Modeling simian immunodeficiency virus (SIV) latency in primary rhesus macaque CD4⁺ T cells

Simian immunodeficiency virus (SIV)-infected rhesus macaques are valuable models for HIV cure research, offering insights into tissue reservoirs and testing reservoir-reduction strategies. Despite this utility, low frequencies of latently infected cells in vivo limit mechanistic studies of viral latency ex vivo. In vitro latency models have addressed this limitation for HIV, advancing our understanding of viral persistence. However, no comparable models exist for SIV. To address this gap, we developed an in vitro model of SIV latency in primary rhesus macaque CD4⁺ T cells, optimizing conditions to promote viral entry while maintaining cells in a minimally activated, non-proliferating state. After 12 days in culture, ~1-3.3% of cells harbored SIV DNA, primarily as intact proviruses within central and transitional memory CD4⁺ T cell subsets. These cells remained quiescent, exhibiting minimal spontaneous viral protein production, but could be reactivated by potent T-cell stimulation and benchmark latency-reversing agents. Collectively, this model generates SIV-latently infected cells that resemble predominant cellular reservoirs in vivo-quiescent memory CD4⁺ T cells carrying inducible proviruses. This system provides a platform for investigating mechanisms of SIV latency, identifying shared and virus-specific features of HIV and SIV persistence, and evaluating strategies to reactivate or silence viral reservoirs.