Adenoviruses

Adenoviruses don’t put their DNA directly into the host genome. Instead,
they exist separately as episomes, so they aren’t as likely to cause mutations
as lentiviruses. The drawback is that the episomes aren’t always replicated
and passed on to daughter cells when the host cell divides. Nonetheless,
adenovirus vectors have been used with notable success — and failure. (See
“Making Slow Progress on the Gene Therapy Front” at the end of the chapter
for the details.)