LIVE POLIO IRUS VACCINES

Da. HORSTMANN: If I may answer for Dr. Paul
on this point: In the beginning, in identifying the
agents isolated, we did not use tissue-culture passages,
but returned to the original rectal-swab
suspensions for neutralization tests, which were
done by the plaque reduction method in agar
overlay bottles.
We found relatively small quantities of the
viruses present, and no evidence of overgrowth of
one or another strain. Subsequently, the neutral-
Discussion 203
Discussion 203
that there has been spread to newborn infants ization tests were done in tubes on first tissueculture
passages, in the usual in the same family.
manner.
DR. VAN ROOYEN: In connection with the question
that Dr. Dick asked Dr. Kimball regarding
the resistance of the human intestinal tract to
poliovirus, Table 1 reveals the effect of repeated
oral feeding with Cox trivalent vaccine in a
group of highly immune adults. Some of these
have received as many as eight doses of Salk
vaccine over a period of five years. Furthermore,
all have had contact with, and exposure to, cases
of paralytic poliomyelitis during the conduct of
their hospital duties over many years. It will be
observed that it has not been possible to establish
infection of gut in some, notwithstanding refeeding.
In others, it will be noted that some excreted
one or two types of virus for variable
intervals of time. Seven months later, following
a second oral dose of trivalent vaccine, some
failed to excrete virus and others excreted
homologous or heterologus virus. In the highly
immune individual, virus was not excreted from
the oropharynx, and the presence of intestinal
infection sometimes occurred without corresponding
elevation in antibody level.
DR. HAMMON: I should like to ask Dr. Paul a
question regarding the data he presented at the
third session, so as to enable me to interpret
them better. After his reply, I shall probably
wish to comment on it.
In connection with his discussion on the data
on interference between enteroviruses, I should
like to know whether the tests for an interfering
virus were made after neutralization of the virus
determined to be present first, or whether a
single test was made each time, without attempting
to neutralize any other virus that might have
been present or known to be present in the stool.
DR. HAMMON: I do not believe you understood
my question, but I shall assume that the answer
is what I believe it to be.
What I was referring to was whether or not, for
example, after poliovirus was isolated from the
stools of a child, polio antiserum of that type was
added to the fecal suspension before the next
test, to see if there was a second virus present
that was being excreted in the intestinal tract
of that individual.
The reason for this question is that data were
presented indicating that there is probably some
interference in the human intestinal tract between
these enteroviruses. I merely wish to point
out that the problem is considerably more complicated
than that.
Dr. Paul indicated already that this is rather
complicated, but there are two things happening
here: There is a possible interference in the
intestinal tract of man, and then there is possible
interference in the tissue-culture tube in which
one is attempting to make the isolation.
So I think these data are rather difficult to
interpret without considering the possibility of
interference between two viruses in the tissueculture
tube so that you come out with only one
of them.
The reason I mention this is the fact that we
ran across this in a longitudinal study of polio
in the Philippines.
We made so many isolations of one ECHO
virus, which we subsequently identified as
ECHO-1, that we made an antiserum to this, and
began adding this antiserum to all our fecal
suspensions, before attempting to isolate poliovirus,
for this was a study on poliovirus alone.
We went back and repeated our isolation attempts
on many of the suspensions that we had
tested before and isolated polioviruses which we
had missed because we had isolated ECHO-1
virus, which was present apparently in larger
quantity in the stool specimen than was the poliovirus.
Then, in two, three, or four subsequent
passages in tissue culture, we were ready to
identify the agent. The smaller amount of poliovirus
had been suppressed, interfered with, and
we had identified only an ECHO-1 virus isolate.