A recombinant adenoviral vector begun to be widely used because it has been recognized as a useful tool not only in gene therapy but also in the basic research field such as analysis of a gene-function. Following three methods are known as a method for generating a first-generation adenoviral vector: a method of Graham et al. (Bett, A. J. et al., Proc. Natl. Acad. Sci. USA, 91: 8802-8806 (1994)) is that, first the full-length adenovirus genome was divided into two parts and cloned into plasmids respectively, then a recombinant adenovirus vector is obtained by homologous recombination between a plasmid in which an expression unit of a desired gene was inserted in the E1-gene deletion site and the other plasmid whose adenovirus genome sequence is partially overlapped with the first plasmid;    a cloned-genome introducing method which become commercially available recently, in which an expression unit of a desired gene is inserted into a cloned full-length viral genome; (JP-A-11-332560, Berkner, K. L. et al., Nuc. Acids Res., 11: 6003-6020 (1983); Mizuguchi, H. et al., Hum. Gene Ther., 10: 2013-2017 (1999); and H. Mizuguchi et al., Experimental medicine, 20: 1799-1804 (2002));    A COS-TPC method using a viral genome with a terminal protein, developed by the present inventors (JP-A-8-308585 and Miyake S. et al., Proc. Natl. Acad. Sci. USA, 93: 1320-1324 (1996)).
The principle of the cloned-genome introducing method has been known from about 20 years ago. Despite of a simple method, a generation efficiency of adenoviruses of this method is low, so that this generation method is not considered practical. The COS-TPC method developed by the present inventors is based on the principle of homologous recombination between a cosmid vector in which a full-length adenoviral genome is cloned and an adenoviral genome DNA with a terminal protein (DNA-TPC) digested with a restriction enzyme such as EcoT22I. Desired recombinant adenoviruses can be efficiently obtained by the COS-TPC method. Thus, numerous example are reported which show generation of an adenovirus vector expressing a desired gene having a potential effect on cells. As is evident from this, the COS-TPC method has been considered variable. However, the COS-TPC method is intricate, so that the COS-TPC method is not always required even for the case where it is satisfactory if a desired recombinant adenoviral vector can be generated even though the generation efficiency is slightly low. From this point of view, a simple “cloned-genome introducing method” has been reconsidered. However, a cosmid vector conventionally used in the COS-TPC method has a deletion at both ends of the adenoviral genome. Therefore, even if the cells are transformed with the cosmid vector in which the viral genome portion is cleaved out and linearized, it is impossible to generate the virus. To overcome this, in order to applicate widely this generation method, it has been desired to develop a simple and practical method for constructing a cosmid vector applicable to not only the COS-TPC method but also the cloned full-length genome introducing method (see FIG. 1).