Application of sandwich ELISA for detecting tag fusion proteins in high throughput.

Based on a series of mAbs against four frequently used tags--the human Ig Fc fragment, GST, maltose-binding protein, and thioredoxin--we developed corresponding sandwich enzyme-linked immunosorbent assay (ELISA) to detect these tag fusion proteins. As a supplement for Western blot, the successfully established ELISA was specific, sensitive, quantitative, easy to perform, time-saving, and last but not least, suitable for high-throughput screening of tag fusion proteins. Determination of soluble tag fusion proteins expressed by various systems with the sandwich ELISA developed in the present study could be a valuable and promising tool for the wide application of tag-protein fusion systems in the rapidly growing field of proteomics research.

Down regulation of TRAIL and FasL on NK cells by Cyclosporin A in renal transplantation patients.

TNF-related apoptosis-inducing ligand (TRAIL) and FasL can participate in cell mediated cytotoxicity via their death domain-mediated apoptotic signaling in the host-versus-graft disease occurred after renal transplantation. However, the effect of Cyclosporin A (CsA) commonly used as a drug to prevent and to treat renal transplant rejection, on these molecules have not been fully determined. In the present study, we found that with CsA administration, the expression of TRAIL and FasL predominantly on NK cells from renal transplantation patients was increased at day 5 after operation and went down to normal level on day 13. While, the levels of soluble TRAIL (sTRAIL) and sFasL in the serum increased within 25 days and went down to normal level three month later. In addition, we showed that a remarkable increase of TRAIL and FasL expression both on the surface of activated lymphocytes especially on NK cells and in the supernatants generated from mixed lymphocytes culture (MLC). Furthermore, the enhancement of these two molecules was greatly decreased by adding 500 ng/mL CsA at the beginning of MLC. We conclude that CsA may inhibit the transplant rejection partially by down-regulating the expression of TRAIL and FasL on NK cells.

[The study of changes on NKT cells of experimental autoimmune encephalomyelitis (EAE) mice].

AIM: To observe the changes of the number of NKT cells in spleens and livers of induced model of experimental autoimmune encephalomyelitis (EAE), and to study the role NKT cells play in the immunoregulation of EAE. METHODS: C57BL/6 mice were immunized with MOG (35-55) peptide and received clinical evaluation daily. The mice were sacrificed at the fastigium and the splenic and hepatic lymphocytes were isolated. The changes of NKT cells in normal and EAE C57BL/6 mice were detected by flow cytometry. RESULTS: The percent of NKT cells in lymphocytes of different organs of EAE model were greater decreased than in that of normal mice. The percent of NKT cells in splenic lymphocytes of normal mice was 2.22+/-0.14, while that in EAE mice was 1.94+/-0.07 (P<0.05). The percent of NKT cells in hepatic lymphocytes of normal mice was 5.52+/-2.17, while that in EAE mice was 2.67+/-1.41 (P<0.05). CONCLUSION: The proliferation of splenic and hepatic NKT cells in C57BL/6 mice are inhibited in EAE model, which may indicate that the immune function conducted by NKT cell is down regulated in EAE mice.

Generation of monoclonal antibodies against Escherichia coli DsbA.

Disulfide oxidoreductase A (also known as disulfide bond formation protein A, or DsbA) is produced in Escherichia coli (E. coli) periplasm, which plays an important role in correct formulation of disulfide bonds during protein exportation in vivo. DsbA prokaryotic expression vectors are designed for periplasmic co-expression of recombinant proteins with an improving secretion. In the present study, the first domain of human CD226 (CD226D1) was expressed as a His-tagged fusion protein with DsbA and purified by Ni-NTA resin. Three monoclonal antibodies (MAbs) against DsbA were raised by using the recombinant fusion protein as immunogen. We have demonstrated that one of them can detect DsbA via Western blotting, in addition to its ability to immunoprecipitate DsbA fusion protein. Furthermore, anti-DsbA MAb can be employed to prepare antibody-coupled affinity column for purification of DsbA fusion protein from E. coli lysate.

Identification and characterization of the CD226 gene promoter.

CD226 is one of the main activating receptors on natural killer cells, and it can induce cytotoxicity to target cells through interaction with its ligands CD155 or CD112. CD226 is also involved in T cell differentiation, activation, and cytotoxicity. The expression of CD226 on natural killer cells and T cells can be regulated by cytokines and chemical stimuli; however, the mechanism of the regulation of the CD226 gene is still unknown. In this study, we have identified two promoters in the human CD226 gene named P1 and P2, which are located at -810 to -287 bp and +33 to +213 bp, respectively, and a negative regulation element between P1 and P2. Both P1 and P2 can be regulated by phorbol ester (12-O-tetradecanoylphorbol-13-acetate) and calcium ionophore (A23187). Bioinformatics analysis shows that, within this CD226 gene region, there are putative binding sites for transcription factors AP-1, Sp1, PEA3, and Ets-1. We have found that transcription factor activating protein-1 (AP-1) can up-regulate CD226 promoters P1 and P2 in human hepatocarcinoma cells, a hepatocarcinoma cell line with low expression of endogenous AP-1 and Ets-1. Interestingly, the transcription factor Ets-1 promotes AP-1-induced P2 activity but inhibits AP-1-induced P1 activity for which a 10-bp AP-1/Ets-1 composite site (CCTTCCTTCC) in P1 may be responsible.

Dynamic changes of apoptosis-inducing ligands and Th1/Th2 like subpopulations in Hantaan virus-induced hemorrhagic fever with renal syndrome.

The expression of the apoptosis-inducing ligands, TNF-alpha, FasL and TRAIL on peripheral blood mononuclear cells (PBMC) and the levels of their soluble form (TNF-alpha, sFasL and sTRAIL) in plasma from 40 hemorrhagic fever with renal syndrome (HFRS) patients as well as 26 healthy blood donors were determined by flow cytometry (FCM) analysis and sandwich ELISA, respectively. The status of Th1, Th2, Tc1 and Tc2 subsets in PBMC was evaluated by intracellular cytokine staining and FCM. Compared to controls, the expression of membrane bound FasL and TRAIL was up-regulated on surface of PBMC isolated from the HFRS patients, particularly on CD8+ T lymphocytes. The levels of TNF-alpha, sFasL and sTRAIL in plasma from the HFRS patients in the acute phase increase 4.7-fold, 6.0-fold and 1.8-fold, respectively, over those from the healthy donors. The percentage of Th1, Tc1 and Tc2 subsets in PBMC from the patients also increased significantly compared with those from healthy donors. These results indicate that dynamic changes occurred in both the membrane bound and soluble forms of apoptosis-inducing ligands (FasL, TRAIL and TNF-alpha) and proportions of Th1 and CTL in HFRS patients increased. Both factors may play an important role in the etiology of Hantaan virus infection in humans.