Single fixed low-dose rituximab as induction therapy suppresses de novo donor-specific anti-HLA antibody production in ABO compatible living kidney transplant recipients

Molecular Signature Associated With Acute Rejection in Vascularized Composite Allotransplantation

Background

A deeper understanding of acute rejection in vascularized composite allotransplantation is paramount for expanding its utility and longevity. There remains a need to develop more precise and accurate tools for diagnosis and prognosis of these allografts, as well as alternatives to traditional immunosuppressive regimens.

Methods

Twenty-seven skin biopsies collected from 3 vascularized composite allotransplantation recipients, consisting of face and hand transplants, were evaluated by histology, immunohistochemistry staining, and gene expression profiling.

Results

Biopsies with clinical signs and symptoms of rejection, irrespective of histopathological grading, were significantly enriched for genes contributing to the adaptive immune response, innate immune response, and lymphocyte activation. Inflammation episodes exhibited significant fold change correlations between the face and hands, as well as across patients. Immune checkpoint genes were upregulated during periods of inflammation that necessitated treatment. A gene signature consisting of CCL5, CD8A, KLRK1, and IFNγ significantly predicted inflammation specific to vascularized composite allografts that required therapeutic intervention.

Conclusions

The mechanism of vascularized composite allograft-specific inflammation and rejection appears to be conserved across different patients and skin on different anatomical sites. A concise gene signature can be utilized to ascertain graft status along with a continuous scale, providing valuable diagnostic and prognostic information to supplement current gold standards of graft evaluation.

European Consensus on the Management of Sensitized Kidney Transplant Recipients: A Delphi Study

An increasing number of sensitized patients awaiting transplantation face limited options, leading to fatalities during dialysis and higher costs. The absence of established evidence highlights the need for collaborative consensus. Donor-specific antibodies (DSA)-triggered antibody-mediated rejection (AMR) significantly contributes to kidney graft failure, especially in sensitized patients. The European Society for Organ Transplantation (ESOT) launched the ENGAGE initiative, categorizing sensitized candidates by AMR risk to improve patient care. A systematic review assessed induction and maintenance regimens as well as antibody removal strategies, with statements subjected to the Delphi methodology. A Likert-scale survey was distributed to 53 European experts (Nephrologists, Transplant surgeons and Immunologists) with experience in kidney transplant recipient care. A rate ≥75% with the same answer was considered consensus. Consensus was achieved in 95.3% of statements. While most recommendations aligned, two statements related to complement inhibitors for AMR prophylaxis lacked consensus. The ENGAGE consensus presents contemporary recommendations for desensitization and immunomodulation strategies, grounded in predefined risk categories. The adoption of tailored, patient-specific measures is anticipated to streamline the care of sensitized recipients undergoing renal allografts. While this approach holds the promise of enhancing transplant accessibility and fostering long-term success in transplantation outcomes, its efficacy will need to be assessed through dedicated studies.

Monthly mini-dose rituximab for primary anti-PLA2R-positive membranous nephropathy: a personalized approach

BACKGROUND

The currently recommended dose of rituximab for primary membranous nephropathy is as high as that for lymphoma. However, the clinical manifestations of membranous nephropathy vary widely. Therefore, achieving individualized treatment is a topic that needs to be explored. This study assessed the efficacy of monthly mini-dose rituximab monotherapy in patients with primary membranous nephropathy.

METHODS

This retrospective study included 32 patients with primary membranous nephropathy treated at Peking University Third Hospital between March 2019 and January 2023. All patients were anti-phospholipase A2 receptor (PLA2R) antibody-positive and received rituximab 100 mg intravenously monthly for at least 3 months without other immunosuppressive therapy. Rituximab infusions were sustained until either remission of the nephrotic syndrome or a minimum serum anti-PLA2R titer ˂ 2 RU/mL was achieved.

RESULTS

The baseline parameters included: proteinuria, 8.5 ± 3.6 g/day; serum albumin, 24.8 ± 3.4 g/L; and anti-PLA2R antibody, 160 (20-2659) RU/mL. B-cell depletion was achieved in 87.5% patients after the first dose of rituximab 100 mg and in 100% after the second equivalent dose. The median follow-up was 24 months (range 18-38). Twenty-seven (84%) patients achieved remission, with 11 (34%) patients achieving complete remission by last follow-up. The relapse-free survival from the last infusion was 13.5 months (range 3-27). Patients were stratified into the low-titer (< 150 RU/mL, n = 17) and high-titer groups (≥ 150 RU/mL, n = 15) based on the anti-PLA2R titer. Sex, age, urinary proteins, serum albumin, and estimated glomerular filtration rate at baseline did not differ significantly between the two groups. At 18 months, compared to the low-titer group, the rituximab dose (960 ± 387 vs 694 ± 270 mg, p = 0.030) was higher, while serum albumin (37.0 ± 5.4 vs 41.3 ± 5.4 g/L, p = 0.033) and the complete remission rate (13% vs 53%, p = 0.000) were both lower in the high-titer group.

CONCLUSIONS

Monthly rituximab 100 mg appeared as a potential effective regimen for treating anti-PLA2R-associated primary membranous nephropathy with a low anti-PLA2R titer. The lower the anti-PLA2R titer, the lower the rituximab dose required to achieve remission.

TRIAL REGISTRATION

A retrospective study, registered at ChiCTR (ChiCTR2200057381) on March 10, 2022.

Effect of Mammalian Target of Rapamycin Inhibition on Activated Regulatory T-Cell Expansion in Kidney Transplantation

BACKGROUND

The mammalian target of rapamycin (mTOR) plays a critical role in the host immune response in organ transplantation. This study evaluates the regulatory benefits of mTOR inhibitors in kidney transplant recipients (KTRs).

METHODS

The mTOR-dependent immune-regulating effects in KTRs were evaluated by examining T-cell subsets among peripheral blood mononuclear cells from 79 KTRs. Recipients included an early introduction of everolimus (EVR) and reduced-exposure tacrolimus group (n = 46) and a standard tacrolimus-based without EVR (non-EVR) group (n = 33).

RESULTS

Trough concentrations of tacrolimus at 3 months and 1 year were significantly lower in the EVR group than the non-EVR group (both P < .001). In addition, the respective proportions of patients without estimated glomerular filtration rate < 20% in the EVR and non-EVR groups were 100% and 93.3% at 1 year, 96.3% and 89.7% at 2 years, and 96.3% and 89.7% at 3 years after blood collection, respectively (P = .079). The frequencies of CD3⁺ T cells and CD4⁺ T cells among peripheral blood mononuclear cells were comparable between groups. Total CD25^highCD127^-CD4⁺ regulatory T (Treg) cells were similar in the EVR and non-EVR groups. In contrast, circulating CD45RA^-CD25^highCD127^-CD4⁺ activated Treg cells were significantly higher in the EVR group (P= .008).

CONCLUSION

These results suggest that the early introduction of mTOR benefits long-term kidney graft function and circulating activated Treg-cell expansion in KTRs.

Burden of neutropenia and leukopenia among adult kidney transplant recipients: A systematic literature review of observational studies

BACKGROUND

Leukopenia and neutropenia (L/N) may affect treatment decisions, potentially resulting in poor clinical and economic outcomes among kidney transplant recipients (KTRs). The burden of L/N is poorly quantified systematically. This systematic literature review aimed to summarize the incidence of, risk factors for, and clinical and economic outcomes associated with L/N post-KT.

METHODS

We systematically searched MEDLINE, Embase, and the Cochrane Library (from database inception-June 14, 2021) and conferences (past 3 years) to identify observational studies examining epidemiology, risk factors, or outcomes associated with L/N among adult KTRs.

RESULTS

Of 2081 records, 82 studies met inclusion criteria. Seventy-three studies reported the epidemiology of L/N post-KT. Pooled incidence of neutropenia, defined as absolute neutrophil counts (ANC) <1000/μl, ranged from 13% to 48% within 1-year post-transplant; ANC <500/μl ranged from 15% to 20%. Leukopenia, defined as white blood cell counts <3500/μl, was 19% to 83%. Eleven studies reported independent risk factors associated with L/N post-KT. D+/R- cytomegalovirus status, mycophenolic acid (MPA), and tacrolimus use were the most consistent risk factors across studies. Fourteen studies reported L/N-associated clinical outcomes. We noted a trend toward a positive association between neutropenia and acute rejection/opportunistic infections. Mixed findings were noted on the association between L/N and graft failure or mortality. Dosage modifications of valganciclovir, MPA, cotrimoxazole, and anti-thymoglobulin and the need for granulocyte colony-stimulating factor (G-CSF) use were common with L/N.

CONCLUSION

Findings suggest post-transplant L/N were common and associated with frequent modifications of immunosuppressive agents, requiring G-CSF use, and rejection or opportunistic infections. Findings highlight the need for interventions to reduce risk of L/N post-KT.

Immunological imprint on peripheral blood in kidney transplant recipients after two doses of SARS-CoV-2 mRNA vaccination in Japan

The immunological imprint after two doses of severe acute respiratory syndrome–coronavirus 2 (SARS-CoV-2) mRNA vaccination for patients after kidney transplantation (KTx) remain unclear. This study included KTx recipients and volunteer healthy controls (HCs) who received two doses of SARS-CoV-2 mRNA vaccine (Pfizer BioNTech) from January 2021 to December 2021. We analyzed safety within 21 days after each vaccination dose and compared the immune response in peripheral blood mononuclear cells (PBMCs) between the two groups. No graft rejection was observed throughout this study. Adverse events were generally observed within 5 days. The KTx group exhibited a significantly lower degree of symptoms between doses 1 and 2 (P &lt; 0.001). Increases in activated subsets of T and B cells expressing human leukocyte antigen (HLA)-DR and/or CD38 were observed in the HC group after dose 2 (both P &lt; 0.001), with the greatest increases in HLA-DR+CD8+ T cells and CD38+CD19+ B cells (P = 0.042 and P = 0.031, respectively). In addition, PD1+CD8+ T cells—but not PD1+CD4+ T cells—increased significantly in the HC group (P = 0.027). In the KTx group, however, activated HLA-DR+, CD38+, and PD1+ cells remained at baseline levels. Immunoglobulin (Ig)G against SARS-CoV-2 was detected in only four KTx recipients (13.3%) after dose 2 (P &lt; 0.001). Multivariate logistic regression analyses revealed that ΔHLA-DR+CD8+ T cells and ΔCD38+CD19+ B cells were significantly associated with IgG formation (both P = 0.02). SARS-CoV-2 mRNA vaccine generates impaired cellular and humoral immunity for KTx recipients. Results indicate the need for modified vaccination strategies in immunocompromised KTx recipients.

Harnessing the B Cell Response in Kidney Transplantation - Current State and Future Directions

Despite dramatic improvement in kidney transplantation outcomes over the last decades due to advent of modern immunosuppressive agents, long-term outcomes remain poor. Antibody-mediated rejection (ABMR), a B cell driven process, accounts for the majority of chronic graft failures. There are currently no FDA-approved regimens for ABMR; however, several clinical trials are currently on-going. In this review, we present current mechanisms of B cell response in kidney transplantation, the clinical impact of sensitization and ABMR, the B cell response under current immunosuppressive regimens, and ongoing clinical trials for ABMR and desensitization treatment.

Complement Components in the Diagnosis and Treatment after Kidney Transplantation-Is There a Missing Link?

Currently, kidney transplantation is widely accepted as the renal replacement therapy allowing for the best quality of life and longest survival of patients developing end-stage renal disease. However, chronic transplant rejection, recurrence of previous kidney disease or newly acquired conditions, or immunosuppressive drug toxicity often lead to a deterioration of kidney allograft function over time. Complement components play an important role in the pathogenesis of kidney allograft impairment. Most studies on the role of complement in kidney graft function focus on humoral rejection; however, complement has also been associated with cell mediated rejection, post-transplant thrombotic microangiopathy, the recurrence of several glomerulopathies in the transplanted kidney, and transplant tolerance. Better understanding of the complement involvement in the transplanted kidney damage has led to the development of novel therapies that inhibit complement components and improve graft survival. The analysis of functional complotypes, based on the genotype of both graft recipient and donor, may become a valuable tool for assessing the risk of acute transplant rejection. The review summarizes current knowledge on the pathomechanisms of complement activation following kidney transplantation and the resulting diagnostic and therapeutic possibilities.

CD45RA-CD25highCD127-CD4+ activated regulatory T cells are correlated with de novo donor-specific anti-HLA antibody formation after kidney transplantation in standard immunosuppression

Although de novo donor-specific anti-HLA antibodies (dnDSA) remain a barrier for human kidney transplantation (KTx), the role of regulatory T (Treg) cells in dnDSA formation remains unknown. To address this question, we evaluated Treg cell subsets in peripheral blood mononuclear cells in 15 healthy volunteers and 59 KTx recipients using flow cytometric analysis. The post-transplant CD25^highCD127^-CD4⁺ Treg cells in KTx recipients were down-regulated compared with those of healthy volunteers (P < .001). Among them, 11 KTx recipients showed dnDSA formation, which was associated with lower frequencies of CD25^highCD127^-CD4⁺ Treg cells (P = .040). Furthermore, of the total Treg cell population, CD45RA^-CD25^highCD127^-CD4⁺ activated Treg (aTreg) cells were significantly dominant in patients with dnDSA (P = .038), but not CD45RA⁺CD25^highCD127^-CD4⁺ resting Treg cells (P = .961). In contrast, non-donor-specific anti-HLA antibody formation was not associated with CD45RA^- aTreg cells (P = .772). Multivariate logistic regression analyses revealed that CD45RA^- aTreg cells were independently associated with dnDSA formation (Odds ratio = 6.69, P = .040). These findings indicate that CD45RA^- aTreg cells are strongly associated with dnDSA formation in KTx recipients and might be an important risk factor of antibody-mediated rejection before clinical diagnosis.