CAR-tropic extracellular vesicles carry tumor-associated antigens and modulate CAR T cell functionality.

Tumor-derived extracellular vesicles (EVs) are active contributors in metastasis and immunosuppression in tumor microenvironment. At least some of the EVs carry tumor surface molecules such as tumor-associated antigens (TAAs) and/or checkpoint inhibitors, and potentially could interact with T cells or CAR T cells. Upon contact with T cells, EVs could alter their phenotype and functions by triggering signaling through TCR or CAR reprogramming them to escape immune response. We hypothesize that EVs that possess TAA on the surface will probably interact with CAR T cells which can recognize and bind corresponding TAA. This interaction between EVs and CAR T cells may change the outcome of CAR T-based cancer immunotherapy since it should affect CAR T cells. Also, EVs could serve as adjuvants and antigenic components of antitumor vaccines. Herein, we isolated EVs from B cell precursor leukemia cell line (pre-B ALL) Nalm-6 and demonstrated that recognition and binding of CD19+EVs with CD19-CAR T cells strongly depends on the presence of CD19 antigen. CD19+EVs induce secretion of pro-inflammatory cytokines (IL-2 and IFN-y) and upregulated transcription of activation-related genes (IFNG, IFNGR1, FASLG, IL2) in CD19-CAR T cells. Tumor necrosis factor receptor superfamily (TNFRSF4 and TNFRSF9) and T-cell exhaustion markers (CTLA4, LAG3, TIM3 and PDCD1LG2) were also upregulated in CD19-CAR T cells after incubation with CD19+EVs. Long-term cultivation of CD19+ or PD-L1+EVs with CD19-CAR T cells led to increased terminal differentiation and functional exhaustion according to elevated expression of PD-1, TIGIT, CD57. In summary, our results suggest that chronic exposure of CD19-CAR T cells to CD19+EVs mediates activation and systemic exhaustion in antigen-specific manner, and this negative effect is accompanied by the impaired cytotoxic activity in vitro.

[Surgical treatment of mesenteric cyst of small bowel]. / Khirurgicheskoe lechenie kisty bryzheiki tonkoi kishki.

A rare case of surgical treatment of mesenteric cyst of the small bowel is described. The diagnosis was confirmed by irrigography and contrast-enhanced computed tomography of the abdomen. The patient underwent small bowel and mesentery resection with subsequent entero-enteroanastomosis. Postoperative period was uneventful. This case confirms advisability of total en-bloc excision of the cyst via resection of intact mesentery and small bowel segment. Literature data indicate that the only treatment method for mesenteric cysts is surgery.

Application of Adeno-Associated Virus Vectors for Engineering SCF-Containing Extracellular Vesicles of Mesenchymal Stromal Cells.

Mesenchymal stromal cells from rat adipose tissue were transduced with adeno-associated viral (AAV) vector encoding stem cell factor SCF that stimulates proliferation of cardiac c-kit+ cells and improved cardiac function and survival of animals after myocardial infarction. Extracellular vesicles isolated from the medium conditioned by mesenchymal stromal cells by ultracentrifugation were characterized by Western blotting, transmission electron microscopy, nanoparticle tracking analysis, immunostaining, and mass spectrometry analysis. Using proteomic analysis, we identified transgenic SCF in extracellular vesicles released by AAV-modified mesenchymal stromal cells and detected some proteins specific of extracellular vesicles secreted by transduced cells. Extracellular vesicles from AAV-transduced mesenchymal stromal cells could be used for delivery of transgenic proteins as they were readily endocytosed by both cardiosphere-derived cells and cardiac-progenitor cells.