T-cell engager antibodies enable T cells to control HBV infection and to target HBsAg-positive hepatoma in mice.

BACKGROUND & AIMS: Hepatitis B virus (HBV) infection is a global health threat responsible for 880,000 deaths per year. Current antiviral therapies control but rarely eliminate the virus, and leave chronic HBV carriers at risk to develop hepatocellular carcinoma (HCC). Lacking or dysfunctional virus-specific adaptive immunity prevents control of HBV and allows the virus to persist. Restoring anti-viral T-cell immunity to achieve HBV elimination in chronically infected patients will help to cure HBV. METHODS: We constructed bispecific T-cell engager antibodies that are designed to induce anti-viral immunity through simultaneous binding of HBV envelope proteins (HBVenv) on infected hepatocytes and cluster of differentiation 3 or 28 on T cells. T-cell engager antibodies were employed in co-cultures with healthy donor lymphocytes and HBV-infected target cells. Activation of T-cell response was determined by detection of pro-inflammatory cytokines, effector function by cytotoxicity and antiviral effects. To study in vivo efficacy, immune-deficient mice were transplanted with HBV envelope-positive and -negative hepatoma cells. RESULTS: The two T-cell engager antibodies synergistically activated T cells to become polyfunctional effectors that in turn elicited potent anti-viral effects by killing infected cells and in addition controlled HBV via non-cytolytic, cytokine-mediated antiviral mechanisms. In vivo in mice, the antibodies attracted T cells specifically to the tumors expressing HBVenv resulting in T-cell activation, tumor infiltration and reduction of tumor burden. CONCLUSION: This study demonstrates that the administration of HBVenv-targeting T-cell engager antibodies facilitates a robust T-cell redirection towards HBV-positive target cells and provides a feasible and promising approach for the treatment of chronic viral hepatitis and HBV-associated HCC. LAY SUMMARY: T-cell engager antibodies are an interesting, novel therapeutic tool to restore immunity in patients with chronic hepatitis B. As bispecific antibodies they on the hand bind HBV envelope proteins displayed on the surface of HBV-infected cells or HBV-positive hepatoma and on the other hand attract and stimulate T cells by binding CD3 or CD28 on the T cell. Hereby, they activate a potent antiviral and cytotoxic response resulting in the elimination of HBV-positive cells. Their potential to activate T cells to resolve HBV infection renders T-cell engagers interesting candidates for the therapy of chronic hepatitis B and HBV-associated hepatocellular carcinoma