Preparation of peptide-targeted phagemid particles using a protein III-modified helper phage

Engineering T7 bacteriophage as a potential DNA vaccine targeting delivery vector

Background

DNA delivery with bacteriophage by surface-displayed mammalian cell penetrating peptides has been reported. Although, various phages have been used to facilitate DNA transfer by surface displaying the protein transduction domain of human immunodeficiency virus type 1 Tat protein (Tat peptide), no similar study has been conducted using T7 phage.

Methods

In this study, we engineeredT7 phage as a DNA targeting delivery vector to facilitate cellular internalization. We constructed recombinant T7 phages that displayed Tat peptide on their surface and carried eukaryotic expression box (EEB) as a part of their genomes (T7-EEB-Tat).

Results

We demonstrated that T7 phage harboring foreign gene insertion had packaged into infective progeny phage particles. Moreover, when mammalian cells that were briefly exposed to T7-EEB-Tat, expressed a significant higher level of the marker gene with the control cells infected with the wide type phage without displaying Tat peptides.

Conclusion

These data suggested that the potential of T7 phage as an effective delivery vector for DNA vaccine transfer.

Engineering bioactive peptide-based therapeutic molecules

Peptides are increasingly emerging as human therapeutic drugs. By screening very large phage display libraries, novel bioactive peptides that bind to the target of interest with desired biological properties can be identified. Peptides that are obtained in this fashion become the basis for therapeutic molecule development. However, naked peptides are usually not sufficient to be therapeutic molecules by themselves. They need to be chemically modified or conjugated to other molecules to obtain desired physicochemical and in vivo properties. In this chapter, we describe a general methodology of identifying bioactive peptides by biopanning of peptide phage libraries. As an example of therapeutic peptide modifications, we also describe a method for fusing the peptides to the Fc portion of antibody molecule to increase in vivo stability and activity.

Metastatic prostate cancer cell-specific phage-like particles as a targeted gene-delivery system

Background

One of the cardinal requirements for effective therapeutic management of tumors is the selective delivery of cancer drugs to the right site by ligand-decorated nanomedicines. Screening of 2 × 10⁹ clone landscape phage library provides a reliable avenue for generating protein ligands specific for tumor cells. It was shown that selective phage proteins derived from landscape phage libraries against breast and prostate cancer cells are able to navigate drug or siRNA loaded liposomes to corresponding cancer cells with minimal toxicity to non-neoplastic cells. In an alternative platform, glioma cell-specific phage proteins were used for assembling in vivo cancer-specific phage-like particles, named ‘phagemid infective particles’ as targeted gene-delivery vehicles.

Methods

To extend the panel of anticancer cell phages, we have screened a 2 × 10⁹ clone landscape phage library f8/8 to select phage clones specific for metastatic prostate cancer cell PC-3M. The phage clones were characterized for their selective interaction with PC-3M cells using phage capture assay, immunofluorescence microscopy and electron microscopy. A prostate cancer selective phage was converted to phage-like particles harboring emerald green fluorescent protein.

Results

Phage clone EPTHSWAT (designated by the sequence of inserted peptide) was found to be most selective for PC-3M cells and was observed to internalize PC-3M cells as revealed by immunofluorescence microscopy and electron microscopy. Conversion of this phage to phage-like particles harboring emerald green fluorescent protein and the expression of emerald green fluorescent protein in the phage-like particles treated PC-3M cells showed potential of adoption of this phage-like particle in prostate cancer therapeutic gene delivery.

Conclusion

Successful employment of phage-like particles expressing emerald green fluorescent protein genes targeted to prostate cancer cells PC-3M confirms a prospect of their use for targeted delivery of therapeutic genes to cancer cells.

Chemical coupling as a potent strategy for preparation of targeted bacteriophage-derived gene nanocarriers into eukaryotic cells

BACKGROUND

The ability to direct efficiently and specifically carriers toward target cells and express the transgene of interest is a critical step in gene therapy trails. The display of targeting molecules on the surface of phage particles might represent a potent solution. In the present study, we evaluated a chemical coupling strategy for displaying human holotransferrin as a targeting molecule on the surface of phage lambda particles for specifically delivering green fluorescent protein (GFP) encoding gene into a human cell line.

METHODS

Human holotransferrin was coupled on the phage lambda particles bearing a GFP-expression cassette by a chemical coupling strategy to formulate transferrin-targeted lambda-GFP (Tf-targeted-λ-GFP) gene nanocarrier. The carrier was then characterized by phage-enzyme-linked immunosorbent assay experiments and used for transfection of the human 293T cell line. Particle internalization into the cells was evaluated by immunocytochemical staining and transfection efficacy was studied using fluorescence-activated cell sorting (FACS) analysis.

RESULTS

Characterization of the nanocarrier showed a rather high copy number (274 molecules) of transferrin molecules coupled per phage particle. Immunocytochemical staining revealed efficient internalization of the Tf-targeted-λ-GFP compared to wild lambda-GFP (λ-GFP) particles. FACS analysis showed 6.72% GFP positive cells for transfections mediated by Tf-targeted-λ-GFP, whereas the value was 0.61% for wild lambda-GFP particles.

CONCLUSIONS

Our findings highlight chemical coupling as an efficient and straightforward strategy for displaying a targeting molecule at high density on the phage surface, which, in turn, may improve the efficiency of phage-mediated gene transfer and expression.

Peptide phage display as a tool for drug discovery: targeting membrane receptors

Ligands selected from phage-displayed random peptide libraries tend to be directed to biologically relevant sites on the surface of the target protein. Consequently, peptides derived from library screenings often modulate the target protein’s activity in vitro and in vivo and can be used as lead compounds in drug design and as alternatives to antibodies for target validation in both genomics and drug discovery. This review discusses the use of phage display to identify membrane receptor modulators with agonistic or antagonistic activities. Because isolating or producing recombinant membrane proteins for use as target molecules in library screening is often impossible, innovative selection strategies such as panning against whole cells or tissues, recombinant receptor ectodomains, or neutralizing antibodies to endogenous binding partners were devised. Prominent examples from a two-decade history of peptide phage display will be presented, focusing on the design of affinity selection experiments, methods for improving the initial hits, and applications of the identified peptides.

Evolution of phage display: from bioactive peptides to bioselective nanomaterials

BACKGROUND

New phage-derived biorecognition nanomaterials have emerged recently as a result of the in-depth study of the genetics and structure of filamentous phage and the evolution of phage display technology.

OBJECTIVE

This review focuses on the progress made in the development of these new nanomaterials and discusses the prospects of using phage as a bioselectable molecular recognition interface in medical and technical devices.

METHODS

The author used data obtained both in his research group and sourced using Science Citation Index (Web of Science) search resources.

RESULTS/CONCLUSION

The merging of phage display technologies with nanotechnology over the past few years has proved promising and has already shown its vitality and productivity by contributing vigorously to different areas of medicine and technology, such as medical diagnostics and monitoring, molecular imaging, targeted drug and gene delivery, vaccine development, as well as bone and tissue repair.

Inhibition of cell growth and invasion by epidermal growth factor-targeted phagemid particles carrying siRNA against focal adhesion kinase in the presence of hydroxycamptothecin

Background

Previous studies demonstrated the EGF-targeted phagemid particles carrying siRNA against Akt could be expressed efficiently in the presence of hydroxycamptothecin (HCPT). However, no significant cell growth inhibition was obtained. This study was to further investigate whether the EGF-targeted phagemid particles carrying siRNA would be a promising tool for anti-cancer siRNA delivery.

Results

We found that pSi4.1-siFAK phagemid particles could significantly inhibit the expression of focal adhesion kinase in the HCPT-treated cells. Moreover, we also observed that the particles could potently suppress cell growth and cell invasion.

Conclusion

These results indicated that EGF-targeted phagemid particles might be a promising tool for anti-cancer siRNA delivery in the presence of HCPT.

Development of efficient RNA interference system using EGF-displaying phagemid particles

AIM

To develop an efficient RNA interference system using phagemid particles displaying the epidermal growth factor (EGF) ligand.

METHODS

pSilencer1.0-siEGFP and pSilencer4.1-siAkt plasmids were constructed by gene clone technology. The modified helper phage genome (plasmid) M13KO7EGFCT was used to package phagemids, such as pSilencer1.0-siEGFP and pSilencer4.1-siAkt. ELISA was used to quantify the titer of the progeny virus particles. Single-strand DNA was extracted and analyzed by agarose gel electrophoresis to evaluate the percentage of the phagemid particles. The expression level of the reporter gene enhanced green fluorescence protein (EGFP) was determined by transducing phagemid particles packaging pSilencer1.0-siEGFP into cells. The level of Akt gene expression in cells transduced phagemid particles packaging pSilencer4.1-siAkt was examined by Western blotting. Hydroxycamptothecin (HCPT) was used to enhance the gene transduction efficiency.

RESULTS

RNAi vectors pSilencer1.0-siEGFP and pSilencer4.1-siAkt were successfully constructed. Phagemid-encoding siRNA can be packaged efficiently. After the cells were infected by EGF displaying phagemid particles in the presence of HCPT, the expression of the target gene EGFP or Akt was substantially downregulated.

CONCLUSION

Cell-targeted phagemid particles are efficient siRNA delivery vectors in the presence of HCPT.