HEPLISAV-B Breaks Immune Tolerance and Induces HBV Control via CD4 T Cell-Dependent Mechanisms in a Chronic Hepatitis B Mouse Model

BackgroundChronic hepatitis B virus (HBV) infection (CHB) affects nearly 300 million individuals globally and remains incurable with current antiviral therapies, which suppress viral replication but rarely achieve functional cure defined by sustained loss of hepatitis B surface antigen (HBsAg). CHB is characterized by profound virus-induced immune tolerance that limits the efficacy of conventional therapeutic vaccination strategies. ObjectiveTo evaluate the therapeutic efficacy and immunological mechanisms of HEPLISAV-B, a CpG-1018-adjuvanted HBsAg vaccine, in breaking immune tolerance and inducing functional cure-like responses in a murine model of CHB. DesignUsing the adeno-associated virus-HBV (AAV-HBV) mouse model, mice with high levels of persistent HBV viremia were vaccinated with two doses of HEPLISAV-B. Virological outcomes in the blood and liver, immune responses and mechanisms were assessed. ResultsHEPLISAV-B induced rapid and durable HBsAg clearance, markedly reduced circulating and intrahepatic HBV DNA and RNA, and suppressed viral replication without hepatocellular injury. Vaccination elicited robust, sustained anti-HBs IgG1 and IgA responses, enhanced HBsAg-specific T and B cell immunity, reduced CD4 regulatory T cells, and decreased PD-1 expression on CD4 T cells. Therapeutic efficacy was strictly dependent on CD4 T cells and the CD40/CD40L signaling pathway, but independent of CD8 T cells, indicating a CD4-driven, non-cytolytic antiviral mechanism critical for HEPLISAV-B induced HBV control. ConclusionHEPLISAV-B effectively breaks HBV-induced immune tolerance and restores coordinated antiviral immunity through a CD4 T cell-/CD40L-dependent pathway. The findings support its potential as a therapeutic vaccine in CHB patients. Key messagesO_ST_ABSWhat is already known on this topicC_ST_ABSChronic HBV infection is marked by profound virus-induced immune tolerance, current antiviral therapies and vaccines fail to reliably induce HBsAg loss or restore effective antiviral immunity, highlighting the need for immune-based therapeutic strategies. What this study addsThis study demonstrates that the clinically approved vaccine HEPLISAV-B can break HBV immune tolerance in a chronic HBV mouse model, inducing durable HBsAg clearance and anti-HBs immunity, non-cytolytic depletion of intrahepatic HBV DNA, through a mechanism strictly dependent on CD4 T cells and CD40/CD40L signaling. How this study might affect research, practice or policyThese findings defined a CD4 T cell-CD40L/CD40 axis that is critical in CHB functional cure, and support testing HEPLISAV-B as a therapeutic vaccine in CHB patients. O_FIG O_LINKSMALLFIG WIDTH=165 HEIGHT=200 SRC="FIGDIR/small/711721v1_ufig1.gif" ALT="Figure 1"> View larger version (34K): org.highwire.dtl.DTLVardef@1d76f4dorg.highwire.dtl.DTLVardef@cc41cborg.highwire.dtl.DTLVardef@1f39288org.highwire.dtl.DTLVardef@192d0e_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract C_FIG