Production of VNPs, VLPs, and Chimeras - Viral Nanoparticles: Tools for Materials Science and Biomedicine - page 58

can be grown in cultured insect cells, such as Spodoptera frugiperda (Sf )

lines 9 and 21 and cells. The gene(s) of interest are typically

placed under control of the viral polyhedrin or p10 promoters; both give
rise to high yields of gene product. A limitation of the system is the large
size of the baculovirus genome; unique restriction sites are not available
for simple cloning. Alternative strategies employ the insertion of the gene
of interest in a shuttle vector and its introduction into the expression
vector by recombination. There are many commercial reagents available to
facilitate baculovirus expression; however, compared with

Trichoplusia ni

- or yeast-
based expression systems these methods are relatively time-consuming and
cumbersome. It typically takes a minimum of several days to a few weeks
until the recombinant virus is constructed and a molecular clone is isolated.
The advantages of the system are reliability with regard to accumulation
of soluble proteins, high probability of self-assembly of VLPs, and post-
translational modifications, such as proteolytic processing, phosphorylation,
and glycosylation. The glycosylation pattern can differ in insect cells
compared with that observed in mammalian cells (reviewed in Schneemann
& Young, 2003). For the production of eukaryotic proteins, the baculovirus-
based expression has long been the system of choice. VLPs are made
commercially in this system. The vaccine

E. coli

, an HPV vaccine based on
HPV VLPs, is produced in the baculovirus system and has been commercialized
in 2007. Cervarix is manufactured by GlaxoSmithKline (www.gsk.com).
—͵Ǥͷ

Cervarix

Figure 3.5 Flock House virus

(FHV) particles and synthetic FHV virus-like particles (VLPs). Authentic particles
were isolated from FHV-infected

Electron micrographs of gradient-purified authentic

Drosophila melanogaster cells (A); synthetic

VLPs were isolated from recombinant baculovirus-infected cells (B).

TEM micrographs were provided by courtesy of Dr. Arno Venter and Prof. Anette
Schneemann (The Scripps Research Institute, La Jolla, CA).

S. frugiperda

For nanotechnology applications, the baculovirus expression system
has been successfully used to produce VLPs of the insect virus FHV, the
mammalian virus CPV, and the plant virus CPMV (Saunders et al. , 2009;