CCL5-Secreting Virtual Memory CD8+ T Cells Inversely Associate With Viral Reservoir Size in HIV-1-Infected Individuals on Antiretroviral Therapy

FLT3L-induced virtual memory CD8 T cells engage the immune system against tumors

BACKGROUND

Previous research in FMS-like tyrosine kinase 3 ligands (FLT3L) has primarily focused on their potential to generate dendritic cells (DCs) from bone marrow progenitors, with a limited understanding of how these cells affect CD8 T cell function. In this study, we further investigated the in vivo role of FLT3L for the immunomodulatory capabilities of CD8 T cells.

METHODS

Albumin-conjugated FLT3L (Alb-FLT3L) was generated and applied for translational medicine purposes; here it was used to treat naïve C57BL/6 and OT1 mice for CD8 T cell response analysis. Syngeneic B16ova and E.G7ova mouse models were employed for adoptive cell transfer to evaluate the effects of Alb-FLT3L preconditioning of CD8 T cells on tumor progression. To uncover the underlying mechanisms of Alb-FLT3L modulation, we conducted bulk RNA-seq analysis of the CD44high CD8 T cells. STAT1-deficient mice were used to elucidate the functional roles of Alb-FLT3L in the modulation of T cells. Finally, antibody blockade of type one interferon signaling and in vitro coculture of plasmacytoid DCs (pDCs) with naive CD8 T cells was performed to determine the role of pDCs in mediating regulation of CD44high CD8 T cells.

RESULTS

CD44high CD8 T cells were enhanced in C57BL/6 mice administrated with Alb-FLT3L. These CD8 T cells exhibited virtual memory features and had greater proliferative and effective functions. Notably, the adoptive transfer of CD44high naïve CD8 T cells into C57BL/6 mice with B16ova tumors led to significant tumor regression. RNA-seq analysis of the CD44high naïve CD8 T cells revealed FLT3L to induce CD44high CD8 T cells in a JAK-STAT1 signaling pathway-dependent manner, as supported by results indicating a decreased ability of FLT3L to enhance CD8 T cell proliferation in STAT1-deficient mice as compared to wild-type control mice. Moreover, antibody blockade of type one interferon signaling restricted the generation of FLT3L-induced CD44high CD8 T cells, while CD44 expression was able to be induced in naïve CD8 T cells cocultured with pDCs derived from FLT3L-treated mice. This suggests the crucial role of pDCs in mediating FLT3L regulation of CD44high CD8 T cells.

CONCLUSIONS

These findings provide critical insight and support the therapeutic potential of Alb-FLT3L as an immune modulator in preconditioning of naïve CD8 T cells for cancer immunotherapy.

The role of TEMRA cell-mediated immune senescence in the development and treatment of HIV disease

Human Immunodeficiency Virus (HIV) has plagued human society for a long time since its discovery, causing a large number of patients to suffer and costing hundreds of millions of medical services every year. Scientists have found that HIV and antiretroviral therapy accelerate immune aging by inducing mitochondrial dysfunction, and that terminal effector memory T cells (TEMRA cells) are crucial in immune aging. This specific subset of effector memory T cells has terminally differentiated properties and exhibits high cytotoxicity and proinflammatory capacity. We therefore explored and described the interplay between exhaustion features, essential markers, functions, and signaling pathways from previous studies on HIV, antiretroviral therapy, immune senescence, and TEMRA cells. Their remarkable antiviral capacity is then highlighted by elucidating phenotypic changes in TEMRA cells during HIV infection, describing changes in TEMRA cells before, during, and after antiretroviral therapy and other drug treatments. Their critical role in complications and cytomegalovirus (CMV)-HIV superinfection is highlighted. These studies demonstrate that TEMRA cells play a key role in the antiviral response and immune senescence during HIV infection. Finally, we review current therapeutic strategies targeting TEMRA cells that may be clinically beneficial, highlight their potential role in HIV-1 vaccine development, and provide perspectives and predictions for related future applications.

Elevated glutamate impedes anti-HIV-1 CD8 + T cell responses in HIV-1-infected individuals on antiretroviral therapy

CD8 + T cells are essential for long-lasting HIV-1 control and have been harnessed to develop therapeutic and preventive approaches for people living with HIV-1 (PLWH). HIV-1 infection induces marked metabolic alterations. However, it is unclear whether these changes affect the anti-HIV function of CD8 + T cells. Here, we show that PLWH exhibit higher levels of plasma glutamate than healthy controls. In PLWH, glutamate levels positively correlate with HIV-1 reservoir and negatively correlate with the anti-HIV function of CD8 + T cells. Single-cell metabolic modeling reveals glutamate metabolism is surprisingly robust in virtual memory CD8 + T cells (TVM). We further confirmed that glutamate inhibits TVM cells function via the mTORC1 pathway in vitro. Our findings reveal an association between metabolic plasticity and CD8 + T cell-mediated HIV control, suggesting that glutamate metabolism can be exploited as a therapeutic target for the reversion of anti-HIV CD8 + T cell function in PLWH.