Objective: To explore the mechanism of excessive senescence in bone marrow-derived mesenchymal stem cells (BM-MSC) of mouse model with severe aplastic anemia (SAA) . Methods: 40 BALB/c mice were randomly assigned to two groups of control (n=20) and AA (n=20) . SAA mouse model was induced by intraperitoneal injection with IFN-γ and intragastric infusion with busulfan. BM-MSC were isolated and cultured from bone marrow of SAA and healthy mice. The cell morphology was observed by inverted microscope and cell cytoskeleton was stained by Rhodamine-Phalloidin; The level of proliferation was analyzed by CCK-8 method, and cell cycle was tested by flow cytometry. Senescence-associated β-galactosidase (SA-β-gal) assay was used to detect senescent BM-MSC; The expression of mTOR protein was detected by Western blot method. Results: BM-MSC from normal mice presented spindle-shaped, clear boundaries and stress fibers were arranged in parallel, neat. while BM-MSCs from SAA mice presented cell volume increases, tiled, ill-shaped and the stress fiber appeared to be disordered. The decreased activity of proliferation [more cells restricted in G₀/G₁ phase [ (77.461±1.567) % vs (46.045±2.055) %, t=-34.384, P<0.001], increased percentage of SA-β-gal positive cells [ (75±11) % vs (28±8) %, t=15.454, P<0.001] and notably enhanced expression of mTOR of BM-MSC from SAA mice were observed when compared with those from normal mice. Conclusion This study clarified senescent BM-MSCs from SAA model mice, which could be caused by the excessive activation of mTOR pathway.

Objective:To screen and identify H-2 d-restricted T cell epitopes in fusion (F) and attachment (G) glycoproteins of Nipah virus (NiV) in mice. Methods:The complete peptides (single peptide contains 15 amino acids, and 10 amino acids were repeated in the front and back peptides) derived from F and G antigens were mixed into peptide libraries. BALB/c mice were immunized with DNA vaccines expressing NiV F and G proteins alone and in combination. The full sequence peptide libraries of F and G antigens were mixed into peptide pools by matrix design, and spleen cells of immunized mice were collected and analyzed by IFN-γ ELISPOT assay to detect the dominant H-2 d-restricted epitope peptides. Results:Twelve dominant H-2 d-restricted peptides were screened from the F protein-specific peptide library and the 56th peptide produced the strongest reaction. Four dominant peptides were screened from the G protein-specific peptide library and the 72nd peptide produced the strongest reaction. Conclusions:In this study, 12 F antigen-specific and 4 G antigen-specific H-2 d restricted dominant T cell epitopes of NiV were screened and identified by IFN-γ ELISPOT, which could provide reference for immunological analysis of NiV and vaccine research.