Accommodation of foreign genes into the Sendai virus genome: sizes of inserted genes and viral replication

Sendai virus (SeV) is an enveloped virus with a negative sense genome RNA o f about 15.3 kb, We previously established a system to recover an infectiou s virus entirely from SeV cDNA and illustrated the feasibility of using SeV as a novel expression vector, Here, me have attempted to insert a series o f foreign genes into SeV of different lengths to learn how far SeV can acco mmodate extra genes and how the length of inserted genes affects viral repl ication in cells cultured in vitro and in the natural host, mice, We show t hat a gene up to 3.2 kb can be inserted and efficiently expressed and that the replication speed as,well as the final virus titers in cell culture are proportionally reduced as the inserted gene length increases, In vivo, suc h a size-dependent effect was not very clear but a remarkably attenuated re plication and pathogenicity were generally seen. Our data further confirmed reinforcement of foreign gene expression in vitro from the V(-) version of SeV in which the accessory V gene had been knocked out. Based on these res ults, we discuss the utility of SeV vector in terms of both efficiency and safety. (C) 1999 Federation of European Biochemical Societies.