Neurotoxicity induced by interleukin-2: involvement of infiltrating immune cells

Low cerebral blood flow is a non-invasive biomarker of neuroinflammation after repetitive mild traumatic brain injury

Previous work has shown that non-invasive optical measurement of low cerebral blood flow (CBF) is an acute biomarker of poor long-term cognitive outcome after repetitive mild traumatic brain injury (rmTBI). Herein, we explore the relationship between acute cerebral blood flow and underlying neuroinflammation. Specifically, because neuroinflammation is a driver of secondary injury after TBI, we hypothesized that both glial activation and inflammatory signaling are associated with acute CBF and, by extension, with long-term cognitive outcome after rmTBI. To test this hypothesis, cortical CBF was non-invasively measured in anesthetized mice 4 h after 3 repetitive closed head injuries spaced once-daily, at which time brains were collected. Right hemispheres were fixed for immunohistochemical staining for glial activation markers Iba1 and GFAP while left hemispheres were used to quantify Iba1 and GFAP expression via Western blot as well as 32 cytokines and 21 phospho-proteins in the MAPK, PI3K/Akt, and NF-κB pathways using a Luminex multiplexed immunoassay. N = 8/7 injured/sham C57/black-6 adult male mice were studied. Within the injured group, CBF inversely correlated with Iba1 expression (R = -0.86, p < .01). Further, partial least squares regression analysis revealed significant correlations between CBF and expression of multiple pro-inflammatory cytokines, including RANTES and IL-17. Finally, within the injured group, phosphorylation of specific signals in the MAPK and NF-κB intracellular signaling pathways (e.g., p38 MAPK and NF-κB) were significantly positively correlated with Iba1. In total, our data indicate that acute cerebral blood flow after rmTBI is a biomarker of underlying neuroinflammatory pathology.

Improved survival and tumor control with Interleukin-2 is associated with the development of immune-related adverse events: data from the PROCLAIMSM registry

BACKGROUND

Immune related adverse events (irAEs) are associated with immunotherapy for cancer and while results suggest improvement in tumor control and overall survival in those experiencing irAEs, the long-term impact is debated. We evaluated irAE reports related to high dose interleukin-2 therapy (IL-2) documented in the PROCLAIMSM registry data base from 2008 to 2016 (NCT01415167, August 9, 2011).

METHODS

Reports on 1535 patients, including 623 with metastatic melanoma (mM) and 919 with metastatic renal cell cancer (mRCC) (7 patients had both diseases), were queried for irAEs. The timing of the event was categorized as occurring before, during or after IL-2 or related to any checkpoint inhibitor (CPI). mM patients and mRCC patients were analyzed separately. Tumor control [complete + partial response + stable disease (CR + PR + SD) was compared between those experiencing no irAE versus those with the development of irAEs. Survival was analyzed by tumor type related to timing of irAE and IL-2, and in those with or without exposure to CPI.

RESULTS

Median follow-up was 3.5+ years (range 1-8+ years), 152 irAEs were reported in 130 patients (8.4% of all PROCLAIMSM patients): 99 (16%) in mM and 53 (5.8%) in mRCC patients. 31 irAEs occurred prior to IL-2, 24 during IL-2, and 97 after IL-2 therapy. 74 irAEs were attributed to IL-2 only (during/ after IL-2). Of the 97 post IL-2 irAEs, 24 were attributed to CPI, and 15 could not be distinguished as caused by IL-2 or CPI. Tumor control was 71% for those experiencing irAE, and 56% for those with no irAE (p = 0.0008). Overall survival was significantly greater for those experiencing irAEs during/ after IL-2 therapy, compared to those with no irAE or irAE before IL-2 therapy, in mM patients, median 48 months vs 18 months (p < 0.0001), and in mRCC patients, median 60 months vs 40 months (p = 0.0302), independent of CPI-related irAEs. IL-2-related irAEs were primarily vitiligo and thyroid dysfunction (70% of IL-2 related irAEs), with limited further impact.

CONCLUSIONS

irAEs following IL-2 therapy are associated with improved tumor control and overall survival. IrAEs resulting from IL-2 and from CPIs are qualitatively different, and likely reflect different mechanisms of action of immune activation and response.

Loss of Neuronal Phenotype and Neurodegeneration: Effects of T Lymphocytes and Brain Interleukin-2

Loss of neuronal phenotype and reversal of neuronal atrophy have been demonstrated in different models of central nervous system (CNS) injury. These processes may be generalizable to different types of brain neurons and circuitry. The idea that some injured neurons may lose their phenotype and/or atrophy with the potential to rejuvenate is a remarkable and potentially promising form of neuronal plasticity that is not well understood. In this paper, we present some of our laboratory's basic neuroimmunology research showing that peripheral T cells entering the CNS, and brain-derived interleukin-2 (IL-2), play significant roles in these intriguing processes. Our findings suggest, for example, that T cell immunosenesence could be involved in related processes of brain aging and contribute to neurodegenerative disease. Neuroimmunological approaches may provide new insights into yet undiscovered factors and brain mechanisms that regulate changes in neuronal integrity associated with aging and disease. Such findings could have important implications for discovering more effective strategies for treating patients with neurotrauma and neurodegenerative diseases (e.g., Alzheimer's disease).

Role of cytotoxic protease granzyme-b in neuronal degeneration during human stroke

Infiltration of leukocytes into post-ischemic cerebrum is a well-described phenomenon in stroke injury. Because CD-8(+) T-lymphocytes secrete cytotoxic proteases, including granzyme-b (Gra-b) that exacerbates post-ischemic brain damage, we investigated roles of Gra-b in human stroke. To study the role of Gra-b in stroke, ischemic and non-ischemic tissues (from post-mortem stroke patients) were analyzed using immunoblotting, co-immunoprecipitation, terminal deoxy uridine nick end labeling (TUNEL) and Annexin-V immunostaining, and in vitro neuron survival assays. Activated CG-SH cells and supernatants were used to model leukocyte-dependent injury. Non-ischemic brain tissues were used as non-pathological controls. Non-activated CG-SH cells and supernatants were used as controls for in vitro experiments. Human stroke (ischemic) samples contained significantly higher levels of Gra-b and interferon-gamma inducible protein-10 (IP-10/CXCL10) than non-ischemic controls. In stroke, poly (ADP-ribose) polymerase-1 and heat shock protein-70 were cleaved to canonical proteolytic "signature" fragments by Gra-b. Gra-b was also found to bind to Bid and caspase-3. Gra-b also co-localized with Annexin-V(+) /TUNEL(+) in degenerating neurons. Importantly, Gra-b inhibition protected both normal and ischemia-reperfused neurons against in vitro neurotoxicity mediated by activated CG-SH cells and supernatants. These results suggest that increased leukocyte infiltration and elevated Gra-b levels in the post-stroke brain can induce contact-dependent and independent post-ischemic neuronal death to aggravate stroke injury.

Granzyme-b is involved in mediating post-ischemic neuronal death during focal cerebral ischemia in rat model

Although peripheral immune cells infiltrate ischemic infarct tissue and elicit immune injury, the role of Cytotoxic T Lymphocytes (CTLs) and the toxins they release in mediating neuronal death is not well understood. Granzyme-b (Gra-b), a serine protease found in the cytoplasmic granules of CTLs and natural killer cells, plays an important role in inducing target cell death by activating several caspases and by initiating caspase-independent pathways that contribute to target cell death. To determine if CTLs and Gra-b are involved in post-ischemic cerebral cell death; we investigated the role of CD8(+) CTLs and Gra-b in ischemic rat brain infarct after transient middle cerebral artery occlusion (tMCAO) and in sham-operated animals. We observed that CTLs infiltrate the ischemic infarct within 1 h of reperfusion. There was a significant increase in Gra-b levels in the ischemic region starting from 1 h until 3 day which correlated with increased levels of chemokines (IP-10/CXCL10, IL-2) and TNF-alpha. Co-immunoprecipitation experiments show that Gra-b interacts with Bid, PARP, and caspase-3 in ischemic samples. Immunofluorescence analysis of Gra-b and TUNEL showed that Gra-b is present both in apoptotic and necrotic cells. Triple immunostaining further confirmed that the Gra-b positive degenerating cells were neurons. CTLs in close spatial proximity to degenerating neurons, increased levels of Gra-b, localization in neurons positive for TUNEL, and interaction with other pro-apoptotic proteins indicate that Gra-b and CTLs play a significant role in neuronal death following cerebral ischemia in the rat brain after tMCAO. Based on the above findings we support our hypothesis that Gra-b secreted from activated CTLs might be involved in aggravating post-ischemic damage by mediating neuronal death.

Sensitization and tolerization to brain antigens in stroke

Despite encounter of novel brain antigens by the systemic immune system following stroke, autoimmune responses to these antigens do not seem to occur. In rats, a systemic inflammatory response at the time of stroke, however, provokes changes that increase the likelihood of developing detrimental autoimmunity. These findings may help to explain why infections in the post-stroke period are associated with worse outcome. In addition, data suggest that the immune response can be manipulated in an antigen specific fashion to improve stroke outcome. Together these data argue that the nature of the post-ischemic immune response influences neurological recovery from stroke.

Increased T-cell reactivity and elevated levels of CD8+ memory T-cells in Alzheimer's disease-patients and T-cell hyporeactivity in an Alzheimer's disease-mouse model: implications for immunotherapy

Neuroinflammation is observed in neurodegenerative diseases like Alzheimer's disease (AD). However, a little is known about the mechanisms of neural-immune interactions. The involvement of peripheral T-cell function in AD is still far from clear, though it plays an important role in immunotherapy. The aim of this study was to determine peripheral T-cell reactivity in AD patients and in an AD mouse model. Mitogenic activation via ligation of the T-cell receptor (TCR) with PHA-L was measured in T lymphocytes from AD patients and Thy1(APP 751SL) x HMG(PS1 M146L)-transgenic mice (APP x PS1). In order to uncover failures in TCR signaling, the TCR was also bypassed by PMA and ionomycin treatment. All patients were sporadic late onset cases and the transgenic mice expressed no mutant APP in lymphocytes, so that direct interactions of mutant APP on T-cell function can be excluded. CD4+ and CD8+ T-cell showed increased reactivity (tyrosine phosphorylation, CD69 expression, and proliferation) in AD, while APP x PS1 transgenic mice displayed hyporeactive CD8+ T-cells after TCR ligation. Increased levels of CD8+ T memory cells and down regulation of CD8 receptor were found in AD and the animal model. Anergic TCR uncoupling was associated with loss of MAPK signaling (p38, ERK1 and ERK2) in APP x PS1. Our data implicate the generation of reactive memory T-cell in AD and of anergic memory T-cells in transgenic mice and should be taken into concern when designing immunotherapy.

Randomized Trial of an Allogeneic Melanoma Lysate Vaccine With Low-Dose Interferon Alfa-2b Compared With High-Dose Interferon Alfa-2b for Resected Stage III Cutaneous Melanoma

Purpose

To compare the overall survival (OS) of patients with resected stage III melanoma administered active specific immunotherapy and low-dose interferon alfa-2b (IFN-α-2b) with the OS achieved using high-dose IFN-α-2b.

Patients and Methods

An Ad Hoc Melanoma Working Group of 25 investigators treated 604 patients from April 1997 to January 2003. Patients were stratified by sex and number of nodes and were randomly assigned to receive either 2 years of treatment with active specific immunotherapy with allogeneic melanoma lysates and low-dose IFN-α-2b (arm 1) or high-dose IFN-α-2b alone for 1 year (arm 2). Active specific immunotherapy was injected subcutaneously (SC) weekly for 4 weeks, at week 8, and bimonthly thereafter. IFN-α-2b SC was begun on week 4 and continued thrice weekly at 5 MU/m2 for 2 years. IFN-α-2b in arm 2 was administered according to the Eastern Cooperative Oncology Group 1684 study regimen.

Results

Median follow-up time was 32 months for all patients and 42 months for surviving patients. Median OS time exceeds 84 months in arm 1 and is 83 months in arm 2 (P = .56). Five-year OS rate is 61% in arm 1 and 57% in arm 2. Estimated 5-year relapse-free survival (RFS) rate is 50% in arm 1 and 48% in arm 2, with median RFS times of 58 and 50 months, respectively. The incidence of serious adverse events as a result of treatment was the same in both arms, but more severe neuropsychiatric toxicity was seen in arm 2.

Conclusion

OS and RFS achieved by active specific immunotherapy and low-dose IFN-α-2b were indistinguishable from those achieved by high-dose IFN-α-2b. Long RFS and OS times were observed in both treatment arms.

Sensitization to brain antigens after stroke is augmented by lipopolysaccharide

After stroke, the blood-brain barrier is transiently disrupted, allowing leukocytes to enter the brain and brain antigens to enter the peripheral circulation. This encounter of normally sequestered brain antigens by the systemic immune system could therefore present an opportunity for an autoimmune response to brain to occur after stroke. In this study, we assessed the immune response to myelin basic protein (MBP) in animals subjected to middle cerebral artery occlusion (MCAO). Some animals received an intraperitoneal injection of lipopolysaccharide (LPS; 1 mg/kg) at reperfusion to stimulate a systemic inflammatory response. At 1 month after MCAO, animals exposed to LPS were more likely to be sensitized to MBP (66.7% versus 22.2%; P=0.007) and had more profound and persistent neurologic deficits than non-LPS-treated animals. Exposure to LPS was associated with increased expression of the costimulatory molecule B7.1 early after stroke onset (P=0.009) and increased brain atrophy 1 month after MCAO (P=0.03). These data suggest that animals subjected to a systemic inflammatory insult at the time of stroke are predisposed to develop an autoimmune response to brain, and that this response is associated with worse outcome. These data may partially explain why patients who become infected after stroke experience increased morbidity.

Circulating autoantibodies recognize and bind dying neurons following injury to the brain

While it is known that autoimmune cells can protect against cell damage following traumatic injury of the brain, the role of autoantibodies in brain injury is less clear. Here we present evidence in adult rats that following a cortical lesion of the brain, circulating IgG autoantibodies bind to dying neurons in the vicinity of the lesion. At intervals that ranged from 4 h to 7 days after making a unilateral lesion of visual cortex, we observed neurons near the lesion that were immunopositive for rat IgG. Many of these IgG-positive neurons were in advanced stages of degeneration. The magnitude of the immunostaining observed was directly proportional to the percent reactivity to rat IgG of the antibodies that were used. Preadsorption of the antibodies with rat serum eliminated the immunostaining. In addition, immunostaining for serum albumin in sections through the cortical lesion was negative, supporting the conclusion that the positive staining for IgG does not result from the passive diffusion of serum proteins into injured cells. Instead, the evidence presented here strongly suggests that naturally occurring IgG autoantibodies bind specifically to dying neurons in the injured brain. We propose that this autoantibody binding may participate in the phagocytosis and removal of injured neurons.

Microglia as a source and target of cytokines

Cytokines constitute a significant portion of the immuno- and neuromodulatory messengers that can be released by activated microglia. By virtue of potent effects on resident and invading cells, microglial cyto- and chemokines regulate innate defense mechanisms, help the initiation and influence the type of immune responses, participate in the recruitment of leukocytes to the CNS, and support attempts of tissue repair and recovery. Microglia can also receive cyto- and chemokine signals as part of auto- and paracrine communications with astrocytes, neurons, the endothelium, and leukocyte infiltrates. Strong responses and modulatory influences can be demonstrated, adding to the emerging view that microglial behavior is highly dependent on the (cytokine) environment and that reactions to a challenge may vary with the stimulation context. In principle, microglial activation aims at CNS protection. However, failed microglial engagement due to excessive or sustained activation could significantly contribute to acute and chronic neuropathologies. Dysregulation of microglial cytokine production could thereby promote harmful actions of the defense mechanisms, result in direct neurotoxicity, as well as disturb neural cell functions as they are sensitive to cytokine signaling.

Age-related impairment of human T lymphocytes' activation: specific differences between CD4(+) and CD8(+) subsets

The relevance of physiological immune aging is of great interest with respect to determining disorders with pathologic immune function in aging individuals. In recent years, the relevance of changes in peripheral lymphocytes in age-associated neurologic diseases has become more evident. Due to the lack of immunological studies, covering more than one event after mitogenic activation, we envisaged a new concept in the present study, aiming to investigate several events, starting from T cell receptor (TCR) ligation up to T cell proliferation. In addition, we addressed the question whether changes are present in the subsets (CD4, CD8) with aging. Phosphorylation of tyrosine residues declines with increasing age in CD4(+) cells. Fewer levels of CD69 positive cells after 4 h mitogenic activation, altered expression of cytokines (IL2, IFN-gamma and TNF-alpha; 22 h) and lower proliferation (72 h) were determined in aging. Moreover, it could be shown that CD8(+) lymphocytes react more effectively to mitogenic stimulation with reference to CD69 expression and proliferation in both age groups (<35 and >60 years old). These data indicate that T cell activation, mediated by TCR engagement, is significantly impaired in aging and both subsets are affected. However, bypassing the TCR does not fully restore T cell function, indicating that there are more mechanisms involved than impaired signal transduction through TCR only. The results will be discussed in relation to their relevance in neurodegenerative and psychiatric disorders.

Allelic expression and interleukin-2 polymorphisms in multiple sclerosis

We have investigated the association of two single nucleotide polymorphisms (SNPs) at positions -384 and 114 in the human interleukin-2 (hIL-2) with multiple sclerosis (MS). For two of the -384 genotypes (G/T, T/T), we observed an association with the susceptibility to secondary progressive (SP) course of MS (P=0.005 and P=0.013, respectively). Expression level differences of the IL-2 alleles (between one- and three-fold) were not attributable to the -384 promoter polymorphism. These data indicate for the first time the relevance of the il-2 gene locus in human MS and its possible involvement in other autoimmune diseases.

Interleukin-2 and interleukin-4 increase the survival of retinal ganglion cells in culture

Natural cell death is a degenerative phenomenon observed during the normal development of the nervous system. The neuroprotective effects of cytokines produced by neuronal, glial or infiltrating cells on neurons have been extensively studied. In this work we studied the role of interleukin (IL)-2 and IL-4 on the survival of retinal ganglion cells (RGC) after 48 h in culture. Our results demonstrate that the effect of both ILs was dose-dependent and the treatment with either IL-2 (50 U/ml) or IL-4 (5 U/ml) induced a 2-fold increase in RGC survival. The effect of IL-4, but not of IL-2, was totally abolished by either 20 microM 5-fluoro-2'-deoxyuridine, an inhibitor of cell proliferation, or by 1 microM telenzepine, an inhibitor of M1 muscarinic receptor. Our results suggest that both cytokines could play an important role during the development of retinal tissue as well as during retina trauma.

IL-10 gene transfer to intracranial 9L glioma: tumor inhibition and cooperation with IL-2

This study examines the effects of interleukin-10 (IL-10) and combination IL-10 + IL-2 gene transfer on experimental brain tumor growth in vivo. 9L gliosarcoma cells were engineered to stably express murine IL-10 (9L-IL-10 cells) and implanted subcutaneously or to the caudate/putamen of syngeneic rats. The growth of tumors expressing IL-10 was substantially reduced compared to that of control tumors (p < 0.05). Intracranial tumors expressing IL-10 and IL-2 were established by co-implanting 9L-IL-10 cells with endothelial cells engineered to express IL-2. At 14 days post-implantation, tumors expressing IL-10 + IL-2 were 99% smaller than control-transfected tumors (p < 0.0001). This extent of anti-tumor effect could not be achieved by expression of IL-10 or IL-2 alone within tumors. Neither IL-10 nor a combination of IL-10 + IL-2 gene delivery inhibited tumor growth in severe combined immunodeficient (SCID-Beige) mice (p > 0.05). Immunohistochemical analysis revealed that IL-10 + IL-2 gene delivery markedly increased T-cell infiltration within the striatum ipsilateral to tumor cell implantation. These findings establish that IL-10 expression, particularly in combination with IL-2 expression, can have significant immune-dependent anti-tumor actions within intracranial gliomas.