I AM fairly SCARED!!!!

[Martinez Hewlett]

>
>The place in the world today where there is the most evolutionary
>pressure on viruses is the laboratory.  Unintentional or intentional.

I really don't think that's true.  Most viruses growing in laboratory are
subjected to such a narrow range of conditions that only a very limited
genotype can survive.  A case in point is poliovirus.  At one point the
CDC looked at (by RNA fingerprinting) samples of poliovirus that had been
propagated for many years in widely separated laboratories.  In all
cases, using this limited technology, the viral RNA was the same.  In
contrast, one passage of vaccine strain through a human can result in any
number of genotypes, some of which may even be revertant.

We found the same thing when examining the laboratory passage of LaCrosse
encephalitis virus and snowshoe hare virus.  Laboratory passage produced
selected few variations in nucleic acid sequence, wherease viruses
isolated in the wild at different times varied widely.  (Reference:  M.
J. Hewlett, J. P. M. Clerx, C. M. Clerx-van Haaster, L. J. Chandler, D.
M. McLean and B. J. Beaty (1992), Genomic and biologic analyses of
snowshoe hare virus field and laboratory strains, Amer. J. Trop. Med.
Hyg., 46, 524-532)

Martin Hewlett
Department of Molecular and Cellular Biology
Univeristy of Arizona
Tucson, Arizona  85721