ENGINEERED HBV-SPECIFIC T CELLS: DISENTANGLING ANTIVIRAL FROM KILLING CAPACITY (Abstrat No G04)
Authors:S. Koh1 , C.Y.L. Tham2, A.T. Tanoto2, A. Pavesi3, R.D. Kamm4,A. Bertoletti2. 1 Singapore Institute for Clinical Sciences A*STAR,2 Emerging Infectious Diseases Program, Duke-NUS Graduate Medical School, 3 Singapore MIT Alliance – SMART, Singapore, Singapore;4 Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, United States
Background and Aims: We have recently demonstrated that adoptive transfer of engineered HBV-specific T cells in a patient with HBsAg-productive HCC cause a profound inhbition of HBsAg production (J Hepatology 2014. doi: 10.1016/j.jhep.2014.10.001.). The difficulty to disentangle the antiviral effect of HBV T cells from their killing ability constitutes a barrier to the application of this immunotherapeutic approach in chronic HBV patients. Therefore, our aim was to produce HBV-specific T cells that can inhibit virus replication without hepatotoxicity and analyzed the antiviral mechanism mediated by these engineered T cells.
Methods: Using messenger RNA electroporation of HBV-T cell receptor in human lymphocytes, we produced HBV-specific T cells characterized by different activation and maturation stages. These distinct HBV-specific T cell populations were tested in 2 dimensional (2D) and 3D in vitro assays for their ability to inhibit HBV replication and/or lyse target cells.
Results: Among different engineered HBV-specific T cell populations, we selected a perforin/granzymelow HBV-specific T cells able to induce 50% drop in HBV viral load in HepG2.2.15 without causing detectable hepatotoxicity at an effector to target ratio of 1:3 (both in 2D and 3D models). After HBV-specific recognition, these resting naïve (CD28+CD27+) T cells produced a large range of cytokines (IFN-gamma, TNF-alpha, GM-CSF and lymphotoxin-alpha and -beta). Analysis of the specific antiviral mechanisms indicated that a specific synergy between classical antiviral cytokines (IFN-gamma, TNF-alpha, GM-CSF) and activator of lymphotoxin-b receptor (LTbR) pathway mediate the antiviral but non-cythopathic effect.
Conclusions: It is possible to produce HBV-specific T cells able to efficiently inhibit HBV replication without causing direct hepatocytes killing. This represents an attractive cell population for adoptive T cell therapy of chronic hepatitis B. The relative contribution of antiviral cytokines and/or LTbR activation to antiviral activity can lead to the development of new targeted combinatorial therapy in HBV infection.