain. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

The effect of coronary angiography on renal function in preemptive renal transplant candidates.

BACKGROUND: Increasing numbers of patients undergo preemptive renal transplantation. Obtaining cardiac catheterizations prior to transplantation to screen for coronary artery disease is controversial because of the perceived risk of inducing contrast nephropathy and the need for dialysis in patients with marginal renal function. We sought to examine the true impact of cardiac catheterization on time to dialysis in a cohort of preemptive renal transplant candidates. METHODS: From a cohort of 376 transplant candidates evaluated preemptively at our program between 2/2001 and 4/2005, 34 patients had positive dobutamine stress echocardiograms. We reviewed the subsequent need for dialysis in these patients. RESULTS: Among candidates undergoing angiography, 8.7% required dialysis within 14 d of contrast administration and 26% eventually needed dialysis prior to transplantation at 5.3 ± 3.7 months after their pre-transplant evaluation. Among patients who did not undergo angiography, 27% needed dialysis prior to transplantation at 2.4 ± 1.8 months after pre-transplant evaluation. CONCLUSIONS: Our results demonstrate a low risk of hastening the need for dialysis after coronary angiography in preemptive renal transplant candidates. Undergoing angiography had no effect on the ultimate need for or timing of dialysis initiation. These findings support completion of full cardiac evaluation as indicated for high-risk preemptive renal transplant candidates.

The (re)emergence of B cells in organ transplantation.

PURPOSE OF REVIEW: To outline recent advances in our understanding of the role of B cells in transplantation. RECENT FINDINGS: While T-cell-mediated alloimmunity has been largely controlled using immunosuppression, the role of B cells in transplantation is just beginning to be understood. Recent studies have outlined some of the important clinical issues involving antibody including early acute humoral rejection and late transplant glomerulopathy. In addition, recent studies have identified bone-marrow-derived long-lived plasma cells that appear to be a major source of donor-specific alloantibody in sensitized renal transplant recipients. New agents are being tested that deplete these cells in vitro and in vivo. Memory B cells appear to be important in early acute humoral rejection, but few basic studies have been performed. Finally, recent studies involving patients undergoing tolerogenic regimens suggest that T-cell tolerance does not always convey tolerance in naive B cells. SUMMARY: Several B cell types have clear and specific roles in transplant recipients. Although our understanding of B cells in transplantation has improved, important gaps remain.

Sensitized renal transplant recipients: current protocols and future directions.

The identification of suitable donor kidneys for transplant candidates with high levels of circulating antibodies against human leukocyte antigen (HLA) is a major challenge and results in prolonged waiting times for transplantation. Technological advances in antibody characterization have permitted a more comprehensive assessment of anti-HLA antibody activity, as well as providing new insights into the clinical effect of HLA antibody class and specificity. Protocols have been developed that enable successful transplantation in patients with donor-specific antibodies (anti-HLA antibodies reactive against their donors). These protocols provide satisfactory early to intermediate-term allograft survival, and constitute an important advance in transplantation. Nevertheless, acute antibody-mediated rejection (AMR) remains a significant challenge, occurring in 20-50% of antibody-incompatible kidney transplantations. Although therapy directed toward lowering donor-specific antibody activity seems to be successful in reversing acute AMR, this condition still has an important negative impact on allograft survival. In addition, subclinical AMR seems to complicate a substantial proportion of positive-crossmatch transplantations even in the absence of allograft dysfunction, and may result in chronic histological abnormalities and shortened allograft function. New interventions for preventing acute AMR, such as anti-C5 antibody-mediated complement blockade and proteasome inhibitor-mediated plasma cell depletion, are promising therapeutic avenues currently under investigation.

Significance and implications of capillaritis during acute rejection of kidney allografts.

BACKGROUND.: Anti-human leukocyte antigen antibodies (a-HLA) cause graft injury identified by C4d in peritubular capillaries. We investigated whether a-HLA relate to episodes of C4d negative acute rejection (AR). METHODS.: We analyzed 878 kidney recipients transplanted from January 2000 to December 2006. Pretransplant, 36% of these crossmatch negative recipients had a-HLA measured by solid phase assays. RESULTS.: AR occurred in 154 patients (18%) and 11 of them (9.4%) were C4d+. Forty-six percent of ARs were diagnosed by protocol biopsy. The risk of C4d-AR was increased in patients with a-HLA class I with donor specificity (DSA-I) (hazard ratio=1.519; confidence interval, 1.02-2.26; P=0.039). DSA-II were not associated with an increased risk of C4d-AR. The relationship between DSA-I and C4d-AR was independent of recipient age, BK nephropathy, and HLA mismatches. Compared with DSA-, in DSA+ recipients C4d-AR were most often histologically "borderline." DSA+ was associated with capillaritis in the biopsy (glomerulitis, 6.1% vs. 32%, P=0.003; peritubular capillaritis: 13% vs. 40%, P=0.0009). Compared with no AR, C4d-AR with capillaritis was associated with reduced graft survival (hazard ratio=4.164; confidence interval, 1.763-9.832; P=0.001), independent of other variables. This association was observed even in the cases of borderline AR. CONCLUSIONS.: DSA-I increases the risk of C4d-AR. The presence of DSA-I or II is associated with capillaritis during AR. Capillaritis is associated with reduced graft survival.

Antibody-mediated rejection following transplantation from an HLA-identical sibling.

Putative antibody-mediated rejection (AMR) in HLA-identical sibling transplantation has rarely been reported and occurred before routine calcineurin inhibitor use. A 29-year-old male developed allograft dysfunction following an HLA-identical renal transplant from his sibling. A pretransplant panel-reactive antibody (PRA) was elevated, pre-transplant crossmatch was negative and no donor-specific antibody (DSA) was identified. Induction with alemtuzumab was followed by maintenance immunosuppression with corticosteroids, tacrolimus and mycophenolate. A biopsy for allograft dysfunction suggested AMR, but DSA could not be detected. Treatment for rejection was transiently successful. Undetectable minor histocompatibility antibodies may have contributed.

Deciphering antibody-mediated rejection: new insights into mechanisms and treatment.

PURPOSE OF REVIEW: To outline recent studies describing the mechanisms of antibody-mediated rejection (AMR) and new clinical protocols aimed at prevention and/or treatment of this difficult clinical entity. RECENT FINDINGS: The natural history of acute AMR after positive cross-match kidney transplantation involves an acute rise in donor-specific alloantibody (DSA) in the first few weeks after transplantation. Whereas the exact cellular mechanisms responsible for AMR are not known, it seems likely that both pre-existing plasma cells and the conversion of memory B cells to new plasma cells play a role in the increased DSA production. One recent study suggested that combination therapy with plasmapheresis, high-dose IVIG and rituximab was more effective treatment for AMR than high-dose intravenous immunoglobulin (IVIG) alone, but the role of anti-CD20 antibody is still unclear. Two new promising approaches to AMR focus on depletion of plasma cells with the proteasome inhibitor, bortezomib, and the inhibition of terminal complement activation with a humanized, anti-C5 antibody, eculizumab. SUMMARY: The pathogenesis of AMR in several different clinical settings is becoming clearer and more effective treatments are being developed. Whether the prevention or successful treatment of AMR will decrease the prevalence of chronic injury and improved long-term graft survival will require longer-term studies.

Kidney transplantation for primary focal segmental glomerulosclerosis: outcomes and response to therapy for recurrence.

BACKGROUND: For a subset of adults and children with primary focal segmental glomerulosclerosis (FSGS), proteinuria and renal dysfunction recur after kidney transplantation (KTx). Predicting recurrence and response to plasmapheresis (PP) or other interventions remains problematic. METHODS: The prevalence, recurrence rate, outcomes, and treatment responses of patients with FSGS were determined among 1573 KTx recipients. Although 5.0% carried some diagnosis of FSGS, only 1.9% (n=30) met strict diagnostic criteria for primary FSGS including biopsy-proven FSGS, lack of secondary factors, negative family history, and progression to end-stage renal disease within 10 years. RESULTS: Of these, 47% had recurrent FSGS compared with 8% of those not meeting strict criteria (P<0.001). Recurrence was more common in children compared with adults (86% vs. 35%, P=0.01). Graft survival was lower for recipients with primary FSGS compared with all others and inferior graft survival was attributable to recurrent FSGS. Fourteen patients received PP preemptively (pre-KTx) or therapeutically (post-KTx) for recurrent disease. Four pediatric patients additionally received anti-CD20 (rituximab) therapy. Of the different treatment approaches, only PP combined with rituximab was associated with prolonged remission of proteinuria. CONCLUSIONS: The results indicate that patients at high risk for FSGS recurrence can be identified and may benefit from carefully planned peritransplant interventions.

Rituximab for successful management of probable pediatric catastrophic antiphospholipid syndrome.

Catastrophic antiphospholipid syndrome (CAPS) is a life-threatening condition characterized by small-vessel thrombi and a rapid onset of multiorgan system failure associated with systemic inflammatory response syndrome. Current treatment options include anticoagulants, corticosteroids, plasma exchange, and intravenous immunoglobulin, but these are not always effective. Rituximab, a chimeric anti-CD20 monoclonal antibody, may help eliminate autoreactive B cells and thus limit the rapid inflammatory process involved in CAPS. We describe the use of rituximab in the successful initial management of a probable case of pediatric CAPS.

Transplant glomerulopathy: risk and prognosis related to anti-human leukocyte antigen class II antibody levels.

BACKGROUND: Transplant glomerulopathy (TG) is a histopathologic entity of kidney allografts related to anti-human leukocyte antigen (HLA) antibodies. The goal of this study was to determine the relationships among antibody characteristics (level and specificity), risk for TG, and graft survival. METHODS: The presence and characteristics of anti-HLA antibody were assessed by single antigen beads assays in stored pretransplant sera from 598 kidney recipients with negative T-cell crossmatch. Transplant glomerulopathy was diagnosed by surveillance and clinical biopsies. RESULTS: Thirty-nine percent of patients presented with anti-HLA antibodies pretransplant. Transplant glomerulopathy was diagnosed in 73 patients (12%) during 54+/-19 months of follow-up. The risk of TG increased with higher anti-HLA-II antibody levels (HR=1.890, 95% CI 1.42-2.52; P<0.0001), donor specificity of the antibodies (3.524 [1.67-7.44]; P=0.001), and in patients with history of antibody-mediated rejection (4.985 [2.77-8.97]; P<0.0001, multivariate Cox). Graft survival during the follow-up period was 95% without TG and 62% with TG (P<0.0001). The presence of C4d in peritubular capillaries was an independent risk factor for graft failure after TG diagnosis. Thus, 25% of TG/C4d and 80% of TG/C4d+ grafts failed (P<0.0001). Of interest, higher anti-HLA-II levels were related to the presence of C4d (3.216 [1.376-7.517]; P=0.007). CONCLUSIONS: In T-cell negative crossmatch patients, higher anti-HLA-II antibody levels are related to the increase in the risk of developing TG. Higher antibody levels are also related to the presence of C4d in peritubular capillaries in TG biopsies. Furthermore, the presence of C4d in TG is related to the reduced graft survival.

ABO incompatible kidney transplantation.

PURPOSE OF REVIEW: Although ABO incompatible kidney transplantation is increasingly recognized as effective, the procedure is still evolving. The purpose of this review is to summarize recent advances in this area. RECENT FINDINGS: Short to intermediate-term outcome appears good, although long-term results are still preliminary. Pretransplant risk stratification based on antidonor antibody titer may be of limited value. Splenectomy, previously reported to be an important component of ABO incompatible transplantation, appears to be avoidable under many circumstances. The wider implementation of A2 blood group incompatible transplantation shortens waiting time for deceased donor transplantation of blood group B recipients without significantly disadvantaging others. The diagnosis of acute humoral rejection has become clearer following the recognition that C4d deposition commonly occurs in well functioning ABO incompatible allografts. The long-term implications of acute humoral rejection appear substantial even following successful acute therapy, with a significant percentage of patients developing chronic humoral rejection manifested as transplant glomerulopathy. Finally, although ABO incompatible transplantation entails increased expense, when compared with maintenance dialysis and taking into account the health related quality of life benefits of a successful transplant, it is clearly cost effective. SUMMARY: ABO incompatible kidney transplantation is an effective therapy, and will become more widely implemented in the future.

The effect of antithymocyte globulin on anti-human leukocyte antigen antibody detection assays.

BACKGROUND: We evaluated the effect of antithymocyte globulin (ATG) on anti-human leukocyte antigen (HLA) antibody assays. METHODS: We tested sera from six in vivo ATG-treated kidney transplant patients after measuring serum concentrations, as well as six nonsensitized sera with ATG added in vitro. T- and B-cell complement-dependent cytotoxicity (CDC), flow cytometric (FXM), and solid-phase HLA class I and II assays based on antigen-coated microspheres and enzyme-linked immunosorbent assay (ELISA) were studied. Sera were then retested after treatment to remove ATG. RESULTS: We found that ATG affects test results differently depending on whether sera is obtained from in vivo treated patients or added in vitro. In vitro treated sera produced ATG concentration-dependent positive results for T/B CDC, FXM, and flow bead testing for HLA I/II, while the ELISA-based assay was unaffected. In vivo treated sera from ATG-treated patients produced positive test results for T CDC and T/B FXM, while the B-cell CDC crossmatch remained negative. Solid phase assays were minimally affected using in vivo treated sera. After ATG extraction, all tests became negative. CONCLUSION: We conclude that ATG produces positive results in anti-HLA antibody testing, and treatment to remove ATG abolishes this effect. This treatment allows ATG-treated patients to be monitored for anti-HLA antibodies.

Complications, resource utilization, and cost of ABO-incompatible living donor kidney transplantation.

BACKGROUND: The transplantation of living donor renal allografts across blood group barriers requires protocols to reduce and maintain anti-blood group antibody at safe levels. These protocols lead to an increase in resource utilization and cost of transplantation and may result in increased complications. METHODS: In this retrospective study, we compared 40 ABO-incompatible to 77 matching ABO-compatible living donor renal allografts with respect to complications, resource utilization, and cost from day -14 to 90 days after transplantation. RESULTS: Overall, surgery-related complications and resource utilization were increased in the ABO-incompatible group, primarily due to the desensitization protocol and antibody-mediated rejection. In the absence of rejection, the mean number of complications was similar for both groups. ABO-incompatible kidney transplantation was approximately 38,000 US dollars more expensive than ABO-compatible transplants, but was cost effective when compared to maintaining the patient on dialysis while waiting for a blood group compatible deceased donor kidney. Actuarial graft and patient survival was similar in the two groups. CONCLUSIONS: We conclude that ABO-incompatible living donor kidney transplantation is a viable option for patients whose only donor is blood group incompatible despite the additional resource utilization and cost of therapy.

A Comparison of splenectomy versus intensive posttransplant antidonor blood group antibody monitoring without splenectomy in ABO-incompatible kidney transplantation.

BACKGROUND: Although most protocols for ABO-incompatible kidney transplantation have employed splenectomy, its utility is unproven. The aim of the current study was to compare the outcomes of ABO-incompatible living donor kidney transplantation with splenectomy versus a protocol involving intensive posttransplant antibody monitoring to maintain low levels of antiblood group antibody. METHODS: We retrospectively studied all ABO-incompatible living donor kidney transplants at our institution between September 1999 and November 2004 (n=34). Prior to May 2003, all patients were included in a protocol involving pretransplant plasmapheresis and splenectomy at the time of transplant (n=23). After May 2003, splenectomy was not performed and a protocol that involved pretransplant anti-CD20 antibody and a more intensive posttransplant plasmapheresis regiment aimed at maintaining low levels of antiblood group antibody during the first 2 weeks following transplantation was utilized (n=11). RESULTS: Patient and graft survival was similar in the two groups. Humoral rejection occurred in 18% nonsplenectomized and 30% of splenectomized patients (P=0.68). Humoral rejection correlated with the baseline antibody titer in both groups. Individuals with elevated baseline antibody titer (> or =1:256) appear to be at high risk for humoral rejection regardless of protocol used. Antiblood group antibody levels 3 and 12 months after transplantation were similar in both groups. CONCLUSIONS: Splenectomy is not essential for successful ABO-incompatible kidney transplantation, although individuals with high baseline antidonor blood group antibody titers are at high risk for humoral rejection. The use of intensive posttransplant monitoring may help prevent antibody-mediated graft damage.