LAUSR

There is global concern about outcomes after COVID-19 in kidney transplant recipients. To date, large cohort studies have shown higher rates of AKI and mortality in kidney transplant recipients who developed COVID-19 than in the general population, however it is still debated whether the immunological response associated with SARS-CoV-2 infection and/or the immunosuppressive modifications increase the risk of rejection [1, 2]. Since the beginning of the COVID-19 pandemic, the decrease in, and withdrawal of immunosuppressors, particularly in severe cases, has been a common practice. However, these strategies are not risk-free [3, 4]. We evaluated the presence of de novo donor specific antibodies (dnDSAs) and kidney biopsies in a group of kidney transplant recipients after recovering from COVID19. Twenty kidney transplant recipients followed-up at the National Institute of Cardiology in Mexico City, with a follow-up of at least 4 weeks after COVID-19 diagnosis, and with eGFR > 20 ml/min/1.73 m2 before COVID-19 diagnosis were included. Four weeks after COVID-19 diagnosis, antiHLA antibodies and kidney graft biopsy were performed (Fig. S1). Detection and characterization of anti-HLA antibodies were performed using Single Antigen Flow Beads assays (LSA class I and class II, Immucor, Norcross, GA). Luminex mean fluorescence intensity (MFI) was measured on a LABscan IS 200, specificities with an MFI ≥ 1000 were considered positive. De novo DSAs (dnDSAs) were considered positive when they had not been identified pre-transplantation. Kidney biopsy was planned 4 weeks after COVID-19 diagnosis, however, some biopsies had to be deferred. All biopsies were analyzed by a single expert kidney pathologist. Histological lesions were classified according to The Banff 2019 Kidney Meeting Report [5]. The baseline characteristics of kidney recipients are shown in Table 1. The details concerning clinical presentation are shown in Table S1. In our center, immunosuppressive treatment was decreased or withdrawn in 60% of patients, and excluding 3 cases, all patients had returned to their usual immunosuppressive regimen at the time of biopsy. We did not find a different pattern of immunosuppressive regimen modification in patients with and without rejection (67 vs 57%, P = 0.33). Thirty percent of patients had no major abnormalities in their kidney biopsy, 20% had chronic active antibodymediated rejection (ABMR), 15% active ABMR, 20% mixed ABMR/ T cell mediated rejection (TCMR), 10% borderline for acute TCMR, and 5% chronic active TCMR (Table S2). All patients who developed dnDSAs (n = 11) were diagnosed with rejection, 27.2% with ABMR, 36.4% mixed ABMR/ TCMR and 36.4% with chronic ABMR. Among cases diagnosed with rejection, 57% were considered subclinical. Subclinical rejection was diagnosed in all cases borderline for active TCMR and active ABMR, in 50% of active chronic ABMR, and in 25% of mixed ABMR/ TCMR, while all TCMR and 16.7% of biopsies with no major abnormalities had persistent kidney injury at biopsy. A detailed description is available in Tables 2 and S3. * César Flores-Gama [email protected]