LIVE POLIO IRUS VACCINES

76
Safety-Laboratory Evidence of Attenuation and Safety
(c) Virus isolation from CNS: With Types 1 third week of the observation period. Particularly
and 2 of the Sabin strain no virus could be
isolated from the central nervous system of any
of the animals (lumbar and cervical cord, brain
stem, precentral gyrus) at the end of the observation
period. With Type 3 isolation attempts
in the animals dying intercurrently polio-
myelitis virus was occasionally also found in the
absence of characteristic histological alterations.
The virus strains isolated from the central
nervous system were examined with reference to
were successful in two cases. With Cox's Type tissue-culture markers d, T, and MS. These
1 strain, virus could be isolated from the CNS examinations appeared promising since in addition
of the monkeys inoculated intraspinally in
to possible mutations of the virus inoculated
numerous cases, not however in animals following
I.C. inoculation. With Cox's Type 2, virus neurotropic poliovirus particles also had to be
the selective effect of central nervous system for
was isolated in more than half of the cases at
considered. With all strains in which an examination
was possible, some of the cases showed al-
the end of the observation period; with Type 3
in only two monkeys who died during the observation
period (indicated by an asterisk, see
terations of one or two markers in comparison
to the initial material. In no instance did these
Table 4).
cases approach the behavior of the virulent
In the monkeys found positive, virus isolation
strains used for controls, however. Compared
was successful in one or more; seldom, however,
in all areas of the central nervous system
with the other strains, the low number of
examined. The virus concentration was lower
changes in genetic behavior found with Cox's
than that found in corresponding areas after inoculation
Type 2 strain was remarkable.
of virulent strains. A comparison of (d) AntiWody formation in animals: With all
the frequency of positive virus findings with the
severity of histological lesions in general showed
strains there appeared to be a relation between
the production of antibodies and the virus concentrations
parallel results. Virus isolation was successful
administered. There was no differ-
especially in those cases in which motor weakness
ence in the results with I.S. and I.C. inoculation,
was still pronounced during the second or however. Antibody formation did not seem
to
TABLE 5.
DILUTION
TYPE
ROUTE
10 °
10-'
10-2
1
I.S.
I.C.
2/3
3/5
0/4
1/5
0/5
0/5
o
2 I.S. 2/4 1/5 0/5
I.C. 3/5 3/5 0/5
3
I.S.
I.C.
1/5
1/5
1/4 0/5
2/5 0/5
1
I.S.
I.C.
0/5
2/4
1/4 0/3
2/5 0/5
._
-m e
2
I.S.
I.C.
4/4
1/3
2/4
2/5
0/4
1/5
3
I.S.
I.C.
1/4
0/4
0/4
0/5
0/5
0/5
No. of monkeys with antibodies/No. of inoculated monkeys.