Theiler's virus as a vector for foreign gene delivery.

DA strain and other strains of the TO subgroup of Theiler's murine encephalomyelitis viruses are members of the Cardiovirus genus of picornaviruses and produce a persistent demyelinating disease in mice. A recent study from our laboratory (W.-P. Kong, G. D. Ghadge, and R. P. Roos, Proc. Natl. Acad. Sci. USA 91:1796-1800, 1994) demonstrated that the leader, which is encoded at the N terminus of the Theiler's murine encephalomyelitis virus polyprotein, can be partially replaced by foreign sequences as well as completely deleted, with no loss of infectivity in BHK-21 cells. In this study, we have inserted up to 724 nucleotides into the leader coding region of an infectious DA clone. Recombinant viruses were produced, and the inserts were shown to be stable for at least three passages in BHK-21 cells.