LIVE POLIO IRUS VACCINES

46
Discussion
a paralytic case. This behaves like the Mahoney
virus.
Two isolates from a child fed the Type 1
vaccine virus were examined. These were isolated
two days and 32 days after feeding. Both
behaved in a similar manner and resembled the
virus fed.
Figure 1 illustrates the behavior of the Mahoney
and LSc 1 ab viruses when eluted from
columns of aluminum hydroxide. The pH of
the buffer added is recorded along the bottom
and the pH of the eluted fractions is illustrated
by the curve with open circles. This is a rather
smooth curve. The fractions collected were
approximately 10 cc. in amount.
The Mahoney virus, as shown in Fig. 1, is
eluted sharply and almost completely when the
pH reaches 6.5, whereas very small amounts of
the LSc 1 ab virus are found in any of the fractions.
We have not yet done any experiments with
the other types of vaccine virus.
DR. SMORODINTSEV
(through an interpreter):
I would like to comment on the evaluation of
different markers for the estimation of vaccine
safety. Among these markers, the pathogenic
behavior in monkeys are the most interesting.
A year ago I reported the results obtained on
prolonged passages of Dr. Sabin's attenuated
strains through children.
We have now finished 12 consecutive passages
for all three strains of viruses. We have noted
the periodic increase in the neurovirulence of
these viruses with cerebral, or with spinal introduction
in monkeys.
Neurovirulence in monkeys sometimes reached
quite a high level corresponding to two and a
half logs of virus concentration for the minimal
paralytic intraspinal dose for monkeys, but in
subsequent passages these strains gave normal
non-pathogenic viruses again.
We have now returned to the strains which
were kept in a deep freeze and have confirmed
the fact that after a six-month or year-and-a-half
observation, they bring about the same results
in monkeys. We have studied the very important
question of whether these viruses are capa-
THE ELUTION PATTERN OF MAHONEY AND SABIN
POLIOVIRUSES FROM AN AL(OH) 3 COLUMN
(Ls c)
FIc. 1