Biology Reference
In-Depth Information
murine polyomavirus
65-68
form virus-like particles (VLPs) when
expressed in insect cells from baculoviral vectors. Electron and con-
forcal microscopy have revealed the entry and the movement of
polyomavirus virions and artificial virus-like particles (VP1 pseudo-
capsids) in mouse fibroblasts and epithelial cells.
69
There are no visible
difference in adsorption and VP1 pseudocapsid (“empty” or con-
taining DNA). Viral particles entered cells internalized in smooth
monopinocytic vesicles, often in the proximity of larger, caveola-like
invaginations. Both the “empty” vesicles derived from caveolae and the
vesicles containing viral particles were stained with the anti-caveolin-1
antibody, and the two types of vesicles often fused in the cytoplasm.
By 3 hour postinfection, a strong signal of the VP1 (but no viral par-
ticles) had accumulated in the proximity of the nuclei, around the
outer nuclear membrane. The vast majority of VP1 pseudocapsids did
not enter the nuclei as seen in SV40 virions.
48
These results provide
important information for the use of VLPs as a tool of drug delivery
carrier. We can assume that VLPs can enter into cells in the same way
same as virions. Nuclear extracts containing the three proteins of
SV40 (VP1, VP2, and VP3) were allowed to interact with purified
SV40 DNA, or with plasmid DNA.
59
These mixtures can deliver
DNAs into the cells. Polyomavirus VP1 capsid particles expressed in
E. coli
and Sf 9 were also packed
in vitro
with anti-sense oligo-
nucleotides
70
and plasmid DNA.
71
Furthermore, JC virus pseudocap-
sids prepared from
E. coli
were also able to deliver exogenous DNA
into human fetal kidney epithelial cells.
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These results indicate that
recombinant JC virus VP1 is able to self-assemble into capsid-like par-
ticles and to package DNA in the absence of the minor capsid proteins,
VP2 and VP3. These prokaryotic assembly systems may facilitate the
investigation of maturation mechanism(s) of polyomaviruses.
Furthermore, capsid-like particles of these VP1 proteins in poly-
omaviridae could potentially be used as a human gene transfer vector.
Not only plasmid DNA but also encapsulation of chemicals was
accomplished with human polyomavirus JC virus (JCV).
73
Propidium
iodide (PI) was packaged into VP1-VLP as a reporter molecule. The
fluorescence intensity of the VP1-VLP depended strongly on the ini-
tial PI concentration. This packaging method is easy to handle and is
