Manipulating Memory CD8 T Cell Numbers by Timed Enhancement of IL-2 Signals

Genome-wide transcriptional profiling and functional analysis of long noncoding RNAs and mRNAs in chicken macrophages associated with the infection of avian pathogenic E. coli

BACKGROUND

Avian pathogenic E. coli (APEC) can cause localized or systemic infections, collectively known as avian colibacillosis, resulting in huge economic losses to poultry industry globally per year. In addition, increasing evidence indicates that long non-coding RNAs (lncRNAs) play a critical role in regulating host inflammation in response to bacterial infection. However, the role of lncRNAs in the host response to APEC infection remains unclear.

RESULTS

Here, we found 816 differentially expressed (DE) lncRNAs and 1,798 DE mRNAs in APEC infected chicken macrophages by RNAseq. The identified DE lncRNA-mRNAs were involved in Toll like receptor signaling pathway, VEGF signaling pathway, fatty acid metabolism, phosphatidylinositol signaling system, and other types of O-glycan biosynthesis. Furthermore, we found the novel lncRNA TCONS_00007391 as an important immune regulator in APEC infection was able to regulate the inflammatory response by directly targeting CD86.

CONCLUSION

These findings provided a better understanding of host response to APEC infection and also offered the potential drug targets for therapy development against APEC infection.

Targeting memory T cell metabolism to improve immunity

Vaccination affords protection from disease by activating pathogen-specific immune cells and facilitating the development of persistent immunologic memory toward the vaccine-specific pathogen. Current vaccine regimens are often based on the efficiency of the acute immune response, and not necessarily on the generation of memory cells, in part because the mechanisms underlying the development of efficient immune memory remain incompletely understood. This Review describes recent advances in defining memory T cell metabolism and how metabolism of these cells might be altered in patients affected by mitochondrial diseases or metabolic syndrome, who show higher susceptibility to recurrent infections and higher rates of vaccine failure. It discusses how this new understanding could add to the way we think about immunologic memory, vaccine development, and cancer immunotherapy.

Eomesodermin Increases Survival and IL-2 Responsiveness of Tumor-specific CD8+ T Cells in an Adoptive Transfer Model of Cancer Immunotherapy

Tumor-specific CD8 T cells often fail to elicit effective antitumor immune responses due to an inability to expand into a substantial effector population and persist long-term in vivo. Using an adoptive transfer model of cancer immunotherapy, we demonstrate that constitutive eomesodermin (Eomes) expression in tumor-specific CD8 T cells improves tumor rejection and survival. The increase in tumor rejection was associated with an increased number and persistence of CD8 T cells in lymphoid tissues during acute tumor rejection, tumor regrowth, and in mice that remained tumor-free. Constitutive Eomes expression increased expression of CD25, and this was associated with enhanced interleukin-2 responsiveness and tumor-specific CD8 T-cell proliferation. Moreover, constitutive Eomes expression improved cell survival. Taken together, our data suggest that constitutive Eomes expression enhances CD8 T-cell proliferation and survival, in part through the enhancement of interleukin-2 responsiveness through CD25 induction.

A next-generation tumor-targeting IL-2 preferentially promotes tumor-infiltrating CD8+ T-cell response and effective tumor control

While IL-2 can potently activate both NK and T cells, its short in vivo half-life, severe toxicity, and propensity to amplify Treg cells are major barriers that prevent IL-2 from being widely used for cancer therapy. In this study, we construct a recombinant IL-2 immunocytokine comprising a tumor-targeting antibody (Ab) and a super mutant IL-2 (sumIL-2) with decreased CD25 binding and increased CD122 binding. The Ab-sumIL2 significantly enhances antitumor activity through tumor targeting and specific binding to cytotoxic T lymphocytes (CTLs). We also observe that pre-existing CTLs within the tumor are sufficient and essential for sumIL-2 therapy. This next-generation IL-2 can also overcome targeted therapy-associated resistance. In addition, preoperative sumIL-2 treatment extends survival much longer than standard adjuvant therapy. Finally, Ab-sumIL2 overcomes resistance to immune checkpoint blockade through concurrent immunotherapies. Therefore, this next-generation IL-2 reduces toxicity while increasing TILs that potentiate combined cancer therapies.

Interleukin-2 (IL-2) based cancer therapy is limited by severe toxicity and strong Treg amplification at the therapeutic dosage. Here, the authors develop a recombinant IL-2 immunocytokine which is comprised of a tumor-targeting antibody fused to a super mutant IL-2 and show in mouse models that this next-generation IL2 has reduced toxicity and enhanced antitumor activity.

Cytokine-Mediated Regulation of CD8 T-Cell Responses During Acute and Chronic Viral Infection

The common γ-chain cytokines, interleukin (IL)-2, IL-7, and IL-15, regulate critical aspects of antiviral CD8 T-cell responses. During acute infections, IL-2 controls expansion and differentiation of antiviral CD8 T cells, whereas IL-7 and IL-15 are key cytokines to maintain memory CD8 T cells long term in an antigen-independent manner. On the other hand, during chronic infections, in which T-cell exhaustion is established, precise roles of these cytokines in regulation of antiviral CD8 T-cell responses are not well defined. Nonetheless, administration of IL-2, IL-7, or IL-15 can increase function of exhausted CD8 T cells, and thus can be an attractive therapeutic approach. A new subset of stem-cell-like CD8 T cells, which provides a proliferative burst after programmed cell death (PD)-1 therapy, has been recently described during chronic viral infection. Further understanding of cytokine-mediated regulation of this CD8 T-cell subset will improve cytokine therapies to treat chronic infections and cancer in combination with immune checkpoint inhibitors.

Regulation of Effector and Memory CD8 T Cell Differentiation by IL-2-A Balancing Act

Interleukin-2 (IL-2) regulates key aspects of CD8 T cell biology–signaling through distinct pathways IL-2 triggers critical metabolic and transcriptional changes that lead to a spectrum of physiological outcomes such as cell survival, proliferation, and effector differentiation. In addition to driving effector differentiation, IL-2 signals are also critical for formation of long-lived CD8 T cell memory. This review discusses a model of rheostatic control of CD8 T cell effector and memory differentiation by IL-2, wherein the timing, duration, dose, and source of IL-2 signals are considered in fine-tuning the balance of key transcriptional regulators of cell fate.

Regulatory T cells impede acute and long-term immunity to blood-stage malaria through CTLA-4

Malaria, caused by the protozoan Plasmodium, is a devastating mosquito-borne disease with the potential to affect nearly half the world's population. Despite mounting substantial T and B cell responses, humans fail to efficiently control blood-stage malaria or develop sterilizing immunity to reinfections. Although forkhead box P3 (FOXP3)⁺CD4⁺ regulatory T (T_reg) cells form a part of these responses, their influence remains disputed and their mode of action is unknown. Here we show that T_reg cells expand in both humans and mice in blood-stage malaria and interfere with conventional T helper cell responses and follicular T helper (T_FH)-B cell interactions in germinal centers. Mechanistically, T_reg cells function in a critical temporal window to impede protective immunity through cytotoxic-T-lymphocyte-associated protein-4 (CTLA-4). Targeting T_reg cells or CTLA-4 in this precise window accelerated parasite clearance and generated species-transcending immunity to blood-stage malaria in mice. Our study uncovers a critical mechanism of immunosuppression associated with blood-stage malaria that delays parasite clearance and prevents development of potent adaptive immunity to reinfection. These data also reveal a temporally discrete and potentially therapeutically amenable functional role for T_reg cells and CTLA-4 in limiting antimalarial immunity.

[Oxidized low-density lipoprotein modulates differentiation of murine memory CD8+ T cell subpopulations]

OBJECTIVE

To investigate effect of oxidized low-density lipoprotein (ox-LDL) on memory CD8⁺ T cell subpopulation differentiation in mice with autoimmune diabetes.

METHODS

Cultured splenic CD8⁺ T cells from pre-diabetic NOD mice isolated with magnetic beads were treated with 30 µg/mL ox-LDL and 10 U/mL interleukin-2 (IL-2) for 24 h and the control cells were treated with IL-2 only. Flow cytometry was used to determine the percentage of splenic CD8⁺IFN-γ⁺ T cells, expressions of CD8, CD44 and CD62L on the T cells, and the activation of T cell factor-1 (TCF-1) and STAT-3. The CD127⁺ memory T cells were purified and transplanted into the pre-diabetic NOD mice via the tail vein, and the blood glucose was recorded weekly and survival time of the mice was monitored.

RESULTS

Treatment with ox-LDL significantly reduced islet β cell-specific cytotoxic CD8⁺T cells as compared with the control group [(0.7∓0.03)% vs (2.7∓0.14)%, P<0.01]. The percentage of effector memory CD8⁺T cells (Tem) in the total memory CD8⁺T cells was reduced [(10.3∓0.71)% vs (30.3∓1.36)%, P<0.01] and that of stem cell-like memory T cells was significantly increased [(72.3∓3.8)% vs (55.1∓2.61)%, P<0.05] following ox-LDL treatment, which also resulted in significantly decreased activation of TCF-1 [(14.5∓0.82)% vs (34.2∓1.23)%, P<0.01] and pSTAT-3 [(3.3∓0.12)% vs (22.1∓1.1)%, P<0.01]. Transplantation of ox-LDL-treated memory T cells in pre-diabetic NOD mice obviously inhibited the increase of blood glucose and prolonged the survival time of the mice (P<0.05).

CONCLUSION

Ox-LDL decreases the activation of transcriptional factors TCF-1 and phosphorylation of STAT-3, inhibits the formation of effector memory CD8⁺ T cells with long-term cytotoxicity, but promote the generation of stem cell-like memory CD8⁺ T cells, which result in suppression of islet β cell-specific effector cytotoxic CD8⁺ T cell differentiation to lessen autoimmune injury to the islet β cells.

Listeria monocytogenes-Induced Cell Death Inhibits the Generation of Cell-Mediated Immunity

The influence of cell death on adaptive immunity has been studied for decades. Despite these efforts, the intricacies of how various cell death pathways shape immune responses in the context of infection remain unclear, particularly with regard to more recently discovered pathways such as pyroptosis. The emergence of Listeria monocytogenes as a promising immunotherapeutic platform demands a thorough understanding of how cell death induced in the context of infection influences the generation of CD8⁺ T-cell-mediated immune responses. To begin to address this question, we designed strains of L. monocytogenes that robustly activate necrosis, apoptosis, or pyroptosis. We hypothesized that proinflammatory cell death such as necrosis would be proimmunogenic while apoptosis would be detrimental, as has previously been reported in the context of sterile cell death. Surprisingly, we found that the activation of any host cell death in the context of L. monocytogenes infection inhibited the generation of protective immunity and specifically the activation of antigen-specific CD8⁺ T cells. Importantly, the mechanism of attenuation was unique for each type of cell death, ranging from deficits in costimulation in the context of necrosis to a suboptimal inflammatory milieu in the case of pyroptosis. Our results suggest that cell death in the context of infection is different from sterile-environment-induced cell death and that inhibition of cell death or its downstream consequences is necessary for developing effective cell-mediated immune responses using L. monocytogenes-based immunotherapeutic platforms.