Early B-cell development and B-cell maturation are impaired in patients with active hemophagocytic lymphohistiocytosis.

Hemophagocytic lymphohistiocytosis (HLH) is characterized by hyperinflammation and multiorgan dysfunction. Infections, including the reactivation of viruses, contribute to significant disease mortality in HLH. Although T-cell and natural killer cell-driven immune activation and dysregulation are well described, limited data exist on the status of B-cell compartment and humoral immune function in HLH. We noted marked suppression of early B-cell development in patients with active HLH. In vitro B-cell differentiation studies after exposure to HLH-defining cytokines, such as interferon gamma (IFN-γ) and tumor necrosis factor, recapitulated B-cell development arrest. Messenger RNA sequencing of human CD34+ cells exposed to IFN-γ demonstrated changes in genes and pathways affecting B-cell development and maturation. In addition, patients with active HLH exhibited a marked decrease in class-switched memory B (CSMB) cells and a decrease in bone marrow plasmablast/plasma cell compartments. The decrease in CSMB cells was associated with a decrease in circulating T follicular helper (cTfh) cells. Finally, lymph node and spleen evaluation in a patient with HLH revealed absent germinal center formation and hemophagocytosis with associated lymphopenia. Reassuringly, the frequency of CSMB and cTfh improved with the control of T-cell activation. Taken together, in patients with active HLH, these changes in B cells may affect the humoral immune response; however, further immune studies are needed to determine its clinical significance.

Multicolor Light-Induced Immune Activation via Polymer Photocaged Cytokines.

Cytokines act as potent, extracellular signals of the human immune system and can elicit striking treatment responses in patients with autoimmune disease, tissue damage, and cancer. Yet, despite their therapeutic potential, recombinant cytokine-mediated immune responses remain difficult to control as their administration is often systemic, whereas their intended sites of action are localized. To address the challenge of spatially and temporally constraining cytokine signals, we recently devised a strategy whereby recombinant cytokines are reversibly inactivated via chemical modification with photo-labile polymers that respond to visible LED light. Extending this approach to enable both in vivo and multicolor immune activation, here we describe a strategy whereby cytokines appended with heptamethine cyanine-polyethylene glycol are selectively re-activated ex vivo using tissue-penetrating near-infrared (NIR) light. We show that NIR LED light illumination of caged, pro-inflammatory cytokines restores cognate receptor signaling and potentiates the activity of T cell-engager cancer immunotherapies ex vivo. Using combinations of visible- and NIR-responsive cytokines, we further demonstrate multiwavelength optical control of T cell cytolysis ex vivo, as well as the ability to perform Boolean logic using multicolored light and orthogonally photocaged cytokine pairs as inputs and T cell activity as outputs. Together, this work demonstrates a novel approach to control extracellular immune cell signals using light, a strategy that in the future may improve our understanding of and ability to treat cancer and other diseases.

A phase 1 study of simvastatin in combination with topotecan and cyclophosphamide in pediatric patients with relapsed and/or refractory solid and CNS tumors.

BACKGROUND: 3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins) can inhibit tumor proliferation, angiogenesis, and restore apoptosis in preclinical pediatric solid tumor models. We conducted a phase 1 trial to determine the maximum tolerated dose (MTD) of simvastatin with topotecan and cyclophosphamide in children with relapsed/refractory solid and central nervous system (CNS) tumors. METHODS: Simvastatin was administered orally twice daily on days 1-21, with topotecan and cyclophosphamide intravenously on days 1-5 of a 21-day cycle. Four simvastatin dose levels (DLs) were planned, 140 (DL1), 180 (DL2), 225 (DL3), 290 (DL4) mg/m2 /dose, with a de-escalation DL of 100 mg/m2 /dose (DL0) if needed. Pharmacokinetic and pharmacodynamic analyses were performed during cycle 1. RESULTS: The median age of 14 eligible patients was 11.5 years (range: 1-23). The most common diagnoses were neuroblastoma (N = 4) and Ewing sarcoma (N = 3). Eleven dose-limiting toxicity (DLT)-evaluable patients received a median of four cycles (range: 1-6). There were three cycle 1 DLTs: one each grade 3 diarrhea and grade 4 creatine phosphokinase (CPK) elevations at DL1, and one grade 4 CPK elevation at DL0. All patients experienced at least one grade 3/4 hematologic toxicity. Best overall response was partial response in one patient with Ewing sarcoma (DL0) and stable disease for four or more cycles in four patients. Simvastatin exposure increased with higher doses and may have correlated with toxicity. Plasma interleukin 6 (IL-6) concentrations (N = 6) showed sustained IL-6 reductions with decrease to normal values by day 21 in all patients, indicating potential on-target effects. CONCLUSIONS: The MTD of simvastatin with topotecan and cyclophosphamide was determined to be 100 mg/m2 /dose.

Talin-dependent integrin activation is required for endothelial proliferation and postnatal angiogenesis.

Integrin activation contributes to key blood cell functions including adhesion, proliferation and migration. An essential step in the cell signaling pathway that activates integrin requires the binding of talin to the ß-integrin cytoplasmic tail. Whereas this pathway is understood in platelets in detail, considerably less is known regarding how integrin-mediated adhesion in endothelium contributes to postnatal angiogenesis. We utilized an inducible EC-specific talin1 knock-out mouse (Tln1 EC-KO) and talin1 L325R knock-in mutant (Tln1 L325R) mouse, in which talin selectively lacks the capacity to activate integrins, to assess the role of integrin activation during angiogenesis. Deletion of talin1 during postnatal days 1-3 (P1-P3) caused lethality by P8 with extensive defects in retinal angiogenesis and widespread hemorrhaging. Tln1 EC-KO mice displayed reduced retinal vascular area, impaired EC sprouting and proliferation relative to Tln1 CTRLs. In contrast, induction of talin1 L325R in neonatal mice resulted in modest defects in retinal angiogenesis and mice survived to adulthood. Interestingly, deletion of talin1 or expression of talin1 L325R in ECs increased MAPK/ERK signaling. Strikingly, B16-F0 tumors grown in Tln1 L325R adult mice were 55% smaller and significantly less vascularized than tumors grown in littermate controls. EC talin1 is indispensable for postnatal development angiogenesis. The role of EC integrin activation appears context-dependent as its inhibition is compatible with postnatal development with mild defects in retinal angiogenesis but results in marked defects in tumor growth and angiogenesis. Inhibiting EC pan-integrin activation may be an effective approach to selectively target tumor blood vessel growth.

Folate dietary insufficiency and folic acid supplementation similarly impair metabolism and compromise hematopoiesis.

While dietary folate deficiency is associated with increased risk for birth defects and other diseases, evidence suggests that supplementation with folic acid can contribute to predisposition to some diseases, including immune dysfunction and cancer. Herein, we show that diets supplemented with folic acid both below and above the recommended levels led to significantly altered metabolism in multiple tissues in mice. Surprisingly, both low and excessive dietary folate induced similar metabolic changes, which were particularly evident for nucleotide biosynthetic pathways in B-progenitor cells. Diet-induced metabolic changes in these cells partially phenocopied those observed in mice treated with anti-folate drugs, suggesting that both deficiency and excessive levels of dietary folic acid compromise folate-dependent biosynthetic pathways. Both folate deficiency and excessive dietary folate levels compromise hematopoiesis, resulting in defective cell cycle progression, persistent DNA damage, and impaired production of lymphocytes. These defects reduce the reconstitution potential in transplantation settings and increase radiation-induced mortality. We conclude that excessive folic acid supplementation can metabolically mimic dietary folate insufficiency, leading to similar functional impairment of hematopoiesis.

Lack of significant association between serum inflammatory cytokine profiles and the presence of colorectal adenoma.

BACKGROUND: Inflammatory cytokines in the colonic microenvironment have been shown to increase with advance colorectal cancer disease state. However, the contribution of inflammatory cytokines to pre-malignant disease, such as the formation of adenomas, is unclear. METHODS: Using the Milliplex® MAP Human Cytokine/ Chemokine Magnetic Bead Panel Immunoassay, serum cytokine and chemokine profiles were assayed among participants without an adenoma (n = 97) and those with an adenoma (n = 97) enrolled in the NCI-funded Insulin Resistance Atherosclerosis Colon Study. The concentrations of interleukin-10 (IL-10), IL-1ß, IL-6, IL-17A, IL-2, IL-4, IL-7, IL-12(p70), interferon-γ (IFN-γ), macrophage chemoattractant protein-1 (MCP-1), regulated on activation, normal T cell expressed and secreted (RANTES), tumor necrosis factor-alpha (TNF-α), vascular endothelial growth factor (VEGF), granulocyte macrophage colony-stimulating factor (GM-CSF), and macrophage inflammatory protein-1ß (MIP-1ß) were determined. Multiple logistic regression analyses were used to evaluate the association between adenoma prevalence and cytokine levels. RESULTS: The presence of colorectal adenomas was not associated with significant increases in the systemic levels of proinflammatory (TNF-α, IL-6, IL-1ß) or T-cell polarizing (IL-12, IL-2, IL-10, IL-4, IL-17, IFN-γ) cytokines. Furthermore, MCP-1 and RANTES levels were equivalent in the serum of study participants with and without adenomas. CONCLUSIONS: These findings suggest colorectal adenoma prevalence may not be associated with significant alterations in systemic inflammation.

Pharmacological suppression of the OTUD4/CD73 proteolytic axis revives antitumor immunity against immune-suppressive breast cancers.

Despite widespread utilization of immunotherapy, treating immune-cold tumors remains a challenge. Multiomic analyses and experimental validation identified the OTUD4/CD73 proteolytic axis as a promising target in treating immune-suppressive triple negative breast cancer (TNBC). Mechanistically, deubiquitylation of CD73 by OTUD4 counteracted its ubiquitylation by TRIM21, resulting in CD73 stabilization inhibiting tumor immune responses. We further demonstrated the importance of TGF-ß signaling for orchestrating the OTUD4/CD73 proteolytic axis within tumor cells. Spatial transcriptomics profiling discovered spatially resolved features of interacting malignant and immune cells pertaining to expression levels of OTUD4 and CD73. In addition, ST80, a newly developed inhibitor, specifically disrupted proteolytic interaction between CD73 and OTUD4, leading to reinvigoration of cytotoxic CD8+ T cell activities. In preclinical models of TNBC, ST80 treatment sensitized refractory tumors to anti-PD-L1 therapy. Collectively, our findings uncover what we believe to be a novel strategy for targeting the immunosuppressive OTUD4/CD73 proteolytic axis in treating immune-suppressive breast cancers with the inhibitor ST80.

The T-cell niche tunes immune function through modulation of the cytoskeleton and TCR-antigen forces.

Obesity is a major public health crisis given its rampant growth and association with an increased risk for cancer. Interestingly, patients with obesity tend to have an increased tumor burden and decreased T-cell function. It remains unclear how obesity compromises T-cell mediated immunity. To address this question, we modeled the adipocyte niche using the secretome released from adipocytes as well as the niche of stromal cells and investigated how these factors modulated T-cell function. We found that the secretomes altered antigen-specific T-cell receptor (TCR) triggering and activation. RNA-sequencing analysis identified thousands of gene targets modulated by the secretome including those associated with cytoskeletal regulation and actin polymerization. We next used molecular force probes to show that T-cells exposed to the adipocyte niche display dampened force transmission to the TCR-antigen complex and conversely, stromal cell secreted factors lead to significantly enhanced TCR forces. These results were then validated in diet-induced obese mice. Importantly, secretome-mediated TCR force modulation mirrored the changes in T-cell functional responses in human T-cells using the FDA-approved immunotherapy, blinatumomab. Thus, this work shows that the adipocyte niche contributes to T-cell dysfunction through cytoskeletal modulation and reduces TCR triggering by dampening TCR forces consistent with the mechanosensor model of T-cell activation.

Declining lymphoid progenitor fitness promotes aging-associated leukemogenesis.

Aging is associated with the functional decline of cells, tissues, and organs. At the same time, age is the single most important prognostic factor in the development of most human cancers, including chronic myelogenous and acute lymphoblastic leukemias initiated by Bcr-Abl oncogenic translocations. Prevailing paradigms attribute the association between aging and cancers to the accumulation of oncogenic mutations over time, because the accrual of oncogenic events is thought to be the rate-limiting step in initiation and progression of cancers. Conversely, aging-associated functional decline caused by both cell-autonomous and non-cell-autonomous mechanisms is likely to reduce the fitness of stem and progenitor cell populations. This reduction in fitness should be conducive for increased selection of oncogenic mutations that can at least partially alleviate fitness defects, thereby promoting the initiation of cancers. We tested this hypothesis using mouse hematopoietic models. Our studies indicate that the dramatic decline in the fitness of aged B-lymphopoiesis coincides with altered receptor-associated kinase signaling. We further show that Bcr-Abl provides a much greater competitive advantage to old B-lymphoid progenitors compared with young progenitors, coinciding with restored kinase signaling pathways, and that this enhanced competitive advantage translates into increased promotion of Bcr-Abl-driven leukemias. Moreover, impairing IL-7-mediated signaling is sufficient to promote selection for Bcr-Abl-expressing B progenitors. These studies support an unappreciated causative link between aging and cancer: increased selection of oncogenic mutations as a result of age-dependent alterations of the fitness landscape.

Siglec-15 Promotes Evasion of Adaptive Immunity in B-cell Acute Lymphoblastic Leukemia.

Siglec-15 (Sig15) has been implicated as an immune checkpoint expressed in solid tumor-infiltrating macrophages and is being targeted in clinical trials with mAbs to normalize the tumor immune microenvironment and stimulate antitumor immunity. However, the role of Sig15 in hematologic malignancies remains undefined. Sig15 mRNA and protein expression levels in hematologic malignancies were determined from publicly available databases, cell lines, and primary patient samples. Human B-cell acute lymphoblastic leukemia (B-ALL) cell lines were used to identify signaling pathways involved in the regulation of Sig15 expression. Secreted/soluble Sig15 and cytokine levels were measured from the plasma of children with leukemia and healthy controls. Knockdown and knockout of Siglec15 in a murine model of B-ALL was used to evaluate the effect of leukemia-derived Sig15 on the immune response to leukemia. We observed pathologic overexpression of Sig15 in a variety of hematologic malignancies, including primary B-ALL samples. This overexpression was driven by NFκB activation, which also increased the surface localization of Sig15. Secreted/soluble Sig15 was found to circulate at elevated levels in the plasma of children with B-ALL and correlated with an immune-suppressive cytokine milieu. Genetic inhibition of Sig15 in murine B-ALL promoted clearance of the leukemia by the immune system and a marked reversal of the immune-privileged leukemia bone marrow niche, including expanded early effector CD8+ T cells and reduction of immunosuppressive cytokines. Thus, Sig15 is a novel, potent immunosuppressive molecule active in leukemia that may be targeted therapeutically to activate T lymphocytes against leukemia cells. Significance: We demonstrate that Sig15 is overexpressed in hematologic malignancies driven by NFκB, is required for immune evasion in a mouse model of leukemia, and, for the first time, that it circulates at high levels in the plasma of children with leukemia.

The 'omics of obesity in B-cell acute lymphoblastic leukemia.

The obesity pandemic currently affects more than 70 million Americans and more than 650 million individuals worldwide. In addition to increasing susceptibility to pathogenic infections (eg, SARS-CoV-2), obesity promotes the development of many cancer subtypes and increases mortality rates in most cases. We and others have demonstrated that, in the context of B-cell acute lymphoblastic leukemia (B-ALL), adipocytes promote multidrug chemoresistance. Furthermore, others have demonstrated that B-ALL cells exposed to the adipocyte secretome alter their metabolic states to circumvent chemotherapy-mediated cytotoxicity. To better understand how adipocytes impact the function of human B-ALL cells, we used a multi-omic RNA-sequencing (single-cell and bulk transcriptomic) and mass spectroscopy (metabolomic and proteomic) approaches to define adipocyte-induced changes in normal and malignant B cells. These analyses revealed that the adipocyte secretome directly modulates programs in human B-ALL cells associated with metabolism, protection from oxidative stress, increased survival, B-cell development, and drivers of chemoresistance. Single-cell RNA sequencing analysis of mice on low- and high-fat diets revealed that obesity suppresses an immunologically active B-cell subpopulation and that the loss of this transcriptomic signature in patients with B-ALL is associated with poor survival outcomes. Analyses of sera and plasma samples from healthy donors and those with B-ALL revealed that obesity is associated with higher circulating levels of immunoglobulin-associated proteins, which support observations in obese mice of altered immunological homeostasis. In all, our multi-omics approach increases our understanding of pathways that may promote chemoresistance in human B-ALL and highlight a novel B-cell-specific signature in patients associated with survival outcomes.

Adipocyte-mediated epigenomic instability in human T-ALL cells is cytotoxic and phenocopied by epigenetic-modifying drugs.

The world's population with obesity is reaching pandemic levels. If current trends continue, it is predicted that there will be 1.5 billion people with obesity by 2030. This projection is alarming due to the association of obesity with numerous diseases including cancer, with recent studies demonstrating a positive association with acute myeloid leukemia (AML) and B cell acute lymphoblastic leukemia (B-ALL). Interestingly, several epidemiological studies suggest the converse relationship may exist in patients with T cell acute lymphoblastic leukemia (T-ALL). To determine the relationship between obesity and T-ALL development, we employed the diet-induced obesity (DIO) murine model and cultured human T-ALL cells in adipocyte-conditioned media (ACM), bone marrow stromal cell-conditioned media, stromal conditioned media (SCM), and unconditioned media to determine the functional impact of increased adiposity on leukemia progression. Whereas only 20% of lean mice transplanted with T-ALL cells survived longer than 3 months post-inoculation, 50%-80% of obese mice with leukemia survived over this same period. Furthermore, culturing human T-ALL cells in ACM resulted in increased histone H3 acetylation (K9/K14/K18/K23/K27) and methylation (K4me3 and K27me3) posttranslational modifications (PTMs), which preceded accelerated cell cycle progression, DNA damage, and cell death. Adipocyte-mediated epigenetic changes in human T-ALL cells were recapitulated with the H3K27 demethylase inhibitor GSK-J4 and the pan-HDAC inhibitor vorinostat. These drugs were also highly cytotoxic to human T-ALL cells at low micromolar concentrations. In summary, our data support epidemiological studies demonstrating that adiposity suppresses T-ALL pathogenesis. We present data demonstrating that T-ALL cell death in adipose-rich microenvironments is induced by epigenetic modifications, which are not tolerated by leukemia cells. Similarly, GSK-J4 and vorinostat treatment induced epigenomic instability and cytotoxicity profiles that phenocopied the responses of human T-ALL cells to ACM, which provides additional support for the use of epigenetic modifying drugs as a treatment option for T-ALL.

Germline ETV6 mutation promotes inflammation and disrupts lymphoid development of early hematopoietic progenitors.

Germline mutations in ETV6 are associated with a syndrome of thrombocytopenia and leukemia predisposition, and ETV6 is among the most commonly mutated genes in leukemias, especially childhood B-cell acute lymphoblastic leukemia. However, the mechanisms underlying disease caused by ETV6 dysfunction are poorly understood. To address these gaps in knowledge, using CRISPR/Cas9, we developed a mouse model of the most common recurrent, disease-causing germline mutation in ETV6. We found defects in hematopoiesis related primarily to abnormalities of the multipotent progenitor population 4 (MPP4) subset of hematopoietic progenitor cells and evidence of sterile inflammation. Expression of ETV6 in Ba/F3 cells altered the expression of several cytokines, some of which were also detected at higher levels in the bone marrow of the mice with Etv6 mutation. Among these, interleukin-18 and interleukin-13 abrogated B-cell development of sorted MPP4 cells, but not common lymphoid progenitors, suggesting that inflammation contributes to abnormal hematopoiesis by impairing lymphoid development. These data, along with those from humans, support a model in which ETV6 dysfunction promotes inflammation, which adversely affects thrombopoiesis and promotes leukemogenesis.

Obesity-induced galectin-9 is a therapeutic target in B-cell acute lymphoblastic leukemia.

The incidence of obesity is rising with greater than 40% of the world's population expected to be overweight or suffering from obesity by 2030. This is alarming because obesity increases mortality rates in patients with various cancer subtypes including leukemia. The survival differences between lean patients and patients with obesity are largely attributed to altered drug pharmacokinetics in patients receiving chemotherapy; whereas, the direct impact of an adipocyte-enriched microenvironment on cancer cells is rarely considered. Here we show that the adipocyte secretome upregulates the surface expression of Galectin-9 (GAL-9) on human B-acute lymphoblastic leukemia cells (B-ALL) which promotes chemoresistance. Antibody-mediated targeting of GAL-9 on B-ALL cells induces DNA damage, alters cell cycle progression, and promotes apoptosis in vitro and significantly extends the survival of obese but not lean mice with aggressive B-ALL. Our studies reveal that adipocyte-mediated upregulation of GAL-9 on B-ALL cells can be targeted with antibody-based therapies to overcome obesity-induced chemoresistance.

B-cell acute lymphoblastic leukemia promotes an immune suppressive microenvironment that can be overcome by IL-12.

Immunotherapies have revolutionized the treatment of B-cell acute lymphoblastic leukemia (B-ALL), but the duration of responses is still sub-optimal. We sought to identify mechanisms of immune suppression in B-ALL and strategies to overcome them. Plasma collected from children with B-ALL with measurable residual disease after induction chemotherapy showed differential cytokine expression, particularly IL-7, while single-cell RNA-sequencing revealed the expression of genes associated with immune exhaustion in immune cell subsets. We also found that the supernatant of leukemia cells suppressed T-cell function ex vivo. Modeling B-ALL in mice, we observed an altered tumor immune microenvironment, including compromised activation of T-cells and dendritic cells (DC). However, recombinant IL-12 (rIL-12) treatment of mice with B-ALL restored the levels of several pro-inflammatory cytokines and chemokines in the bone marrow and increased the number of splenic and bone marrow resident T-cells and DCs. RNA-sequencing of T-cells isolated from vehicle and rIL-12 treated mice with B-ALL revealed that the leukemia-induced increase in genes associated with exhaustion, including Lag3, Tigit, and Il10, was abrogated with rIL-12 treatment. In addition, the cytolytic capacity of T-cells co-cultured with B-ALL cells was enhanced when IL-12 and blinatumomab treatments were combined. Overall, these results demonstrate that the leukemia immune suppressive microenvironment can be restored with rIL-12 treatment which has direct therapeutic implications.

Interleukin-37 improves T-cell-mediated immunity and chimeric antigen receptor T-cell therapy in aged backgrounds.

Aging-associated declines in innate and adaptive immune responses are well documented and pose a risk for the growing aging population, which is predicted to comprise greater than 40 percent of the world's population by 2050. Efforts have been made to improve immunity in aged populations; however, safe and effective protocols to accomplish this goal have not been universally established. Aging-associated chronic inflammation is postulated to compromise immunity in aged mice and humans. Interleukin-37 (IL-37) is a potent anti-inflammatory cytokine, and we present data demonstrating that IL-37 gene expression levels in human monocytes significantly decline with age. Furthermore, we demonstrate that transgenic expression of interleukin-37 (IL-37) in aged mice reduces or prevents aging-associated chronic inflammation, splenomegaly, and accumulation of myeloid cells (macrophages and dendritic cells) in the bone marrow and spleen. Additionally, we show that IL-37 expression decreases the surface expression of programmed cell death protein 1 (PD-1) and augments cytokine production from aged T-cells. Improved T-cell function coincided with a youthful restoration of Pdcd1, Lat, and Stat4 gene expression levels in CD4+ T-cells and Lat in CD8+ T-cells when aged mice were treated with recombinant IL-37 (rIL-37) but not control immunoglobin (Control Ig). Importantly, IL-37-mediated rejuvenation of aged endogenous T-cells was also observed in aged chimeric antigen receptor (CAR) T-cells, where improved function significantly extended the survival of mice transplanted with leukemia cells. Collectively, these data demonstrate the potency of IL-37 in boosting the function of aged T-cells and highlight its therapeutic potential to overcome aging-associated immunosenescence.

Dendritic cells inhibit the progression of Listeria monocytogenes intracellular infection by retaining bacteria in major histocompatibility complex class II-rich phagosomes and by limiting cytosolic growth.

Dendritic cells (DC) provide a suboptimal niche for the growth of Listeria monocytogenes, a facultative intracellular bacterial pathogen of immunocompromised and pregnant hosts. This is due in part to a failure of large numbers of bacteria to escape to the cytosol, an essential step in the intracellular life cycle that is mediated by listeriolysin O (LLO). Here, we demonstrate that wild-type bacteria that failed to enter the cytosol of bone marrow-derived DC were retained in a LAMP2+ compartment. An isogenic L. monocytogenes strain that produces an LLO protein with reduced pore-forming activity had a severe escape and growth phenotype in DC. Few mutant bacteria entered the cytosol in the first 2 h and were instead found in LAMP2+, major histocompatibility complex class II+ (MHC-II+) H2-DM vesicles characteristic of MHC-II antigen loading compartments (MIIC). In contrast, the mutant had a minor phenotype in bone marrow-derived macrophages (BMM) despite the reduced LLO activity. In the first hour, DC phagosomes acidified to a pH that was, on average, half a point higher than that of BMM phagosomes. Unlike BMM, L. monocytogenes growth in DC was minimal after 5 h, and consequently, DC remained viable and matured late in infection. Taken together, the data are consistent with a model in which phagosomal maturation events associated with the acquisition of MHC-II molecules present a suboptimal environment for L. monocytogenes escape to the DC cytosol, possibly by limiting the activity of LLO. This, in combination with an undefined mechanism that controls bacterial growth late in infection, promotes DC survival during the critical maturation response.

The roles of IL-12 and IL-23 in CD8+ T cell-mediated immunity against Listeria monocytogenes: Insights from a DC vaccination model.

Listeria monocytogenes infection induces a strong inflammatory response characterized by the production of IL-12 and IFN-gamma and protective immunity against this pathogen is dependent on CD8+ T cells (CTL). Recent studies have suggested that these inflammatory cytokines affect the rate of memory CD8+ T cell generation as well as the number of short-lived effector cells generated. The role of the closely related cytokine, IL-23, in this response has not been examined. We hypothesized that IL-12 and IL-23 produced by dendritic cells collectively enhance the generation and function of memory cells. To test this hypothesis, we employed a DC vaccination approach. Mice lacking IL-12 and IL-23 were vaccinated with wild-type (WT), IL-12(-/-), or IL-12/23(-/-) DC and protection to Lm was monitored. Mice vaccinated with WT and IL-12(-/-) DC were resistant to lethal challenge with Lm. Surprisingly, mice vaccinated with IL-12/23(-/-) DC exhibited significantly reduced protection when challenged. Protection correlated with the relative size of the memory pools generated. In summary, these data indicate that IL-23 can partially compensate for the lack of IL-12 in the generation protective immunity against Lm.

IL-12 produced by dendritic cells augments CD8+ T cell activation through the production of the chemokines CCL1 and CCL17.

IL-12 family members are an important link between innate and adaptive immunity. IL-12 drives Th1 responses by augmenting IFN-gamma production, which is key for clearance of intracellular pathogens. IL-23 promotes the development of IL-17-producing CD4(+) T cells that participate in the control of extracellular pathogens and the induction of autoimmunity. However, recent studies have shown that these cytokines can modulate lymphocyte migration and cellular interactions. Therefore, we sought to determine the individual roles of IL-12 and IL-23 in naive CD8(+) T cell activation by addressing their ability to influence IFN-gamma production and cellular interaction dynamics during priming by Listeria monocytogenes-infected dendritic cells (DC). We found that IL-12 was the major cytokine influencing the level of IFN-gamma production by CD8(+) T cells while IL-23 had little effect on this response. In addition, we observed that IL-12 promoted longer duration conjugation events between CD8(+) T cells and DC. This enhanced cognate interaction time correlated with increased production of the chemokines CCL1 and CCL17 by WT but not IL-12-deficient DC. Neutralization of both chemokines resulted in reduced interaction time and IFN-gamma production, demonstrating their importance in priming naive CD8(+) T cells. Our study demonstrates a novel mechanism through which IL-12 augments naive CD8(+) T cell activation by facilitating chemokine production, thus promoting more stable cognate interactions during priming.

Aging and immunotherapies: New horizons for the golden ages.

The life expectancy of the world's elderly population (65 and older) continues to reach new milestones with older individuals currently comprising greater than 8.5% (617 million) of the world's population. This percentage is predicted to approach 20% of the world's population by 2050 (representing 1.6 billion people). Despite this amazing feat, many healthcare systems are not equipped to handle the multitude of diseases that commonly manifest with age, including most types of cancers. As the world's aging population grows, cancer treatments continue to evolve. Immunotherapies are a new drug class that has revolutionized our ability to treat previously intractable cancers; however, their efficacy in patients with compromised immune systems remains unclear. In this review, we will discuss how aging-associated losses in immune homeostasis impact the efficacy and safety of immunotherapy treatment in preclinical models of aging. We will also discuss how these findings translate to elderly patients receiving immunotherapy treatment for refractory and relapsed cancers, as well as, strategies that could be explored to improve the efficacy of immunotherapies in aged patients.