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Arthritis Rheumatol ; 2021 Dec 28.
Article in English | MEDLINE | ID: covidwho-1589171


OBJECTIVES: Patients with autoimmune inflammatory rheumatic diseases receiving rituximab (RTX) therapy are at higher risk for poor COVID-19 outcomes and show substantially impaired humoral anti-SARS-CoV-2 vaccine responses. However, the complex relationship between antigen-specific B 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 rheumatoid arthritis (RA) and ANCA-associated vasculitis (AAV) patients receiving RTX, 12 RA patients on other therapies and 30 healthy controls after SARS-CoV-2 vaccination with either mRNA or vector based vaccines. RESULTS: A minimum of 10 B cells/µL (0,4% of lymphocytes) in the peripheral circulation appeared to be required in RTX patients to mount seroconversion to anti-S1 IgG upon SARS-CoV-2 vaccination. RTX patients lacking IgG seroconversion showed reduced RBD+ B cells, lower frequency of TfH-like cells as well as less activated CD4 and CD8 T cells compared to IgG seroconverted RTX patients. Functionally relevant B cell depletion resulted in impaired IFNγ secretion by spike-specific CD4 T cells. In contrast, antigen-specific CD8 T cells were reduced in patients, independently of IgG formation. CONCLUSIONS: In patients receiving RTX, a minimum of 10 B cells/µl in the peripheral circulation candidates as 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 co-stimulatory B cell functions for the proper induction of CD4 responses propagating vaccine-specific B and plasma cell differentiation.

Eur J Immunol ; 52(1): 138-148, 2022 01.
Article in English | MEDLINE | ID: covidwho-1479399


The interferon pathway, a key antiviral defense mechanism, is being considered as a therapeutic target in COVID-19. Both, substitution of interferon and JAK/STAT inhibition to limit cytokine storms have been proposed. However, little is known about possible abnormalities in STAT signaling in immune cells during SARS-CoV-2 infection. We investigated downstream targets of interferon signaling, including STAT1, STAT2, pSTAT1 and 2, and IRF1, 7 and 9 by flow cytometry in 30 patients with COVID-19, 17 with mild, and 13 with severe infection. We report upregulation of STAT1 and IRF9 in mild and severe COVID-19 cases, which correlated with the IFN-signature assessed by Siglec-1 (CD169) expression on peripheral monocytes. Interestingly, Siglec-1 and STAT1 in CD14+ monocytes and plasmablasts showed lower expression among severe cases compared to mild cases. Contrary to the baseline STAT1 expression, the phosphorylation of STAT1 was enhanced in severe COVID-19 cases, indicating a dysbalanced JAK/STAT signaling that fails to induce transcription of interferon stimulated response elements (ISRE). This abnormality persisted after IFN-α and IFN-γ stimulation of PBMCs from patients with severe COVID-19. Data suggest impaired STAT1 transcriptional upregulation among severely infected patients may represent a potential predictive biomarker and would allow stratification of patients for certain interferon-pathway targeted treatments.

COVID-19/immunology , Monocytes/immunology , SARS-CoV-2/immunology , STAT1 Transcription Factor/immunology , Signal Transduction/immunology , Up-Regulation/immunology , Adult , Aged , Female , Humans , Interferon Regulatory Factors/immunology , Male , Middle Aged , Patient Acuity , Phosphorylation/immunology