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3081 Characterisation of Human CD83 Expression on Immune Cells and Their Targeting with CD83 Antibodies to Prevent Graft Versus Host Disease in Allogeneic Haematopoietic Cell Transplantation

Experimental Transplantation: Immune Function, GVHD and Graft-versus-Tumor Effects
Program: Oral and Poster Abstracts
Session: 702. Experimental Transplantation: Immune Function, GVHD and Graft-versus-Tumor Effects: Poster II
Sunday, December 6, 2015, 6:00 PM-8:00 PM
Hall A, Level 2 (Orange County Convention Center)

Derek NJ Hart1,2, Xinsheng Ju1,2*, Zehra Elgundi1,2*, Nirupama Verma1,2*, Pablo Silveira1,2*, Phillip Fromm1,2*, Renz Alingcastre1*, Blake Hsu1*, David J Munster3,4*, Therese Seldon3,4*, Yonghua Sheng3,4*, Martina Jones5*, Trent Munro5*, Stephen Mahler5*, Ross Barnard6,7*, Ai Vu1*, Tsun Ho Lo1*, Kifah Shahin1,8*, Stephen Robert Larsen, MBBS PhD FRCPA FRACP9, Kenneth Bradstock1,6* and Georgina Clark1,2*

1Dendritic Cell Research Group, ANZAC Research Institute, Concord, Australia
2Sydney Medical School, The University of Sydney, Sydney, Australia
3Cooperative Research Centre for Biomarker Translation, Melbourne, Australia
4Mater Medical Research Institute, South Brisbane, Australia
5Australian Institute of Bioengineering and Nanotechnology, The University of Queensland, Brisbane, Australia
6Blood and Marrow Transplant Service, Westmead Hospital, Westmead, Australia
7School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Australia
8Flow Cytometry Unit, Westmead Hospital, Westmead, Australia
9Institute of Haematology, Royal Prince Alfred Hospital, Camperdown, Australia

Introduction: CD83 is an important marker of activated dendritic cells (DC) but it is also expressed on other immune cells. Polyclonal anti-CD83 antibody depletes activated DC and prevents human peripheral blood mononuclear cell (PBMC) induced xenogeneic graft versus host disease (GVHD) in immunosuppressed SCID mice (J Exp Med 2009;206;387). We therefore generated a potential therapeutic human anti-CD83 mAb (3C12C), which had similar efficacy and T cell sparing effects in the same model (Leukemia 2015; in press).  To investigate the specific immunosuppressive effect of 3C12C further, we undertook a comprehensive analysis of CD83 expression and its glycosylation pattern on various immune cell populations and tested the effect of 3C12C on T cell function using preclinical models, including a human CD83 (hCD83) knock in (KI) mouse.

Methods: A panel of mouse and recombinant mAbs to hCD83 were used to analyse its expression by flow cytometry on resting and activated healthy donor PBMC. The expression of potential CD83 splice variants was examined by PCR. T cell expression was examined by flow cytometry and confocal microscopy after PHA, CD3/CD28 beads and allogeneic mixed leukocyte reaction (alloMLR) culture. Control human IgG1 (trastuzumab) and 3C12C mAbs were tested (0.125mg d-1) in a xenogeneic model of GVHD utilizing human PBMC transplanted into total body irradiation and anti-NK conditioned SCID mice. The genetically engineered hCD83 KI mouse was shown to be immune-competent and used to test the effect of 3C12C on LPS activated DC and T cells.   

Results: There were distinct CD83 splice variants (full length CD83, splicing variant CD83a, CD83b and CD83c) in different immune cells.  CD83 glycosylation status also differed with high glycosylation required for surface expression on activated DC, whereas its expression on activated B cells and monocytes was resistant to de-glycosylation. Increases in CD83 expression on T cells occurred early with different kinetics, underlining the distinct signal pathway involved. The 3C12C mAb reduced T cell proliferation in the alloMLR but did not affect cytomegalovirus (CMV) or influenza (Flu) specific CD8+T cell numbers. Treatment with 3C12C prevented GVHD in human PBMC transplanted SCID mice, which otherwise developed histological GVHD between d8-13. Human DC were activated by d2 and expressed the CMRF-44 activation marker plus CD83, CD80 and CD86. Treatment with 3C12C mAb eliminated CD83+ CMRF44+ DC early post-transplant and reduced T cell activation.  Further studies, established CMV and Flu specific T cells were retained and responded to antigen by IFNg production. Furthermore, Treg numbers were preserved. The 3C12C mAb depleted LPS activated DC in hCD83 KI mice in experiments performed prior to commencing transplant studies.

Conclusion: These findings suggest that the potential therapeutic human anti-CD83 mAb induced significant immune suppression, by depletion of activated DC and consequential modulation of T cell activation. The reduction in allo/xeno activated T cells may result in part from a direct effect of anti-CD83 on early T cell responses. This apparently selective immunosuppressive effect preserves anti-viral T cell immunity and Treg pathways, suggesting that 3C12C merits further investigation as a novel agent for GVHD prophylaxis.

Disclosures: Hart: DendroCyte BioTech Pty Ltd: Equity Ownership . Clark: DendroCyte BioTech Pty Ltd: Equity Ownership .

*signifies non-member of ASH