Analysis of Cross-sectional and Longitudinal HLA and Anti-viral Responses After COVID Infection in Renal Allograft Recipients: Differences and Correlates.

BACKGROUND: Characterization of anti-HLA versus anti-severe acute respiratory syndrome coronavirus 2 (anti-SARS-CoV-2) immune globulin isotypes in organ transplant recipients after coronavirus disease 2019 (COVID-19) infection has not been reported. We aimed to determine changes in anti-HLA antibodies in renal transplant patients with COVID-19 and compare the immunoglobulin and epitope-binding pattern versus anti-SARS-CoV-2 antibodies. METHODS: This is a cross-sectional study of 46 kidney transplant recipients including 21 with longitudinal sampling. Using a semi-quantitative multiplex assay, we determined immunoglobulin (Ig) M, IgA, IgG, and IgG1-2-3-4 antibodies against Class I and Class II HLA, and 5 SARS-CoV-2 epitopes including the nucleocapsid protein and multiple regions of the spike protein. RESULTS: Fourteen of 46 (30%) patients had donor-specific anti-HLA antibodies (donor-specific antibody [DSA]), 12 (26%) had non-DSA anti-HLA antibodies and 45 (98%) had anti-SARS-CoV-2 antibodies. Most DSAs targeted HLA-DQ (71%), with a dominant IgG isotype and IgG1 subtype prevalence (93%), and/or IgG3 (64%), followed by IgG2 (36%). Comparatively, there was a higher prevalence of IgA (85% versus 14%, P = 0.0001) and IgM (87%, versus 36%, P = 0.001) in the anti-SARS-CoV-2 antibody profile, when compared to DSAs, respectively. Anti-SARS-CoV-2 antibody profile was characterized by increased prevalence of IgM and IgA, when compared to DSAs. The median calculated panel reactive antibody before COVID-19 diagnosis (24%) tended to decrease after COVID-19 diagnosis (10%) but it was not statistically significant ( P = 0.1). CONCLUSIONS: Anti-HLA antibody strength and calculated panel reactive antibody in kidney transplant recipients after COVID-19 do not significantly increase after infection. Although the IgG isotype was the dominant form in both HLA and SARS-CoV-2 antigens, the alloimmune response had a low IgA pattern, whereas anti-SARS-CoV-2 antibodies were high IgA/IgM.

Delayed Kinetics of IgG, but Not IgA, Antispike Antibodies in Transplant Recipients following SARS-CoV-2 Infection.

BACKGROUND: Kidney transplant recipients are at increased risk of severe outcomes during COVID-19. Antibodies against the virus are thought to offer protection, but a thorough characterization of anti-SARS-CoV-2 immune globulin isotypes in kidney transplant recipients following SARS-CoV-2 infection has not been reported. METHODS: We performed a cross-sectional study of 49 kidney transplant recipients and 42 immunocompetent controls at early (≤14 days) or late (>14 days) time points after documented SARS-CoV-2 infection. Using a validated semiquantitative Luminex-based multiplex assay, we determined the abundances of IgM, IgG, IgG1-4, and IgA antibodies against five distinct viral epitopes. RESULTS: Kidney transplant recipients showed lower levels of total IgG antitrimeric spike (S), S1, S2, and receptor binding domain (RBD) but not nucleocapsid (NC) at early versus late time points after SARS-CoV-2 infection. Early levels of IgG antispike protein epitopes were also lower than in immunocompetent controls. Anti-SARS-CoV-2 antibodies were predominantly IgG1 and IgG3, with modest class switching to IgG2 or IgG4 in either cohort. Later levels of IgG antispike, S1, S2, RBD, and NC did not significantly differ between cohorts. There was no significant difference in the kinetics of either IgM or IgA antispike, S1, RBD, or S2 on the basis of timing after diagnosis or transplant status. CONCLUSIONS: Kidney transplant recipients mount early anti-SARS-CoV-2 IgA and IgM responses, whereas IgG responses are delayed compared with immunocompetent individuals. These findings might explain the poor outcomes in transplant recipients with COVID-19. PODCAST: This article contains a podcast at https://www.asn-online.org/media/podcast/JASN/2021_11_23_briggsgriffin112321.mp3.

Reducing Donor-specific Antibody During Acute Rejection Diminishes Long-term Renal Allograft Loss: Comparison of Early and Late Rejection.

BACKGROUND: Reduction in donor-specific antibody (DSA) has been associated with improved renal allograft survival after antibody-mediated rejection (AMR). These observations have not been separately analyzed for early and late AMR and mixed acute rejection (MAR). The purpose of this study was to evaluate long-term responses to proteasome inhibitor-based therapy for 4 rejection phenotypes and to determine factors that predict allograft survival. METHODS: Retrospective cohort study evaluating renal transplant recipients with first AMR episodes treated with proteasome inhibitor-based therapy from January 2005 to July 2015. RESULTS: A total of 108 patients were included in the analysis. Immunodominant DSA reduction at 14 days differed significantly (early AMR 79.6%, early MAR 54.7%, late AMR 23.4%, late MAR 21.1%, P < 0.001). Death-censored graft survival (DCGS) differed at 3 years postrejection (early AMR 88.3% versus early MAR 77.8% versus late AMR 56.7% versus late MAR 54.9%, P = 0.02). Multivariate analysis revealed that immunodominant DSA reduction > 50% at 14 days was associated with improved DCGS (odds ratio, 0.12, 95% CI, 0.02-0.52, P = 0.01). CONCLUSIONS: In summary, significant differences exist across rejection phenotypes with respect to histological and DSA responses. The data suggest that DSA reduction may be associated with improved DCGS in both early and late AMR.

A prospective, iterative, adaptive trial of carfilzomib-based desensitization.

Proteasome inhibitor-based strategies hold promise in transplant but have yielded varying results. Carfilzomib, a second-generation proteasome inhibitor, may possess advantages over bortezomib, the first-generation proteasome inhibitors. The purpose of this study was to evaluate the safety, toxicity, and preliminary efficacy of carfilzomib in highly HLA-sensitized kidney transplant candidates. Renal transplant candidates received escalating doses of carfilzomib followed by plasmapheresis (group A) or an identical regimen with additional plasmapheresis once weekly before carfilzomib dosing. Thirteen participants received carfilzomib, which was well tolerated with most adverse events classified as low grade. The safety profile was similar to bortezomib desensitization; however, neurotoxicity was not observed with carfilzomib. Toxicity resulted in permanent dose reduction in 1 participant but caused no withdrawals or deaths. HLA antibodies were substantially reduced with carfilzomib alone, and median maximal immunodominant antibody reduction was 72.8% (69.8% for group A, P = .031, 80.1% for group B, P = .938). After depletion, rebound occurred rapidly and antibody levels returned to baseline between days 81 and 141. Bone marrow studies revealed that approximately 69.2% of plasma cells were depleted after carfilzomib monotherapy. Carfilzomib monotherapy-based desensitization provides an acceptable safety and toxicity profile while leading to significant bone marrow plasma cell depletion and anti-HLA antibody reduction.

Proteasomal adaptations underlying carfilzomib-resistance in human bone marrow plasma cells.

Donor-specific antibodies (DSAs) have a deleterious effect on allografts and remain a major immunologic barrier in transplantation. Current therapies to eliminate DSAs are ineffective in highly HLA-sensitized patients. Proteasome inhibitors have been employed as a strategy to target bone marrow plasma cells (BMPCs), the source of long-term antibody production; however, their efficacy has been limited by poorly defined drug-resistance mechanisms. Here, we performed transcriptomic profiling of CD138+ BMPCs that survived in vivo desensitization therapy with the proteasome inhibitor carfilzomib to identify mechanisms of drug resistance. The results revealed a genomic signature that included increased expression of the immunoproteasome, a highly specialized proteasomal variant. Western blotting and functional studies demonstrated that catalytically active immunoproteasomes and the immunoproteasome activator PA28 were upregulated in carfilzomib-resistant BMPCs. Carfilzomib-resistant BMPCs displayed reduced sensitivity to the proteasome inhibitors carfilzomib, bortezomib, and ixazomib, but enhanced sensitivity to an immunoproteasome-specific inhibitor ONX-0914. Finally, in vitro carfilzomib treatment of BMPCs from HLA-sensitized patients increased levels of the immunoproteasome ß5i (PSMB8) catalytic subunit suggesting that carfilzomib therapy directly induces an adaptive immunoproteasome response. Taken together, our results indicate that carfilzomib induces structural changes in proteasomes and immunoproteasome formation.

IGG3 anti-HLA donor-specific antibodies and graft function in pediatric kidney transplant recipients.

Anti-HLA DSAs are associated with ABMR and graft loss in KT recipients, yet the influence of DSA IgG subclass on outcomes in pediatric KT recipients is not completely understood. We performed a single-center retrospective chart review of pediatric KT recipients with anti-HLA DSAs, aiming to study the association between specific DSA IgG subclasses and graft outcomes, including ABMR and significant graft dysfunction (graft loss or 50% decrease in eGFR). Thirty-six patients (mean age 15.4y) with DSAs initially detected 1 month-14.3 years post-transplantation were followed for a median of 2.8 years. Rates of IgG1, 2, 3, and 4 subclass detection were 92%, 33%, 58%, and 25%, respectively. Twenty-two patients (61%) had clinical ABMR, whereas 19% had subclinical ABMR, and 13 (36%) experienced significant graft dysfunction. Patients with IgG3+ DSAs had a higher risk of graft dysfunction compared with IgG3- patients (52% vs 13%, P = .03). In a multiple Cox proportional regression analysis, the presence of IgG3+ DSA was independently associated with significant graft dysfunction (HR 10.45, 95% CI 1.97-55.55, P = .006). In conclusion, IgG3 subclass DSAs are associated with graft dysfunction and may be useful for risk stratification and treatment decisions in DSA-positive pediatric KT recipients.

Successful Simultaneous Liver-Kidney Transplantation in the Presence of Multiple High-Titered Class I and II Antidonor HLA Antibodies.

The results of simultaneous liver-kidney transplants in highly sensitized recipients have been controversial in terms of antibody-mediated rejection and kidney allograft outcomes. This case report provides a detailed and sophisticated documentation of histocompatibility and pathologic data in a simultaneous liver-kidney transplant performed in a recipient with multiple high-titered class I and II antidonor HLA antibodies and a strongly positive cytotoxic crossmatch. Patient received induction with steroids, rituximab, and eculizumab without lymphocyte depleting agents. The kidney transplant was delayed by 6 hours after the liver transplant to allow more time to the liver allograft to "absorb" donor-specific antibodies (DSA). Interestingly, the liver allograft did not prevent immediate antibody-mediated injury to the kidney allograft in this highly sensitized recipient. Anti-HLA single antigen bead analysis of liver and kidney allograft biopsy eluates revealed deposition of both class I and II DSA in both liver and kidney transplants during the first 2 weeks after transplant. Afterward, both liver and kidney allograft functions improved and remained normal after a year with progressive reduction in serum DSA values.

Acute Rejection Clinically Defined Phenotypes Correlate With Long-term Renal Allograft Survival.

BACKGROUND: Classification of acute rejection (AR) based on etiology and timing may provide a means for enhancing therapeutic results and allograft survival. This study evaluated graft and patient survival after the first AR episodes among kidney transplant recipients with an early or late antibody-mediated rejection (AMR), acute cellular rejection (ACR) or mixed AR (MAR). METHODS: A prospective institutional review board-approved database was queried to identify biopsy-proven first AR episodes occurring from January 2005 to October 2012. The ACR was defined by Banff criteria; borderline AR was excluded. The AMR was defined as 3 of 4 criteria: renal dysfunction, donor specific antibody, C4d positivity on biopsy, and histological changes. The MAR met criteria for both ACR and AMR. Early AR occurred within six months post-transplant. AR episodes were then assigned to 1 of the 6 categories--early AMR, early ACR, early MAR, late AMR, late ACR, and late MAR. RESULTS: One hundred eighty-two kidney transplant recipients identified with a first AR episode. Mean follow-up was 773 days (± 715 days). No difference was observed in patient survival. Death-censored graft survival was 84%. Death-censored graft loss was higher with late versus early AMR (P = 0.01) and late versus early ACR (P = 0.03), but not late versus early MAR (P = 0.3). CONCLUSIONS: The AR type demonstrated a hierarchy for graft survival with ACR better than MAR better than AMR, which persisted for both early and late AR. Improvement in long-term results of AR may require development of specific treatment for individual AR types.

Prospective evaluation of the toxicity profile of proteasome inhibitor-based therapy in renal transplant candidates and recipients.

BACKGROUND: A prospective intermediate-term evaluation of toxicities associated with bortezomib therapy for antibody-mediated rejection (AMR) and desensitization was conducted. METHODS: Patients were graded for bortezomib-related toxicities: hematologic and gastrointestinal toxicities by Common Terminology Criteria for Adverse Events and peripheral neuropathy by modified Functional Assessment of Cancer Therapy questionnaire and Common Terminology Criteria for Adverse Events. RESULTS: Fifty-one patients treated for AMR and 19 patients treated for desensitization received 96 bortezomib cycles (1.3 mg/m(2) ×4 doses); mean (SD) follow-up was 16.3 (9.0) months. Patients treated for AMR and patients treated for desensitization were similar in age, gender, ethnicity, and baseline peripheral neuropathy. Patients treated for AMR received a mean (SD) of 4.9 (2.0) bortezomib doses in 1.3 (0.5) cycles; and patients treated for desensitization, a mean of 7.3 (1.6) doses in 1.8 (0.4) cycles. Prevalence of diabetes and anemia were higher at baseline in patients treated for AMR. In the AMR cohort, two cases of cytomegalovirus infection, two cases of BK virus infection, and one case of Epstein-Barr virus infection were observed. No cases of viral infection were observed in the desensitization cohort. Malignancies were not observed. Significant bortezomib toxicities included anemia and peripheral neuropathy, which were manageable. Anemia was more common in patients treated for AMR; and peripheral neuropathy, more common in patients treated for desensitization. CONCLUSIONS: Bortezomib-related toxicities in kidney transplant candidates and recipients are low in incidence and severity and vary based on treatment population.

Proteasome inhibitor-based therapy for antibody-mediated rejection.

The development of donor-specific anti-human leukocyte antigen antibodies (DSAs) following renal transplantation significantly reduces long-term renal graft function and survival. The traditional therapies for antibody-mediated rejection (AMR) have provided inconsistent results and transient effects that may be due to a failure to deplete mature antibody-producing plasma cells. Proteasome inhibition (PI) is a novel AMR therapy that deletes plasma cells. Initial reports of PI-based AMR treatment in refractory rejection demonstrated the ability of bortezomib to deplete plasma cells producing DSA, reduce DSA levels, provide histological improvement or resolution, and improve renal allograft function. These results have subsequently been confirmed in a multicenter collaborative study. PI has also been shown to provide effective primary AMR therapy in case reports. Recent studies have demonstrated that PI therapy results in differential responses in early and late post-transplant AMR. Additional randomized studies are evaluating the role of PI in transplant induction, acute AMR, and chronic rejection in renal transplantation. An important theoretical advantage of PI-based regimens is derived from several potential strategies for achievement of synergy.

Proteasome inhibitor treatment of antibody-mediated allograft rejection.

PURPOSE OF REVIEW: Bortezomib is a first-in-class proteasome inhibitor that was originally Food and Drug Administration approved for the treatment of multiple myeloma. In the past few years, off-label use in solid organ transplant recipients has demonstrated its ability to provide plasma cell-targeted therapy in humans. The purpose of this review is to provide an update of recent basic science and clinical results with bortezomib in treating antibody-mediated rejection (AMR) that occurs in solid organ transplant recipients. RECENT FINDINGS: Proteasome inhibitor therapy for AMR in kidney transplant recipients is effective both as primary and as rescue therapy. Optimal responses with proteasome inhibitor therapy are obtained when AMR is diagnosed promptly and early in the posttransplant period. However, proteasome inhibitor therapy for late AMR (i.e., occurring 6 months or later posttransplant) provides less predictable results, likely due to the existence of a substantial bone marrow niche-resident long-lived plasma cell population. Proteasome inhibitor therapy has also recently been shown to provide effective therapy for AMR in heart, and also, transplant recipients. SUMMARY: Proteasome inhibitor therapy with bortezomib provides effective treatment for AMR in solid organ transplant recipients. As the first plasma cell-targeted therapy, proteasome inhibitor therapy provides the additional advantage of opening new possibilities for biologically defined plasma cell-targeted therapies.

Early and late acute antibody-mediated rejection differ immunologically and in response to proteasome inhibition.

BACKGROUND: The efficacy of plasma cell targeted therapies for antibody-mediated rejection (AMR) has not been defined in detail. The purpose of this study was to compare early and late acute AMR in terms of immunologic characteristics and responses with proteasome inhibitor (PI) therapy. METHODS: Renal transplant recipients with acute AMR were treated with PI-based regimens. Early acute AMR was defined as occurring within 6 months posttransplant. Immunodominant donor-specific antibody (iDSA) was defined as the DSA with the highest level. RESULTS: Results are expressed as early or late acute AMR. Thirty AMR episodes (13 early, 17 late) were treated in 12 and 16 patients. Early but not late AMR was associated with presensitization. Late AMR iDSA levels were higher, and specificities were primarily class II (DQ being most frequent). Early AMR patients demonstrated greater reduction in iDSA at 7, 14, and 30 days and at the posttreatment nadir (81.5%+21.2% vs. 51.4%+27.6%; P<0.01). Early AMR patients were more likely to demonstrate histologic resolution/improvement (87.5% vs. 53.8%; P=0.13). Both groups demonstrated significant improvement in renal function. CONCLUSIONS: Early and late AMR exhibit distinct immunologic characteristics and respond differently to PI therapy.

Antihuman leukocyte antigen­specific antibody strength determined by complement-dependent or solid-phase assays can predict positive donor-specific crossmatches.

CONTEXT: The association of circulating donor-specific antibody (DSA) strength with crossmatch results is of potential interest to predict allograft outcome. OBJECTIVES: To systematically investigate the aforementioned association and to attempt to define a cutoff value for DSA strength that can predict a positive crossmatch result. DESIGN: We analyzed DSA strength and crossmatch results from the 2006 to 2008 proficiency testing samples of the American Society of Histocompatibility and Immunogenetics (n  =  50). We further validated our findings in candidates for potential kidney transplant (n  =  19). RESULTS: Proficiency test samples with positive antihuman globulin T-cell crossmatch results had significantly higher DSA strength, as assessed by Luminex (Austin, Texas) mean fluorescent intensity (MFI; MFI [SD], 7860 [4770]), compared with samples with negative crossmatch results (MFI [SD], 2900 [1820]; P  =  .001). Similarly, higher Luminex values were observed in samples from candidates for transplant with positive antihuman globulin T-cell crossmatch results (MFI [SD], 7910 [2370] versus 2840 [1960]; P < .001). The MFI value of 6540 had 61% and 75% sensitivity and 92% and 94% specificity for predicting positive antihuman globulin T-cell crossmatches in proficiency test samples and in candidates for transplant, respectively. CONCLUSIONS: The DSA strength correlates well with crossmatch results. An MFI of 6540 predicted a positive antihuman globulin T-cell crossmatch.

Liver transplant recipients weaned off immunosuppression lack circulating donor-specific antibodies.

Human leukocyte antigen (HLA)-specific antibodies (Abs) were examined in 73 clinically stable liver transplant recipients divided into group A (n = 19; clinically tolerant), group B (n = 34; undergoing weaning, on minimal immunosuppression), and group C (n = 20; had failed drug withdrawal or weaning never attempted). Of 19 patients in group A, six (32%) had anti-HLA Abs; none were donor-specific. In contrast, 23 of 34 patients (67%) in group B and nine of 20 patients (45%) in group C exhibited anti-HLA Abs (p = 0.02). Furthermore, 15 of 19 patients in groups B and C (9/12, p = 0.01 and 6/7, p = 0.01, respectively) exhibited donor-specific anti-HLA Abs. The prevalence of donor-specific HLA Abs was significantly higher in nontolerant patients. Five years after initial evaluation, >90% (18/19) group A patients remained off immunosuppression. One of seven of these patients available for retesting exhibited donor-specific Abs. In group B, two-fourths of 34 patients (12%) weaned successfully were HLA-Ab negative; four patients who experienced rejection while undergoing weaning exhibited anti-HLA Ab initially and at 5 years. Thus, most of the liver recipients off immunosuppression lacked donor-specific alloAbs. The occurrence of these alloAbs should now be examined prospectively in a drug weaning trial.

The significance of renal C4d staining in patients with BK viruria, viremia, and nephropathy.

Peritubular capillary C4d staining in allograft kidney is an important criterion for antibody-mediated rejection. Whether BK virus infection can result in complement activation is not known. We studied 113 renal allograft biopsies from 52 recipients with a history of BK virus activation. The samples were classified into four groups according to the concurrent detection of BK virus DNA in urine, plasma, and/or biopsy: BK-negative (n=37), viruria (n=53), viremia (n=7), and nephropathy (n=16) groups. The histological semiquantitative peritubular capillary C4d scores in the viremia (0.3+/-0.8) and BK nephropathy (0.6+/-0.9) groups were lower than those in the BK-negative group (1.2+/-1.1, P=0.05 and P=0.06, respectively) and the viruria group (1.2+/-1.1, P=0.04 and P=0.06, respectively). Diffuse or focal peritubular capillary C4d staining was present in 9/76 (12%) and 14/76 (19%) of all samples with concurrent BK virus reactivation (viruria, viremia, and nephropathy). The diagnosis of antibody-mediated rejection could be established in 7/9 (78%) and 5/14 (36%) of these samples, respectively. Diffuse tubular basement membrane C4d staining was restricted to BK nephropathy cases (4/16, 25%). Semiquantitative tubular basement membrane C4d scores were higher in BK nephropathy (1.2+/-1.3) compared with BK-negative (0.05+/-0.3, P=0.017) and viruria (0.0+/-0.0, P=0.008) groups. Bowman's capsule C4d staining was more frequent in BK nephropathy (5/16) compared with the aforementioned groups (2/36 (P=0.023) and 4/51 (P=0.03), respectively). Within the BK nephropathy group, samples with tubular basement membrane stain had more infected tubular epithelial cells (12.1+/-7.6% vs 4.4+/-5.0%, P=0.03) and a trend toward higher interstitial inflammation scores. In conclusion, peritubular capillary C4d staining remains a valid marker for the diagnosis of antibody-mediated rejection in the presence of concurrent BK virus infection. A subset of biopsies with BK nephropathy shows tubular basement membrane C4d staining, which correlates with marked viral cytopathic effect.

Genotypic variation and phenotypic characterization of granzyme B gene polymorphisms.

BACKGROUND: Granzyme B has been associated with allograft rejection in solid organ transplantation. Single nucleotide polymorphisms (SNPs) in the granzyme B gene might impact its expression. The aims of this study were (1) to establish the frequency of two granzyme B SNPs (A-295G; Q-55R) in pediatric heart transplant (PHTx) recipients and (2) to determine their phenotypic expression in healthy individuals. METHODS: Three hundred ninety-six PHTx patients (245 white non-Hispanic, 49 black non-Hispanic, 82 Hispanics, and 20 others) and 52 healthy controls were screened for Q-55R and A-295G. For the control samples, we assessed the frequency of granzyme B positive cells by ELISPOT assay after mitogen stimulation. RESULTS: Among the PHTx recipients, 57% percent of the population carried the Q/Q genotype, whereas 6% were R/R homozygotes. Seven of 49 (14%) black non-Hispanics were R/R homozygotes, whereas 13 of 245 (5%) of white non-Hispanics and 5 of 82 (6%) Hispanics carried the R/R genotype (P=0.02). The A allele frequency of granzyme B A-295G (49.6%) was similar to that of the G allele (50.4%). However, 80% of Black non-Hispanics were A allele carriers compared with 68% of White non-Hispanics (P<0.0001). After mitogen stimulation, the frequency of granzyme B positive cells was higher in the Q/Q homozygotes compared with R/R carriers (P=0.006), whereas a similar frequency of granzyme B positive cells was noticed among the genotypes of A-295G SNP. CONCLUSIONS: These data indicate that 55 Q/Q genotype is associated with increased in vitro expression of granzyme B.

Emerging role of donor-specific anti-human leukocyte antigen antibody determination for clinical management after solid organ transplantation.

Preformed and de novo donor-specific HLA antibodies (DSA) have been associated with allograft dysfunction and failure. The application of solid-phase methods have increased the sensitivity and specificity of antibody detection; however the clinical significance of these DSA is under evaluation. In the present study, we summarize six cases (four renal transplant recipients, one multivisceral recipient, and one heart-and-lung transplant recipient) to illustrate the role of the histocompatibility laboratory in providing the most comprehensive workup to assess the risk of graft dysfunction associated with antibody-mediated rejection (AMR). These cases illustrate the potential risk assessment for AMR in various situations: (1) in patients exhibiting low levels of DSA pretransplantation; (2) protocol immunosuppression minimization during stepwise weaning; and (3) desensitization protocols. Furthermore, increased sensitivity of DSA determination is indicated for the interpretation of focal C4d and its clinical significance. The clinical relevance of monitoring for circulating DSA with solid-phase single-antigen assays is also discussed. These cases exemplify the rationale for all patients to be monitored for DSA post-transplantation, with the frequency adjusted based on the individual risk for AMR.

Neutrophilic tubulitis as a marker for urinary tract infection in renal allograft biopsies with C4d deposition.

BACKGROUND: Neutrophilic tubulitis accompanied by intratubular neutrophil clusters in the renal allograft is a surrogate marker for urinary tract infection (UTI). Overlapping histologic findings can occur in antibody-mediated rejection, which is characterized by peritubular capillary (PTC) deposition of C4d. This study evaluated the incidence of UTI in biopsies with concurrent neutrophilic tubulitis and PTC C4d staining. METHODS: Thirty-three allograft biopsies from 27 patients selected for the presence of simultaneous C4d staining and neutrophilic tubulitis were correlated with urine culture (U/C) results. RESULTS: U/C obtained on the same day as the biopsy confirmed UTI in 13 of 33 (39%) biopsies. Among 20 patients with negative U/C; prior culture results within 10 days of the biopsy were available for nine patients, and 5 of 9 (55%) were positive. Thus, UTI was confirmed in 18 of 33 (54%) biopsies. Biopsy interpretation and clinical management was confounded by changes of concurrent acute cellular rejection and antibody-mediated rejection confirmed by demonstration of donor-specific antibodies. Combined therapy with antibiotics and antirejection medications (ART) was administered to 12 of 18 (67%) patients. CONCLUSIONS: Neutrophilic tubulitis accompanied by neutrophil clusters in the tubular lumen is a useful marker of UTI, even in the presence of PTC C4d deposition. Therapeutic response to antibiotics is limited by co-existent T-cell or antibody-mediated rejection and underlying chronic allograft nephropathy.

Bortezomib-based treatment of antibody mediated rejection in pancreas allograft recipients.

This report presents the first experience with plasma cell-targeted therapy in treating antibody mediated rejection in pancreas transplant recipients. In this experience, bortezomib provided results similar to those previously reported in kidney transplant recipients, with the exception that DSA responses were not quite as dramatic in pancreas transplant recipients. However, even in patients with antibody mediated rejection refractory to standard therapies, significant responses were obtained with the proteasome inhibitor, bortezomib. These results confirm the potential for bortezomib-based therapies in pancreas transplant recipients, and also demonstrate that rejection following pancreas transplantation may require innovative approaches to provide optimal results.

Pediatric intestinal retransplantation: techniques, management, and outcomes.

BACKGROUND: Intestinal retransplantation (Re-ITx) has historically been associated with high morbidity and mortality. METHODS: The outcomes of all children receiving Re-ITx between 1990 and 2007 at our center were reviewed. RESULTS: One hundred seventy-two children received primary intestinal grafts. Fourteen children (8.1%) were retransplanted with 15 grafts. Causes of graft failure were acute cellular rejection (ACR, n=4), liver failure (n=2), chronic rejection (n=3), posttransplant lymphoproliferative disorder (n=1), graft dysmotility or dysfunction (n=3), ACR with severe infection (n=1), and arterial graft aneurysm (n=1). Initial transplants were isolated bowel in nine, liver-bowel in five, and one multivisceral. The mean time of initial graft survival was 34.2 months. Re-ITx was with isolated bowel in two, liver-bowel in four, and multivisceral in nine (four with kidney). Initial immunosuppression was Tac-Pred based in nine and rabbit antithymocyte globulin-Tac based in six cases. Re-ITx was carried out under Tac-Pred in six, rabbit antithymocyte globulin-Tac in eight, and alemtuzumab monoclonal anti-CD52 antibody in one. Ten (71.4%) patients are alive with functioning grafts at a mean current follow-up time of 55.9 months. Four patients died from posttransplant lymphoproliferative disorder, severe ACR, fungal sepsis, and bleeding from pseudoaneurysm, respectively, at a mean time of 5.7 months post-Re-ITx. All surviving patients weaned-off total parenteral nutrition at a median time of 32 days and 90% are off intravenous fluids. CONCLUSIONS: Improved long-term survival and outcome in pediatric Re-ITx may be attributed to improvements in initial immunosuppression protocols, technical modifications, proper timing, and improved infectious disease monitoring. Careful patient selection and posttransplant management are essential for successful long-term outcome.