PFU does NOT = infectious particles

[Michael L. Perdue]

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
Ph: 706-546-3435
Fx: 706-546-3161
mperdue at asrr.arsusda.gov