Background:
Due to the chronic nature of HIV infection, cytotoxic CD8 T lymphocytes (CTL) are limited in their capacity to provide sustained control of HIV infection in part due to exhaustion. In contrast, chronic cytomegalovirus (CMV) infection induces a unique CTL response termed memory inflation characterized by continued expansion following priming, maintained “effector‐memory” phenotype, and sustained functionality. As T cell activation is crucial to enable lentivector transduction, we hypothesized that we could selectively transduce CMV-specific CTL with a lentivector expressing an HIV-specific TCR by using a novel immunotherapeutic, CMV-synTac, which selectively activates and expands CMV-specific CTL (JCI 2021;131:e141051). This would convert CMV-specific CTL into bispecific CTL capable of suppressing HIV infection while exhibiting the memory inflation phenotype.
Methods:
After CMV-synTac treatment, CMV-specific CTL were selectively transduced with a lentivirus encoding a chimeric T cell receptor (TCR) containing a murine constant region fused to a human variable region specific for the HIV-1 Gag epitope, SL9. Use of the mouse constant region prevents mispairing of endogenous and lentivector-encoded alpha and beta TCR chains. TCR Expression was determined by tetramer staining and functional activity of the bispecific CTL was detected by ELISpot.
Results:
CMV-specific CTL were selectively transduced with an SL9-specific TCR lentivector after activation with CMV-synTac, but not after anti-CD3/CD28 activation. Lentivector-encoded SL9-TCR function was demonstrated by markedly increased luciferase expression after coculturing SL9-TCR lentivector-transduced Jurkat T cells with an NFAT-regulated luciferase reporter with SL9-peptide but not irrelevant peptide-loaded T2 cells. Dual expression of the exogenous SL9-TCR and endogenous CMV-TCR in transduced donor CD8 T cells was detected by tetramer staining and flow cytometry. Lastly, functionality of both SL9- and CMV- TCRs were validated by interferon-gamma ELISpot assays after either SL9 or CMV peptide stimulation.
Conclusions:
CMV-synTac enables antigen-specific transduction of CMV-specific CTL with a lentivector expressing an SL9-TCR which confers them with additional functional activity against HIV-infected cells. We anticipate that these bispecific CTLs should also express the memory inflation phenotype of the CMV-specific CTL enabling them to display sustained anti-HIV activity after infusion into PWH and thereby contribute to a functional cure.