[Clinical Analysis of Salvage Treatment of Glucocorticoid Resistant Graft-Versus-Host Disease with Vedolizumab in Children].

OBJECTIVE: To investigate the efficacy and safety of VDZ (Vedolizumab) in the salvage treatment of glucocorticoid resistance to gastrointestinal graft-versus-host disease (GR-GI GVHD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) in children. METHODS: The clinical data of 5 patients with refractory GI GVHD who received allo-HSCT in Wuhan Children's Hospital from December 2020 to December 2021 were retrospectively analyzed with VDZ salvage therapy. RESULTS: Among the 5 children with refractory GI GVHD, there were 1 male and 4 female, including 2 cases of extremely severe aplastic anemia, 1 case of acute myeloid leukemia (M2, high-risk), 1 case of fanconi anemia and 1 case of myelodysplastic syndrome. The median age of transplant recipients was 54.4 (12-164) months. The median treatment time from transplantation to VDZ was 1.4 (0.6-6.8) months. On average, 3.5 (2-5) doses of VDZ were received. After receiving treatment, 2 patients achieved a complete response (CR), 2 patients achieved a very good partial response (VGPR), 1 patient was non-responsive (NR) after a short-term partial response (PR). Compared with that before VDZ treatment, the amount of diarrhea, stool color, blood and traits of the children after medication were effectively improved. The median follow-up time was 9.3 (7.23-12.83) months. No disseminated or severe bacterial/fungal infections occurred during VDZ treatment and follow-up, and 2 children died of leukemia recurrence and pulmonary bronchiolitis obliterans. CONCLUSION: VDZ salvage treatment of refractory GI GVHD in children has obvious short-term efficacy and good safety.

Electron ultra-high dose rate FLASH irradiation study using a clinical linac: Linac modification, dosimetry, and radiobiological outcome.

PURPOSE: Ultra-high dose rate FLASH irradiation (FLASH-IR) has been shown to cause less normal tissue damage compared with conventional irradiation (CONV-IR), this is known as the "FLASH effect." It has attracted immense research interest because its underlying mechanism is scarcely known. The purpose of this study was to determine whether FLASH-IR and CONV-IR induce differential inflammatory cytokine expression using a modified clinical linac. MATERIALS AND METHODS: An Elekta Synergy linac was used to deliver 6 MeV CONV-IR and modified to deliver FLASH-IR. Female FvB mice were randomly assigned to three different groups: a non-irradiated control, CONV-IR, or FLASH-IR. The FLASH-IR beam was produced by single pulses repeated manually with a 20-s interval (Strategy 1), or single-trigger multiple pulses with a 10 ms interval (Strategy 2). Mice were immobilized in the prone position in a custom-designed applicator with Gafchromic films positioned under the body. The prescribed doses for the mice were 6 to 18 Gy and verified using Gafchromic films. Cytokine expression of three pro-inflammatory cytokines (tumor necrosis factor-α [TNF-α], interferon-γ [IFN-γ], interleukin-6 [IL-6]) and one anti-inflammatory cytokine (IL-10) in serum samples and skin tissue were examined within 1 month post-IR. RESULTS: The modified linac delivered radiation at an intra-pulse dose rate of around 1 × 106 Gy/s and a dose per pulse over 2 Gy at a source-to-surface distance (SSD) of 13 to 15 cm. The achieved dose coverage was 90%-105% of the maximum dose within -20 to 20 mm in the X direction and 95% within -30 to 30 mm in the Y direction. The absolute deviations between the prescribed dose and the actual dose were 2.21%, 6.04%, 2.09%, and 2.73% for 6, 9, 12, and 15 Gy as measured by EBT3 films, respectively; and 4.00%, 4.49%, and 2.30% for 10, 14, and 18 Gy as measured by the EBT XD films, respectively. The reductions in the CONV-IR versus the FLASH-IR group were 4.89%, 10.28%, -7.8%, and -22.17% for TNF-α, IFN-γ, IL-6, and IL-10 in the serum on D6, respectively; 37.26%, 67.16%, 56.68%, and -18.95% in the serum on D31, respectively; and 62.67%, 35.65%, 37.75%, and -12.20% for TNF-α, IFN-γ, IL-6, and IL-10 in the skin tissue, respectively. CONCLUSIONS: Ultra-high dose rate electron FLASH caused lower pro-inflammatory cytokine levels in serum and skin tissue which might mediate differential tissue damage between FLASH-IR and CONV-IR.

Expression and characterization of the carboxyl esterase Rv3487c from Mycobacterium tuberculosis.

Rv3487c (lipF), a member of the lipase family of Mycobacterium tuberculosis, is related to virulence of this pathogen. Real-time RT-PCR analysis indicated that Rv3487c was induced at low pH in M. tuberculosis cultured in vitro. The gene of Rv3487c was cloned and expressed as fusion protein in Escherichia coli. After removal of the N-terminal domain of the fusion partner by enterokinase treatment, the effect of pH, temperature, and detergents on the purified enzyme activity and stability was characterized. Rv3487c could efficiently hydrolyze short chain esters. The catalytic triad of Rv3487c consists of residues Ser90, Glu189, and His219 as demonstrated by amino acid sequence alignment, three-dimensional modeling, and site-directed mutagenesis.