Approaches for Controlling Antibody-Mediated Allograft Rejection Through Targeting B Cells

Innate and adaptive effector immune drivers of cytomegalovirus disease in lung transplantation: a double-edged sword

Up to 90% of the global population has been infected with cytomegalovirus (CMV), a herpesvirus that remains latent for the lifetime of the host and drives immune dysregulation. CMV is a critical risk factor for poor outcomes after solid organ transplant, though lung transplant recipients (LTR) carry the highest risk of CMV infection, and CMV-associated comorbidities compared to recipients of other solid organ transplants. Despite potent antivirals, CMV remains a significant driver of chronic lung allograft dysfunction (CLAD), re-transplantation, and death. Moreover, the extended utilization of CMV antiviral prophylaxis is not without adverse effects, often necessitating treatment discontinuation. Thus, there is a critical need to understand the immune response to CMV after lung transplantation. This review identifies key elements of each arm of the CMV immune response and highlights implications for lung allograft tolerance and injury. Specific attention is paid to cellular subsets of adaptive and innate immune cells that are important in the lung during CMV infection and reactivation. The concept of heterologous immune responses is reviewed in depth, including how they form and how they may drive tissue- and allograft-specific immunity. Other important objectives of this review are to detail the emerging role of NK cells in CMV-related outcomes, in addition to discussing perturbations in CMV immune function stemming from pre-existing lung disease. Finally, this review identifies potential mechanisms whereby CMV-directed treatments may alter the cellular immune response within the allograft.

Utility of Routine Post Kidney Transplant Anti-HLA Antibody Screening

Introduction

De novo donor-specific antibody (dnDSA) is a strong biomarker associated with the development of antibody-mediated rejection (AMR) and graft loss after kidney transplantation. This procedure is expensive; however, systematic annual screening was recommended by some national organ transplant agencies or societies even though its clinical utility was not clearly established.

Methods

To address this question, we retrospectively assessed the incidence of dnDSA according to the test justification (clinically indicated or systematic) in a cohort of low-immunological risk patients, defined by being nonhuman leukocyte antigen (non-HLA)-sensitized and having no previous kidney transplants.

Results

A total of 1072 patients, for whom 4611 anti-HLA tests were performed, were included in the study. During the follow-up period of 8 (interquartile range, IQR: 5-11) years, 77 recipients developed dnDSA (prevalence of 7.2%). Thirty-five of these dnDSAs (45.5%) were detected during the first year posttransplantation. In 95% of patients with dnDSA, an immunizing event was identified in their medical records. dnDSA was detected in 46 of 4267 systematic screening tests (1.08%) performed. Active and chronic AMR were frequently observed in biopsies performed after systematic DSA testing (17.9% and 15.4%, respectively).

Conclusion

Our results suggest that the detection by systematic screening of dnDSA in low-immunological risk kidney transplant patients without sensitizing events is a rare event, especially after 1 year. Moreover, in real life, systematic annual screening for dnDSA, seems having a limited impact to detect AMR at an earlier stage compared to patients in whom dnDSA was detected after a clinically indicated test.

Repurposing of rituximab biosimilars to treat B cell mediated autoimmune diseases

Rituximab, the first monoclonal antibody approved for the treatment of lymphoma, eventually became one of the most popular and versatile drugs ever in terms of clinical application and revenue. Since its patent expiration, and consequently, the loss of exclusivity of the original biologic, its repurposing as an off-label drug has increased dramatically, propelled by the development and commercialization of its many biosimilars. Currently, rituximab is prescribed worldwide to treat a vast range of autoimmune diseases mediated by B cells. Here, we present a comprehensive overview of rituximab repurposing in 115 autoimmune diseases across 17 medical specialties, sourced from over 1530 publications. Our work highlights the extent of its off-label use and clinical benefits, underlining the success of rituximab repurposing for both common and orphan immune-related diseases. We discuss the scientific mechanism associated with its clinical efficacy and provide additional indications for which rituximab could be investigated. Our study presents rituximab as a flagship example of drug repurposing owing to its central role in targeting cluster of differentiate 20 positive (CD20) B cells in 115 autoimmune diseases.

Anti-CD20 Antibody and Calcineurin Inhibitor Combination Therapy Effectively Suppresses Antibody-Mediated Rejection in Murine Orthotopic Lung Transplantation

Antibody-mediated rejection (AMR) is a risk factor for chronic lung allograft dysfunction, which impedes long-term survival after lung transplantation. There are no reports evaluating the efficacy of the single use of anti-CD20 antibodies (aCD20s) in addition to calcineurin inhibitors in preventing AMR. Thus, this study aimed to evaluate the efficacy of aCD20 treatment in a murine orthotopic lung transplantation model. Murine left lung transplantation was performed using a major alloantigen strain mismatch model (BALBc (H-2d) → C57BL/6 (BL/6) (H-2b)). There were four groups: isograft (BL/6→BL/6) (Iso control), no-medication (Allo control), cyclosporine A (CyA) treated, and CyA plus murine aCD20 (CyA+aCD20) treated groups. Severe neutrophil capillaritis, arteritis, and positive lung C4d staining were observed in the allograft model and CyA-only-treated groups. These findings were significantly improved in the CyA+aCD20 group compared with those in the Allo control and CyA groups. The B cell population in the spleen, lymph node, and graft lung as well as the levels of serum donor-specific IgM and interferon γ were significantly lower in the CyA+aCD20 group than in the CyA group. Calcineurin inhibitor-mediated immunosuppression combined with aCD20 therapy effectively suppressed AMR in lung transplantation by reducing donor-specific antibodies and complement activation.

Seventh Day Syndrome Revisited: Early Recognition of the Clinical Syndrome and an Evolving Understanding of Its Etiology

Background

Unexplained acute failure of an initially functioning liver graft early post-transplant has been described as Seventh-Day Syndrome (7DS). The aims of this study were to describe the clinical syndrome in detail based on an institutional case series and literature review.

Methods

A retrospective review of adult patients that underwent deceased donor liver transplantation at our institution between January 2010 and 2020 was performed to identify patients that developed 7DS. Relevant clinical variables were obtained from medical records. Existing cases in the literature were identified by a systematic literature search according to PRISMA guidelines. Pooled analysis was used to describe the incidence, retransplantation, and mortality rate. Histological findings from institutional and published literature cases were collected and appraised.

Results

Six of 1,907 liver transplantations at our institution (0.3%) developed 7DS. Seven case series, describing 42 patients with 7DS, and two single case reports were identified from literature review. Pooled incidence of 7DS was low (2.1%, 95%CI: 0.7-3.9%) and associated with high mortality (74.8%, 95%CI: 49.2-94.6%). Retransplantation was performed in 23/42 (55%) patients and 4/23 (17%) survived. Review of histology showed frequent intrahepatic thrombi and arteritis. Rejection, with features of potential antibody mediated rejection, often preceded or accompanied progressive zonal coagulative necrosis and hemorrhage.

Conclusions

7DS is a rare clinical syndrome after liver transplantation and associated with high mortality. Antibody-mediated rejection, as suggested in early reports, is likely to be involved in the pathogenesis. Early recognition would allow rapid clinical diagnostics and expedited decisions, such as treatment of AMR if diagnosed or early retransplantation.