LIVE POLIO IRUS VACCINES

104 Safety-Laboratory Evidence of Attenuation and Safety
TABLE 2. DIFFERENCE IN RATE OF PROPAGATION AND EFFICIENCY OF INFECTION AT 360 C AND
250 C OF DIFFERENT TYPE 1 PLAQUE PURIFIED 250 C MUTANT POLIOVIRUSES
DILUTION DAY OF FIRST APPEARANCE OF CPE IN EACH MK CULTURE TUBE
INOCULATED P 2226, Zab P Z149, la 2 b
0. Z ML 250C 36 0 C 250C 36 0 C
UNDILUTED 1,1 1,1 1,1 1,1
10-1 2.2 1,1 1,1 1,1
10- 2 3;3 3,3 2,2 4,4
10 - 3 3,3 3,3 2,4 4,5
10 - 4 3,3,3,4 (Z)* 5,5 7,7 (1-2)*
10 - 5 55,5,,66 4,4,4,4,4 (Z) 5;5.5,5,55 7,7,8,8,8 (1-2)
7,7,7,7,7 4,4,4.4,4 6,6,6,6,7 8,8,8,8,8
1 0 -' 7,7,7,7,7 4,4,44,4 (Z-3) 7,7,7,8,8 8,9,9.9.9 (2-3)
7,8,8,8,8 5,5,5,5;7 8,8.8,8,8 9,9,9,9,10
10 - 7 7,7,7,8,8 4,4,5,5,5(3-4-°) 8,9,9.9,9 10,15,0.0,0 (2-3-0)
8,10,12,0.0 6,6,7,0,0 9,10,10,10,10 0,0,0,0.0
10 - 8 9,14,14,0,0 0,0,0,0,0 (0) 8,10,12,13,0 0,0,0,0,0 (0)
0,0,00,0 0,0,0,0,0 0,0,0,0,0 0,0,0,0.0
LOG 10
TCD 5 0 / ML 8.3 8.1 8.5 7.3
* Figures in parenthesis indicate
propagated at 36 ° C.
days of first appearance of CPE at 36 °
C of original parent virus
capacity originally to multiply at 25 ° C., it increased
further, but the total yield finally was
lower than with the other strains.
The Type 3 Glenn strain originally did not
produce a complete cytopathogenic effect at
250 C., but there was this gradual alteration in
the viral population, so that with the final plaque
purified material it multiplied somewhat better
at 250 C. than at 36 ° .
Table 2 shows the difference in the rate of
propagation and efficiency of infection at 360
C. and 250 C. of different Type 1 plaque-purified
25 ° C. polioviruses.
This particular strain (P 2226, 2ab) infected
the monkey-kidney cells in as small a dose at
250 C. as at 360 C. But the rapidity of action
is still greater at 36 ° C. than at 25 ° C.
On the other hand, with strain P 2149, lab,
which had been submitted to the same procedure,
multiplication is much slower at 36 ° C. than at
25 ° C., and with approximately 10 to 20 infective
units of virus it is not possible to initiate a
cytopathogenic effect at 36 ° C.
It is important to point out that in children
this strain P 2149, la1b did not multiply at all,
even with a dose of about five million to ten mil
lion tissue-culture infective doses. Strain P 2226,
2ab multiplied in a few, though still rather
poorly, despite its good capacity for multiplication
at 360 C. tissue culture.
Table 3 shows that the Type 3 strain (Glenn,
3ab) which multiplies more slowly at 250 C.
than at 360 C. but can initiate CPE more readily
at 25° C.-a difference of almost two logs-multiplied
fairly well in the children. The Type 2,
which multiplies more slowly' at 36 ° C. than at
250 C, multiplied poorly or not at all in children.
1 should point out here that these modified