LIVE POLIO IRUS VACCINES

Behavior of Cold Mutants of Poliovirus in Human Beings 105
TABLE 3. RATE OF PROPAGATION AND EFFICIENCY OF INFECTION AT 36' C AND 250 C OF TYPE 2
AND TYPE 3 PLAQUE PURIFIED 25' C MUTANT POLIOVIRUSES
DILUTION | DAY OF FIRST APPEARANCE OF CPE IN EACH MK CULTURE TUBE
INOCULATED TYPE 2 - P 712, Zazb TYPE 3 - GLENN, 3a 2 b
0.2 ML
25 0 C 36°C Z5 0 C 36 0 °C
UNDILUTED 1,1 1,1 1,1 1.1
10-1 1,1 1.1 1,1 1,1
10-2 2,2 1,1 2,2 2,2
10 - 3 2,2 4,4 2,4 3,3
10 - 4 4,4 6,6 (2)* 6,6 4,4 (1)*
10 - 5 4,4,4.4,4 6,6,7,8,10 (2) 6,8,8,8,8 4,4,5,5,6 (Z)
10 4,4,4,4,4 10,10,0,0,0 (2-3) 8,8.8,9,9 6.6,6,9,0 (2)
5,5,5,5,5 0,0,0,0,00 9,9,9,10,10 0,0,0,0,0
10 - 7 6,6,6,6,6 9,0,0,0,0 (3-6-0) 9,10,11,12,12 0,0,0,0,0 (2Z-5)
7,7,7,8,8 0,0,0,0,0 14,15,16,16,18 0,0,0,0,0
10 - 8 8,8,11,12,14 0,0,0,0,0 (4-0) 130,0,0,00 0,0,0,0,0 (3-5-0)
0,0,0,0,0 0-0.0,0,0 0,0,0,0,0 0,0,0,0,0 0,0,0,0,0
10 - 9 0,0,0,0,0 0,0,0,0,0 0,0,0,0,0 0,0,0,0,0 (0)
LOG 10
TCD 5 0 /ML 8.7 6.4 8,3 6,5
* Figures in parenthesis indicate
propagated at 36 ° C.
days of first appearance of CPE at 360 C. of original parent virus
viruses do not behave like the usual polioviruses
because the cytopathogenic effect may start at six
days and it may take four days before it goes to
completion.
As for Table 4, I should like to point out that
the two Type 1 strains, P 2149 and P 2226, were
originally eliminated from consideration for
practical use because we could not get rid of
the spinal neurovirulence, even though on intracerebral
inoculation they were avirulent. However,
after these selective procedures, it was possible
to inoculate huge amounts intraspinally
without getting any paralytic effect at all, even
using a somewhat more sensitive method with a
smaller needle. In most instances, the lesions
were limited to the site of the scar without any
spread beyond it.
On the other hand, with the Type 1 vaccine
strain (LSc, 2ab) it was not possible, by passages
at 30 ° C., to influence the residual spinal neurovirulence,
and even after 20 passages at 250
C., there was still some residual greater action
than in the other strains.
With the Type 2 strain shown in Table 5, it
was possible to obtain virus which, on intraspinal
inoculation, was virtually without effect. On the'
other hand, the 25 ° C. variant of the current
Type 3 vaccine strain (Leon 12atb) retained the
ability to produce mutants in the spinal cord of
an occasional monkey. These occasional
monkeys that exhibited paralysis after inoculation
with the 25 ° C. virus showed a completely
altered virus in the spinal cord from that originally
inoculated, in that it also possessed the
capacity to multiply at 40 ° C.
However, a totally different result was ob-