3 Recent Advances 512002). There is an already established infrastructure
for the production, harvesting, and processing of
chicken eggs (Ivarie 2003).
Recently, a group of researchers from the biotech
company AviGenics, Athens, Georgia, successfully
introduced, expressed, and secreted a bacterial gene
in the egg white of transgenic chicken (Harvey et al.
2002). The transgene chosen was the E. coli-lacta-
mase (EC 3.5.2.6) reporter gene because it is easily
secreted and assayed from eukaryotic cells. A repli-
cation-deficient retroviral vector, named NLB, from
the avian leucosis virus (ALV) was used to express
the transgene. The -lactamase coding sequence
was inserted into the pNLB-CMV-BL viral vector
and placed under the control of the ubiquitous cyto-
megalovirus (CMV) promoter. The protein -lacta-
mase was found to be biologically active and was
secreted in the blood and egg white, and its expres-
sion levels remained constant across four genera-
tions of transgenic hens. These results demonstrate
that it is technically possible to express and secret
foreign proteins in the chicken egg, making it an
attractive candidate for a bioreactor. The main work
that needs to be done with the chicken model is to
develop more efficient nonviral-based methods for
creation of transgenic chicken and to identify, iso-
late, and characterize gene enhancers and promoters
that have high activity and drive tissue-specific
expression of proteins in adult oviducts (Harvey et
al. 2002).BIOENGINEERED FISH
Out of all the transgenic, domesticated animals that
have been produced so far, fish are considered safest
for human consumption and are expected to be the
first transgenic animal to be approved as a food item
(Niiler 2000). The company AquaBounty has an
application under review with the FDA for the com-
mercialization of Atlantic salmon carrying a growthFigure 3.11.Fatty acids differences in the carcass composition of rBGH transgenic and wild-type pigs. (From
Solomon et al. 1994.)