Chronic hepatitis B virus (HBV) infection is marked by dysfunctional HBV-specific CD8+ T cells, and restoring their effector activity is a major therapeutic goal. Here, we generated HBV-specific CD4+ T cell receptor transgenic mice to show that CD4+ effector T cells can prevent and reverse the CD8⁺ T cell dysfunction induced by hepatocellular priming. This rescue enhances antiviral CD8+ T cell function and suppresses viral replication. CD4+ T cell help occurs directly within the liver, independent of secondary lymphoid organs, and requires local antigen recognition. Kupffer cells, rather than dendritic cells, are the critical antigen-presenting platform. CD4+ T cells license Kupffer cells via CD40-CD40L interactions, triggering interleukin (IL)-12 and IL-27 production. IL-12 expands the CD4+ T cell pool, while IL-27 is essential for CD8+ T cell rescue. Exogenous IL-27 similarly restores HBV-specific CD8+ T cell function in mice and in T cells isolated from chronically infected patients. These findings identify IL-27 as a tractable immunotherapeutic target in chronic HBV infection.
© 2025. The Author(s).

Reversing CD8+ T cell dysfunction is crucial in treating chronic hepatitis B virus (HBV) infection, yet specific molecular targets remain unclear. Our study analyzed co-signaling receptors during hepatocellular priming and traced the trajectory and fate of dysfunctional HBV-specific CD8+ T cells. Early on, these cells upregulate PD-1, CTLA-4, LAG-3, OX40, 4-1BB, and ICOS. While blocking co-inhibitory receptors had minimal effect, activating 4-1BB and OX40 converted them into antiviral effectors. Prolonged stimulation led to a self-renewing, long-lived, heterogeneous population with a unique transcriptional profile. This includes dysfunctional progenitor/stem-like (TSL) cells and two distinct dysfunctional tissue-resident memory (TRM) populations. While 4-1BB expression is ubiquitously maintained, OX40 expression is limited to TSL. In chronic settings, only 4-1BB stimulation conferred antiviral activity. In HBeAg+ chronic patients, 4-1BB activation showed the highest potential to rejuvenate dysfunctional CD8+ T cells. Targeting all dysfunctional T cells, rather than only stem-like precursors, holds promise for treating chronic HBV infection.
Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.

Natural killer (NK) cells are cytotoxic lymphocytes capable of rapid cytotoxicity, cytokine secretion, and clonal expansion. To sustain such energetically demanding processes, NK cells must increase their metabolic capacity upon activation. However, little is known about the metabolic requirements specific to NK cells in vivo. To gain greater insight, we investigated the role of aerobic glycolysis in NK cell function and demonstrate that their glycolytic rate increases rapidly following viral infection and inflammation, prior to that of CD8+ T cells. NK cell-specific deletion of lactate dehydrogenase A (LDHA) reveals that activated NK cells rely on this enzyme for both effector function and clonal proliferation, with the latter being shared with T cells. As a result, LDHA-deficient NK cells are defective in their anti-viral and anti-tumor protection. These findings suggest that aerobic glycolysis is a hallmark of NK cell activation that is key to their function.
Copyright © 2021 The Author(s). Published by Elsevier Inc. All rights reserved.

The process of affinity maturation, whereby T and B cells bearing antigen receptors with optimal affinity to the relevant antigen undergo preferential expansion, is a key feature of adaptive immunity. Natural killer (NK) cells are innate lymphocytes capable of "adaptive" responses after cytomegalovirus (CMV) infection. However, whether NK cells are similarly selected on the basis of their avidity for cognate ligand is unknown. Here, we showed that NK cells with the highest avidity for the mouse CMV glycoprotein m157 were preferentially selected to expand and comprise the memory NK cell pool, whereas low-avidity NK cells possessed greater capacity for interferon-γ (IFN-γ) production. Moreover, we provide evidence for avidity selection occurring in human NK cells during human CMV infection. These results delineate how heterogeneity in NK cell avidity diversifies NK cell effector function during antiviral immunity, and how avidity selection might serve to produce the most potent memory NK cells.
Copyright © 2019 Elsevier Inc. All rights reserved.