Mafosfamide Boosts GMI-HBVac against HBV via Treg Depletion in HBV-Infected Mice

Chronic hepatitis B infection remains a significant worldwide health burden, placing persons at risk for hepatocellular cancer and hepatic fibrosis. Chronic hepatitis B virus (CHB) infection is characterized by elevated levels of immunosuppressive regulatory T cells (Tregs), which can inhibit the function of effector T cells and lead to an insufficient immune clearance response against HBV. Theoretically, suppression of Treg cell functionality and percentage could increase anti-HBV reactivity in CHB-infected patients, although this has not yet been explored. We attempted to enhance our previously established anti-CHB protocol utilizing the GM-CSF+IFN-& alpha;+rHBVvac regimen (GMI-HBVac) by incorporating mafosfamide (MAF), which has been utilized in anticancer therapy in the past. Intravenous administration of MAF to rAAV8-1.3HBV-infected mice resulted in a dose-dependent reduction of Tregs in the blood, rebounding to pretreatment levels 10 days later. To assess the potential benefit of adding MAF to the anti-CHB protocol, 2 & mu;g/mL MAF was combined with the GMI-HBVac as an anti-Treg treatment in an HBV-infected animal model. When rAAV8-1.3HBV-infected mice were immunized with MAF+GMI-HBVac, peripheral blood Tregs decreased significantly, leading to dendritic cell activation, HBV-specific T cell proliferation, and the upregulation of IFN-gamma-producing CD8(+)T cells. In addition, MAF+GMI-HBVac vaccination stimulated T cell infiltration in HBV-infected livers. These effects may contribute to an enhanced immune response and the clearance of HBV-associated antigens, including serum HBsAg, serum HBcAg, and HBcAg(+) hepatocytes. Overall, this is the first indication that MAF can act as an adjuvant with GMI-HBVac to deplete Tregs in mice with an established CHB infection. This unique therapeutic vaccine regimen produced a functional cure, as revealed by the remarkable clearance of HBsAg.

Automated summary

Chronic hepatitis B infection is a global health burden with risks for hepatocellular cancer and hepatic fibrosis. Elevated levels of immunosuppressive regulatory T cells (Tregs) in chronic hepatitis B virus (CHB) infection suppress effector T cell function and immune clearance against HBV. This study explored the potential use of mafosfamide (MAF) as an adjuvant to deplete Tregs in an HBV infection model. Administration of MAF reduced Tregs in HBV-infected mice and combined MAF with an anti-CHB protocol resulted in decreased Tregs, dendritic cell activation, increased HBV-specific T cell proliferation, and enhanced immune response. This therapeutic vaccine regimen showed promise in clearing HBV-associated antigens and achieving functional cure.