Clinical grade multiparametric cell sorting and gene-marking of regulatory T cells.

BACKGROUND AIMS: Regulatory T cells (Tregs) are the main mediators of peripheral tolerance. Treg-directed therapy has shown promising results in preclinical studies of diverse immunopathologies. At present, the clinical applicability of adoptive Treg transfer is limited by difficulties in generating Tregs at sufficient cell dose and purity. METHODS: We developed a Good Manufacturing Practice (GMP) compliant method based on closed-system multiparametric Fluorescence-Activated Cell Sorting (FACS) to purify Tregs, which are then expanded in vitro and gene-marked with a clinical grade retroviral vector to enable in vivo fate tracking. Following small-scale optimization, we conducted four clinical-scale processing runs. RESULTS: We showed that Tregs could be enriched to 87- 92% purity following FACS-sorting, and expanded and transduced to yield clinically relevant cell dose of 136-732×106 gene-marked cells, sufficient for a cell dose of at least 2 × 106 cells/kg. The expanded Tregs were highly demethylated in the FOXP3 Treg-specific demethylated region (TSDR), consistent with bona fide natural Tregs. They were suppressive in vitro, but a small percentage could secrete proinflammatory cytokines, including interferon-γ and interleukin-17A. CONCLUSIONS: This study demonstrated the feasibility of isolating, expanding and gene-marking Tregs in clinical scale, thus paving the way for future phase I trials that will advance knowledge about the in vivo fate of transferred Tregs and its relationship with concomitant Treg-directed pharmacotherapy and clinical response.

IL-6-mediated endothelial injury impairs antiviral humoral immunity after bone marrow transplantation.

Endothelial function and integrity are compromised after allogeneic bone marrow transplantation (BMT), but how this affects immune responses broadly remains unknown. Using a preclinical model of CMV reactivation after BMT, we found compromised antiviral humoral responses induced by IL-6 signaling. IL-6 signaling in T cells maintained Th1 cells, resulting in sustained IFN-γ secretion, which promoted endothelial cell (EC) injury, loss of the neonatal Fc receptor (FcRn) responsible for IgG recycling, and rapid IgG loss. T cell-specific deletion of IL-6R led to persistence of recipient-derived, CMV-specific IgG and inhibited CMV reactivation. Deletion of IFN-γ in donor T cells also eliminated EC injury and FcRn loss. In a phase III clinical trial, blockade of IL-6R with tocilizumab promoted CMV-specific IgG persistence and significantly attenuated early HCMV reactivation. In sum, IL-6 invoked IFN-γ-dependent EC injury and consequent IgG loss, leading to CMV reactivation. Hence, cytokine inhibition represents a logical strategy to prevent endothelial injury, thereby preserving humoral immunity after immunotherapy.