Patients with kidney failure are at increased risk of SARS-CoV-2 infection, making effective vaccinations a critical need. It is not known how well mRNA vaccines induce B and plasma cell responses in dialysis patients (DPs) or kidney transplant recipients (KTRs) compared with healthy controls (HCs). We studied humoral and B cell responses of 35 HCs, 44 DPs, and 40 KTRs. Markedly impaired anti-BNT162b2 responses were identified among KTRs and DPs compared with HCs. In DPs, the response was delayed (3 to 4 weeks after boost) and reduced with anti-S1 IgG and IgA positivity in 70.5 and 68.2%, respectively. In contrast, KTRs did not develop IgG responses except for one patient who had a previous unrecognized infection and developed anti-S1 IgG. Most antigen-specific B cells (RBD⁺) were identified in the plasmablast or post-switch memory B cell compartments in HCs, whereas RBD⁺ B cells were enriched among pre-switch and naïve B cells from DPs and KTRs. The frequency and absolute number of antigen-specific circulating plasmablasts in the cohort correlated with the Ig response, a characteristic not reported for other vaccinations. In conclusion, these data indicated that immunosuppression resulted in impaired protective immunity after mRNA vaccination, including Ig induction with corresponding generation of plasmablasts and memory B cells. Thus, there is an urgent need to improve vaccination protocols in patients after kidney transplantation or on chronic dialysis.

Novel mRNA-based vaccines have been proven to be powerful tools in combating the global pandemic caused by SARS-CoV-2, with BNT162b2 (trade name: Comirnaty) efficiently protecting individuals from COVID-19 across a broad age range. Still, it remains largely unknown how renal insufficiency and immunosuppressive medication affect development of vaccine-induced immunity. We therefore comprehensively analyzed humoral and cellular responses in kidney transplant recipients after the standard second vaccination dose. As opposed to all healthy vaccinees and the majority of hemodialysis patients, only 4 of 39 and 1 of 39 transplanted individuals showed IgA and IgG seroconversion at day 8 ± 1 after booster immunization, with minor changes until day 23 ± 5, respectively. Although most transplanted patients mounted spike-specific T helper cell responses, frequencies were significantly reduced compared with those in controls and dialysis patients and this was accompanied by a broad impairment in effector cytokine production, memory differentiation, and activation-related signatures. Spike-specific CD8⁺ T cell responses were less abundant than their CD4⁺ counterparts in healthy controls and hemodialysis patients and almost undetectable in transplant patients. Promotion of anti-HLA antibodies or acute rejection was not detected after vaccination. In summary, our data strongly suggest revised vaccination approaches in immunosuppressed patients, including individual immune monitoring for protection of this vulnerable group at risk of developing severe COVID-19.

Significance statement: Protection of solid organ transplant recipients against SARS-CoV-2 by vaccination remains an unmet need, given the low immunogenicity of available vaccines in the presence of immunosuppression. Administration of a third dose to 25 kidney transplant recipients (KTR) resulted in seroconversion in 36% of patients, associated with significant quantitative and functional changes within the spike-antigen–specific B cell and CD4⁺ T-helper cell compartment. Our data support the need for individual humoral monitoring of immunosuppressed individuals after vaccination and continued efforts to adapt vaccination protocols for this at-risk group. Background: Accumulating evidence sugges ts solid organ transplant recipients, as opposed to the general population, show strongly impaired responsiveness toward standard SARS-CoV-2 mRNA-based vaccination, demanding alternative strategies for protectio n o f this vulnerable group. Methods: In line with recent recommendations, a third dose of either heterologous ChAdOx1 (AstraZeneca) or homologous BNT162b2 (BioNTech) was administered to 25 kidney transplant recipients (KTR) without humoral response after two doses of BNT162b2, followed by analysis of serological responses and vaccine-specific B- and T-cell immunity. Results: Nine out of 25 (36%) KTR under standard immunosuppressive treatment seroconverted until day 27 after the third vaccination, whereas one patient developed severe COVID-19 infection immediately after vaccination. Cellular analysis 7 days after the third dose showed significantly elevated frequencies of viral spike-protein receptor-binding domain-specific B cells in humor al responders as compared with nonresponders. Likewise, portions of spike-reactive CD4⁺ T helper cells were significantly elevated in patients who were seroconverting. Furthermore, overall frequencies of IL-2⁺, IL-4⁺, and polyfunctional CD4⁺ T cells significantly increased after the third dose, whereas memory/effector differentiation remained unaffected. Conclusions: Our data suggest a fraction of transplant recipients benefit from triple vaccination, where seroconversion is associated with quantitative and qualitative changes of cellular immunity. At the same time, the study highlights that modified vaccination approaches for immunosuppressed patients remain an urgent medical need. Podcast: This article contains a podcast athttps://www.asn-online.org/media/podcast/JASN/2021_11_23_briggsgriffin112321.mp3

Transplant recipients exhibit an impaired protective immunity after SARS-CoV-2 vaccination, potentially caused by mycophenolate (MPA) immunosuppression. Recent data from patients with autoimmune disorders suggest that temporary MPA hold might greatly improve booster vaccination outcomes. We applied a fourth dose of SARS-CoV-2 vaccine to 29 kidney transplant recipients during a temporary (5 weeks) MPA/azathioprine hold, who had not mounted a humoral immune response to previous vaccinations. Seroconversion until day 32 after vaccination was observed in 76% of patients, associated with acquisition of virus-neutralizing capacity. Interestingly, 21/25 (84%) calcineurin inhibitor–treated patients responded, but only 1/4 belatacept-treated patients responded. In line with humoral responses, counts and relative frequencies of spike receptor binding domain–specific (RBD-specific) B cells were markedly increased on day 7 after vaccination, with an increase in RBD-specific CD27 ⁺⁺ CD38 ⁺ plasmablasts. Whereas overall proportions of spike-reactive CD4 ⁺ T cells remained unaltered after the fourth dose, frequencies were positively correlated with specific IgG levels. Importantly, antigen-specific proliferating Ki67 ⁺ and in vivo–activated programmed cell death 1–positive T cells significantly increased after revaccination during MPA hold, whereas cytokine production and memory differentiation remained unaffected. In summary, antimetabolite hold augmented all arms of immunity during booster vaccination. These data suggest further studies of antimetabolite hold in kidney transplant recipients.

Mortality from COVID-19 among kidney transplant recipients (KTR) is high, and their response to three vaccinations against SARS-CoV-2 is strongly impaired. We retrospectively analyzed the serological response of up to five doses of the SARS-CoV-2 vaccine in KTR from 27 December 2020 until 31 December 2021. Particularly, the influence of the different dose adjustment regimens for mycophenolic acid (MPA) on serological response to fourth vaccination was analyzed. In total, 4277 vaccinations against SARS-CoV-2 in 1478 patients were analyzed. Serological response was 19.5% after 1203 basic immunizations, and increased to 29.4%, 55.6%, and 57.5% in response to 603 third, 250 fourth, and 40 fifth vaccinations, resulting in a cumulative response rate of 88.7%. In patients with calcineurin inhibitor and MPA maintenance immunosuppression, pausing MPA and adding 5 mg prednisolone equivalent before the fourth vaccination increased the serological response rate to 75% in comparison to the no dose adjustment (52%) or dose reduction (46%). Belatacept-treated patients had a response rate of 8.7% (4/46) after three vaccinations and 12.5% (3/25) after four vaccinations. Except for belatacept-treated patients, repeated SARS-CoV-2 vaccination of up to five times effectively induces serological response in kidney transplant recipients. It can be enhanced by pausing MPA at the time of vaccination.

Objective: Patients with autoimmune inflammatory rheumatic diseases receiving rituximab (RTX) therapy are at higher risk of poor COVID‐19 outcomes and show substantially impaired humoral immune response to anti–SARS–CoV‐2 vaccine. However, the complex relationship between antigen‐specific B cells and T cells and the level of B cell repopulation necessary to achieve anti‐vaccine responses remain largely unknown.Methods: Antibody responses to SARS–CoV‐2 vaccines and induction of antigen‐specific B and CD4/CD8 T cell subsets were studied in 19 patients with rheumatoid arthritis (RA) or antineutrophil cytoplasmic antibody–associated vasculitis receiving RTX, 12 patients with RA receiving other therapies, and 30 healthy controls after SARS–CoV‐2 vaccination with either messenger RNA or vector‐based vaccines.Results: A minimum of 10 B cells per microliter (0.4% of lymphocytes) in the peripheral circulation appeared to be required for RTX‐treated patients to mount seroconversion to anti‐S1 IgG upon SARS–CoV‐2 vaccination. RTX‐treated patients who lacked IgG seroconversion showed reduced receptor‐binding domain–positive B cells (P = 0.0005), a lower frequency of Tfh‐like cells (P = 0.0481), as well as fewer activated CD4 (P = 0.0036) and CD8 T cells (P = 0.0308) compared to RTX‐treated patients who achieved IgG seroconversion. Functionally relevant B cell depletion resulted in impaired interferon‐γ secretion by spike‐specific CD4 T cells (P = 0.0112, r = 0.5342). In contrast, antigen‐specific CD8 T cells were reduced in both RA patients and RTX‐treated patients, independently of IgG formation.Conclusion: In RTX‐treated patients, a minimum of 10 B cells per microliter in the peripheral circulation is a candidate biomarker for a high likelihood of an appropriate cellular and humoral response after SARS–CoV‐2 vaccination. Mechanistically, the data emphasize the crucial role of costimulatory B cell functions for the proper induction of CD4 responses propagating vaccine‐specific B cell and plasma cell differentiation.