Biology Reference
In-Depth Information
Chapter 5
Alphavirus-Based Vectors
Kenneth Lundstrom
Abstract
Alphavirus vectors have been developed for transient gene expression. The most common approach has
been to generate replication-defi cient vectors based on Semliki Forest virus, Sindbis virus, or Venezuelan
equine encephalitis virus. All these alphavirus vectors have demonstrated effi cient transduction of neurons
in primary cultures, slices and in vivo. Wild-type vectors are cytotoxic resulting in host cell death. Mutant
vectors have showed reduced toxicity and prolonged host cell survival. Engineering of temperature-
sensitive mutants has allowed controlled expression and targeting to interneurons and astrocytes.
Alphaviruses have been used in addition to neurobiology in drug discovery, structural biology, vaccine
development, and cancer therapy.
Key words Semliki Forest virus, Sindbis virus, Venezuelan equine encephalitis virus, Transgene
expression, Neurons, Temperature-sensitive mutants
1
Introduction
Alphaviruses possess single-stranded RNA of positive polarity and
are encapsulated by a capsid protein and a membrane envelope
structure. The close to 30 members of alphaviruses belong to the
family of Togaviridae [ 1 ]. Although certain alphaviruses such as
Eastern enquine encephalitis virus (EEE) and Western equine
encephalitis virus (WEE) regularly cause fatal encephalitis in
humans [ 2 ], those applied for the engineering of viral expression
vectors have been considered as mild pathogens for humans despite
their association with a couple of epidemics in Africa [ 3 ]. Three
members of the family have been frequently used as expression
vectors: Semliki Forest virus (SFV) [ 4 ], Sindbis virus [ 5 ], and
Venezuelan equine encephalitis virus (VEE) [ 6 ]. Expression vec-
tors have been designed according to three variations (Fig. 1 ) [ 7 ].
(a) Replication-defi cient vectors, which consist of a two vector system
with an expression vector carrying the viral replicase genes and the
gene of interest, and the helper vector providing the viral structural
genes. Due to the presence of the RNA packaging signal only on
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