FRI351 Immunogenicity and efficacy of an HBV vaccine with an intrinsic checkpoint inhibitor
Mohadeseh Hasanpourghadi1, Andrew Luber2, Colin Magowan2, Xiang Zhou1, Hildegund Ertl1
1The Wistar Institute, Philadelphia, United States, 2Virion Therapeutics, Newark, United States
Email: [email protected]
Background and aims: CD8+ T-cells are critical for control of HBV infection, but their activity is hampered by low antigen immunogenicity and T-cell exhaustion. HSV-1 glycoprotein D (gD), when genetically expressed as a fusion protein with target antigens, serves as a checkpoint inhibitor of the B and T cell attenuator (BTLA)-herpes virus entry mediator (HVEM) pathway, which acts early during T cell activation. HSV-1 gD thereby augments antigen-driven CD8+ T-cell responses. We describe the immunogenicity and antiviral activity of two distinct chimpanzee adenoviral vector (AdC) vaccines containing key HBV sequences fused into gD.
Method: Adenoviral vectors of chimpanzee serotypes AdC7 and AdC6 expressing three different HBV sequences, which are conserved between HBV strains and carry human T-cell epitopes, were generated in HEK 293 cells. Each vector was injected at different doses intramuscularly into different strains of mice - in some experiments mice were primed with AdC6 and boosted 6-8 weeks later with AdC7. Blood- or spleen-derived lymphocytes were tested 2-8 weeks after immunization for CD8+ and CD4+ T-cell responses upon a brief in vitro stimulation with peptide pools representing the HBV sequences and then stained for T-cell surface markers and intracellular IFN-gamma and analyzed by flow cytometry. Individual epitopes in different mouse strains were determined using peptide matrices. An adeno-associated virus (AAV) vector of serotype 8 expressing the 1.3 HBV genome was injected i.v. at doses ranging from 1 x 1010 – 3 x 1011 genome copies (gc) into C57Bl/6 mice. Mice were vaccinated 4-8 weeks later or left untreated. HBV genome copies in serum were assessed before and after vaccination using a quantitative PCR.
Results: The vaccines were highly immunogenic and induced sustained T-cell responses. Multiple CD8+ and CD4+ epitopes were identified in different strains of mice including HLA-A2 transgenic mice. At low vaccine doses the response could be increased by a booster immunization with a heterologous AdC vector. Boosting furthermore increased the breadth of the T-cell responses. A single IM injection of the AdC6 vector produced sustained HBV DNA viral load declines of -2.0, -1.3 and -1.0 log10 mL through 8 weeks in animals injected with 1x1010, 1x1011 and 1.5x1011 gc of AAV8-1.3HBV, respectively.
Conclusion: These HBV vaccines induced high immunogenicity and significant antiviral efficacy; a Phase 1b trial in HBV-infected patients is in development.作者: StephenW 时间: 2020-7-3 22:03
