LIVE POLIO IRUS VACCINES

8. BEHAVIOR OF COLD MUTANTS OF POLIOVIRUS IN
HUMAN BEINGS
DR. ALBERT B. SABIN
The Children's Hospital Research Foundation
Cincinnati College of Medicine
Cincinnati, Ohio
DR. SABIN: The work I am about to describe
was carried out in association with Doctors
Barnes, Michaels, and Vignec.
The tests in human beings on the 25 ° C.
mutants are still in progress, but I think the results
already are of sufficient interest to warrant
this report.
The purpose of these studies was to select
poliovirus mutants which would be able to multiply
extensively at relatively low temperatures
-by that I mean about 25 ° C.-and to determine
how this affected their capacity to reproduce
at higher temperatures, that is, body temperature
of man, for example, in tissue cultures,
as well as in the spinal cord of monkeys and
in the alimentary tract of human beings.
Accordingly, only strains which had already
been tested extensively in monkeys and human
beings were selected for this study, so that any
changes that would occur might be related to
the manipulations that we carried out, because
if you start with a strain of virus whose capacity
for multiplication in the human alimentary
tract you do not know, you could not interpret
the results.
We worked with six strains of virus: the
three current vaccines that I used, two new
Type 1 strains, and one new Type 3 strain.
The two Type 1 strains were derived from
stools of healthy non-contact children during a
non-epidemic period in Louisiana, and were
originally of low thalamic virulence for monkeys.
The Type 3 strain which we used was similarly
obtained from a healthy child in Cincinnati.
The original stool culture in monkeykidney
cells was rct/40-.
I want to explain this expression (rct/40-)
because it is different from what people have
been using to designate the reproductive capacity
of a virus at a given temperature.
101
In a manuscript which has been distributed
to some of you, I indicated my preference for
expressing the capacity of a poliovirus to multiply
at a certain temperature as reproductive
capacity at the temperature indicated, because
the T marker has been used very extensively to
indicate sensitivity to inactivation by certain
temperatures.
I do not ask you to accept this, but I want
you to know what I mean when I speak of rct/
40+, rct/40-, rct/25+, or rct/25-. This
is to represent the capacity of polioviruses to
multiply at these different temperatures.
I repeat that this Type 3 strain that we started
with, the naturally occurring one, was rct/40-
originally, and this is particularly important
in view of what I shall state later.
All six strains were first propagated for seven
passages at 330 C., and when this was found
to have little effect on the ability of the resulting
populations to propagate at 25 ° C., propagation
at 30 ° C. was begun.
After the first five passages at 30 ° C., an increase
in activity at 25 ° C., was noted with all
strains, an increase which, however, was not
significantly enhanced by further five passages
at 30 ° C. At this stage, propagation was shifted
to 250 C. and continued for 20 consecutive passages.
Table 1 shows the gradual transformation in
the properties of the virus, by illustrating the effects
obtained with just one strain. It illustrates
the results that were obtained in the
selective enrichment of the 25 ° C. variant by
serial propagation at progressively lower temperatures
for the Type 1 current vaccine strain.
The original material which had been cultivated
at 36 ° C., when tested in monkey-kidney culture
tubes at the indicated temperatures, gave
about the same titer when the test was carried