Transduction of Recombinant M3-p53-R12 Protein Enhances Human Leukemia Cell Apoptosis.

Tumor suppressor protein p53 plays important roles in initiating cell cycle arrest and promoting tumor cell apoptosis. Previous studies have shown that p53 is either mutated or defective in approximately 50% of human cancers; therefore restoring normal p53 activity in cancer cells might be an effective anticancer therapeutic approach. Herein, we designed a chimeric p53 protein flanked with the MyoD N-terminal transcriptional activation domain (amino acids 1-62, called M3) and a poly-arginine (R12) cell penetrating signal in its N-and C-termini respectively. This chimeric protein, M3-p53-R12, can be expressed in E. coli and purified using immobilized metal ion chromatography followed by serial refolding dialysis. The purified M3-p53-R12 protein retains DNA-binding activity and gains of cell penetrating ability. Using MTT assay, we demonstrated that M3-p53-R12 inhibited the growth of K562, Jurkat as well as HL-60 leukemia cells carrying mutant p53 genes. Results from FACS analysis also demonstrated that transduction of M3-p53-R12 protein induced cell cycle arrest of these leukemia cells. Of special note, M3-p53-R12 has no apoptotic effect on normal mesenchymal stem cells (MSC) and leukocytes, highlighting its differential effects on normal and tumor cells. To sum up, our results reveal that purified recombinant M3-p53-R12 protein has functions of suppressing the leukemia cell lines' proliferation and launching cell apoptosis, suggesting the feasibility of using M3-p53-R12 protein as an anticancer drug. In the future we will test whether this chimeric protein can preferentially trigger the death of malignant cancer cells without affecting normal cells in animals carrying endogenous or xenographic tumors.

Development and characterization of a potential diagnostic monoclonal antibody against capsid protein VP1 of the chicken anemia virus.

Chicken anemia virus (CAV) is an important viral pathogen that causes anemia and severe immunodeficiency syndrome in chickens worldwide. In this study, a potential diagnostic monoclonal antibody against the CAV VP1 protein was developed which can precisely recognize the CAV antigen for diagnostic and virus recovery purposes. The VP1 gene of CAV encoding the N-terminus-deleted VP1 protein, VP1Nd129, was cloned into an Escherichia (E.) coli expression vector. After isopropyl-ß-D-thiogalactopyronoside induction, VP1Nd129 protein was shown to be successfully expressed in the E. coli. By performing an enzyme-linked immunoabsorbent assay using two coating antigens, purified VP1Nd129 and CAV-infected liver tissue lysate, E3 monoclonal antibody (mAb) was found to have higher reactivity against VP1 protein than the other positive clones according to the result of limiting dilution method from 64 clones. Using immunohistochemistry, the presence of the VP1-specific mAb, E3, was confirmed using CAV-infected liver and thymus tissues as positive-infected samples. Additionally, CAV particle purification was also performed using an immunoaffinity column containing E3 mAb. The monoclonal E3 mAb developed in this study will not only be very useful for detecting CAV infection and performing histopathology studies of infected chickens, but may also be used to purify CAV particles in the future.

Purified recombinant TAT-homeobox B4 expands CD34(+) umbilical cord blood and peripheral blood progenitor cells ex vivo.

Hematopoietic stem cells (HSCs) are commonly used in clinical transplantation protocols to treat a variety of diseases. However, efficient transplantation requires a substantial amount of HSCs from different sources and may require expansion. Therefore, effective expansion of HSCs remains a technical hurdle blocking the development of advanced cell therapies. The product of the human homeobox B4 (HOXB4) gene was recently demonstrated to effectively expand HSCs from umbilical cord blood (UCB) or bone marrow in either a retroviral or recombinant protein form. Our study purified TAT-HOXB4 proteins and demonstrated their ability to expand UCB and peripheral blood (PB) progenitor cells. The results showed that the TAT-HOXB4 gene product expanded the CD34(+) progenitor cells from UCB and PB by approximately 7.5-fold. The results from a semisolid cloning assay, a human long-term culture-initiating cell assay, and a nonobese diabetic-severe combined immunodeficiency mice repopulating assay showed that TAT-HOXB4 expanded hematopoietic progenitor cells while retaining their repopulating capacity and multipotency. TAT-HOXB4 protein also expanded engrafted stem cells that were previously expanded in a secondary transplantation assay. The results demonstrated the feasibility of using TAT-HOXB4 to expand UCB and PB progenitor cells, which are readily available to treat different hematological malignancies and nonhematological diseases.

Purification of capsid-like particles of infectious bursal disease virus (IBDV) VP2 expressed in E. coli with a metal-ion affinity membrane system.

Protein VP2, matured from the polyprotein encoded by the genome of infectious bursal disease virus (IBDV) and the primary host-protective immunogen of this virus, together with its two N-terminal truncated mutants were cloned and expressed in Escherichia coli. To obtain pure recombinant proteins for the development of an efficient subunit vaccine against IBDV infection, these three proteins were fused with six additional histidine residues at their C-termini as a His-purification-tag. Following purification employing immobilized metal-ion (Ni2+) affinity chromatography (IMAC), a purification fold of approximately 104 was achieved. Electron microscopic observation also demonstrated that all three E. coli-derived proteins form the morphology of icosahedral particles of approximately 25 nm in diameter. To reduce the cost of resin used for IMAC, self-prepared immobilized metal-ion affinity membranes (IMAM), i.e., commercial, regenerated cellulose membrane modified with iminodiacetic acid and immobilized with nickel ions, was applied to purify particles formed by these three proteins. A 104-fold of purification efficiency was also achieved by this membrane, showing that under the same conditions the recovery and purification efficiency of IMAM are comparable with those of IMAC. The pure VP2-formed particles thus obtained, coupled with their uniform dimensions, not only facilitate a better understanding of the structural biology of these immunogenic particles but also help the development of improved vaccines against this avian virus.