Antoine Durrbach

Introduction: BKPyV-associated nephropathy (BKPyVAN) is a major complication in kidney transplantation. An exhaustion of BKPyV-specific T-cells but not T-cells against other viruses is observed, suggesting a mechanism specifically mediated by BKPyV-specific CD8 ⁺ T lymphocytes (BKPyV-LT-CD8). Methods: We analyzed the proliferation and specific functions in response to stimulation with BKPyV or CEF peptides of T-cells from 41 kidney transplants (23 without BKPyV-DNAemia and 18 with presumed BKPyVAN). We performed comparative transcriptomics on peripheral BKPyV-LT-CD8 and EBV-LT-CD8 cells, and kidney biopsy specimens from patients with BKPyVAN and stable transplants (GSE47199 dataset). The factors identified were validated by immunohistochemistry on graft biopsy specimens. Results: Levels of the KLRC1 transcript encoding NKG2A were higher in peripheral BKPyV-LT-CD8 than in EBV-LT-CD8 cells. They were also higher in BKPyVAN than in stable kidneys. Immunohistochemistry revealed a higher quantity of NKG2A ⁺ cells and of NKG2A ⁺ CD8 T-cells in BKPyVAN samples. Furthermore, the NKG2A ligand HLA-E tended to be more abundant in tubular epithelial cells from patients with BKPyVAN than in stable kidneys and located close to NKG2A. Conclusion: These findings identify NKG2A as a checkpoint inhibitor associated with impaired BKPyV-LT-CD8 function in presumed BKPyVAN. The NKG2A/HLA-E pathway therefore plays a key role in BKPyVAN.

Background.: BK polyomavirus (BKPyV) nephropathy is a significant complication of kidney transplantation associated with high levels of BKPyV replication in plasma and poor graft survival. It is currently treated by reducing immunosuppression to restore the immune response. Methods.: We analyzed circulating T cells from 28 kidney transplant recipients with detectable levels of BKPyV DNA in the blood (BKPyV DNAemia). Immunosuppression was significantly reduced in all these patients. We evaluated BKPyV-specific T-cell functionality and phenotype and assessed graft outcomes prospectively. Results.: BKPyV DNAemia was rapidly controlled in 13 patients (controllers [C] group), whereas viral replication was sustained in the other 15, who were considered not to have responded to reduced immunosuppression (noncontroller [NC] group). The induction and maintenance therapies used were similar in the C and NC groups. The slope of renal function decline tended to be worse in the NC group than in the C group ( P < 0.055). BKPyV-specific T-cell functions (T-cell proliferation and cytokine secretion) were weaker in the NC group than in the C group. This functional impairment was associated with an overexpression of several inhibitory receptors (programmed cell death protein 1 [PD1], T-cell immunoreceptor with Ig and immunoreceptor tyrosine-based inhibitory motif domains, or T-cell immunoglobulin and mucin-containing protein 3 [TIM3]), highlighting an exhausted-like phenotype of BKPyV-specific CD4 and CD8 T cells in the NC group. T-cell inhibition was not overcome by a single blocking antibody against inhibitory receptors, whereas a combination of anti-PD1 and anti-TIM3 antibodies significantly restored BKPyV-specific CD8 T-cell functions ( P < 0.05). Conclusions.: Sustained BKPyV DNAemia was associated with an exhausted phenotype of BKPyV-specific T cells despite immunosuppression reduction in kidney transplant recipients. We show that anti-BKPyV-specific CD8 functions can be restored ex vivo by blocking the PD1 and TIM3 pathways, paving the way for new treatment strategies.

Background: The impact of new immunosuppressive strategies to prevent graft rejection on prescribing patterns is poorly documented. The objective of this study was to describe immunosuppressive medication use and survival outcomes in patients undergoing kidney transplantation in France between 2009 and 2020. Methods: This retrospective cohort study was performed using data from the French national healthcare database. All adult patients undergoing kidney transplantation between 2009 and 2020 were identified, and followed from transplantation until study end, death or graft failure. All immunosuppressive drug deliveries from pharmacies were documented. Survival and death-censored graft failure were estimated using Kaplan-Meier analysis. Results: Thirty four thousand six hundred kidney transplantation patients were eligible. Median follow-up duration was 4.0 years [IQR: 1.6–7.0 years]. Five-year survival probability was 0.890 [0.885–0.895], and death-censored graft survival was 0.850 [0.844–0.856]. Overall survival, but not graft survival was age-dependent. Calcineurin inhibitors were delivered to 29,573 patients (91.3%), antimetabolites to 29,318 (90.5%), corticosteroids to 28,536 (88.1%), mTOR inhibitors to 5231 (16.1%) and belatacept to 1272 (3.9%). The use of tacrolimus, everolimus and belatacept increased over time, while the use of corticosteroids, ciclosporin and sirolimus declined. Immunosuppressive treatment was maintained by 22,963 patients (76.5%) throughout follow-up. Conclusions: In this comprehensive study of kidney transplant recipients in France, we observed high rates of overall patient and graft survival. Over the study period, immunosuppressive treatment patterns were relatively stable and dominated by the use of calcineurin inhibitors. These results provide important insights into the state of post-transplant care and the potential implications of increased availability of innovative therapies.

Calcineurin inhibitors have improved graft survival in solid-organ transplantation but their use is limited by toxicity, requiring a switch to another immunosuppressor in some cases. Belatacept is one option that has been shown to improve graft and patient survival despite being associated with a higher risk of acute cellular rejection. This risk of acute cellular rejection is correlated with the presence of belatacept-resistant T cells. We performed a transcriptomic analysis of in vitro-activated cells to identify pathways affected by belatacept in belatacept-sensitive cells (CD4⁺CD57⁻) but not in belatacept-resistant CD4⁺CD57⁺ T cells. mTOR was significantly downregulated in belatacept-sensitive but not belatacept-resistant T cells. The inhibition of mTOR strongly decreases the activation and cytotoxicity of CD4⁺CD57⁺ cells. In humans, the use of a combination of mTOR inhibitor and belatacept prevents graft rejection and decreases the expression of activation markers on CD4 and CD8 T cells. mTOR inhibition decreases the functioning of belatacept-resistant CD4⁺CD57⁺ T cells in vitro and in vivo. It could potentially be used in association with belatacept to prevent acute cellular rejection in cases of calcineurin intolerance.

Immunocompromised patients have a high risk of death from SARS-CoV-2 infection. Vaccination with an mRNA vaccine may protect these patients against severe COVID-19. Several studies have evaluated the impact of immune-suppressive drug regimens on cellular and humoral responses to SARS-CoV-2 variants of concern in this context. We performed a prospective longitudinal study assessing specific humoral (binding and neutralizing antibodies against spike (S) and T-lymphocyte (cytokine secretion and polyfunctionality) immune responses to anti-COVID-19 vaccination with at least two doses of BNT162b2 mRNA vaccine in stable kidney transplant recipients (KTR) on calcineurin inhibitor (CNI)- or belatacept-based treatment regimens. Fifty-two KTR−31 receiving CNI and 21 receiving belatacept—were enrolled in this study. After two doses of vaccine, 46.9% of patients developed anti-S IgG. Anti-spike IgG antibodies were produced in only 21.4% of the patients in the belatacept group, vs. 83.3% of those in the CNI group. The Beta and Delta variants and, more importantly, the Omicron variant, were less well neutralized than the Wuhan strain. T-cell functions were also much weaker in the belatacept group than in the CNI group. Renal transplant patients have an impaired humoral response to BNT162b2 vaccination. Belatacept-based regimens severely weaken both humoral and cellular vaccine responses. Clinically, careful evaluations of at least binding IgG responses, and prophylactic or post-exposure strategies are strongly recommended for transplant recipients on belatacept-based regimens.

Background: Acute rejection rate is low after simultaneous liver–kidney transplantation (SLKT), leading some groups to minimize immunosuppressive (IS) regimens. However, the impact of preformed (pDSA) or de novo donor-specific antibodies (dnDSA) on the graft remains unclear.Methods: We performed a retrospective analysis of 102 consecutive SLKT patients to study the impact of anti-HLA antibodies.Results: Anti-HLA antibodies were detected in 75 recipients (class I 23.8%, both classes I and II 23.8%, and class II 14.3%). In total, 42.8% of the patients had pDSA and 21.7% developed dnDSA. Overall patient survival at 1–3 and 5 years, was respectively 88, 84, and 80%. Acute rejection occurred respectively in 3 (2.9%) liver and 6 kidney (5.9%) recipients. pDSA with titers over 10,000 mean fluorescence intensity (14.3%) was associated with lower patient survival (40 vs. 82%) but not with acute rejection. In a multivariable Cox regression analysis, the risk of death was associated with maleness, the highest titer of pDSA (p < 0.0007) or the sum of pDSA >10,000. Renal function did not differ between patients with class I pDSA (p = 0.631) and those with class II pDSA (p = 0.112) or between patients with and without a positive cross-match (p = 0.842). dnDSA were not associated with acute rejection, graft dysfunction or patient survival. IS minimization was not associated with rejection, graft dysfunction or death.Conclusion: In SLKT, high levels of pDSA >10,000 were associated with lower patient survival, but not rejection or graft survival. Minimization of maintenance immunosuppression regimen was not associated with a poorer outcome.

BK-virus-associated nephropathy (BKvAN) is a major complication in kidney transplant recipients, associated with a higher level of BK-virus (BKv) replication and leading to poor graft survival. In a large cohort of kidney transplant recipients with various BKv reactivation levels, we found that BKvAN was associated with a low BKv-specific memory CD8 T-cell functionality and an exhausted-like phenotype. This severe lymphocyte impairment was associated with a low level of class II HLA mismatches. In vitro experiments showed that allogeneic CD4 T cells partly restored BKv-specific memory CD8 T-cell responses. Our results suggest that in kidney transplant recipient, allogeneic CD4 T cells may provide a heterospecific help that maintain an effective BKv-specific memory CD8 T-cell response, and allows a better control of BKv replication in the kidney graft.