Repost re: possible reservoir for Ebola/Marburg

[ncel]

On Wed, 17 May 1995, Giovanni Maga wrote:
> It's not a matter if they count or not, simply plant cells are too much
> different from animal cells to allow any precise comparison. BTW, the
> origin of this debate was about the probability that viral DNA or RNA
> itself could be the cause of natural occurring infections. This means
> outside the controlled enviroment of a lab. I think that if TMV still
> carries its virion means that its RNA has better chance to infect than if
> it was naked. Beyond that, viral penetrance in permissive animal cells (in
> natural infections) often require interaction with particular receptors of
> the cell surface and such interactions are mediated by the viral envelope.
> Natural occurring transfection in animal cells (i.e. self-penetration of
> DNA or RNA into the cell) seems to me a little bit hard to occurr. Of
> course, once inside the cell it is possible that under some circumstances a
> viral DNA/RNA could give a viral progeny. But virions are made just to
> allow host-to-host transitions of the viral genome, thus if we substitute
> for them by injecting DNA/RNA in the right cell we are far from any
> physiological situation. The undoubtful scientific value of this kind of
> research is another story, of course.
> Regards, G.Maga
> maga at vetbio.unizh.ch
 
Your points are thoughtful and well taken. I only responded because the 
question of RNA infectivity was asked in a *general* way and not at all 
restricted to animal systems.
One additional point: I am aware of at least one plant viral system that
is transmitted *in mature* by free RNA (aside from viroids, of course): the
so-called winter forms of tobacco rattle virus (TRV), which turned out to
be TRV isolates (from the field, not the lab!) lacking the short rod that
contains the coat protein code and thus consisting solely of the large 
viral RNA. It is true, though, that such "strains" are unusual and that they 
don't succeed well in nature. 
All the best, Ted