Background/Purpose: The control of autoreactive T cells in an antigen-specific manner in autoimmune diseases is a major clinical research goal. Various regulatory immune signatures have emerged from the analysis of patients with type 1 diabetes (T1D), multiple sclerosis or allogeneic stem cell transplantation who achieve prolonged disease remission or a favorable response to immunotherapies designed to control T cells. These include CD4+CD25+CD127hi T helper (Th) cells producing Th2 cytokines, IL-10-producing CD4+ regulatory type 1 (Tr1) T cells, and EOMES+TIGIT+KLRG1+ “partially exhausted” CD8+ T cells. Transcriptomic and T cell receptor (TCR) sequencing analysis of rheumatoid arthritis (RA) peripheral blood (PB) and synovial T cells has identified large populations of clonally expanded CD4+ and CD8+ cytotoxic T cells (CTL) in RA patients. DEN-181 is a liposome immunotherapy encapsulating 40mg/ml collagen II_259-273 (CII) peptide + 400ng/ml calcitriol, which is presented by lymph node dendritic cells after s.c. injection. Here we assessed the impact of a single ascending dose of DEN-181 on PB CII-specific and bystander citrullinated (Cit) Cit64vimentin_59-71 autoreactive T cell responses, CD4+ T cells, and CTL.

Methods: Stored PBMC from 11 ACPA+ HLA-DRB1*0401 or *0101+ RA patients who received vehicle or 3 dose levels of DEN-181, in clinical trial protocol A-RA—0081, were evaluated for number of CII- and Cit64vimentin_59-71-specific CD4+ T cells 0, 7 and 28 days post-dosing with flow cytometry using haplotype-specific tetramers in a recently-qualified assay. CD45+ leukocytes from cryopreserved PBMC of one patient per cohort at 0 and 28 days post-dose were sequenced using 5’ RNA/TCR single-cell 10x Genomics kits. We identified clonally expanded TCR and mapped the clonotypes to their respective transcriptome using the Seurat package in R.

Results: The number of CII-specific T cells and Cit64vimentin_59-71-specific bystander T cells decreased at day 7 and 28 relative to baseline with similar trends in cohorts receiving 1ml or 3ml but not 0.3ml DEN-181 or placebo. Transcriptomics identified 16 unique CD3+TCR+ PB populations, including activated and exhausted CTL, naïve, Th2-like memory and regulatory CD4+ T cells. The most expanded clonotypes were CD8+ CTL. While the polyfunctional CD8+ CTL cluster decreased at day 28 after 0.3, 1 or 3ml DEN-181, exhausted CTL uniquely increased after 1ml DEN-181. In contrast to 0.3 or 3ml, all but one of the TCR clonotypes shared across time points after 1ml DEN-181 expanded its proportion of exhausted cells at day 28. Naïve-like T cells decreased and CD4^lo central memory Th-like T cells increased uniquely after 1ml DEN-181.

Conclusion: In T1D, CTL exhaustion reflects a favorable response to T cell immunotherapy. One ml of antigen-specific tolerising immunotherapy, DEN-181, controlled antigen-specific and autoreactive bystander CD4+ T cell numbers, and enhanced bystander CTL clonal exhaustion in RA PB.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/antigen-specific-and-bystander-autoreactive-t-cell-control-in-peripheral-blood-of-acpa-rheumatoid-arthritis-patients-administered-antigen-specific-tolerising-immunotherapy/