Repost re: possible reservoir for Ebola/Marburg

[Giovanni Maga]

In article <Pine.SOL.3.91.950516202805.1111A-100000 at asrr.arsusda.gov>,
tdiener at ASRR.ARSUSDA.GOV (ncel) wrote:

> "Those who are ignorant of history...." See Fraenkel-Conrat *1956* and 
> Gierer and Schramm, 1956, who conclusively showed that tobacco mosaic 
> virus RNA by itself is infectious when inoculated into susceptible plants 
> with the production of a normal crop of progeny virus (with capsids). But 
> then, I guess, to medics plants don't count. They sure rely on them, however,
> for survival!
> Ted Diener 

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