Molecular cloning of polyoma virus DNA in Escherichia coli: lambda phage vector system.

The biological activity of recombinant phage and recombinant phage DNA containing monomeric or dimeric polyoma DNA inserts was examined in mice and cultured mouse cells. Recombinant preparations containing a single copy of viral DNA were invariably noninfectious; molecules containing a dimeric polyoma DNA insert were at least seven orders of magnitude less infectious than polyoma virions after parenteral inoculation. No infection was detected with any recombinant preparation after oral administration.