LIVE POLIO IRUS VACCINES

Experimental Studies on Animals with Attenuated Poliovirus
69
were examined daily with special care regarding
motor function and reflex behavior, particularly
the patellar reflexes.
Histological techniques. Brain and spinal
cord were removed and fixed in 10 per cent
formalin solution for histological examination.
Paraffine blocks, staining according to Nissl, van
Gieson, Heidenhain and with hematoxylin-eosin.
The lumbar and cervical intumescence were imbedded
in six blocks, from each block one section
plane was examined. In the same manner three
levels of the thoracic cord were examined, from
the brain stem the upper and lower portion.
Both sides of the precentral gyrus (apical portion)
were examined. Grading of lesions from
1 - 4+ and determination of the extent of
lesions in the spinal cord were carried out according
to the method of Melnick.
Findings.
(a) Observation of the animals: Following intracerebral
inoculation traumatic disturbances
occurred in three cases. During the further
period of observation weakness of the extremities
was found in none of the animals inoculated intracerebrally.
Following intraspinal inoculation
all of the animals, in which regular injections
had been made into the lumbar cord, developed
paralyses immediately after the inoculation, with
an increase during the following 1-2 days in some
cases. 'Essentially, these traumatic paralyses
consisted in motor weakness of the flexor of feet
and toes, more rarely of the legs. It proved
difficult to distinguish these traumatic paralyses
from those caused by the poliovirus. For this
reason, motor weakness appearing within 48
hours after injection was considered as being of
traumatic origin, whereas paralyses developing
subsequently were attributed to virus action.
The latter lesions also consisted in motor weakness
of the leg and foot musculature, more seldom
of the upper leg and thigh; all degrees from
slight paresis to complete paralysis were encountered.
Slight paresis of the upper extremities
were seen in four cases following I.S. inoculation
with Type 1 Cox's strain.
In general the motor weakness described
reached maximum development about the 10th
day after injection; the general condition of the
animals remained good in all cases. The arrest
of the process was occasionally manifested by a
return of the patellar reflex. In one monkey
(No. 99), inoculated with Type 2 Cox's strain,
an ascending paralysis of Landry type followed
I.S. injection of virus. The animal was sacrificed
in moribund condition six days after inoculation.
(b) Pathological anatomy: The quality of
histologic alterations corresponded to those
found in not too severe poliomyelitis with a destruction
of nerve cells and inflammatory reaction.
The slight extent of active neuronophagia
may be attributed to the duration of the process.
BLE 1.
TYPE 1
l
Cox (6.5PFU/1.0)
SABIN (6.7PFU/1.0)
L.
C.
B.S.
C.A. L.
C.
B.S.
C.A.
10 °
10-1
10-2
3/3
4/4
5/5
3
3
5
3
2
1
I.S. Inoculation
0 5/5
1 4/4
1 3/3
o
o
2
o
o
1
o
o
o
10 °
10-1
10-2
0/5
0/5
0/5
o
o
o
o
0
I.C. Inoculation
0 0/4
0 0/5
0 0/5
No. of menkeys with polio lesiens / No. of inoculatcd monkeys~~~~~~~~~~~~~
No. of monkeys w·ith polio lesions / No. of inoculated monkeys
o
o
o
o
o
o
o
o
o