Humoral and Cellular Immunity Are Significantly Affected in Renal Transplant Recipients, following Vaccination with BNT162b2.

Background: Renal transplant recipients (RTRs) tend to mount weaker immune responses to vaccinations, including vaccines against the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

Methods: Humoral immunity was assessed using anti-receptor binding domain (RBD) and neutralizing antibodies (NAb) serum levels measured by ELISA, and cellular immunity was assessed using T-, B-, NK, natural killer-like T (NKT)-cell subpopulations, and monocytes measured by flow cytometry, and also specific T-cell immunity, at predefined time points after BNT162b2 vaccination, in 57 adult RTRs.

Results: Administration of three booster doses was necessary to achieve anti-RBD and NAb protective levels in almost all patients (92.98%). Ab production, at several time points, was positively correlated with the corresponding renal function and inversely correlated with hemodialysis vintage (HDV) and treatment with mycophenolic acid (MPA). A gradual rise in several cell subpopulations, including total lymphocytes ( = 0.026), memory B cells ( = 0.028), activated CD4 ( = 0.005), and CD8 cells ( = 0.001), was observed even after the third vaccination dose, while a significant reduction in CD3+PD1+ ( = 0.002), NKT ( = 0.011), and activated NKT cells ( = 0.034) was noted during the same time interval. Moreover, SARS-CoV-2-specific T-cells were present in 41% of the patients who were unable to develop Nabs, and their positivity rates four months after the second dose were in inverse correlation with monocytes ( = 0.045) and NKT cells ( = 0.01).

Conclusions: SARS-CoV-2-specific T-cell responses preceded the humoral ones, while two booster doses were needed for this group of immunocompromised patients to mount a protective immune response.