Construction of hybrib Autographa californica nuclear polyhedrosis bacmid by modification of p143 helicase

A model for targeting colon carcinoma cells using single-chain variable fragments anchored on virus-like particles via glycosyl phosphatidylinositol anchor

PURPOSE

VLPs displaying tumor targeting single-chain variable fragments (VLP-rscFvs) which targets tumor-associated glycoprotein-72 (TAG-72) marker protein have a potential for immunotherapy against colon carcinoma tumors. In this study, scFvs anchored on VLPs using glycosylphosphatidylinositol (GPI) were prepared to target colon carcinoma spheroids in vitro.

METHODS

VLPs-rscFvs were produced by co-injecting two types of Bombyx mori nucleopolyhedrovirus (BmNPV) bacmids, encoding RSV-gag and rscFvs cDNA into silkworm larvae. Large unilamellar vesicles (LUVs) of 100 nm in diameter were made using 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and packaged with Sulforhodamine B (SRB). LUV-SRB was used to associate with VLP-rscFvs assisted by GP64 present on VLP-rscFvs to produce VLP-rscFv associated SRB (VLP-rscFvs-SRB) at pH 7.5.

RESULTS

The antigenicity of the purified VLPs-rScFvs was confirmed by enzyme-linked immunosorbent assay (ELISA) using TAG-72 as antigen. LUV-SRB made of DOPC was used to associate with 100 μg of VLP-rscFvs to produce VLP-rscFv-SRB. Specific delivery and penetration of SRB up to 100 μm into the spheroids shows the potential of the new model.

CONCLUSIONS

The current study demonstrated the display, expression and purification of VLP-rscFvs efficiently. As a test model VLP-rscFv-SRB were prepared which can be used for immunotherapy. rscFvs provide the specificity needed to target tumors and VLPs serve as carrier transporting the dye to target.

A baculovirus isolated from wild silkworm encompasses the host ranges of Bombyx mori nucleopolyhedrosis virus and Autographa californica multiple nucleopolyhedrovirus in cultured cells

A baculovirus, named BomaNPV S2, was isolated from a diseased larva of the wild silkworm, Bombyx mandarina. Notably, BomaNPV S2 exhibited a distinguishing feature in that its host range covered that of both Bombyx mori nucleopolyhedrosis virus (BmNPV) and Autographa californica multiple nucleopolyhedrovirus (AcMNPV) in cultured cells. It could replicate in cells of B. mori (Bm5 and BmN), Spodoptera frugiperda (Sf9) and Trichoplusia ni (Tn-5B1-4). However, occlusion-derived virions of BomaNPV S2 in B. mori cells contained only a single nucleocapsid, whereas they contained multiple nucleocapsids in Tn-5B1-4 cells. The complete genome sequence of BomaNPV S2, including predicted ORFs, was determined and compared with the genome sequence of its close relatives. The comparison results showed that most of the BomaNPV S2 genome sequence was shared with BmNPV (BmNPV T3) or BomaNPV S1, but several regions seemed more similar to regions of AcMNPV. This observation might explain why BomaNPV S2 covers the host ranges of BmNPV and AcMNPV. Further recombinant virus infection experiments demonstrated that GP64 plays an important role in BomaNPV S2 host-range determination.

Expression of an RSV-gag virus-like particle in insect cell lines and silkworm larvae

Rous sarcoma virus group antigen protein-based virus-like particles (VLPs) are well known for their structural integrity and ease of handling. VLPs play an important role in drug delivery systems because they can be manipulated with ease. In this study, a new method was established for expressing Rous sarcoma virus group antigen protein based VLPs in silkworm larvae and establishing stably expressing insect cell lines. These VLPs have been isolated by ultracentrifugation using a sucrose step gradient of 10-60% (v/v), and their spherical structure has been confirmed using transmission electron microscopy (TEM). The spherical morphology is similar in both the silkworm larvae and in stably expressing cell lines. Silkworm larvae are better suited for producing Rous sarcoma virus group antigen protein-based VLPs on a large scale; yields from silkworm larvae were approximately 8.2-fold higher than yields from stable cell lines. These VLPs provide a new method for large-scale application in vaccine development and drug delivery systems.

Silkworm expression system as a platform technology in life science

Many recombinant proteins have been successfully produced in silkworm larvae or pupae and used for academic and industrial purposes. Several recombinant proteins produced by silkworms have already been commercialized. However, construction of a recombinant baculovirus containing a gene of interest requires tedious and troublesome steps and takes a long time (3-6 months). The recent development of a bacmid, Escherichia coli and Bombyx mori shuttle vector, has eliminated the conventional tedious procedures required to identify and isolate recombinant viruses. Several technical improvements, including a cysteine protease or chitinase deletion bacmid and chaperone-assisted expression and coexpression, have led to significantly increased protein yields and reduced costs for large-scale production. Terminal N-acetyl glucosamine and galactose residues were found in the N-glycan structures produced by silkworms, which are different from those generated by insect cells. Genomic elucidation of silkworm has opened a new chapter in utilization of silkworm. Transgenic silkworm technology provides a stable production of recombinant protein. Baculovirus surface display expression is one of the low-cost approaches toward silkworm larvae-derived recombinant subunit vaccines. The expression of pharmaceutically relevant proteins, including cell/viral surface proteins, membrane proteins, and guanine nucleotide-binding protein (G protein) coupled receptors, using silkworm larvae or cocoons has become very attractive. Silkworm biotechnology is an innovative and easy approach to achieve high protein expression levels and is a very promising platform technology in the field of life science. Like the "Silkroad," we expect that the "Bioroad" from Asia to Europe will be established by the silkworm expression system.