Herpes Simplex Virus 1 (HSV-1)-Based Vectors - Viral Vector Approaches in Neurobiology and Brain Diseases - page 76

by amplicons in tumors in vivo. In a similar experiment, expression
of a secreted version of TRAIL (S-TRAIL) induced apoptosis in
surrounding cells in vivo, resulting in a dramatic reduction of gli-
oma size in mouse tumor models via a bystander effect [ 190 ].
During these experiments, gene delivery was monitored in vivo in
real time by dual enzyme substrate (Renilla luciferase/Firefl y lucif-
erase) imaging. More recently, using an amplicon vector codifying
caspase 1 driven by the Schwann cell-specifi c promoter P0, the
same team was able to induce selective apoptosis only affecting the
schwannoma cells [ 191 ]. For an exhaustive review of previous
work on in vivo imaging of amplicon vectors delivery and gene
expression in tumor models, please refer to the review by Shah and
Breakefi eld [ 192 ].

14.5 Behavioral
Traits

Amplicon vectors designed to express or to block expression of
neuroreceptor subunits or proteins involved in neuron signaling
have been delivered into distinct brain regions to investigate com-
plex aspects of the normal functioning of the CNS. In this chapter,
we summarize some examples to illustrate the powerfulness of
amplicon vectors to address these questions. For a more compre-
hensive review of previous works on the use of amplicons to study
behavior, see [ 114 ].
Different challenges to fi nd causal relationships between neu-
ronal molecular mechanisms and learning and memory processes
have been solved by the use of amplicon vectors. These vectors
were used, for example, to study the role of NMDAR in learning
and memory. In these studies, amplicons were used to investigate
the role of hippocampal NMDAR by modifying the expression of
the essential NR1 subunit in the rat CNS. The vectors expressed
sequences in either sense or antisense orientations of the NR1 sub-
unit gene, in addition to EGFP. The ability to modify endogenous
levels of NR1 was fi rst tested in primary cultures of rat embryo
neocortical neurons [ 140 , 193 ]. Adult rats inoculated into the
dorsal hippocampus with vectors expressing NR1 antisense per-
formed signifi cantly worse than control rats in an inhibitory avoid-
ance task and did not show habituation by repeated exposure to an
open fi eld. Immune-histochemistry performed in brain slices from
the same animals, showed that the transduced cells represented
approximately 6-7 % of hippocampal pyramidal neurons in CA1
region [ 194 ], indicating that a single gene knockdown of NR1 in
a small number of those neurons could signifi cantly impair mem-
ory formation.
Amplicons expressing a constitutively active catalytic domain
of the rat protein kinase C (PKC) II were used to transduce hip-

pocampal dentate granule neurons. Activation of PKC pathways in
a small percentage of these neurons was suffi cient to enhance rat
auditory discrimination reversal learning and suggests a hippocampal
auditory mediated learning in the rat [ 195 ].

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