Clonally Focused Public and Private T Cells in Resected Brain Tissue From Surgeries to Treat Children With Intractable Seizures

Characterization of immune cell profiles in the blood of children and adults with tuberous sclerosis complex disease

BACKGROUND

Tuberous sclerosis (TSC) is characterised by the formation of benign tumours across various organs, particularly in the central nervous system (CNS), where they can lead to epilepsy and neurodevelopmental disorders. TSC results from variants in either TSC1 or TSC2 genes, leading to hyperactivation of the mTORC1 pathway, which plays a pivotal role in regulating cell growth and survival. While the influence of mTOR on immune function has been extensively investigated, our understanding of the composition of immune cells in TSC patients remains limited.

OBJECTIVE

Blood immune cell profiles from healthy controls, epilepsy patients, and TSC patients (with or without mTOR inhibitor therapy) were collected and analyzed via flow cytometry in a multicenter study.

RESULTS

Between 12/2020 and 12/2023, 47 blood samples (mean age: 21 years, range 1-52, 72.3 % female) were analyzed via flow cytometry. Overall, we could not observe a unique immune cell profile between the subgroups as a potential distinguishing feature. However, a few cell populations (T cells, CD8+ T cells) seem to shift in patients with epilepsy (independent of TSC diagnosis) or those receiving mTOR inhibitor therapy (B cells, plasma cells) compared with healthy controls.

CONCLUSION

The overall blood immune cell profile is not changed in patients with epilepsy or TSC. However, analysis of subpopulations (T cells and B cells) has revealed changes in immune cell constitution in patients with epilepsy and those receiving mTOR inhibitor therapy.

Distinct peripheral pro-inflammatory profile associated with tuberous sclerosis complex and epilepsy

OBJECTIVE

Tuberous sclerosis complex (TSC) is a monogenetic disorder associated with sustained mechanistic target of rapamycin (mTOR) activation, leading to heterogeneous clinical manifestations. Epilepsy and renal angiomyolipoma are the most important causes of morbidity in adult people with TSC (pwTSC). mTOR is a key player in inflammation, which in turn could influence TSC-related clinical manifestations. Reliable biomarkers are lacking to monitor and predict evolution and response to treatment for epilepsy in pwTSC. Inflammation has been implicated in epileptogenesis in non-TSC-related epilepsy. We aimed to characterize the relation between markers of neuroglial activation/injury, markers of peripheral inflammation, and active epilepsy in pwTSC to identify accessible biomarkers and potential new therapeutic targets.

METHODS

We performed a cross-sectional study to investigate markers of central nervous system (CNS) (neurofilament light [NfL] and glial fibrillary acidic protein [GFAP]) and peripheral (45 cytokines) inflammation in the peripheral blood of pwTSC (n = 46) vs age- and sex-matched healthy controls (HCs) (n = 26). In pwTSC, markers associated with active epilepsy (n = 23/46) were compared to non-TSC epilepsy controls (n = 18). Observations on markers of neuroglial activation/injury (GFAP, NfL) were confirmed in an independent TSC cohort (n = 45; 69% with active epilepsy).

RESULTS

We report that TSC is characterized by elevated serum levels of marker of astrogliosis (GFAP), pro-inflammatory molecules (interleukin 1β [IL-1β], CXCL8) and trophic factor (epidermal growth factor [EGF]) compared to HCs and to non-TSC-related epilepsy controls. Among pwTSC, renal angiomyolipoma presence and size was associated with IL-15. It is notable that active epilepsy in pwTSC was associated with higher levels of GFAP compared to pwTSC without epilepsy, which was confirmed in an external validation cohort, and with elevated levels of pro-inflammatory cytokines (IL-17A, IL-17C, tumor necrosis factor α [TNF-α]), not significantly related to seizure activity or treatment with mTOR inhibitor. These associations remained significant after adjusting for age and sex.

SIGNIFICANCE

These results suggest that key inflammatory mediators could contribute to epileptogenesis and represent novel biomarkers and therapeutic targets in TSC.

Immunity and neuroinflammation in early stages of life and epilepsy

The immune system is crucial for the correct brain development, and recent findings also point toward central control of immune response. As the immune system is not fully developed at birth, the early years become an important window for infections and for the development of epilepsy. Both central and even peripheral inflammation may impact brain function, promoting opening of the blood-brain/blood and cerebrospinal barriers and allowing entry of immune cells and cytokines, which in turn may affect neuron function and connections. The resident brain immune cells, microglia, besides providing protection, also affect neurons, myelination, and astrocyte function. They may, via the complement system, remove synapses, both physiologically and pathologically. After seizures during development, activated microglia releases proinflammatory molecules, which are detrimental for neurons, and inhibition of microglial activation shows promising antiepileptogenic effects. In addition to cytokines, seizures and excessive excitability stimulate calpain 2 expression, which can promote neuron loss and contribute to amplification of inflammatory responses via stimulation of proinflammatory cytokines. In summary, the immature immune system during postnatal early life may be an important target for the development of long-desired antiepileptogenic drugs.

Repetitive antigen stimulation in the periphery dictates the composition and recall responses of brain-resident memory CD8+ T cells

The human brain harbors virus-specific, tissue-resident memory (TRM) CD8+ T cells. However, the impact of repeated peripheral viral infection on the generation, phenotype, localization, and recall responses of brain TRM remains elusive. Here, utilizing two murine models of peripheral viral infection, we demonstrate that circulating memory CD8+ T cells with previous antigen exposure exhibit a markedly reduced capacity to form brain TRM compared to naive CD8+ T cells. Repetitively stimulated brain TRM also demonstrate differential inhibitory receptor expression, preserved functionality, and divergent localization patterns compared to primary memory counterparts. Despite these differences, repetitively stimulated brain TRM provide similar protection against intracranial infection as primary populations with superior recall-based recruitment of peripheral lymphocytes. As CD8+ T cells may distinctly seed the brain with each repeated infection of the same host, these findings point to heterogeneity in the brain TRM pool that is dictated by prior peripheral antigen stimulation history.

TCR Repertoire Analysis During Therapeutic Interventions in Liver Diseases Using Next-Generation Sequencing

BACKGROUND AND AIM

The T cell receptor (TCR) can recognize a vast number of antigens and is closely associated with the pathogenesis of various diseases including autoimmune diseases and malignancies. However, the clinical significance of the TCR repertoire and its post-treatment changes remain unclear in liver diseases.

METHODS

We performed next-generation sequencing (NGS)-based TCR analysis using DNA obtained from peripheral blood mononuclear cells (PBMCs) of healthy donors (HD, n = 5), primary biliary cholangitis (PBC, n = 5), autoimmune hepatitis (AIH, n = 5), and hepatocellular carcinoma (HCC, n = 5) and evaluated the changes after treatment.

RESULTS

Baseline TCR repertoire analysis demonstrated that TCR clonotype usage is restricted and diversity is low in all three disease groups (PBC, AIH, and HCC), particularly in PBC and AIH compared to HD (p < 0.05). Following treatment, clonotype usage and diversity did not change significantly, except in AIH, where diversity decreased further (p < 0.05 for clone Shannon diversity and clone evenness). Disease-specific usage of TCR beta genes and specific changes after therapy were observed in all groups. Analysis of clonotypes shared with other individuals (public clonotypes) revealed that nine public clonotypes in PBC, eight in AIH, and eight in HCC disappeared after treatment. Motif analysis identified one characteristic motif (NQPQH) in PBC.

CONCLUSIONS

The diversity of the TCR repertoire, TCR beta chain usage, clonotypes, and motifs and their post-treatment changes are disease-specific in each liver disease, indicating that further TCR repertoire studies are needed to accelerate the understanding of liver disease pathogenesis from an immunological perspective.

CNS autoimmune response in the MAM/pilocarpine rat model of epileptogenic cortical malformation

The development of seizures in epilepsy syndromes associated with malformations of cortical development (MCDs) has traditionally been attributed to intrinsic cortical alterations resulting from abnormal network excitability. However, recent analyses at single-cell resolution of human brain samples from MCD patients have indicated the possible involvement of adaptive immunity in the pathogenesis of these disorders. By exploiting the MethylAzoxyMethanol (MAM)/pilocarpine (MP) rat model of drug-resistant epilepsy associated with MCD, we show here that the occurrence of status epilepticus and subsequent spontaneous recurrent seizures in the malformed, but not in the normal brain, are associated with the outbreak of a destructive autoimmune response with encephalitis-like features, involving components of both cell-mediated and humoral immune responses. The MP brain is characterized by blood-brain barrier dysfunction, marked and persisting CD8+ T cell invasion of the brain parenchyma, meningeal B cell accumulation, and complement-dependent cytotoxicity mediated by antineuronal antibodies. Furthermore, the therapeutic treatment of MP rats with the immunomodulatory drug fingolimod promotes both antiepileptogenic and neuroprotective effects. Collectively, these data show that the MP rat could serve as a translational model of epileptogenic cortical malformations associated with a central nervous system autoimmune response. This work indicates that a preexisting brain maldevelopment predisposes to a secondary autoimmune response, which acts as a precipitating factor for epilepsy and suggests immune intervention as a therapeutic option to be further explored in epileptic syndromes associated with MCDs.

Keeping T cell memories in mind

The mammalian central nervous system (CNS) contains a vibrant community of resident adaptive immune cells at homeostasis. Among these are memory CD8+ and CD4+ T cells, which reside in the CNS in the settings of health, aging, and neurological disease. These T cells commonly exhibit a tissue-resident memory (TRM) phenotype, suggesting that they are antigen-experienced and remain separate from the circulation. Despite these characterizations, T cell surveillance of the CNS has only recently been studied through the lens of TRM immunology. In this Review, we outline emerging concepts of CNS TRM generation, localization, maintenance, function, and specificity. In this way, we hope to highlight roles of CNS TRM in health and disease to inform future studies of adaptive neuroimmunity.

The CD8 T Cell-Epstein-Barr Virus-B Cell Trialogue: A Central Issue in Multiple Sclerosis Pathogenesis

The cause and the pathogenic mechanisms leading to multiple sclerosis (MS), a chronic inflammatory disease of the central nervous system (CNS), are still under scrutiny. During the last decade, awareness has increased that multiple genetic and environmental factors act in concert to modulate MS risk. Likewise, the landscape of cells of the adaptive immune system that are believed to play a role in MS immunopathogenesis has expanded by including not only CD4 T helper cells but also cytotoxic CD8 T cells and B cells. Once the key cellular players are identified, the main challenge is to define precisely how they act and interact to induce neuroinflammation and the neurodegenerative cascade in MS. CD8 T cells have been implicated in MS pathogenesis since the 80's when it was shown that CD8 T cells predominate in MS brain lesions. Interest in the role of CD8 T cells in MS was revived in 2000 and the years thereafter by studies showing that CNS-recruited CD8 T cells are clonally expanded and have a memory effector phenotype indicating in situ antigen-driven reactivation. The association of certain MHC class I alleles with MS genetic risk implicates CD8 T cells in disease pathogenesis. Moreover, experimental studies have highlighted the detrimental effects of CD8 T cell activation on neural cells. While the antigens responsible for T cell recruitment and activation in the CNS remain elusive, the high efficacy of B-cell depleting drugs in MS and a growing number of studies implicate B cells and Epstein-Barr virus (EBV), a B-lymphotropic herpesvirus that is strongly associated with MS, in the activation of pathogenic T cells. This article reviews the results of human studies that have contributed to elucidate the role of CD8 T cells in MS immunopathogenesis, and discusses them in light of current understanding of autoreactivity, B-cell and EBV involvement in MS, and mechanism of action of different MS treatments. Based on the available evidences, an immunopathological model of MS is proposed that entails a persistent EBV infection of CNS-infiltrating B cells as the target of a dysregulated cytotoxic CD8 T cell response causing CNS tissue damage.