Development and Validation of Multivariable Prediction Models of Serological Response to SARS-CoV-2 Vaccination in Kidney Transplant Recipients (preprint)

Background Repeated vaccination against SARS-CoV-2 increases serological response in kidney transplant recipients (KTR) with high interindividual variability. No decision support tool exists to predict SARS-CoV-2 vaccination response in KTR. Methods We developed, internally and externally validated five different multivariable prediction models of serological response after the third and fourth vaccine dose against SARS-CoV-2 in KTR. Using 27 candidate predictor variables, we applied statistical and machine learning approaches including logistic regression (LR), LASSO-regularized LR, random forest, and gradient boosted regression trees. For development and internal validation, data from 585 vaccinations were used. External validation was performed in four independent, international validation datasets comprising 191, 184, 254, and 323 vaccinations, respectively. Findings LASSO-regularized LR performed on the whole development dataset yielded a 23- and 11- variable model, respectively. External validation showed AUC-ROC of 0.855, 0.749, 0.828, and 0.787 for the sparser 11-variable model, yielding an overall performance 0.819. Interpretation An 11-variable LASSO-regularized LR model predicts vaccination response in KTR with good overall accuracy. Implemented as an online tool, it can guide decisions when choosing between different immunization strategies to improve protection against COVID-19 in KTR.

Time-Limited Therapy With Belatacept in Kidney Transplant Recipients (preprint)

In kidney transplant recipients, belatacept is usually pursued indefinitely after it has been started. In the setting of the belatacept shortage and after having evaluated the benefit-risk ratio, we established a strategy consisting of time-limited belatacept therapy / transient calcineurin inhibitor withdrawal, whose results are analyzed in that study. We considered all the kidney transplant recipients that had been switched from conventional immunosuppressive therapy to belatacept and then for whom belatacept has been withdrawn intentionally. Furthermore, in the first 8 patients, we assessed changes in peripheral blood mononuclear cells (PBMC) transcriptome using RNAseq before and 3 months after belatacept withdrawal. Over the study period, 28 out of 94 patients had belatacept intentionally withdrawn including 25 (89%) switched to low-dose CNI. One rejection due to poor compliance occurred. The eGFR after 12 months remained stable from 48 ± 19 ml.1.73m-2 to 46 ±17 ml.1.73m-2 (p = 0.68). However, patients that resumed belatacept / withdrew CNIs (n=10) had a trend towards a better eGFR comparing with the others (n =15): 54 ± 20 ml.1.73m-2 vs eGFR 43 ± 16 ml.1.73m-2 respectively (p = 0.15). The only factor associated with belatacept resumption was when the withdrawal took place during the COVID-19 outbreak. Transcriptome analysis of PBMCs, did not support rebound in alloimmune response. These findings underpin the use of belatacept as part of a time-limited therapy, in selected kidney transplant recipients, possibly as an approach to allow efficient vaccination against SARS-Cov-2.

Changing of therapeutic trends between the 1st and 2nd wave did not reduce COVID-19 related mortality of renal transplant recipients: a national registry study. (preprint)

SARS-CoV-2 pandemic evolved in two consecutive waves over 2020 (for France: 1st wave from March 1 to July 31; and 2nd wave from August 1 to December 31). Improvements in the management of COVID-19 led to a reduction of mortality rates in hospitalized patients during the second wave. Whether this progress also benefited to kidney transplant recipients (KTR), a population particularly vulnerable to severe COVID-19, remained unclear. In France, 957 KTR were hospitalized for COVID-19 in 2020 and their data were prospectively collected in the French SOT COVID registry. The presentation, management, and outcomes of the 359 KTR diagnosed during the 1st wave were compared to those of the 598 of the 2nd wave. Baseline comorbidities were largely similar between KTR of the 2 waves. Maintenance immunosuppression was reduced in most patients but withdrawal of antimetabolite (73.7% vs 58.4%, p<0.001) or CNI (32.1% vs 16.6%, p<0.001) was less frequent during the 2nd wave. Hydroxychloroquine and azithromycin that were commonly used during the 1st wave (21.7% and 30.9%, respectively) were almost abandoned during the 2nd. In contrast, the use of high dose corticosteroids doubled (19.5% vs. 41.6%, p<0.001). Despite these changing trends in COVID-19 management, 60-day mortality was not statistically different between the 2 waves (25.3% vs. 23.9%; Log Rank, p=0.48). We conclude that changing of therapeutic trends during 2020 did not reduce COVID-19 related mortality in KTR. Our data indirectly support the importance of vaccination and monoclonal neutralizing anti-SARS-CoV-2 antibodies to protect KTR from severe COVID-19.

Antibody response to a fourth mRNA Covid-19 vaccine boost in weak responder kidney transplant recipients (preprint)

The US FDA has recently authorized immunocompromised people to receive a third dose of mRNA Covid-19 vaccine following the two-doses regimen to further boost protection. Unfortunately, a non-negligible proportion of people treated with immunosuppressive drugs either do not respond or show only a weak response after a third boost and should, therefore, still be considered at risk of severe Covid-19. As of June 2021, we were granted the opportunity to offer a fourth vaccine dose to French solid organ transplant recipients who still showed a weak antibody response after the third dose. In this multicenter study, we demonstrate that that the protection conferred by a fourth dose is adequate for the majority of kidney transplant recipients.