Re infectivity of naked viral DNA

[Ed Rybicki]

> From:          SOMERS at PICARD.EVMS.EDU
> Subject:       Re infectivity of naked viral DNA

> The recent posting citing the article in Science 259:1745-49 as evidence
> for infectivity of naked viral DNA does not demonstrate viral DNA infectivity.
> Rather, if this is the paper I think it is (sorry I didnt look it up), the
> paper reports the use of viral cDNA inserted into a plasmid vector and then
> injected intramuscularly into an animal as a way to induce an immune response.
> In this case the so called polynucleotide vaccine induced protection against
> influenza.  This approach has been used in other systems as well.  This is
> not the same as demonstration of infectivity of naked viral DNA in vivo.  
> There is no evidence that the plasmid DNA with the influenza insert is
> replicating in vivo; only expressing the inserted influenza cDNA.

But you CAN inoculate cDNA clones of plant viruses (and I am sure, of 
picornaviruses) into susceptible hosts, and get production of native 
virus - IF you have a suitable promoter that starts transcription at 
or near the 5'-terminus of the viral RNA, and terminates at or just 
3' of the normal 3' terminus.  With plant viruses, cDNA clones of 
viruses as big as potyviruses (>10kb) have been rendered infectious 
in this way.  So it is not a dream or so unlikely for mammalian / 
animal systems; all you need is to get the DNA into a suitable cell, 
which (given the success of naked DNA vaccines) is not all that 
difficult.

Of course, this has very litle to do with Ebola, which ain't like 
that.
 ______________________________________________________
 |     Ed Rybicki, PhD      |  ed at molbiol.uct.ac.za   |
 |    Dept Microbiology     | University of Cape Town |
 | Private Bag, Rondebosch  |   7700, South Africa    |
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