Background
While adoptive cell transfer of HIV-specific T cells is a promising immunotherapy to provide a functional cure for HIV, its development and broader application is limited by the cost, logistical complexity, and variability of current methods for ex vivo expansion of HIV-specific T cells. To address these needs, we describe a novel modular and highly scalable lentiviral-based immunotherapeutic platform, VirTac (Viral particle-based T cell Activator), which consist of lentiviral particles (LVP) containing integral membrane proteins for the ex vivo and in vivo expansion of viral-specific T cells recognizing highly conserved virus-derived peptide antigens.
Methods
We constructed plasmids encoding single chain HLA-A*0201 MHC molecules tethered to viral-derived peptides, either alone (modless) or in combination with an agonist αCD28 scFv, to generate non-infectious LVP that can mimic APC to activate and selectively expand HIV (SL9), CMV (NLV) or CoV-2 (YLQ)-specific CD8 T cells. Expansion of virus-specific CD8 T cells was determined by tetramer staining. Cytotoxicity against peptide-loaded T2 cells and cytokine production were determined by flow cytometry. Viral suppression assays were performed using HIV and CMV with luciferase gene reporters.
Results
In vitro treatment of PBMC (n=2-5 donors) with VirTac presenting HIV-, CMV- or CoV-2-peptide MHC constructs markedly expanded the fraction of CD8 T cells that were HIV-specific (up to 23%) CMV-specific (up to 87%) or CoV2-specific (up to 67%), respectively (Fig. 1A, upper panel). Intravenous infusion of HIV- or CMV-VirTacs expanded HIV- and CMV-specific T cells, respectively, by ~30-fold in NSG mice intrasplenically engrafted with donor PBMCs (Fig. 1A, lower panel). Inclusion of agonist αCD28 scFv in the HIV-, CMV- or CoV-2-VirTacs increased in vitro or in vivo expansion of HIV-, CMV- or CoV-2-specific CD8 T cells in some donors. Antigen-specific T cells expanded with VirTac were highly functional, displaying potent cytotoxic capacity (Fig. 1B), antigen-specific IFNg and TNFα production and suppression of in vitro HIV or CMV infections.
Conclusions
VirTac represents a flexible and robust platform for the ex vivo expansion of CD8 T cells targeting HIV and other viral-derived epitopes for adoptive cell transfer. This strategy may also support in vivo modulation to provide sustained anti-HIV activity and enable personalized antigen-specific strategies to achieve a functional cure for HIV.