Does bortezomib influence pre-transplant desensitization therapy or benefit post-heart transplant outcomes for highly sensitized patients?

BACKGROUND: The use of bortezomib which is a proteasome inhibitor has been demonstrated to be efficacious in small number of patients as a desensitization strategy in heart transplant. We reviewed our single center's experience using Bortezomib along with plasmapheresis as desensitization therapy for highly sensitized patients to assess pre- and post-transplant outcomes. METHOD: We assessed 43 highly sensitized patients awaiting HTx (defined as cPRA > 50%) between 2010 and 2021 who underwent desensitization therapy with bortezomib. Only those patients who subsequently underwent HTx were included in this study. Enrolled patients received up to four doses of bortezomib (1.3 mg/m2 ) over 2 weeks in conjunction with plasmapheresis. The efficacy of PP/BTZ was assessed by comparing the calculated panel reactive antibodies to HLA class I or class II antigens. Post-transplant outcomes including overall survival and incidence of rejection were compared to those of non-sensitized patients (PRA < 10%, n = 649) from the same center. RESULTS: The average cPRA prior to PP/BTZ was 94.5%. Post-PP/BTZ there was no statistically significant decline in mean cPRA, class I cPRA, or class II cPRA, though the average percentage decrease in class I cPRA (8.7 ± 17.0%) was higher than the change in class II cPRA (4.4 ± 13.3%). Resulted were also replicated with C1q-binding antibodies showing more effect on I class compared to class II (15.0 ± 37.4% vs. 6.8 ± 33.6%) as well as with 1:8 dilutional assay (14.0 ± 23.0% vs. 9.1 ± 34.9%). Additionally, PP/BTZ treated patients and the control group of non-sensitized patients had similar overall 1 year survival (95.4 vs. 92.5%) but patients with PP/BTZ had increased incidence of AMR (79.1% vs. 97.1%, p = < .001), any treated rejection (62.8% vs. 86.7%, p = < .001) and de novo DSA development (81.4% vs. 92.5%, p = .007). Major side effects of PP/BTZ included thrombocytopenia (42%), infection requiring antibiotics (28%), and neuropathy (12%). CONCLUSION: The use of bortezomib in highly sensitized patients does not significantly lower circulating antibodies prior to heart transplantation. However, its use may improve the chances of obtaining an immuno-compatible donor heart and contribute to acceptable post-transplant outcomes.

Clazakizumab for desensitization in highly sensitized patients awaiting transplantation.

Alloantibodies are a significant barrier to successful transplantation. While desensitization has emerged, efficacy is limited. Interleukin-6 (IL-6) is an important mediator of inflammation and immune cell activation. Persistent IL-6 production increases the risk for alloantibody production. Here we report our experience with clazakizumab (anti-IL-6) for desensitization of highly HLA-sensitized patients (HS). From March 2018 to September 2020, 20 HS patients were enrolled in an open label pilot study to assess safety and limited efficacy of clazakizumab desensitization. Patients received PLEX, IVIg, and clazakizumab 25 mg monthly X6. If transplanted, graft function, pathology, HLA antibodies and regulatory immune cells were monitored. Transplanted patients received standard immunosuppression and clazakizumab 25 mg monthly posttransplant. Clazakizumab was well tolerated and associated with significant reductions in class I and class II antibodies allowing 18 of 20 patients to receive transplants with no DSA rebound in most. Significant increases in Treg and Breg cells were seen posttransplant. Antibody-mediated rejection occurred in three patients. The mean estimated glomerular filtration rate at 12 months was 58 ± 29 ml/min/1.73 m2 . Clazakizumab was generally safe and associated with significant reductions in HLA alloantibodies and high transplant rates for highly-sensitized patients. However, confirmation of efficacy for desensitization requires assessment in randomized controlled trials.

Long term tolerability and clinical outcomes associated with tocilizumab in the treatment of refractory antibody mediated rejection (AMR) in pediatric renal transplant recipients.

BACKGROUND: Treatment options for antibody-mediated rejection (AMR) are limited. Recent studies have shown that inhibition of interleukin-6 (IL-6)/interleukin-6 receptor (IL-6R) signaling can reduce inflammation and slow AMR progression. METHODS: We report our experience using monthly tocilizumab (anti-IL6R) in 25 pediatric renal transplant recipients with AMR, refractory to IVIg/Rituximab. From January 2013 to June 2019, a median (IQR) of 12 (6.019.0) doses of tocilizumab were given per patient. Serial assessments of renal function, biopsy findings, and HLA DSA (by immunodominant HLA DSA [iDSA] and relative intensity score [RIS]) were performed. RESULTS: Median (IQR) time from transplant to AMR was 41.4 (24.367.7) months, and time from AMR to first tocilizumab was 10.6 (8.317.6) months. At median (IQR) follow up of 15.8 (8.435.7) months post-tocilizumab initiation, renal function was stable except for 1 allograft loss. There was no significant decrease in iDSA or RIS. Follow up biopsies showed reduction in peritubular capillaritis (p = .015) and C4d scoring (p = .009). The most frequent adverse events were cytopenias. CONCLUSIONS: Tocilizumab in pediatric patients with refractory AMR was well tolerated and appeared to stabilize renal function. The utility of tocilizumab in the treatment of AMR in this population should be further explored.

Use of a donor-derived cell-free DNA assay to monitor treatment response in pediatric renal transplant recipients with allograft rejection.

BACKGROUND: Detection of donor-derived cell-free DNA (dd-cfDNA) reliably identifies allograft rejection in pediatric and adult kidney transplant (KT) recipients. Here, we evaluate the utility of dd-cfDNA for monitoring response to treatment among pediatric renal transplant recipients suffering graft rejection. METHODS: 58 pediatric transplant recipients were enrolled between April 2018 and March 2020 and underwent initial dd-cfDNA testing to monitor for rejection. Allograft biopsy was performed for dd-cfDNA scores >1.0%. Patients with histologically proven rejection formed the study cohort and underwent appropriate treatment. Results of dd-cfDNA, serum creatinine (SCr), biopsy findings, and treatment outcomes were evaluated. Standard statistical analyses were applied. RESULTS: Nineteen of 58 (31%) patients had dd-cfDNA score >1.0%, of which 18 (94.7%) had biopsy-proven rejection. Median dd-cfDNA value was 1.90% (interquartile range 1.43%-3.23%), and biopsy results showed 11 patients (61.1%) with antibody-mediated rejection (AMR), 2 patients (11.1%) with T-cell mediated rejection (TCMR), and 5 patients (27.7%) with mixed AMR/TCMR. SCr at time of biopsy was 1.28 ± 1.09 mg/dl. Following treatment, dd-cfDNA scores decreased for all types of rejection but still remained >1.0% in both AMR (1.50% [0.90%-3.10%]) and mixed (1.40% [0.95%-4.15%]) groups. Repeat dd-cfDNA values were <1.0% for patients with TCMR (0.20%-0.28%). SCr showed minimal change from pre-treatment levels regardless of rejection subtype. CONCLUSIONS: Patients with TCMR may be reliably followed by dd-cfDNA; however, it remains unclear whether persistently elevated dd-cfDNA levels in AMR is a reflection of ongoing subclinical rejection or an inherent limitation of the assay's utility.

Pre-transplant angiotensin II receptor type I antibodies in pediatric renal transplant recipients: An observational cohort study.

BACKGROUND: The role of angiotensin II type 1 receptor antibodies (AT1R-Ab) in pediatric renal transplantation is unclear. Here, we evaluated pre-transplant AT1R-Ab on transplant outcomes in the first 5 years. Secondary analysis compared pre-transplant AT1R-Ab levels by age. METHODS: Thirty-six patients, 2-20 years old, were divided into two groups: pre-transplant AT1R-Ab- (<17 U/ml; n = 18) and pre-transplant AT1R-Ab+ (≥17 U/ml; n = 18). eGFR was determined at 6-month, 1-, 2-, and 4-year post-transplant. Allograft biopsies were performed in the setting of strong HLA-DSA (MFI > 10 000), AT1R-Ab ≥17 U/ml, and/or elevated creatinine. RESULTS: Mean age in pre-transplant AT1R-Ab- was 13.3 years vs. 11.0 in pre-transplant AT1R-Ab+ (p = 0.16). At 6 months, mean eGFR was 111.3 ml/min/1.73 m2 in pre-transplant AT1R-Ab- vs. 100.2 in pre-transplant AT1R-Ab + at 1 year, 103.6 ml/min/1.73 m2 vs. 100.5; at 2 years, 98.9 ml/min/1.73 m2 vs. and 93.7; at 4 years, 72.6 ml/min/1.73 m2 vs. 80.9. 11/36 patients had acute rejection (6 in pre-transplant AT1R-Ab-, 5 in pre-transplant AT1R-Ab + ). There was no difference in rejection rates. All 6 subjects with de novo HLA-DSA and AT1R-Ab ≥17 U/ml at the time of biopsy experienced rejection. Mean age in those with the AT1R-Ab ≥40 U/ml was 10.0 years vs. 13.2 in those <40 U/ml (p = 0.07). CONCLUSION: In our small cohort, pre-transplant AT1R-Ab ≥17 U/ml was not associated with reduced graft function or rejection. The pathogenicity of pre-transplant AT1R-Ab in pediatric kidney transplantation requires further investigation.

Stem cell donor HLA typing improves CPRA in kidney allocation.

The Organ Procurement and Transplantation Network (OPTN) Kidney Allocation System provides a priority to sensitized candidates based on the calculated panel reactive antibody (CPRA) value. The human leukocyte antigen (HLA) haplotype reference panel used for calculation of the CPRA by the United Network for Organ Sharing (UNOS), the OPTN contractor, has limitations. We derived a novel panel from the National Marrow Donor Program HLA haplotype data set and compared the accuracy of CPRA values generated with this panel (NMDP-CPRA) to those generated from the UNOS panel (UNOS-CPRA), using predicted and actual deceased donor kidney offers for a cohort of 24 282 candidates. The overall accuracy for kidney offers was similar using NMDP-CPRA and UNOS-CPRA. Accuracy was slightly higher for NMDP-CPRA than UNOS-CPRA for candidates in several highly sensitized CPRA categories, with deviations in linkage disequilibrium for Caucasians and the smaller size of the UNOS panel as contributing factors. HLA data derived from stem cell donors yields CPRA values that are comparable to those derived from deceased kidney donors while improving upon several problems with the current reference panel. Consideration should be given to using stem cell donors as the reference panel for calculation of CPRA to improve equity in kidney transplant allocation.

Complement inhibition for prevention of antibody-mediated rejection in immunologically high-risk heart allograft recipients.

Allosensitization represents a major barrier to heart transplantation (HTx). We assessed the efficacy and safety of complement inhibition at transplant in highly sensitized heart transplant recipients. We performed a single-center, single-arm, open-label trial (NCT02013037). Patients with panel reactive antibodies (PRA) ≥70% and pre-formed donor-specific antibodies (DSA) were eligible. In addition to standard of care, patients received nine infusions of eculizumab during the first 2 months posttransplant. The primary composite endpoint was antibody-mediated rejection (AMR) ≥pAMR2 and/or left ventricular dysfunction during the first year. Secondary endpoints included hemodynamic compromise, allograft rejection, and patient survival. Twenty patients were included. Median cPRA and mean fluorescence intensity of immunodominant DSA were 95% (90%-97%) and 6250 (5000-10 000), respectively. Retrospective B cell and T cell flow crossmatches were positive in 14 and 11 patients, respectively. The primary endpoint occurred in four patients (20%). Survival at 1 year was 90% with no deaths resulting from AMR. In a prespecified analysis comparing treated patients to matched control patients, we observed a dramatic reduction in the risk of biopsy-proven AMR in patients treated with eculizumab (HR = 0.36, 95% CI = 0.14-0.95, p = .032). Our findings support the prophylactic use of complement inhibition for heart transplantation at high immunological risk. ClinincalTrials.gov, NCT02013037.

Crossing low/moderate-level donor-specific antibodies during heart transplantation.

Donor-specific antibodies (DSAs) in patients prior to heart transplantation are associated with increased risk of rejection and can lead to longer waitlist times, but it is not known whether patients with low/moderate-level DSA at transplant have acceptable post-transplant outcomes. We performed a single-center, retrospective review to examine outcomes associated with crossing pre-existing low/moderate-level DSA. We assessed 864 patients awaiting heart transplantation between 2010 and 2018, identified 67 patients with low/moderate-level DSA and compared them to patients who were sensitized without DSA at the time of heart transplantation, as well as a control group of non-sensitized patients. Outcomes included 3-year survival, freedom from cardiac allograft vasculopathy (CAV), freedom from non-fatal major adverse cardiac events (NF-MACE), and 1-year freedom from rejection. In the first-year post-transplant, there was decreased freedom from antibody-mediated rejection (AMR) in the patients with pre-existing DSA compared with patients sensitized without DSA and non-sensitized patients. However, the DSA group experienced similar 3-year post-transplant survival, freedom from CAV, and freedom from NF-MACE compared with the other study groups. Our findings suggest that crossing low/moderate-level DSA does not lead to worse outcomes in heart transplantation and may offer a viable way to increase a sensitized patient's chance to obtain a suitable donor.

The effects of donor-specific antibody characteristics on cardiac allograft vasculopathy.

BACKGROUND: Cardiac allograft vasculopathy (CAV) causes late graft dysfunction and post-transplant mortality. Currently, the effects of different donor-specific antibodies (DSA) on the severity of CAV remain unclear. METHOD: We evaluated 526 adult heart transplant recipients at a single center between January 2010 and August 2015. Subjects were divided into those with DSA (n = 142) and those without DSA (n = 384, control). The DSA group was stratified into persistent DSA (n = 34), transient DSA (n = 105), 1:8 dilution DSA (n = 45), complement-binding (C1q) DSA (n = 36), Class I DSA (n = 37), and Class II DSA (n = 105). The primary outcome was the incidence of moderate-to-severe CAV (CAV 2/3) at 5-year follow-up. RESULTS: Subjects with persistent DSA, 1:8 dilution DSA, and C1q DSA had higher incidence of CAV 2/3 compared the control group (17.6%, 13.3%, and 16.7% vs. 3.1%, respectively; P≤ .001). The incidence of CAV 2/3 between subjects with transient DSA and the control group was similar (2.8% vs. 3.1%; P = .888). Subjects with Class II DSA also had higher incidence of CAV 2/3 (7.6% vs. 3.1%; P = .039). CONCLUSION: DSA that are persistent, 1:8 dilution positive, C1q positive, and Class II are associated with more severe grades of CAV. These DSA characteristics may prognosticate disease and warrant consideration for treatment.

Use of Rituximab for persistent EBV DNAemia, and Its effect on donor-specific antibody development in pediatric renal transplant recipients: A case series.

INTRODUCTION: Persistent EBV DNAemia (PEBV) is associated with late-onset PTLD. The efficacy of rituximab in PEBV is not conclusive. We monitored PEBV and DSA in pediatric kidney transplant patients with or without rituximab. METHODS: 13 PEBV patients received standard treatment with immunosuppression reduction and valganciclovir, with or without IVIG; 5/13 were further treated with rituximab. RESULTS: All Rituximab-treated and 6/7 No-Rituximab patients were EBV seronegative at transplant and seroconverted post-transplant. Peak EBV PCR levels were lower in No-Rituximab than Rituximab patients and all No-Rituximab patients cleared PEBV after standard treatment. Additional 1-2 doses of rituximab reduced EBV PCR levels in all 5 Rituximab patients, 3 cleared PEBV. One No-Rituximab patient developed localized PLTD. None of Rituximab patients developed de novo DSA, while 4/8 No-Rituximab patients did: 2/4 had ABMR. 1/5 Rituximab and 5/8 No-Rituximab patients had acute rejection. There was no change in eGFR between pre-EBV DNAemia and follow-up in Rituximab patients, while reduction in No-Rituximab patients was found. There was no difference in graft and patient survival. CONCLUSIONS: While early intervention with rituximab in pediatric patients with PEBV may reduce viral load and PTLD, we observed a slower development of de novo DSA, and rejection and maintenance of eGFR.

Comparative transcriptome analysis of rhizome nodes and internodes in Panax. japonicus var. major reveals candidate genes involved in the biosynthesis of triterpenoid saponins.

The rhizome of P. japonicus var. major, one of the important herbs in Traditional Chinese medicine (TCM), has been used as tonic and hemostatic drugs in Tujia and Miao ethnic groups of China for thousand years. In this study, comparative metabolite and transcriptome analysis of rhizome nodes and internodes of wild P. japonicus var. major was performed to reveal their different roles in the biosynthesis of triterpene saponins. The results showed that the node was the crucial section for the synthesis of ginsenosides in the rhizome. The content of oleanane-type ginsenosides in the node was much higher than those in the internode. Most isoprenoid biosynthesis-related genes were highly expressed in the node. And, candidate UDP-glycosyltransferase (UGT) genes were also found to be differentially expressed between node and internode. Our study will provide a better understanding of the metabolism of ginsenosides in the rhizome of P. japonicus var. major.

IgG Endopeptidase in Highly Sensitized Patients Undergoing Transplantation.

BACKGROUND: Donor-specific antibodies create an immunologic barrier to transplantation. Current therapies to modify donor-specific antibodies are limited and ineffective in the most highly HLA-sensitized patients. The IgG-degrading enzyme derived from Streptococcus pyogenes (IdeS), an endopeptidase, cleaves human IgG into F(ab')2 and Fc fragments inhibiting complement-dependent cytotoxicity and antibody-dependent cellular cytotoxicity, which suggests that IdeS might be useful for desensitization. We report on the combined experience of two independently performed open-label, phase 1-2 trials (conducted in Sweden and the United States) that assessed the efficacy of IdeS with regard to desensitization and transplantation of a kidney from an HLA-incompatible donor. METHODS: We administered IdeS to 25 highly HLA-sensitized patients (11 patients in Uppsala or Stockholm, Sweden, and 14 in Los Angeles) before the transplantation of a kidney from an HLA-incompatible donor. Frequent monitoring for adverse events, outcomes, donor-specific antibodies, and renal function was performed, as were renal biopsies. Immunosuppression after transplantation consisted of tacrolimus, mycophenolate mofetil, and glucocorticoids. Patients in the U.S. study also received intravenous immune globulin and rituximab after transplantation to prevent antibody rebound. RESULTS: Recipients in the U.S. study had a significantly longer cold ischemia time (the time elapsed between procurement of the organ and transplantation), a significantly higher rate of delayed graft function, and significantly higher levels of class I donor-specific antibodies than those in the Swedish study. A total of 38 serious adverse events occurred in 15 patients (5 events were adjudicated as being possibly related to IdeS). At transplantation, total IgG and HLA antibodies were eliminated. A total of 24 of 25 patients had perfusion of allografts after transplantation. Antibody-mediated rejection occurred in 10 patients (7 patients in the U.S. study and 3 in the Swedish study) at 2 weeks to 5 months after transplantation; all these patients had a response to treatment. One graft loss, mediated by non-HLA IgM and IgA antibodies, occurred. CONCLUSIONS: IdeS reduced or eliminated donor-specific antibodies and permitted HLA-incompatible transplantation in 24 of 25 patients. (Funded by Hansa Medical; ClinicalTrials.gov numbers, NCT02224820 , NCT02426684 , and NCT02475551 .).

HLA Class II-Triggered Signaling Cascades Cause Endothelial Cell Proliferation and Migration: Relevance to Antibody-Mediated Transplant Rejection.

Transplant recipients developing donor-specific HLA class II (HLA-II) Abs are at higher risk for Ab-mediated rejection (AMR) and transplant vasculopathy. To understand how HLA-II Abs cause AMR and transplant vasculopathy, we determined the signaling events triggered in vascular endothelial cells (EC) following Ab ligation of HLA-II molecules. HLA-II expression in EC was induced by adenoviral vector expression of CIITA or by pretreatment with TNF-α/IFN-γ. Ab ligation of class II stimulated EC proliferation and migration. Class II Ab also induced activation of key signaling nodes Src, focal adhesion kinase, PI3K, and ERK that regulated downstream targets of the mammalian target of rapamycin (mTOR) pathway Akt, p70 ribosomal S6 kinase, and S6 ribosomal protein. Pharmacological inhibitors and small interfering RNA showed the protein kinases Src, focal adhesion kinase, PI3K/Akt, and MEK/ERK regulate class II Ab-stimulated cell proliferation and migration. Treatment with rapalogs for 2 h did not affect HLA-II Ab-induced phosphorylation of ERK; instead, mTOR complex (mTORC)1 targets were dependent on activation of ERK. Importantly, suppression of mTORC2 for 24 h with rapamycin or everolimus or treatment with mTOR active-site inhibitors enhanced HLA-II Ab-stimulated phosphorylation of ERK. Furthermore, knockdown of Rictor with small interfering RNA caused overactivation of ERK while abolishing phosphorylation of Akt Ser473 induced by class II Ab. These data are different from HLA class I Ab-induced activation of ERK, which is mTORC2-dependent. Our results identify a complex signaling network triggered by HLA-II Ab in EC and indicate that combined ERK and mTORC2 inhibitors may be required to achieve optimal efficacy in controlling HLA-II Ab-mediated AMR.

Impact and production of Non-HLA-specific antibodies in solid organ transplantation.

Organ transplantation is an effective way to treat end-stage organ disease. Extending the graft survival is one of the major goals in the modern era of organ transplantation. However, long-term graft survival has not significantly improved in recent years despite the improvement of patient management and advancement of immunosuppression regimen. Antibody-mediated rejection is a major obstacle for long-term graft survival. Donor human leucocyte antigen (HLA)-specific antibodies were initially identified as a major cause for antibody-mediated rejection. Recently, with the development of solid-phase-based assay reagents, the contribution of non-HLA antibodies in organ transplantation starts to be appreciated. Here, we review the role of most studied non-HLA antibodies, including angiotensin II type 1 receptor (AT1 R), K-α-tubulin and vimentin antibodies, in the solid organ transplant, and discuss the possible mechanism by which these antibodies are stimulated.

[Study on interaction between ginsenosides Rg_1,Rb_1 and Ro and bovine serum albumin].

Small molecules with physiological or pharmacological activities need to interact with biological macromolecules in order to function in the body. As the protein with the highest proportion of plasma protein,serum albumin is the main protein binding to various endogenous or exogenous small molecules. Serum albumin interacts with small molecules in a reversible non-covalent manner and transports small molecules to target sites. Bovine serum albumin( BSA) is an ideal target protein for drug research because of its low cost and high homology with human serum albumin. The research on the interaction between drugs and BSA has become a hotspot in the fields of pharmacy,medicine,biology and chemistry. In this research,molecular docking method was used to study the interaction between three small ginsenosides with high pharmacological value( Rg_1,Rb_1,Ro) and bovine serum albumin( BSA),and the binding mode information of three ginsenosides interacting with BSA was obtained. The results of molecular docking showed that ginsenosides and amino acid residues in the active pocket of proteins could be combined by hydrophobic action,hydrogen bonding and electrostatic action. The interaction between small ginsenosides and bovine serum albumin is not the only form,and their interaction has many forms of force. The interaction between these molecules and various weak forces is the key factor for the stability of the complex. The results of this study can provide the structural information of computer simulation for the determination of the interaction patterns between active components and proteins of ginseng.

Revealing a new mode of sensitization induced by mechanical circulatory support devices: Impact of anti-AT1 R antibodies.

BACKGROUND: Increased levels of angiotensin II type 1 receptor (AT1 R) antibody have been shown to be associated with allograft rejection. This study aims to determine the rate of development of antibody to AT1 R after mechanical circulatory support device (MCS) implantation, and if the development of strong binding AT1 R antibodies is associated with survival. METHODS: Eighty-eight patients who had one MCS implantation were accessed based on serum availability. Mechanical circulatory support devices in this cohort included pneumatic bilateral paracorporeal ventricular assist device, continuous flow left ventricular assist device, and total artificial heart. RESULTS: Of 88 patients, seven patients had AT1 R antibodies ≥40 U/mL preimplantation. For 81 patients who had AT1 R antibodies <40 U/mL, the median value was 8 U/mL. Of these 81 patients, AT1 R antibody levels in 55 (68%) patients reached the saturated concentration (≥40 U/mL) postimplantation (P < .0001), with the highest percentage of patients with the saturated level of AT1 R antibody observed in the pneumatic bilateral paracorporeal ventricular assist device group. Compared to patients without the saturated level of AT1 R antibodies, patients with the saturated AT1 R antibody level had lower 18-month survival (P = .040). CONCLUSION: Mechanical circulatory support devices implantation significantly increases AT1 R antibody levels. The saturated level of AT1 R antibodies is associated with lower patient survival postimplantation.

Clinical and histopathologic features of antibody-mediated rejection among pediatric renal transplant recipients with preformed vs de novo donor-specific antibodies.

Preformed and de novo donor specific antibodies (pDSA and dnDSA) are risk factors for ABMR. This study compares the effects of pDSA vs dnDSA in pediatric kidney transplant recipients. Sixteen pediatric patients with biopsy-proven ABMR were evaluated. Strong DSA (MFI >10 000) was recorded at transplant, rejection, and follow-up. DSAs with the highest MFI were termed iDSAs. Allograft biopsies were scored according to Banff 2013 criteria. Seven of 16 (44%) patients had pDSA at transplant; 9 (56%) developed dnDSA. Patients with pDSA developed ABMR earlier (median = 63 vs 1344 days, P = .017), while patients with dnDSA were more likely to have strong Class II iDSA (100% vs 28%, P = .009). Viral infection or non-adherence was more common in patients developing dnDSA (88.8% vs 28.6%, P < .01). Pathology in those with pDSAs demonstrated worse transplant glomerulitis (g score 1.57 ± 0.98 vs 0.56 ± 0.73, P = .031); however, those with dnDSAs exhibited higher C4d+ ABMR (P = .013). Patients developing dnDSAs showed ABMR later post-transplant with predominance of HLA-Class II iDSAs. Inadequate immunosuppression likely contributes to dnDSA formation. Patients with no DSA who have unprotocolized decreases in immunosuppression should be screened for dnDSA as it could lead to early intervention and potentially better outcomes.

Non-human leukocyte antigen-specific antibodies in thoracic transplantation.

PURPOSE OF REVIEW: Development of donor human leukocyte antigen (HLA)-specific antibodies is associated with graft loss, yet the role of non-HLA antibodies in solid organ transplant needs to be further defined. It is suggested that HLA antibodies and non-HLA antibodies collaborate together to impact graft outcome. This review focuses on the latest findings on antibodies against these non-HLA antigens in thoracic organ transplant. RECENT FINDINGS: These non-HLA antigens include signaling proteins expressed on the cell surface, such as angiotensin II type 1 receptor (AT1R), endothelin type A receptor, and structure proteins, such as myosin, vimentin, and Kα1 tubulin, and extracellular matrix protein collagen. Antibodies against these antigens may impact the allograft in different ways. Although these non-HLA antibodies can damage the allograft through complement-mediated or cell-mediated cytotoxicity, antibodies against AT1R and endothelin type A receptor can also alter the endothelial cell function by activating intracellular signals. The presence of these non-HLA antibodies may predispose the patient to develop HLA-specific antibodies. Recently, it has been shown patients with AT1R antibodies pretransplant have a higher chance to develop de-novo donor-specific HLA antibodies. SUMMARY: The findings suggest it is important to stratify the patient's immunologic risk by assessing both the HLA and non-HLA-specific antibodies.

Reduction of HLA antibodies by bi-specific antibody blinatumomab.

Donor specific antibodies against human leukocyte antigen (HLA) can cause engraftment failure in hemopoietic stem cell transplantation, or antibody mediated rejection in solid organ transplantation. To increase the chance of successful transplants, donor specific antibodies have to be reduced or depleted in patients with high levels of HLA antibodies. However, no current therapies have been proven to remove or reduce HLA antibodies effectively in the majority of patients. Blinatumomab, a bi-specific antibody, is used as a treatment for B-cell acute lymphoblastic leukemia (ALL) by targeting B cells. To determine if blinatumomab can reduce HLA antibodies, we tested HLA antibodies pre- and post-blinatumomab treatment in 7 B-ALL patients who had HLA antibodies. We found that 6 of 7 patients showed a substantial reduction in HLA antibodies after blinatumomab infusion. Calculated Panel Reactive Antibody (cPRA), a measurement of the possibility of getting immunologically compatible donors, was also lowered after blinatumomab infusion. Our observation suggests that blinatumomab can be a potential drug for desensitization therapy.

Assessment of IgM DSAs in Transplant Recipients: Relationship to De Novo IgG DSAs and Risk for Antibody Rejection.

Background: The presence of anti-HLA donor-specific antibodies (DSAs) is associated with antibody-mediated rejection (AMR) and inferior graft survival. However, recent data suggest that ~50% of AMR episodes are IgG DSA negative and possibly related to non-HLA DSAs. After the initial activation of B cells to alloantigen, IgM is the first immunoglobulin produced. In addition, both IgM and IgG isotopes can activate the classic complement pathway and induce complement-dependent cytotoxicity to allograft targets. Current practices focus on the assessment of IgG DSAs with little concern for the assessment of IgM DSAs. Methods: Here, we examined anti-HLA IgM in a cohort of 22 patients who developed de novo IgG DSAs by a modified single-antigen bead-based test. Results: We found IgM HLA DSAs developed before IgG DSAs. The median time from the detection of IgM DSAs to the appearance of de novo IgG DSAs was 461 d. Most patients had IgM DSAs against the same HLA-DQ antigens, for which IgG de novo DSAs were also later detected. IgM DSAs were detected in patients with biopsies suspected of AMR. Conclusions: The detection of IgM DSAs could be an early indicator of alloimmune responses to allografts before IgG de novo DSAs appear.