LIVE POLIO IRUS VACCINES

128
Safety-Field Evidence óf Safety
Virus
Source
Log 10
PFU 360 C./40 0 C. (Log 1 0 ) Threhod
Threshold I S
0 1 2 3 4 5 6 7 01 2 3 4 5 6
S3 SEED
MAHONEY
S3 PLAQUE
FIc. 4.
Effect of laboratory procedures on T character and monkey neurovirulence.
from subject 1202, is shown in Fig. 5 and compared
with the original seed virus and the virulent
Mahoney Type 1 strain. In confirmation of
the work of Stuart-Harris et al., on these same
stool specimens,' 8 the T character of the excreted
virus changed toward the value of the
Mahoney strain. As may be seen in Fig. 6, the
VIRUS PFU 360 C./PFU 39.50 C.
SOURCE
Log 10
-1 0 1 2 3 4 5 6
virus in stools of patient 1203 shows a similar
change of T character. Figure 7 illustrates similar
results from patient 1205. In order to obtain
sufficient virus for monkey virulence tests, the
virus in the 20 day stool specimen was passaged
once in monkey-kidney cell cultures and the resulting
fluid was inoculated I TH, IS, and IM
into monkeys. This single passage resulted in
some loss of ability of the virus to propagate at
39.5 ° C. and was, thus, intermediate in T character.
As illustrated, a moderate increase in
neurovirulence following I TH and IS inoculation
was observed.
53 SEED
MAHONEY
STOOLS
DAY 2
3
5
6
7
8
10
11
13
14
c. . T character of excreted virus (1202).
VIRUS
SOURCE
53 SEED
MAHONEY
STOOLS
DAY 5
12
13
PFU 360 C./39.5 0 C.
Log
-1 0 1 2 3 4 5 6
¡ a a
FIG. 5. T character of excreted virus (1202).
FiG. 6. T character of excreted virus (1203).