Noyenber 20, 1952

Dr. W. Henle

Babies Hospital
University of Pennsylvania
Philadelphia Pa.

Dear Dr. Henle:

Thank you for the collection of reprints on your work on influenza
virus, sent some few waeke ago. I have been reading these with craat
interest. Shortly, I hope ts reclorecate with ow recent studies invol-
ving bacterial viruses, and look forward to a continued oxchanze.

One point in your stutfee of cingle step crowth curves of influenza
wae especially striking, but I could not clear 4% up in my own wind. I am
referring to the apparent equilibrium between added and adsorbed virus
during the first few houre efter inoculation. It is stated, I believe,
that about the came percentage adsorption is seen for large and for auite
erall inocula, but that the residual virus 4s adsorbed to the same extent
when reinoovlated into a second egg. If a much larger dose is (ineompletely)
adsorbed, the incomplete adsorption can hardly be due to a saturation of
the adsorptive sites. Why then does the residual virus remain free in the
firet fluid, but is adsorbed to the same extent in a second eget tnilesa I
have nisinterpreted your findings, it would seem that during the first stages,
an egg is somehow conditioned, even by emall dogas, so thet adsorption does
not continus over sn extended time. Your rainoculetion experiment shows that
the virue itself is not conditioned, or coriginelly heteroseneous. Such a prompt
conditioning would be a rencrkkble effect te impose on an entire ege by a
few thousand De). Would it not be feasible to inveetigate this by following
a emall ineculuf, which hee reached equilibrium, by a second much larger one7
If the egg has been conditioned, and thie ie the basie of the firet equili-
briun, the adsorption of the second should be inhibited.

PerHapes this experiment has already been reported, or I have overlooked
some other pertinent observations.

Yeurs sincerely,

Joshua Legerberg