Declining Course of Humoral Immune Response in Initially Responding Kidney Transplant Recipients after Repeated SARS-CoV-2 Vaccination (preprint)

Immunogenicity of SARS-CoV-2 vaccines in kidney transplant recipients is limited, resulting in inadequately low serological response rates and low immunoglobulin (Ig) levels, correlating with reduced protection against death and hospitalization from COVID-19. We retrospectively examined the time course of anti-SARS-CoV-2 Ig antibody levels after up to five repeated vac-cinations in 644 previously nonresponding kidney transplant recipients. Using anti SARS-CoV-2 IgG/IgA ELISA and the total Ig ECLIA assays, we compare antibody levels at 1 month with levels at 2 and 4 months, respectively. Additionally, we correlate the measurements of the used assays. Between 1 and 2 months, and between 1 and 4 months, mean anti-SARS-CoV-2 Ig levels in re-sponders decreased by 14% and 25%, respectively, depending on the assay. Absolute Ig values and time course of antibody levels and showed high interindividual variability. Ig levels de-creased by at least 20% in 77 of 148 paired samples with loss of sufficient serological protection over time occurring in 18 out of 148 (12.2%). IgG ELISA and total Ig ECLIA assays showed a strong positive correlation (Kendall's tau=0.78), yet the two assays determined divergent results in 99 of 751 (13.2%) measurements. IgG and IgA assays showed overall strong correlation but divergent results in 270 of 1.173 (23.0%) cases and only weak correlation of antibody levels in positive samples. Large interindividual variability and significant loss of serological protection after 4 months supports repeated serological sampling and consideration of shorter vaccination intervals in kidney transplant recipients.

Serological Response to Three, Four and Five Doses of SARS-CoV-2 Vaccine in Kidney Transplant Recipients (preprint)

Background Mortality from COVID-19 among kidney transplant recipients (KTR) is high, and their response to three vaccinations against SARS-CoV-2 is strongly impaired. Methods We retrospectively analyzed serological response of up to five doses of SARS-CoV-2 vaccine in KTR from December 27, 2020, until December 31, 2021. Particularly, the influence of different dose adjustment regimens for mycophenolic acid (MPA) on serological response to fourth vaccination was analyzed. Results In total, 4.277 vaccinations against SARS-CoV-2 in 1.478 patients were analyzed. Serological response was 19.5% after 1.203 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 serological response rate to 75% in comparison to 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. Conclusion 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.

Temporary hold of mycophenolate boosts SARS-CoV-2 vaccination-specific humoral and cellular immunity in kidney transplant recipients (preprint)

Transplant recipients exhibit an impaired protective immunity after SARS-CoV-2 vaccination, potentially caused by mycophenolate (MPA) immunosuppression. Recent data from autoimmune patients suggest that temporary MPA hold might significantly improve booster vaccination outcomes. We applied a fourth dose of SARS-CoV-2 vaccine during temporary (5 weeks) MPA hold to 29 kidney transplant recipients, 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%) CNI-treated patients responded, but only 1/4 Belatacept-treated patients. In line with humoral responses, counts and relative frequencies of spike receptor binding domain (RBD) specific B cells were significantly 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 PD1+ T cells significantly increased after re-vaccination during MPA hold, whereas cytokine production and memory differentiation remained unaffected. In summary, MPA hold was safe and augmented all arms of immunity during booster vaccination, suggesting its implementation in vaccination protocols for clinically stable transplant recipients.

B and T cell responses after a third dose of SARS-CoV-2 vaccine in Kidney Transplant Recipients (preprint)

BackgroundAccumulating evidence suggests that solid organ transplant recipients, as opposed to the general population, show strongly impaired responsiveness towards standard SARS-CoV-2 mRNA-based vaccination, demanding alternative strategies for protection of this vulnerable group. MethodsIn 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 2 doses of BNT162b2, followed by analysis of serological responses and vaccine-specific B- and T-cell immunity. Results9/25 (36%) KTR under standard immunosuppressive treatment seroconverted until day 27 after the third vaccination, while one patient developed severe COVID-19 infection immediately after vaccination. Cellular analysis seven days after the third dose showed significantly elevated frequencies of viral spike protein receptor binding domain specific B cells in humoral responders as compared to non-responders. Likewise, portions of spike-reactive CD4+ T helper cells were significantly elevated in seroconverting patients. 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. ConclusionsOur data suggest that a fraction of transplant recipients benefits 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 still remain an urgent medical need. Significance statementProtection 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 as well as continued efforts to adapt vaccination protocols for this at-risk group.

Impaired antigen-specific memory B cell and plasma cell responses including lack of specific IgG upon SARS-CoV-2 BNT162b2 vaccination among Kidney Transplant and Dialysis patients (preprint)

Patients with kidney failure are at increased risk during the COVID-19 pandemic and effective vaccinations are needed. It is not known how efficient mRNA vaccines mount B and plasma cell responses in dialysis patients (DP) or kidney transplant recipients (KTR) compared to healthy controls (HC). We studied humoral and B cell responses of 25 HC, 44 DP and 40 KTR. Markedly impaired anti-BNT162b2 responses were identified among KTR and DP compared to 100% seroconversion in HC. In DP, the response was delayed (3-4 weeks after boost) and reduced with anti-S1 IgG positivity in 31 (70.5%) and anti-S1 IgA in 30 (68.2%) of 44, respectively. In contrast, KTR did not develop IgG response except one patient who had prior unrecognized infection and developed anti-S1 IgG. The majority of antigen-specific B cells (RBD+) were identified in the plasmablast or post-switch memory B cell compartments in HC, whereas these RBD+ B cells were enriched among pre-switch and naive B cells from DP and KTR. Single cell transcriptome and CITE-seq analyses found reduced frequencies of plasmablasts, TCF7+CD27+GZMK+ T cells and proliferating MKI67-expressing lymphocytes among KTR non-responders. Importantly, the frequency and absolute number of antigen-specific circulating plasmablasts in the whole cohort correlated with the Ig response, a characteristic not reported for other vaccinations. In conclusion, this data indicate that lack of T cell help related to immunosuppression results in impaired germinal center differentiation of B and plasma cell memory. There is an urgent need to improve vaccination protocols in patients after kidney transplantation or on chronic dialysis. One Sentence SummaryKidney transplant recipients and dialysis patients show a markedly diminished humoral response and impaired molecular B cell memory formation upon vaccination with BNT162b2.

Impaired Humoral and Cellular Immunity after SARS-CoV2 BNT162b2 (Tozinameran) Prime-Boost Vaccination in Kidney Transplant Recipients (preprint)

Novel mRNA-based vaccines have been proven powerful tools to combat the global pandemic caused by SARS-CoV2 with BNT162b2 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 prime-boost vaccination with BNT162b2. As opposed to all healthy vaccinees and the majority of hemodialysis patients, only 4/39 and 1/39 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 to controls and dialysis patients, 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. Signs of alloreactivity promoted by BNT162b2 were not documented within the observation period. In summary, our data strongly suggest revised vaccination approaches in immunosuppressed patients, including individual immune monitoring for protection of this vulnerable group at risk to develop severe COVID-19.

Immunogenicity of COVID-19 Tozinameran Vaccination in Patients on Chronic Dialysis (preprint)

ObjectivePatients with kidney failure have notoriously weak responses to common vaccines. Thus, immunogenicity of novel SARS-CoV-2 vaccines might be impaired in this group. To determine immunogenicity of SARS-CoV-2 vaccination in patients with chronic dialysis, we analyzed the humoral and T-cell response after two doses of mRNA vaccine Tozinameran (BNT162b2 BioNTech/Pfizer). Design, Settings, and ParticipantsThis observational study included 43 patients on dialysis before vaccination with two doses of Tozinameran 21 days apart. Overall, 36 patients completed the observation period. Serum samples were analyzed by SARS-CoV-2 specific antibodies [~]1 and [~]3-4 weeks after the second vaccination. In addition, SARS-CoV-2-specific T-cell responses were assessed at the later time point by an interferon-gamma release assay (IGRA). Outcomes at later timepoints were compared to a group of 44 elderly patients with no dialysis after immunization with Tozinameran. ExposuresBlood drawings during regular laboratory routine assessment right before start of dialysis therapy or at the time of vaccination and at follow-up study visits. Main Outcomes and MeasuresAssessment of immunogenicity after vaccination against SARS-CoV-2 in patients on and without dialysis. ResultsMedian age of patients on chronic dialysis was 74.0 years (IQR 66.0, 82.0). The proportion of males was higher (69.4%) than females. Only 20/36 patients (55.6%, 95%CI: 38.29-71.67) developed SARS-CoV-2-IgG antibodies at first sampling, whereas 32/36 patients (88.9%, 95%CI:73.00-96.38) demonstrated seropositivity at the second sampling. Seroconversion rates and antibody titers were significantly lower compared to a cohort of vaccinees with similar age but no chronic dialysis (>90% seropositivity). SARS-CoV-2-specific T-cell responses 3 weeks after second vaccination were detected in 21/31 vaccinated dialysis patients (67.7%, 95%CI: 48.53-82.68) compared to 42/44 (93.3%, 95%CI: 76.49-98.84) in controls of similar age. Conclusion and RelevancePatients on dialysis demonstrate a delayed, but robust immune response three weeks after the second dose, which indicates effective vaccination of this vulnerable group. However, the lower immunogenicity of Tozinameran in these patients needs further attention to develop potential countermeasures such as an additional booster vaccination.