Background. In kidney patients COVID-19 is associated with severely increased morbidity and mortality. A comprehensive comparison of the immunogenicity, tolerability, and safety of COVID-19 vaccination in different cohorts of kidney patients and a control cohort is lacking. Methods. This investigator driven, prospective, controlled multicenter study included 162 participants with chronic kidney disease (CKD) stages G4/5 (eGFR < 30 mL/min/1.73m2), 159 participants on dialysis, 288 kidney transplant recipients, and 191 controls. Participants received 2 doses of the mRNA-1273 COVID-19 vaccine (Moderna). The primary endpoint was seroconversion. Results. Transplant recipients had a significantly lower seroconversion rate when compared with controls (56.9% versus 100%, P < 0.001), with especially mycophenolic acid, but also, higher age, lower lymphocyte concentration, lower eGFR, and shorter time after transplantation being associated with nonresponder state. Transplant recipients also showed significantly lower titers of neutralizing antibodies and T-cell responses when compared with controls. Although a high seroconversion rate was observed for participants with CKD G4/5 (100%) and on dialysis (99.4%), mean antibody concentrations in the CKD G4/5 cohort and dialysis cohort were lower than in controls (2405 [interquartile interval 1287-4524] and 1650 versus 3186 [1896-4911] BAU/ mL, P = 0.06 and P < 0.001, respectively). Dialysis patients and especially kidney transplant recipients experienced less systemic vaccination related adverse events. No specific safety issues were noted. Conclusions. The immune response following vaccination in patients with CKD G4/5 and on dialysis is almost comparable to controls. In contrast, kidney transplant recipients have a poor response. In this latter, patient group development of alternative vaccination strategies are warranted.

Background In the general population, illness after infection with the SARS-CoV-2 Omicron variant is less severe compared with previous variants. Data on the disease burden of Omicron in immunocompromised patients are lacking. We investigated the clinical characteristics and outcome of a cohort of immunocompromised patients with COVID-19 caused by Omicron. Methods Solid organ transplant recipients, patients on anti-CD20 therapy, and allogenic hematopoietic stem cell transplantation recipients on immunosuppressive therapy infected with the Omicron variant, were included. Patients were contacted regularly until symptom resolution. Clinical characteristics of consenting patients were collected through their electronic patient files. To identify possible risk factors for hospitalization, a univariate logistic analysis was performed. Results A total of 114 consecutive immunocompromised patients were enrolled. Eighty-nine percent had previously received three mRNA vaccinations. While only one patient died, 23 (20%) required hospital admission for a median of 11 days. A low SARS-CoV-2 IgG antibody response (&lt;300 BAU/mL) at diagnosis, higher age, being a lung transplant recipient, more comorbidities and a higher frailty were associated with hospital admission (all p &lt; 0.01). At the end of follow-up, 25% had still not fully recovered. Of the 23 hospitalized patients, 70% had a negative and 92% a low IgG (&lt;300 BAU/mL) antibody response at admission. Sotrovimab was administered to 17 of them, of which one died. Conclusions While the mortality in immunocompromised patients infected with Omicron was low, hospital admission was frequent and the duration of symptoms often prolonged. Besides vaccination, other interventions are needed to limit the morbidity from COVID-19 in immunocompromised patients.

Tissue-resident memory T (T RM ) cells are characterized by their surface expression of CD69 and can be subdivided in CD103+ and CD103− T RM cells. The origin and functional characteristics of T RM cells in the renal allograft are largely unknown. To determine these features we studied T RM cells in transplant nephrectomies. T RM cells with a CD103+ and CD103− phenotype were present in all samples ( n = 13) and were mainly CD8+ T cells. Of note, donor-derived T RM cells were only detectable in renal allografts that failed in the first month after transplantation. Grafts, which failed later, mainly contained recipient derived T RM cells. The gene expression profiles of the recipient derived CD8+ T RM cells were studied in more detail and showed a previously described signature of tissue residence within both CD103+ and CD103− T RM cells. All CD8+ T RM cells had strong effector abilities through the production of IFNγ and TNFα, and harboured high levels of intracellular granzyme B and low levels of perforin. In conclusion, our results demonstrate that donor and recipient T RM cells reside in the rejected renal allograft. Over time, the donor-derived T RM cells are replaced by recipient T RM cells which have features that enables these cells to aggressively respond to the allograft.

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Background The immune response to COVID-19 vaccination is inferior in kidney transplant recipients (KTR), and to a lesser extent in patients on dialysis or with chronic kidney disease (CKD). We assessed the immune response 6 months after mRNA-1273 vaccination in kidney patients and compared this to controls. Methods 152 participants with CKD stages G4/5 (eGFR &lt;30  mL/min/1.73m2), 145 participants on dialysis, 267 KTR, and 181 controls were included. SARS-CoV-2 Spike S1-specific IgG antibodies were measured by fluorescent bead-based multiplex-immunoassay, neutralizing antibodies to ancestral, Delta and Omicron (BA.1) variants by plaque reduction, and T-cell responses by IFN-γ release assay. Results At 6 months after vaccination S1-specific antibodies were detected in 100% of controls, 98.7% of CKD G4/5 patients, 95.1% of dialysis patients, and 56.6% of KTR. These figures were comparable to the response rates at 28 days, but antibody levels waned significantly. Neutralization of the ancestral and Delta variant was detected in most participants, whereas neutralization of Omicron was mostly absent. S-specific T-cell responses were detected 6 months in 75.0% of controls, 69.4% of CKD G4/5 patients, 52.6% of dialysis patients, and 12.9% of KTR. T-cell responses at 6 months were significantly lower than responses at 28 days. Conclusions Although seropositivity rates at 6 months were comparable to that at 28 days after vaccination, significantly decreased antibody levels and T-cell responses were observed. The combination of low antibody levels, reduced T-cell responses, and absent neutralization of the newly-emerging variants indicates the need for additional boosts or alternative vaccination strategies in KTR.