Low switched memory B cells are associated with no humoral response after SARS-CoV-2 vaccine boosters in kidney transplant recipients.

Introduction: The humoral response after SARS-CoV-2 vaccination and boosters in kidney transplant recipients (KTRs) is heterogeneous and depends on immunosuppression status. There is no validated immune measurement associated with serological response in clinical practice. Multicolor flow cytometric immunophenotyping could be useful for measuring immune response. This study aimed to study B- and T-cell compartments through Standardized EuroFlow PID Orientation after SARS-CoV-2 vaccination and their association with IgG SARS-CoV-2 seropositivity status after two doses or boosters. Methods: We conducted a multicenter prospective study to evaluate humoral response after SARS-CoV-2 vaccination in KTRs. Heterologous regimen: two doses of inactivated SARS-CoV-2 and two boosters of BNT162b2 mRNA (n=75). Homologous vaccination: two doses of BNT162b2 mRNA and one BNT162b2 mRNA booster (n=13). Booster doses were administrated to KTRs without taking into account their IgG SARS-CoV-2 seropositivity status. Peripheral blood samples were collected 30 days after the second dose and after the last heterologous or homologous booster. A standardized EuroFlow PID Orientation Tube (PIDOT) and a supervised automated analysis were used for immune monitoring cellular subsets after boosters. Results: A total of 88 KTRs were included and divided into three groups according to the time of the first detected IgG SARS-CoV-2 seropositivity: non-responders (NRs, n=23), booster responders (BRs, n=41), and two-dose responders (2DRs, n=24). The NR group was more frequent on mycophenolate than the responder groups (NRs, 96%; BRs, 80%; 2DRs, 42%; p=0.000). Switched memory B cells in the 2DR group were higher than those in the BR and NR groups (medians of 30, 17, and 10 cells/ul, respectively; p=0.017). Additionally, the absolute count of central memory/terminal memory CD8 T cells was higher in the 2DR group than in the BR and NR groups. (166, 98, and 93 cells/ul, respectively; p=0.041). The rest of the T-cell populations studied did not show a statistical difference. Conclusion: switched memory B cells and memory CD8 T-cell populations in peripheral blood were associated with the magnitude of the humoral response after SARS-CoV-2 vaccination. Boosters increased IgG anti-SARS-CoV-2 levels, CM/TM CD8 T cells, and switched MBCs in patients with seropositivity after two doses. Interestingly, no seropositivity after boosters was associated with the use of mycophenolate and a lower number of switched MBCs and CM/TM CD8 T cells in peripheral blood.

Peripheral and respiratory muscle impairment during murine acute lung injury.

Acute respiratory distress syndrome is associated with skeletal muscle compromise, which decreases survival and impairs functional capacity. A comparative analysis of peripheral and respiratory muscles' atrophy and dysfunction in acute lung injury (ALI) has not been performed. We aimed to evaluate diaphragmatic and peripheral muscle mass and contractility in an ALI animal model. ALI was induced in C57BL/6 mice by intratracheal lipopolysaccharides instillation. Muscle mass and in vitro contractility were evaluated at different time points in hindlimb soleus (slow-twitch) and extensor digitorum longus (EDL, fast-twitch), as well as in the main respiratory muscle diaphragm. Myogenic precursor satellite cell-specific transcription factor Pax7 expression was determined by Western blot. Lung injury was associated with atrophy of the three studied muscles, although it was more pronounced and persistent in the diaphragm. Specific contractility was reduced during lung injury in EDL muscle but restored by the time lung injury has resolved. Specific force was not affected in soleus and diaphragm. A persistent increase in Pax7 expression was detected in diaphragm and EDL muscles after induction of ALI, but not in soleus muscle. Different peripheral and respiratory skeletal muscles are distinctly affected during the course of ALI. Each of the studied muscles presented a unique pattern in terms of atrophy development, contractile dysfunction and Pax7 expression.

Comparison of antibody response to SARS-CoV-2 after two doses of inactivated virus and BNT162b2 mRNA vaccines in kidney transplant.

BACKGROUND: Antibody response against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) after mRNA or adenoviral vector-based vaccines is weak in kidney transplant (KT) patients. However, few studies have focused on humoral response after inactivated virus-based vaccines in KT. Here, we compare antibody response following vaccination with inactivated virus (CoronaVac®) and BNT162b2 mRNA. METHODS: A national multicentre cross-sectional study was conducted. The study group was composed of patients from all KT centres in Uruguay, vaccinated between 1 and 31 May 2021 (CoronaVac®, n = 245 and BNT162b2, n = 39). The control group was constituted of 82 healthy individuals. Participants had no prior confirmed coronavirus disease 2019 (COVID-19) test. Blood samples were collected between 30 and 40 days after the second dose. Serum-specific immunoglobulin G (IgG) antibodies against the receptor-binding domain (RBD) of SARS-CoV-2 Spike protein were determined using the COVID-19 IgG QUANT ELISA Kit. RESULTS: Only 29% of KT recipients showed seroconversion (36.5% BNT162b2, 27.8% inactivated virus, P = 0.248) in comparison with 100% in healthy control with either vaccine. Antibody levels against RBD were higher with BNT162b mRNA than with inactivated virus [median (interquartile range) 173 (73-554) and 29 (11-70) binding antibody units (BAU)/mL, P < 0.034] in KT and 10 times lower than healthy control [inactivated virus: 308 (209-335) and BNT162b2: 2638 (2608-3808) BAU/mL, P < 0.034]. In multivariate analysis, variables associated with negative humoral response were age, triple immunosuppression, estimated glomerular filtration rate and time post-KT. CONCLUSION: Seroconversion was low in KT patients after vaccination with both platforms. Antibody levels against SARS-CoV-2 were lower with inactivated virus than BNT162b mRNA. These findings support the need for strategies to improve immunogenicity in KT recipients after two doses of either vaccine.

Recomendaciones sobre la vacunación contra SARS-CoV-2 / COVID-19 en pacientes con enfermedad renal y trasplante renal / Recommendations for the SARS-CoV-2 vaccination of patients with kidney disease and transplant recipients / Recomendações sobre vacinação contra SARS-CoV-2 / COVID-19 em pacientes com doença renal e transplante renal

Resumen: Este documento de recomendaciones tiene como objetivo orientar a médicos nefrólogos y no nefrólogos que asisten a pacientes con enfermedad renal crónica (ERC) en todas las etapas de la misma, en el proceso de vacunación contra el SARS-CoV-2. Como consecuencia de la situación epidemiológica y de los tiempos del proceso de elaboración de las vacunas disponibles, no se ha generado evidencia lo suficientemente potente, por lo que las recomendaciones no se acompañan del nivel de evidencia. Se fundamenta la necesidad de priorizar la vacunación en este grupo de pacientes en el mayor riesgo de adquirir la infección por SARS-CoV-2, desarrollar la enfermedad COVID-19 con mayor gravedad y presentar una mortalidad más elevada que la población general. Las recomendaciones se organizan por grupos de pacientes considerando pacientes con ERC no dialítica, diálisis y trasplante renal, y pacientes bajo tratamiento inmunosupresor.

Summary The objective of this document containing recommendations is to provide guidelines for nephrologists and non-nephrologists who assist patients with chronic kidney disease (CKD) at all stages of the disease on the vaccination process against SARS-CoV-2. As a consequence of the current epidemiological situation and the timing of the COVID-19 vaccine development -for available vaccines- there is no solid evidence, and thus, recommendations are not accompanied by the due medical proof. The need to prioritize vaccination in this group of patients is based on the increased risk of acquiring the SARS-CoV-2 infection, developing the COVID-19 disease with greater severity and presenting higher mortality rates than the general population. The recommendations are organized by groups of patients, considering patients with non-dialytic CKD, dialysis and kidney transplantation, and patients under immunosuppressive treatment.

Resumo: O objetivo deste documento de recomendações é orientar os nefrologistas e não nefrologistas que atendem pacientes com doença renal crônica (DRC) em todas as fases da doença, no processo de vacinação contra a SARS-CoV-2. Como consequência da situação epidemiológica e do momento do processo de produção das vacinas disponíveis, não foram geradas evidências suficientemente potentes, de modo que as recomendações não são acompanhadas de seu nível de evidência. A necessidade de priorizar a vacinação neste grupo de pacientes baseia-se no maior risco de adquirir a infecção pelo SARS-CoV-2, desenvolver a doença COVID-19 com maior gravidade e apresentar mortalidade superior à da população em geral. As recomendações são organizadas por grupos de pacientes, considerando pacientes com DRC não dialítica, em diálise, com transplante renal, e pacientes em tratamento imunossupressor.

Role of peroxynitrite in sepsis-induced acute kidney injury in an experimental model of sepsis in rats.

The mechanisms involved in sepsis-induced acute kidney injury (AKI) are unknown. We investigated the role of nitrosative stress in sepsis-induced AKI by studying the effects of manganese (III) tetrakis-(1-methyl-4-pyridyl) porphyrin pentachloride (MnTMPyP), a peroxynitrite decomposition catalyst, and aminoguanidine (AG), a selective nitric oxide synthase 2 (NOS2) inhibitor and peroxynitrite scavenger, on kidney function of rats subjected to cecal ligation and puncture (CLP). Sprague-Dawley rats (weighing 350 [SD, 50] g) were treated with MnTMPyP (6 mg/kg i.p.) or AG (50 mg/kg i.p.) at t = 12 and 24 h after CLP or sham procedure. At t = 36 h, mean arterial pressure and aortic blood flow were measured, and blood and urine samples were obtained for biochemical determinations, including creatinine clearance, fractional excretion of sodium, and neutrophil gelatinase-associated lipocalin concentration in the urine. Kidney tissue samples were obtained for (i) light microscopy, (ii) immunofluorescence and Western blot for 3-nitrotyrosine and NOS2, (iii) gene expression (quantitative real-time polymerase chain reaction) studies (NOS1, NOS2, NOS3, and superoxide dismutase 1), and (iv) matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Mean arterial pressure was unchanged and aortic blood flow decreased 25% in CLP animals. The sepsis-induced (i) decreased urine output and creatinine clearance and increased fractional excretion of sodium and urinary neutrophil gelatinase-associated lipocalin concentration, (ii) increased protein nitration and NOS2 protein, and (iii) NOS1 and NOS2 upregulation were all significantly attenuated by treatment with MnTMPyP or AG. Nitrated proteins in renal tissue from CLP animals (matrix-assisted laser desorption ionization time-of-flight mass spectrometry) were glutamate dehydrogenase, methylmalonate-semialdehyde dehydrogenase, and aldehyde dehydrogenase, mitochondrial proteins involved in energy metabolism or antioxidant defense. Nitro-oxidative stress is involved in sepsis-induced AKI, and protein nitration seems to be one mechanism involved.