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All authors have seen and agreed to the final version of the paper

All authors have seen and agreed to the final version of the paper. recognizes the 30 aa extra-loop of the first N-terminal D1 domain of human LAG3)(EnzoLab) were used as positive controls. All Abs were resuspended in 2% MPBS. O.D.: optical density. B. Western blotting assay with LAG3 under reducing and non-reducing conditions. 0.5?g of glucose oxidase (GO) and of recombinant LAG3 proteins (the latter under three different conditions, namely: -DTT (reducing agent)/?boiling, ?DTT/+boiling 5?min, +DTT/+boiling 5?min) were Rosavin loaded as specified in replicate wells on a 12% SDS-PAGE and transferred to filter paper. Portions from the filter were then incubated with the indicated primary antibodies. An Anti-6 his mAb was used as a positive control for LAG3 recombinant protein Rosavin (which has a 6-histidines tag at its C terminal end). Arrows indicate relevant signals. The different molecular weights observed for LAG3 are obviously attributable to the impact of the different experimental conditions (non-reducing and reducing) on the SDS-PAGE separation. Molecular markers in kilodaltons (kDa) are reported on the right. The reactivity of the supernatants (scFvGO and scFvF7) used was previously checked in ELISA (bottom). (PPTX 125 kb) 12896_2019_559_MOESM1_ESM.pptx (152K) GUID:?28868DF9-BDE5-4D65-8379-1CC93BBCD068 Additional file 2: Figure S7AII. The treatment with the divalent scFvF7-Fc Ab increases the activation of peptide-stimulated Nef-specific CD8+ T lymphocytes in terms of IFN- secretion (Exp. I and Exp. III). For details see Legend of Fig. ?Fig.7a.7a. (PPTX 40 kb) 12896_2019_559_MOESM2_ESM.pptx (55K) GUID:?45090729-F736-4CFD-8912-7B6D2B4ED0FA Additional file 3: Figure S7AIII. The treatment with the divalent scFvF7-Fc Ab increases EZR the activation of peptide-stimulated Mart1-specific CD8+ T lymphocytes in terms of IFN- secretion (Exp. II and Exp. III). For details see Legend of Fig. ?Fig.7a.7a. (PPTX 41 kb) 12896_2019_559_MOESM3_ESM.pptx (55K) GUID:?12E0B546-8598-4940-B729-8E422D7854C0 Additional file 4: Figure S7BII. Dose-response effect of the divalent scFvF7-Fc Ab and inhibition by recombinant LAG3 (Exp. II). For details Rosavin see Legend of Fig. ?Fig.7b.7b. (PPTX 36 kb) 12896_2019_559_MOESM4_ESM.pptx (45K) GUID:?1E53C41D-7930-456B-AE20-49F5FE3E7314 Additional file 5: Figure S7CII. Effects of the divalent scFvF7-Fc as sensed by IFN- ELISPOT assay (Exp. II). For details see Legend of Figure ?Figure7c.7c. (PPTX 36 kb) 12896_2019_559_MOESM5_ESM.pptx (44K) GUID:?313A7A08-CC49-4EF8-A45C-F26F21CD920B Data Availability StatementThe datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request. Abstract Background Lymphocyte-activation gene (LAG)3 is a 498 aa transmembrane type I protein acting as an immune inhibitory receptor. It is expressed on activated lymphocytes, natural killer cells and plasmacytoid dendritic cells. In activated lymphocytes, LAG3 expression is involved in negative control of cell activation/proliferation to ensure modulation and control of immune responses. In view of its deregulated expression in tumor-infiltrating lymphocytes, LAG3, together with the additional immune checkpoint inhibitors CTLA4 and PD1, is considered a major target in order to reverse the immunosuppression typically mounting in oncologic diseases. Since many patients still fail to respond to current immune checkpoints-based therapies, the identification of new effective immune inhibitors is a priority in the ongoing fight against cancer. Results We identified a novel human single-chain variable fragment (scFv) Ab against a conformational epitope of LAG3 by in vitro phage display technology using the recombinant antigen as a bait. This scFv (referred to as F7) was characterized in terms of binding specificity to both recombinant antigen Rosavin and human LAG3-expressing cells. It was then rebuilt into an IgG format pre-optimized for clinical usage, and the resulting bivalent construct was shown to preserve its ability to bind LAG3 on human cells. Next, we analyzed the activity of the Rosavin anti-LAG3 scFvF7 using two different antigen-specific CD8+ T lymphocyte clones as target cells. We proved that the reconstituted anti-LAG3 F7 Ab efficiently binds the cell membrane of both cell clones after peptide-activation. Still more significantly, we observed a striking increase in the peptide-dependent cell activation upon Ab treatment as measured in terms of IFN- release by both ELISA and ELISPOT assays. Conclusions Overall, the biotechnological strategy described herein represents a guiding development model for the search of novel useful immune checkpoint inhibitors. In addition, our functional data propose a novel candidate reagent for consideration as a cancer treatment. TGI cells before and after each round of selection. Enrichment was calculated as ratio between outputs from each cycle and the output from the first one Open in a separate window Fig. 2 Nucleotide and amino acid sequences of scFvF7The whole scFvF7 sequence, including tags, is.