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PFU/Particle ratios

Bruce Phillips bap at MED.PITT.EDU
Mon Jul 31 12:14:05 EST 1995

	I would like to take exception to the recent explanation for high
particle/pfu ratios as merely reflecting an excess of noninfectious particles.
This explanation presumes that the efficiency of infection is 100%- and
that is clearly untrue for most if not all viruses.  Clearly, a number
of cxritical events must progress for the final outcome of an infection
to yield infectious progeny, the absolute requirement for plaque formation.
A viable particle that infects a cell and kills it (or doesn't kill it)
fails to produce progeny virus particles will not yield a plaque.  I
believe experiments have been done in which the virus containing supernatant,
after the usual excess adsorption period, was still found to have pfu's
in it.  In fact, we published a paper on a urea-resistant poliovirus mutant
which attached, eluted, but remained infectious.
	Particle/pfu ratios can be a real pain in devising or explaining
certain kinds of experimental results.

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