Cumba Garcia, Luz M

Extracellular vesicles (EVs) are membrane-bound particles released by all cells. Previous research has found that these microscopic vesicles contribute to intercellular signaling and communication. EVs carry a variety of cargo, including nucleic acids, proteins, metabolites, and lipids. The composition of EVs varies based on cell of origin. Therefore, EVs can serve as an important biomarker in the diagnosis and treatment of various cancers. EVs derived from glioblastoma (GBM) cells carry biomarkers, which could serve as the basis for a potential diagnostic strategy known as liquid biopsy. Multiple EV isolation techniques exist, including ultrafiltration, size exclusion chromatography, flow field-flow fractionation, sequential filtration, differential ultracentrifugation, and density-gradient ultracentrifugation. Recent and ongoing work aims to identify cellular markers to distinguish GBM-derived EVs from those released by noncancerous cells. Strategies include proteomic analysis of GBM EVs, identification of GBM-specific metabolites, and use of Food and Drug Administration-approved 5-aminolevulinic acid—an oral agent that causes fluorescence of GBM cells—to recognize GBM EVs in a patient's blood. In addition, accurately and precisely monitoring changes in EV cargo concentrations could help differentiate between pseudoprogression and GBM recurrence, thus preventing unnecessary surgical interventions.

Abstract Background Glioblastoma (GBM), the most common primary brain tumor, has a median survival of 15–16 months. Immunotherapy is promising but GBM-mediated immunosuppression remains a barrier. GBMs express the interferon-gamma (IFN-γ)-responsive immunosuppressive molecules programmed cell death ligand 1 (PD-L1) and indoleamine 2,3-dioxygenase 1 (IDO1). Extracellular vesicles (EVs) have also been implicated in GBM-mediated immunosuppression, in part through PD-L1. We therefore sought to determine if GBM IFN-γ exposure increased GBM EV-mediated immunosuppression and mechanisms underlying this. Methods Human GBM-derived cells were cultured in the presence/absence of IFN-γ. EVs were harvested. PD-L1, IDO1, and EV-associated protein expression was assessed. GBM EVs (+/−IFN-γ) were cultured with healthy donor monocytes. Immunosuppressive myeloid-derived suppressor cell (MDSC) and nonclassical monocyte (NCM) frequency was determined. Impact of GBM (+/−IFN-γ) EV-treated monocytes on CD3/CD28-mediated T cell proliferation was assessed. The impact of PD-L1 and IDO1 knockdown in GBM EVs in this system was evaluated. Results IFN-γ exposure increased PD-L1 and IDO1 expression in GBM cells and EVs without altering EV size or frequency. IFN-γ-exposed GBM EVs induced more MDSC and NCM differentiation in monocytes and these monocytes caused more T cell inhibition than IFN-γ-naive GBM EVs. PD-L1 and/or IDO1 knockdown in GBM cells abrogated the immunosuppressive effects of IFN-γ-exposed GBM EVs on monocytes. Conclusions IFN-γ exposure such as might occur during an antitumor immune response results in superinduction of GBM EVs’ baseline immunosuppressive effects on monocytes. These effects are mediated by increased PD-L1 and IDO1 expression in GBM EVs. These data highlight mechanisms of GBM EV-mediated immunosuppression and identify therapeutic targets (PD-L1, IDO1) to reverse these effects.

OBJECTIVE The objective of this study was to isolate extracellular vesicles (EVs) from plasma in a cohort of patients with traumatic brain injury (TBI) and analyze their contents for novel biomarkers that could prove useful for rapid diagnosis and classification of brain injury during initial evaluation. METHODS Plasma EVs were isolated by serial ultracentrifugation from patients with TBI (n = 15) and healthy controls (n = 5). Samples were obtained from the TRACK-TBI biorepository (2010–present). Size and concentration were determined by nanoparticle tracking. Glial fibrillary acidic protein (GFAP) concentration was determined in EV protein. EV RNA was isolated and deep sequencing of short noncoding RNA was performed. RESULTS Plasma EVs are physically similar but contained approximately 10 times more GFAP in TBI patients with altered consciousness than patients and controls with normal consciousness. Eleven highly differentially expressed microRNAs (miRNAs) were identified between these groups. Genes targeted by these miRNAs are highly associated with biologically relevant cellular pathways, including organismal injury, cellular development, and organismal development. Multiple additional coding and noncoding RNA species with potential biomarker utility were identified. CONCLUSIONS Isolating plasma EVs in patients with TBI is feasible. Increased GFAP concentration—a validated plasma TBI marker—in EVs from TBI patients with altered consciousness, along with differential expression of multiple miRNAs targeting TBI-relevant pathways, suggests that EVs may be a useful source of TBI biomarkers. Additional evaluation in larger patient cohorts is indicated.

ABSTRACT Brain atrophy is a common feature of numerous neurologic diseases in which the role of neuroinflammation remains ill‐defined. In this study, we evaluated the contribution of major histocompatibility complex class I molecules to brain atrophy in Theiler's murine encephalomyelitis virus (TMEV)–infected transgenic FVB mice that express the D b class I molecule. FVB/D b and wild‐type FVB mice were evaluated for changes in neuroinflammation, virus clearance, neuropathology, and development of brain atrophy via T2‐weighted MRI and subsequent 3‐dimensional volumetric analysis. Significant brain atrophy and hippocampal neuronal loss were observed in TMEV‐infected FVB/D b mice, but not in wild‐type FVB mice. Brain atrophy was observed at 1 mo postinfection and persisted through the 4‐mo observation period. Of importance, virus‐infected FVB/D b mice elicited a strong CD8 T‐cell response toward the immunodominant D b ‐restricted TMEV‐derived peptide, VP2 121–130 , and cleared TMEV from the CNS. In addition, immunofluorescence revealed CD8 T cells near virus‐infected neurons; therefore, we hypothesize that class I restricted CD8 T‐cell responses promote development of brain atrophy. This model provides an opportunity to analyze the contribution of immune cells to brain atrophy in a system where persistent virus infection and demyelination are not factors in long‐term neuropathology.—Huseby Kelcher, A. M., Atanga, P. A., Gamez, J. D., Cumba Garcia, L. M., Teclaw, S. J., Pavelko, K. D., Macura, S. I., Johnson, A. J. Brain atrophy in picornavirus‐infected FVB mice is dependent on the H‐2Db class I molecule. FASEB J. 31, 2267–2275 (2017). www.fasebj.org