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Der p 2, a major allergen derived from the house dust mite Dermatophagoides pteronyssinus , is one of the most clinically relevant allergens worldwide. Recombinant Der p 2 (rDer p 2) is useful in clinical diagnosis and disease-specific immunotherapy. However, previous studies showed that Der p 2 can only be expressed in Escherichia coli ( E. coli ) cells as inclusion bodies, thus protein refolding is required to obtain functional products. Here we report a new method to produce biologically active Der p 2 protein in E. coli . N-terminal hexahistidine- and trigger factor (TF)-tagged Der p 2 was expressed in soluble form in E. coli and purified using a combination of chromatography processes. This procedure produced milligram-level high purity Der p 2 per liter of bacterial culture. Moreover, far-UV region circular dichroism (CD) analysis and serum specific IgE reactivity test demonstrated that the secondary structure and IgE reactivity properties of rDer p 2 produced in our study were almost identical to those of natural Der p 2 (nDer p 2). In conclusion, the method developed in this work provides a useful tool for the production of immunologically active recombinant Der p 2 for clinical applications. [ABSTRACT FROM AUTHOR]

A persimmon tannin- Aloe vera composite powder (PT-A) was investigated for its capacity to protect against ionizing radiation. Human hepatic cells (L02 cells) and human hepatoma cells (HepG2 cells) were pretreated with different concentrations of PT-A or the single compounds (PT or Aloe vera ) and radiated with X-rays. After radiation and post-incubation for 12 h or 24 h, the cell viability, apoptosis, and reactive oxygen species (ROS) production were analyzed by Cell Counting Kit 8 (CCK-8), 2',7'-dichlorfluorescein diacetate (DCFH-DA) staining, and Hoechst 33258 staining/flow cytometry, respectively. CCK-8 results illustrated that the optimal radiation dose L02 cells was 8 Gy for L02 cells, and the cell activity was 71.72% (IC 50 = 412.1 μg/mL) after post-radiation incubation of 12 h. For HepG2 cells, the optimal radiation dose was 8 Gy, and the cell activity was 62.37% (IC 50 = 213.0 μg/mL). The cell apoptotic rate was the lowest at a PT-A concentration of 200 μg/mL in L02 cells (4.32%, P < 0.05), and at 100 μg/mL in HepG2 cells (9.80%, P < 0.05). ROS production induced by radiation could be effectively inhibited by 200 μg/mL of PT-A in L02 cells, and by 100 μg/mL of PT-A in HepG2 cells. The PT-A composite has good radioprotective effects on cell vitality and apoptosis of X-rays radiation exposure towards L02 cells and HepG2 cells compared to the persimmon tannin or Aloe vera . Therefore, PT-A composite might be useful as a natural, harmless anti-ionizing radiation agent, and has various clinical application prospects in future.