Human CFTR-expressing recombinant adenovirus vectors have been constructed from genetic 
material derived from human adenovirus serotype 5. The recombinant vector is a generation 1 
adenoviral (Avl) vector, termed AvlCF2. AvlCF2 contains (from the left end of the geneome) 
the inverted terminal repeat (ITR) followed by the packaging signal (\p) and Ela enhancer, and 
an expression cassette consisting of an rous sarcoma virus promoter (RSV) and a spliced form 
of the Ad5 tripartite leader (TPL), the human CFTR cDNA coding sequence and an SV40 poly 
A signals. This is followed by the remainder of the Ad5 genome from position 3328 to the right 
end except for the deletion contained within the E3 region (AE3). AvlCF2 is similar to another 
human CFTR expressing recombinant adenoviral vector (AvlCFl) which has been described in 
detail in a protocol previously reviewed and approved by the NIH RAC (Crystal et.al., RAC 
Proposal, 1992). The principle differences from AvlCF2 include the use of a copy of the Ad5 
major late promoter (MLP) instead of the RSV promoter and the use of the Elb poly adenylation 
signal (AvlCFl does not contain an SV40 poly A signal) in the expression cassette. For 
simplicity, only the details of the construction of AvlCF2 will be illustrated; AvlCFl was con- 
structed using an identical approach (Crystal et.al., RAC proposal, 1992; see below for a details 
of the genomic organization and a comparison of the minor differences among the vectors used 
in this study). Because of the similarities in structure and function of AvlCF2 and AvlCF2, 
they have both been used for preclinical studies in this proposal. However, we will use AvlCF2 
in the clinical protocol. 
2.1. Clinical Aspects and Molecular Biology of Human Adenoviruses: Adenoviruses 
(reviewed in Ginsburg, 1984) are small (80-90 nm diameter), non-enveloped viral particles with 
a spiked, icosohedral morphology and a molecular mass of 175 - 185 X 10 6 Da. The genome 
consists of a linear, double stranded DNA of approximately 36 kb in length which codes for at 
least 30 different mRNA molecules. The virion is composed of approximately 85 % protein, 13 
% DNA, 1 % carbohydrate with no lipid component and has a density in isopycnic gradients of 
1.33 g/ml. Serologically, adenoviruses have been classified into 45 - 50 distinct types 
(Hierholzer, 1992). Based on rodent studies, the various adenonviral serotypes can be further 
grouped into 5 subgroups base4 on their ability to induce tumors in newborn hamsters. Thus, 
group A adenoviruses (serotypes 12, 18, 31) are able to induce tumors in newborn hamsters with 
the highest frequency, group B (serotypes 3, 7, 11, 14, 16, 21) less frequently while those in 
group C (serotypes 1, 2, 5, 6), D (serotypes 8 -10, 13, 15, 17, 19, 20, 22-30, 32, 33, 36, 37), 
and group E (serotype 4) do not induce tumors. It is important to recognize despite the 
existence of a classification based on tumor formation in newborn hamsters, adenoviruses have 
never been associated with tumors of any type in humans. 
Clinically, adenoviral infection results in several types of illnesses, the nature of which 
depends on the serotype of the adenovirus involved (Straus, 1984). One of the most common 
illnesses caused by adenoviruses is an upper respiratory infection resulting in acute febrile 
pharangitis accounting for 5 - 15 % of occurrences of the "common cold . The spectrum of 
common adenoviral associated illnesses also includes kerato-conjunctivitis and self-limited 
gastroenteritis. Although less common, adenoviruses can also cause pneumonia, bronchitis, 
hepatitis and cystitis. In immunocompromised individuals, adenoviral infection can result in a 
life-threatening illness. Thus, while adenoviral infections are very common in the general 
population, in most individuals they cause only a mild illness. This is supported by the fact that 
by early adulthood, nearly all ( >95 %) normal, healthy individuals have serologic evidence of 
previous adenoviral infection. Further, fully replicative, wild-type adenoviruses have been used 
in multiple clinical protocols involving several serotypes administered to a number of patients 
Recombinant DNA Research, Volume 17 
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