Transgene IL-21-Engineered T Cell-Based Vaccine Potently Converts CTL Exhaustion via the Activation of the mTORC1 Pathway in Chronic Infection

摘要

CD8~(+) cytotoxic T lymphocyte (CTL) exhaustion is one of the major obstacles for the effectiveness of virus control in chronic infectious diseases. We previously generated novel ovalbumin (OVA)-specific 41BBL-expressing OVA-T_(EXO) and human immunodeficiency virus (HIV-1) Gag-specific Gag-T_(EXO) vaccines, inducing therapeutic immunity in wild-type C57BL/6 (B6) mice, and converting CTL exhaustion in recombinant OVA-specific adenovirus AdV_(OVA)-infected B6 (AdV_(OVA)-B6) mice with chronic infection. IL-21 cytokine plays an important role in controlling chronic infections. Therefore, in this study, we constructed recombinant transgene IL-21-expressing AdV_(IL-21), and generated IL-21-expressing OVA-T_(EXO/IL-21) and Gag-T_(EXO/IL21) vaccines, or control vaccines (OVA-T_(EXO/Null) and Gag-T_(EXO/Null)) by infecting OVA-T_(EXO )and Gag-T_(EXO) cells with AdV_(IL-21) or the control AdV_(Null), lacking transgene, and assessed their effects in B6 or AdV_(OVA)-B6 mice. We demonstrate that both OVA-T_(EXO/IL-21) and control OVA-T_(EXO/Null )vaccines are capable of converting CTL exhaustion in chronic infection. However, the OVA-T_(EXO/IL-21) vaccine more efficiently rescues exhausted CTLs by increasing stronger CTL proliferation and effector cytokine IFN- γ expression than the control OVA-T_(EXO/Null )vaccine in AdV_(OVA)-B6 mice with chronic infection, though both vaccines stimulated comparable OVA-specific CTL responses and protective immunity against OVA-expressing BL6-10_(OVA) melanoma lung metastasis in wild-type B6 mice. In vivo , the OVA-T_(EXO/IL-21)-stimulated CTLs more efficiently up-regulate phosphorylation of mTORC1-controlled EIF4E and expression of mTORC1- regulated T-bet molecule than the control OVA-T_(EXO/Null)-stimulated ones. Importantly, the Gag-T_(EXO/IL21) vaccine induces stronger Gag-specific therapeutic immunity against established Gag-expressing BL6-10_(Gag) melanoma lung metastases than the control Gag-T_(EXO/Null )vaccine in chronic infection. Therefore, this study should have a strong impact on developing new therapeutic vaccines for patients with chronic infections.