IL-21 Expands HIV-1-Specific CD8(+) T Memory Stem Cells to Suppress HIV-1 Replication In Vitro

Due to the existence of viral reservoirs, the rebound of human immunodeficiency virus type 1 (HIV-1) viremia can occur within weeks after discontinuing combined antiretroviral therapy. Immunotherapy could potentially be applied to eradicate reactivated HIV-1 in latently infected CD4(+) T lymphocytes. Although the existence of HIV-1-specific CD8(+) T memory stem cells (T(SCM)s) is well established, there are currently no reports regarding methods using CD8(+) T(SCM)s to treat HIV-1 infection. In this study, we quantified peripheral blood antigen-specific CD8(+) T(SCM)s and then expanded HIV-1-specific T(SCM)s that targeted optimal antigen epitopes (SL9, IL9, and TL9) in the presence of interleukin- (IL-) 21 or IL-15. The suppressive capacity of the expanded CD8(+) T(SCM)s on HIV-1 production was measured by assessing cell-associated viral RNA and performing viral outgrowth assays. We found that the number of unmutated TL9-specific CD8(+) T(SCM)s positively correlated with the abundance of CD4(+) T cells and that the expression of IFN-γ was higher in TL9-specific CD8(+) T(SCM)s than that in non-TL9-specific CD8(+) T(SCM)s. Moreover, the antiviral capacities of IL-21-stimulated CD8(+) T(SCM)s exceeded those of conventional CD8(+) memory T cells and IL-15-stimulated CD8(+) T(SCM)s. Thus, we demonstrated that IL-21 could efficiently expand HIV-1-specific CD8(+) T(SCM)s to suppress HIV-1 replication. Our study provides new insight into the function of IL-21 in the in vitro suppression of HIV-1 replication.