LIVE POLIO IRUS VACCINES

Laboratory Investigations of Attenuated Vaccine Strains 129
Virus PFU 36' C./39.5 0 C. Maximum PFU (Logl0) Causing no Lesions
Lo.a 10
Source l1I TH IS IM
53 SEED
MAHONEY
STOOLS
DAY 1
2
12
15
20
20MKI
-1 0 1 2 3 4,5 6 0 1 2 3 4 5 6 7 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8
1 . . I . . . . & .a I I . I I I *i I I I . I .
FIG. 7. T character and monkey neurovirulence of excreted virus (1205).
The T character of Koprowski Type 1 virus, neurovirulence following CNS inoculation as
determined directly on two stool specimens from demonstrated by the lower threshold value and
contacts of persons fed vaccine virus, is shown higher rate of occurrence of paralysis.
in Fig. 8. An increase of ability of excreted The T character of the Lederle Type 3 virus
virus to propagate at 39.5 ° C. was observed and in the stool of subject J.S. who was fed trivalent
one monkey-kidney cell culture passage at 360 C. vaccine is shown in Fig. 9. The virus in the
again altered the T character, but this time to- stool demonstrated marked ability to propagate
ward greater ability to grow at 39.5 ° C. Corre- at 40 ° C. and this ability was retained after one
lated with the changed T character after passage passage in monkey-kidney cell cultures at 36 ° C.,
in cell culture, was a definite increase of monkey but was partially lost after a second passage in
Virus
Source
K1 SEED
10A- 1 1
K1 SEED
WC 13
MAHONEY
CONTACT
STOOL 224
PFU 36 ° C./40 ° C. MAXIMUM PFU (Logl 0 ) CAUSING NO LESIONS
Log 0 1I TH IS IM
-1 0 1 2 3 4 5 6 0 1 2 3 4 5 6 7 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8
276
276MK1
FIG. 8.
T character and monkey neurovirulence of excreted virus.