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.

Spontaneous tumors that arise in genetically engineered mice recapitulate the natural tumor microenvironment and tumor-immune coevolution observed in human cancers, providing a more physiologically relevant preclinical model relative to implanted tumors. Similar to many cancer patients, oncogene-driven spontaneous tumors are often resistant to immunotherapy, and thus novel agents that can effectively promote antitumor immunity against these aggressive cancers show considerable promise for clinical translation, and their mechanistic assessment can broaden our understanding of tumor immunology. In this study, we performed extensive immune profiling experiments to investigate how tumor-targeted TLR9 stimulation remodels the microenvironment of spontaneously arising tumors during an effective antitumor immune response. To model the clinical scenario of multiple tumor sites, we used MMTV-PyMT transgenic mice, which spontaneously develop heterogeneous breast tumors throughout their 10 mammary glands. We found that i.v. administration of a tumor-targeting TLR9 agonist, referred to as PIP-CpG, induced a systemic T cell-mediated immune response that not only promoted regression of existing mammary tumors, but also elicited immune memory capable of delaying growth of independent newly arising tumors. Within the tumor microenvironment, PIP-CpG therapy initiated an inflammatory cascade that dramatically amplified chemokine and cytokine production, prompted robust infiltration and expansion of innate and adaptive immune cells, and led to diverse and unexpected changes in immune phenotypes. This study demonstrates that effective systemic treatment of an autochthonous multisite tumor model can be achieved using a tumor-targeted immunostimulant and provides immunological insights that will inform future therapeutic strategies.
Copyright © 2023 by The American Association of Immunologists, Inc.

The SARS-CoV-2 pandemic has necessitated the rapid development of prophylactic vaccines. Two mRNA vaccines have been approved for emergency use by the FDA and have demonstrated extraordinary effectiveness. The success of these mRNA vaccines establishes the speed of development and therapeutic potential of mRNA. These authorized vaccines encode full-length versions of the SARS-CoV-2 spike protein. They are formulated with lipid nanoparticle (LNP) delivery vehicles that have inherent immunostimulatory properties. Different vaccination strategies and alternative mRNA delivery vehicles would be desirable to ensure flexibility of future generations of SARS-CoV-2 vaccines and the development of mRNA vaccines in general. Here, we report on the development of an alternative mRNA vaccine approach using a delivery vehicle called charge-altering releasable transporters (CARTs). Using these inherently nonimmunogenic vehicles, we can tailor the vaccine immunogenicity by inclusion of coformulated adjuvants such as oligodeoxynucleotides with CpG motifs (CpG-ODN). Mice vaccinated with the mRNA-CART vaccine developed therapeutically relevant levels of receptor binding domain (RBD)-specific neutralizing antibodies in both the circulation and in the lung bronchial fluids. In addition, vaccination elicited strong and long-lasting RBD-specific TH1 T cell responses including CD4+ and CD8+ T cell memory.
© 2021 The Authors. Published by American Chemical Society.

Inhibitors of cyclin-dependent kinases 4 and 6 (CDK4/6i) delay progression of metastatic breast cancer. However, complete responses are uncommon and tumors eventually relapse. Here, we show that CDK4/6i can enhance efficacy of T cell-based therapies, such as adoptive T cell transfer or T cell-activating antibodies anti-OX40/anti-4-1BB, in murine breast cancer models. This effect is driven by the induction of chemokines CCL5, CXCL9, and CXCL10 in CDK4/6i-treated tumor cells facilitating recruitment of activated CD8+ T cells, but not Tregs, into the tumor. Mechanistically, chemokine induction is associated with metabolic stress that CDK4/6i treatment induces in breast cancer cells. Despite the cell cycle arrest, CDK4/6i-treated cells retain high metabolic activity driven by deregulated PI3K/mTOR pathway. This causes cell hypertrophy and increases mitochondrial content/activity associated with oxidative stress and inflammatory stress response. Our findings uncover a link between tumor metabolic vulnerabilities and anti-tumor immunity and support further development of CDK4/6i and immunotherapy combinations.
Copyright © 2021. Published by Elsevier Inc.