Infectivity of DNA/RNA

[welkin]

It is standard laboratory technique to create
stocks of many viruses by "transfecting" naked
viral DNA into host cells.  The only real limitation
is whether the virus relies solely on host factors
for its replication, that is to say that viruses such
as HIV (and all retroviruses) can be propagated
from DNA.  Moreover, the same is generally 
true of +strand (code directly for protein)
RNA viruses (the RNA can be used to infect) but obviously 
not of -strand RNA because a reverse transcriptase 
is required.  
However, this does not mean that naked viral
DNA is inherently dangerous, it usually takes
a bit of chemical or electrical coaxing to get the
DNA into the cell in the first place.