LCMV induced down-regulation of HVEM on anti-viral T cells is critical for an efficient effector response

T‐cell responses against tumors and pathogens are critically shaped by cosignaling molecules providing a second signal. Interaction of herpes virus entry mediator (HVEM, CD270, TNFRSF14) with multiple ligands has been proposed to promote or inhibit T‐cell responses and inflammation, dependent on the context. In this study, we show that absence of HVEM did neither affect generation of effector nor maintenance of memory antiviral T cells and accordingly viral clearance upon acute and chronic lymphocytic choriomeningitis virus (LCMV) infection, due to potent HVEM downregulation during infection. Notably, overexpression of HVEM on virus‐specific CD8⁺ T cells resulted in a reduction of effector cells, whereas numbers of memory cells were increased. Overall, this study indicates that downregulation of HVEM driven by LCMV infection ensures an efficient acute response at the price of impaired formation of T‐cell memory.

DSP107 combines inhibition of CD47/SIRPα axis with activation of 4-1BB to trigger anticancer immunity

Background

Treatment of Diffuse Large B Cell Lymphoma (DLBCL) patients with rituximab and the CHOP treatment regimen is associated with frequent intrinsic and acquired resistance. However, treatment with a CD47 monoclonal antibody in combination with rituximab yielded high objective response rates in patients with relapsed/refractory DLBCL in a phase I trial. Here, we report on a new bispecific and fully human fusion protein comprising the extracellular domains of SIRPα and 4-1BBL, termed DSP107, for the treatment of DLBCL. DSP107 blocks the CD47:SIRPα ‘don’t eat me’ signaling axis on phagocytes and promotes innate anticancer immunity. At the same time, CD47-specific binding of DSP107 enables activation of the costimulatory receptor 4-1BB on activated T cells, thereby, augmenting anticancer T cell immunity.

Methods

Using macrophages, polymorphonuclear neutrophils (PMNs), and T cells of healthy donors and DLBCL patients, DSP107-mediated reactivation of immune cells against B cell lymphoma cell lines and primary patient-derived blasts was studied with phagocytosis assays, T cell activation and cytotoxicity assays. DSP107 anticancer activity was further evaluated in a DLBCL xenograft mouse model and safety was evaluated in cynomolgus monkey.

Results

Treatment with DSP107 alone or in combination with rituximab significantly increased macrophage- and PMN-mediated phagocytosis and trogocytosis, respectively, of DLBCL cell lines and primary patient-derived blasts. Further, prolonged treatment of in vitro macrophage/cancer cell co-cultures with DSP107 and rituximab decreased cancer cell number by up to 85%. DSP107 treatment activated 4-1BB-mediated costimulatory signaling by HT1080.4-1BB reporter cells, which was strictly dependent on the SIRPα-mediated binding of DSP107 to CD47. In mixed cultures with CD47-expressing cancer cells, DSP107 augmented T cell cytotoxicity in vitro in an effector-to-target ratio-dependent manner. In mice with established SUDHL6 xenografts, the treatment with human PBMCs and DSP107 strongly reduced tumor size compared to treatment with PBMCs alone and increased the number of tumor-infiltrated T cells. Finally, DSP107 had an excellent safety profile in cynomolgus monkeys.

Conclusions

DSP107 effectively (re)activated innate and adaptive anticancer immune responses and may be of therapeutic use alone and in combination with rituximab for the treatment of DLBCL patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02256-x.

A role for the thermal environment in defining co-stimulation requirements for CD4(+) T cell activation

Maintenance of normal core body temperature is vigorously defended by long conserved, neurovascular homeostatic mechanisms that assist in heat dissipation during prolonged, heat generating exercise or exposure to warm environments. Moreover, during febrile episodes, body temperature can be significantly elevated for at least several hours at a time. Thus, as blood cells circulate throughout the body, physiologically relevant variations in surrounding tissue temperature can occur; moreover, shifts in core temperature occur during daily circadian cycles. This study has addressed the fundamental question of whether the threshold of stimulation needed to activate lymphocytes is influenced by temperature increases associated with physiologically relevant increases in temperature. We report that the need for co-stimulation of CD4+ T cells via CD28 ligation for the production of IL-2 is significantly reduced when cells are exposed to fever-range temperature. Moreover, even in the presence of sufficient CD28 ligation, provision of extra heat further increases IL-2 production. Additional in vivo and in vitro data (using both thermal and chemical modulation of membrane fluidity) support the hypothesis that the mechanism by which temperature modulates co-stimulation is linked to increases in membrane fluidity and membrane macromolecular clustering in the plasma membrane. Thermally-regulated changes in plasma membrane organization in response to physiological increases in temperature may assist in the geographical control of lymphocyte activation, i.e., stimulating activation in lymph nodes rather than in cooler surface regions, and further, may temporarily and reversibly enable CD4+ T cells to become more quickly and easily activated during times of infection during fever.

TCR-Engineered T Cells Meet New Challenges to Treat Solid Tumors: Choice of Antigen, T Cell Fitness, and Sensitization of Tumor Milieu

Adoptive transfer of T cells gene-engineered with antigen-specific T cell receptors (TCRs) has proven its feasibility and therapeutic potential in the treatment of malignant tumors. To ensure further clinical development of TCR gene therapy, it is necessary to target immunogenic epitopes that are related to oncogenesis and selectively expressed by tumor tissue, and implement strategies that result in optimal T cell fitness. In addition, in particular for the treatment of solid tumors, it is equally necessary to include strategies that counteract the immune-suppressive nature of the tumor micro-environment. Here, we will provide an overview of the current status of TCR gene therapy, and redefine the following three challenges of improvement: “choice of target antigen”; “fitness of T cells”; and “sensitization of tumor milieu.” We will categorize and discuss potential strategies to address each of these challenges, and argue that advancement of clinical TCR gene therapy critically depends on developments toward each of the three challenges.

Expression and Function of TLR2 on CD4 Versus CD8 T Cells

Background

Toll-like receptors (TLRs) play a fundamental role in innate immunity through their capacity to recognize pathogen-associated molecular patterns. Also, TLRs that are expressed in T cells are reported to function as co-stimulatory receptors. However, the functional capacity of TLRs on CD4 T and CD8 T cells has not been directly compared. Here we compared CD4 and CD8 T cell responses to TLR2 ligand plus TCR-mediated stimulation.

Methods

TLR2 expression was analyzed on T cell subsets under naïve and alloantigen-primed conditions. We analyzed the effects of TLR2 co-stimulation on proliferation and survival of T cell subsets in vitro when stimulated with soluble anti-CD3 in the presence or absence of synthetic ligand Pam₃CSK₄.

Results

TLR2 expression on CD8 T cells was induced following activation; this expression was much higher than on CD4 T cells. Thus, the molecule was constitutively expressed on Listeria-specific memory CD8 T cells. Based on these expression levels, proliferation and survival were markedly elevated in CD8 T cells in response to the TLR2 co-stimulation by Pam₃CSK₄ compared with those in CD4 T cells.

Conclusion

Our data show that TLR2 co-stimulation is more responsible for proliferation and survival of CD8 T cells than for that of CD4 T cells.