Biology Reference
In-Depth Information
Chapter 3
Capsid Modifi cation Strategies for Detargeting
Adenoviral Vectors
Alan L. Parker , Angela C. Bradshaw , Raul Alba , Stuart A. Nicklin ,
and Andrew H. Baker
Abstract
Adenoviral vectors hold immense potential for a wide variety of gene therapy based applications; however,
their effi cacy and toxicity is dictated by “off target” interactions that preclude cell specifi c targeting to sites
of disease. A number of “off target” interactions have been described in the literature that occur between
the three major capsid proteins (hexon, penton, and fi ber) and components of the circulatory system,
including cells such as erythrocytes, white blood cells, and platelets, as well as circulatory proteins includ-
ing complement proteins, coagulation factors, von Willebrand Factor, p-selectin as well as neutralizing
antibodies. Thus, to improve effi cacious targeting to sites of disease and limit nonspecifi c uptake of virus
to non-target tissues, specifi cally the liver and the spleen, it is necessary to develop suitable strategies for
genetically modifying the capsid proteins to preclude these interactions. To this end we have developed
versatile systems based on homologous recombination for modifi cation of each of the major capsid pro-
teins, which are described herein.
Key words
Adenovirus, Replication defi cient, Gene therapy, Hexon, Penton base, Fiber, Capsid
modifi cation, Homologous recombination
1
Introduction
To date, some 57 different serotypes of human adenovirus have
been described, divided into seven separate species A-G on the basis
of their sequence alignments, hemagglutination patterns, and recep-
tor usage (reviewed in [
1
]). Clinically, infections caused by adeno-
viruses tend to be self limiting, resulting in respiratory diseases
(primarily species B and C), conjunctivitis (species B and D) and
gastroenteritis (species F and G). Due to their remarkable capacity
to transduce a diverse variety of cells both in vitro and in vivo, they
are useful tools experimentally for over expression of transgenes.
Furthermore, their progression to the clinic for therapeutic pur-
poses has been rapid, and they are now the most commonly
