HIV infection is associated with an increase in the proportion of activated CD8+ memory T cells (Tmem) that express CX3CR1, but how these cells are generated and maintained in vivo is unclear. We demonstrate that increased CX3CR1 expression on CD8+ Tmem in people living with HIV (PLWH) is dependent on coinfection with human CMV, and CX3CR1+CD8+ Tmem are enriched for a putatively immunosenescent CD57+CD28– phenotype. The cytokine IL-15 promotes the phenotype, survival, and proliferation of CX3CR1+CD57+CD8+ Tmem in vitro, whereas T cell receptor stimulation leads to their death. IL-15–driven survival is dependent on STAT5 and Bcl-2 activity, and IL-15–induced proliferation requires STAT5 and mTORC1. Thus, we identify mechanistic pathways that could explain how “inflammescent” CX3CR1+CD57+ CD8+ Tmem dominate the overall memory T cell pool in CMV-seropositive PLWH and that support reevaluation of immune senescence as a nonproliferative dead end.
Stephen R. Morris, Bonnie Chen, Joseph C. Mudd, Soumya Panigrahi, Carey L. Shive, Scott F. Sieg, Cheryl M. Cameron, David A. Zidar, Nicholas T. Funderburg, Souheil-Antoine Younes, Benigno Rodriguez, Sara Gianella, Michael M. Lederman, Michael L. Freeman
IL-15 promotes proliferation of CCR7–CX3CR1+CD57+CD28–CD8+ Tmem via STAT5 and mTORC1 activity.