Repeated COVID-19 Vaccination Drives Memory T- and B-cell Responses in Kidney Transplant Recipients: Results From a Multicenter Randomized Controlled Trial.

BACKGROUND: Insight into cellular immune responses to COVID-19 vaccinations is crucial for optimizing booster programs in kidney transplant recipients (KTRs). METHODS: In an immunologic substudy of a multicenter randomized controlled trial (NCT05030974) investigating different repeated vaccination strategies in KTR who showed poor serological responses after 2 or 3 doses of an messenger RNA (mRNA)-based vaccine, we compared SARS-CoV-2-specific interleukin-21 memory T-cell and B-cell responses by enzyme-linked immunosorbent spot (ELISpot) assays and serum IgG antibody levels. Patients were randomized to receive: a single dose of mRNA-1273 (100 µg, n = 25), a double dose of mRNA-1273 (2 × 100 µg, n = 25), or a single dose of adenovirus type 26 encoding the SARS-CoV-2 spike glycoprotein (Ad26.COV2.S) (n = 25). In parallel, we also examined responses in 50 KTR receiving 100 µg mRNA-1273, randomized to continue (n = 25) or discontinue (n = 25) mycophenolate mofetil/mycophenolic acid. As a reference, the data were compared with KTR who received 2 primary mRNA-1273 vaccinations. RESULTS: Repeated vaccination increased the seroconversion rate from 21% to 66% in all patients, which was strongly associated with enhanced levels of SARS-CoV-2-specific interleukin-21 memory T cells (odd ratio, 3.84 [1.89-7.78]; P < 0.001) and B cells (odd ratio, 35.93 [6.94-186.04]; P < 0.001). There were no significant differences observed in these responses among various vaccination strategies. In contrast to KTR vaccinated with 2 primary vaccinations, the number of antigen-specific memory B cells demonstrated potential for classifying seroconversion after repeated vaccination (area under the curve, 0.64; 95% confidence interval, 0.37-0.90; P = 0.26 and area under the curve, 0.95; confidence interval, 0.87-0.97; P < 0.0001, respectively). CONCLUSIONS: Our study emphasizes the importance of virus-specific memory T- and B-cell responses for comprehensive understanding of COVID-19 vaccine efficacy among KTR.

SARS-CoV-2-specific immune responses converge in kidney disease patients and controls with hybrid immunity.

Healthy individuals with hybrid immunity, due to a SARS-CoV-2 infection prior to first vaccination, have stronger immune responses compared to those who were exclusively vaccinated. However, little is known about the characteristics of antibody, B- and T-cell responses in kidney disease patients with hybrid immunity. Here, we explored differences between kidney disease patients and controls with hybrid immunity after asymptomatic or mild coronavirus disease-2019 (COVID-19). We studied the kinetics, magnitude, breadth and phenotype of SARS-CoV-2-specific immune responses against primary mRNA-1273 vaccination in patients with chronic kidney disease or on dialysis, kidney transplant recipients, and controls with hybrid immunity. Although vaccination alone is less immunogenic in kidney disease patients, mRNA-1273 induced a robust immune response in patients with prior SARS-CoV-2 infection. In contrast, kidney disease patients with hybrid immunity develop SARS-CoV-2 antibody, B- and T-cell responses that are equally strong or stronger than controls. Phenotypic analysis showed that Spike (S)-specific B-cells varied between groups in lymph node-homing and memory phenotypes, yet S-specific T-cell responses were phenotypically consistent across groups. The heterogeneity amongst immune responses in hybrid immune kidney patients warrants further studies in larger cohorts to unravel markers of long-term protection that can be used for the design of targeted vaccine regimens.

Endothelial Cell Replacement of Human Veins, Modeling Vascular Repair and Endothelial Cell Chimerism.

Allogeneic transplant organs are potentially highly immunogenic. The endothelial cells (ECs) located within the vascular system serve as the primary interface between the recipient's immune system and the donor organ, playing a key role in the alloimmune response. In this study, we investigated the potential use of recipient-derived ECs in a vein recellularization model. In this study, human iliac veins underwent complete decellularization using a Triton X-100 protocol. We demonstrated the feasibility of re-endothelializing acellular blood vessels using either human umbilical cord vein endothelial cell or human venous-derived ECs, with this re- endothelialization being sustainable for up to 28 days in vitro. The re-endothelialized veins exhibited the restoration of vascular barrier function, along with the restoration of innate immunoregulatory capabilities, evident through the facilitation of monocytic cell transmigration and their polarization toward a macrophage phenotype following transendothelial extravasation. Finally, we explored whether recellularization with EC of a different donor could prevent antibody-mediated rejection. We demonstrated that in chimeric vessels, allogeneic EC became a target of the humoral anti-donor response after activation of the classical immune complement pathway whereas autologous EC were spared, emphasizing their potential utility before transplantation. In conclusion, our study demonstrates that replacement of EC in transplants could reduce the immunological challenges associated with allogeneic grafts.

Th1-dominant cytokine responses in kidney patients after COVID-19 vaccination are associated with poor humoral responses.

Cytokines are regulators of the immune response against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). However, the contribution of cytokine-secreting CD4+ and CD8+ memory T cells to the SARS-CoV-2-specific humoral immune response in immunocompromised kidney patients is unknown. Here, we profiled 12 cytokines after stimulation of whole blood obtained 28 days post second 100 µg mRNA-1273 vaccination with peptides covering the SARS-CoV-2 spike (S)-protein from patients with chronic kidney disease (CKD) stage 4/5, on dialysis, kidney transplant recipients (KTR), and healthy controls. Unsupervised hierarchical clustering analysis revealed two distinct vaccine-induced cytokine profiles. The first profile was characterized by high levels of T-helper (Th)1 (IL-2, TNF-α, and IFN-γ) and Th2 (IL-4, IL-5, IL-13) cytokines, and low levels of Th17 (IL-17A, IL-22) and Th9 (IL-9) cytokines. This cluster was dominated by patients with CKD, on dialysis, and healthy controls. In contrast, the second cytokine profile contained predominantly KTRs producing mainly Th1 cytokines upon re-stimulation, with lower levels or absence of Th2, Th17, and Th9 cytokines. Multivariate analyses indicated that a balanced memory T cell response with the production of Th1 and Th2 cytokines was associated with high levels of S1-specific binding and neutralizing antibodies mainly at 6 months after second vaccination. In conclusion, seroconversion is associated with the balanced production of cytokines by memory T cells. This emphasizes the importance of measuring multiple T cell cytokines to understand their influence on seroconversion and potentially gain more information about the protection induced by vaccine-induced memory T cells.

PRMT3 inhibitor SGC707 reduces triglyceride levels and induces pruritus in Western-type diet-fed LDL receptor knockout mice.

Protein arginine methyltransferase 3 (PRMT3) is a co-activator of liver X receptor capable of selectively modulating hepatic triglyceride synthesis. Here we investigated whether pharmacological PRMT3 inhibition can diminish the hepatic steatosis extent and lower plasma lipid levels and atherosclerosis susceptibility. Hereto, male hyperlipidemic low-density lipoprotein receptor knockout mice were fed an atherogenic Western-type diet and injected 3 times per week intraperitoneally with PRMT3 inhibitor SGC707 or solvent control. Three weeks into the study, SGC707-treated mice developed severe pruritus and scratching-associated skin lesions, leading to early study termination. SGC707-treated mice exhibited 50% lower liver triglyceride stores as well as 32% lower plasma triglyceride levels. Atherosclerotic lesions were virtually absent in all experimental mice. Plasma metabolite analysis revealed that levels of taurine-conjugated bile acids were ~ threefold increased (P < 0.001) in response to SGC707 treatment, which was paralleled by systemically higher bile acid receptor TGR5 signalling. In conclusion, we have shown that SGC707 treatment reduces hepatic steatosis and plasma triglyceride levels and induces pruritus in Western-type diet-fed LDL receptor knockout mice. These findings suggest that pharmacological PRMT3 inhibition can serve as therapeutic approach to treat non-alcoholic fatty liver disease and dyslipidemia/atherosclerosis, when unwanted effects on cholesterol and bile acid metabolism can be effectively tackled.

An Implantable Artificial Atherosclerotic Plaque as a Novel Approach for Drug Transport Studies on Drug-Eluting Stents.

Atherosclerotic arteries are commonly treated using drug-eluting stents (DES). However, it remains unclear whether and how the properties of atherosclerotic plaque affect drug transport in the arterial wall. A limitation of the currently used atherosclerotic animal models to study arterial drug distribution is the unpredictability of plaque size, composition, and location. In the present study, the aim is to create an artificial atherosclerotic plaque-of reproducible and controllable complexity and implantable at specific locations-to enable systematic studies on transport phenomena of drugs in stented atherosclerosis-mimicking arteries. For this purpose, mixtures of relevant lipids at concentrations mimicking atherosclerotic plaque are incorporated in gelatin/alginate hydrogels. Lipid-free (control) and lipid-rich hydrogels (artificial plaque) are created, mounted on DES and successfully implanted in porcine coronary arteries ex-vivo. Matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) is used to measure local drug distribution in the arterial wall behind the prepared hydrogels, showing that the lipid-rich hydrogel significantly hampers drug transport as compared to the lipid-free hydrogel. This observation confirms the importance of studying drug transport phenomena in the presence of lipids and of having an experimental model in which lipids and other plaque constituents can be precisely controlled and systematically studied.