ABSTRACT
Purpose: COVID-19-related morbidity and mortality is high among kidney patients. Several studies recently suggested low humoral and cellular immune responses after two doses of mRNA-1273 (Moderna) in these patients. Interleukin (IL)-21 is key in orchestrating an effective immune response against viral infections, is mainly produced by activated CD4+ T-cells and stimulates both humoral and cellular immunity. However, T-cell function may be impaired in kidney patients and this may explain the poor response to vaccination. Currently, there is limited data available on the vaccine-induced IL-21 memory T-cell response in these patients. We studied the induction of SARS-CoV-2-specific IL-21 memory T-cell response after mRNA- 1273 vaccination in 3 groups of kidney patients. Method(s): 113 participants were randomly selected from a prospective controlled multicenter cohort study, including 38 controls, 19 chronic kidney disease (CKD) stages G4/5 (eGFR <30 mL/min/1.73m2), 20 dialysis and 36 kidney transplant patients. All participants received 2 doses of mRNA-1273. To assess the vaccineinduced IL-21 memory T-cell response, we performed an IL-21 ELISpot (per 3.105 PBMCs) in these participants at baseline and 28 days after the second vaccination. SARS-CoV-2 S1-specific IgG antibody levels were already measured in the context of the multicenter cohort study. Result(s): Kidney transplant recipients had a significantly lower number of SARSCoV- 2-specific IL-21 producing memory T-cells when compared to controls (median of 46 versus 146, P<0.001). Participants with CKD G4/5 or on dialysis also had reduced SARS-CoV-2-specific IL-21 producing memory T-cells compared to controls (median of 128 [19-658] and 124 [7-654] versus 146 [10-635], p=0.43 and p=0.45, respectively), but the difference was less pronounced. In addition, a positive correlation was found between the number of SARS-CoV-2-specific IL-21 producing memory T-cells and SARS-CoV-2 S1-specific IgG antibody levels for all groups (Pearson correlation coefficient of 0.2, p=0.028). Conclusion(s): Kidney transplant recipients have an impaired antibody response after two doses of mRNA-1273 (Moderna), which correlates with poor SARS-CoV- 2-specific T-cell reactivity. These findings suggest that poor IL-21 memory T-cell response might hamper protection against COVID-19.