HIV-1 infection converts CD4⁺ T cells to HLA class II-restricted CD8⁺ T cells

As the primary receptor for HIV-1 entry, human CD4 is widely recognized as the hallmark of HIV-1 target cells. However, viral negative factor (Nef) and viral protein U (Vpu) down-regulate surface CD4 on infected cells, raising an intriguing question: If an infected CD4⁺ T cell survives and establishes latency, can CD4 expression recover? By tracking the fate of HIV-1-infected CD4⁺ T cells, we unexpectedly found that a subset of these cells directly convert to CD8⁺ T cells. T cell receptor (TCR) sequencing and single-cell RNA sequencing data revealed that these induced CD8⁺ T cells primarily originated from regulatory CD4⁺ T cells, which retained a regulatory-like phenotype postconversion. Mechanistically, HIV-1 viral protein R (Vpr) specifically induced this conversion by up-regulating transforming growth factor-β1 (TGF-β1), which, in turn, activates a TGF-β-dependent signaling pathway essential for CD8 lineage reprogramming. Critically, ex vivo analyses confirmed that CD8⁺ T cells from both untreated and antiretroviral therapy (ART)-suppressed people living with HIV-1 (PLWH) harbor transcriptionally active viral RNA or intact proviral DNA. Furthermore, we identified that human leukocyte antigen (HLA) class II-restricted CD8⁺ T cells, which were present in PLWH but absent in healthy controls, share TCR clonotypes with their antigen-specific CD4⁺ T cell counterparts, providing direct evidence for HIV-1-driven CD4-to-CD8 conversion in vivo. Collectively, these findings uncover a viral mechanism of host-cell reprogramming, demonstrate that CD8⁺ T cells constitute a previously overlooked component of the HIV-1 reservoir, and broaden our understanding of latent reservoir heterogeneity, an essential consideration for future cure strategies.