Targeting the Adenosine–Adenosine Deaminase-1 Axis to Restore HIV-Specific CD8⁺ T Cell Function

Introduction/Rationale: Despite suppressive antiretroviral therapy (ART), HIV reservoirs rapidly rebound upon treatment interruption, driven in part by progressive dysfunction of HIV-specific CD8⁺ T cells. Current strategies targting CD8+T cell dysfunction in cancer show limited benefit in people living with HIV (PLWH), underscoring the need for alternative approaches tailored to the unique immunological landscape of HIV infection. Adenosine (ADO) signaling is a potent immunoregulatory pathway regulated by adenosine deaminase-1 (ADA-1) that becomes dysregulated in PLWH and is associated with viral persistence. However, more work is needed to define its direct contribution to HIV-specific CD8⁺ T-cell dysfunction.

Methods: Using primary samples from PLWH, we applied three complementary approaches: (1) multi-omic and phenotypic profiling of tetramer-sorted HIV- and CMV-specific CD8⁺ T cells to assess regulation of ADA and ADO-signaling components; (2) ex vivo functional assays measuring cytokine production and degranulation following ADO or 2-chloroadenosine exposure with ADA-1 inhibition; and (3) CD8-targeted lipid nanoparticles (CD8-ADA-LNPs) to selectively deliver ADA-1 mRNA and assess functional improvement.

Results: HIV-specific CD8⁺ T cells exhibited repression of the ADA locus, increased expression of CD39 and the A2a adenosine receptor, indicating potential heightened sensitivity to ADO-mediated suppression. Functionally, ADO-exposure impaired CD8⁺ T-cell function, dependent on ADA-1. Targeted ADA-1 mRNA delivery via CD8-ADA-LNPs restored ADA-1 expression and improved antigen-specific CD8⁺ T-cell function in PLWH ex vivo.

Conclusion: These findings identify dysregulated ADO signaling and ADA-1 deficiency as contributors to HIV-specific CD8⁺ T-cell dysfunction and establish targeted ADA-1 delivery as a novel strategy to enhance CD8⁺ T-cell function. This approach provides a framework for targeting ADO-mediated immune suppression of CD8+T cells in HIV and other disease landscapes, including cancer.