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

A series of recombinant plasmids containing polyoma virus (PY) DNA were constructed, and their biological activity was evaluated in mice and in cultured mouse cells. While all of the recombinants studied contain the complete, potentially infectious viral DNA, in no case was the intact recombinant PY-plasmid DNA, or live Escherichia coli containing the recombinant plasmids, capable of inducing PY infection of mice, either by feeding or by parenteral injection.