I believe the original comment regarding (+) vs. (-) strand was in
reference to RNA viruses (ie, J.P. gives picornaviridae as an example).
Parvoviruses are ssDNA, so they don't really seem to count as an example
of what he is looking for. (That is, expression of an infectious dsDNA
clone to (+) RNA ->(-)RNA for packaging.)
Also, with the Parvos whether (+) or (-) strands are packaged can
vary not only with virus but also with cell type (although with the one I
work on, MVM, we only get (-) packaging in any of the common cell lines.)
Just my addled thoughts on the matter.....
On Fri, 27 May 1994 Benoit_Hebert at IAF.UQUEBEC.CA wrote:
> Dr. J.P. Clewley (jclewley at crc.ac.uk) wrote:
>> > One thing I forgot to mention is that its more difficult to engineer
> > a negative strand virus than a positive strand one. If its +ve, you
> > can make a cDNA clone & transfect it in cells & recover progeny virus.
> > Works for alphaviruses (eg. Sindbis) picornaviruses (e.g. polio),
> > retroviruses (e.g. HIV). Recovering -ve strand virus from transfected
> > DNA has not been done reproducibly, as far as I know. Is there a
> > confirmed example I'm missing?
>> yes... Parvoviruses!
>> We generate infectious clones of the NADL-2 strain cloned in pUC19 by
> transfection. The virus is produced even if the vector is double stranded. We
> are currently doing this with other strains as well. Furthermore, this enables
> me to generate chimeric viruses and mutants in pUC and then producing the
> virus by transfection (paper to be submitted shortly... film at eleven!).
>> Benoit Hebert
>Benoit_Hebert at iaf.uquebec.ca>> Armand-Frappier Institute
> Virology Research Center
> Laval, Quebec, Canada H7N 4Z3
> phone: (514) 687-5010, ext. 4636
> fax: (514) 686-5626