Regarding the discussion on PFU vs infectious particle, I'll echo Dan's
response with the example of avian influenza viruses which we readily
titrate as 10 to 100 times more concentrated when using eggs versus chick
fibroblasts with trypsin in the overlay (pfu). What I find fascinating is
that we see these different ratios of egg titer vs cell culture pfu between
strains. I think this reflects the remarkable variability of these
viruses and indicates that the "junk" not found by the plaque assays may be
the most interesting stuff to look at.
Michael L. Perdue, Ph.D.
Athens, Georgia 30605
mperdue at asrr.arsusda.gov