Cancer Research - Europa

BACULOGENES
Use of baculovirus as a vector
for gene therapy
Summary
Keywords | Baculovirus | gene delivery | insect cells | vertebrate cells | adeno-associated virus (AAV) |
prostate cancer | age-related macular degeneration (AMD) | muscular disorders (MD) |
Gene therapy is a technique to deliver therapeutic nucleic
acids into somatic cells and is one of the most promising
therapeutic methods under development for treating a large
scope of pathologies, ranging from genetic disorders
(e.g. myopathies) to degeneration syndromes or cancers.
The potential of gene therapy is still not fully exploited
mainly because of signifi cant limitations related to the safety,
gene delivery capacities and some other properties of
the currently used vectors. Baculoviruses (BVs) are insect
pathogenic DNA viruses and are not known to replicate in
mammalian cells giving them an advantage in terms of
safety over classical mammalian viruses currently used as
vectors such as adeno-associated virus (AAV), adenovirus,
murine retroviruses and lentiviruses. The most promising
baculovirus for gene therapy is the well known Autographa
californica multiple nucleopolyhedrovirus (AcMNPV). It is
inherently safe and can deliver large pieces of DNA on its
genome (≥50 Kbp). BV replication and virus production
does not occur in mammalian cells and BV is not known to
be associated with any human disease. However, by using
a vertebrate active expression cassette as a part of baculovirus
genome, effi cient gene expression can also be directed
in non-target cells. A large range of vertebrate cells has been
shown to be permissive for AcMNPV transduction in vitro
and in vivo. BV technology has been used for years for producing
recombinant proteins and thus large scale production
technology is readily adaptable for the exploitation of gene
therapy approaches. In addition, BV vectors can be used
effi ciently for producing other gene therapy vectors such as
AAVs. The BV genome is well-known and several selective
targeting approaches engineered into the virus envelope
and capsid have been developed. The BACULOGENES project
aims to develop clinically suitable methods for the development,
production, testing and validation of next generation
stabilised and selective BV vectors for gene therapy applications
as well as to optimize production of new AAV serotype
vectors. Target diseases for in vivo gene delivery with selectively
targeted BV include muscle disorders, age-related
macular degeneration and prostate cancer. The BACULO-
GENES consortium consists of 8 partners from 6 countries,
including pioneers in the use of BVs for mammalian gene
transfer applications and 2 major established gene therapy
vector producing companies in EU. The consortium will
devote its eff orts not only to BV gene therapy applications,
but also to the development of large scale production,
downstream processing, purifi cation and analysis methods.
The quality control and validation assays, and all issues
related to regulatory aspects required for the clinical
exploitation of BV technology will be covered.
Problem
Validation of BV as a vector for gene therapy and AAV production
implies meeting several challenges including solving
production issues. In fact, the use of BVs to be used as new
effi cient and adapted vectors for gene therapy fully lies on
the demonstration of their ability to:
• carry large and/or multiple genes;
• exclusively target selected tissues;
• deliver the therapeutic gene with a high effi ciency;
• generate an acceptable immunological and toxicological
response;
• show high stability;
• be able to be produced and purifi ed in large quantities. The
BACULOGENES project precisely addresses these issues.
Aim
The innovative strategy of BACULOGENES relies on the
original engineering of BVs (AcMNPV) to make them safe,
specifi c and effi cient vectors for gene therapy. BACULO-
GENES approach consists in stabilizing the BV genome
through deletion and insertion of specifi c sequences in combination
with transgenes relevant to the disease targeted.
The ‘stabilized’ BVs will then be engineered to:
• enhance the capacity to deliver the therapeutic gene(s)
to the right cells;
• optimize the therapeutic gene expression in the right
cells;
• make BVs less immunogenic and potentially invisible for
the immune system (stealth virus).
Such improvements of the BV will be obtained through envelope
protein, capsid and genome modifi cations. In parallel,
the baculovirus expression system will be optimized for the
production of diff erent serotypes of AAV by using stabilized
constructs. In addition, the development of baculovirus constructs
allowing the production of recombinant AAV without
the concomitant production of baculovirus is planned.
170 CANCER RESEARCH PROJECTS FUNDED UNDER THE SIXTH FRAMEWORK PROGRAMME