LIVE POLIO IRUS VACCINES

5. EXPERIMENTAL STUDIES ON ANIMALS WITH ATTENUATED
POLIOVIRUS (COX AND SABIN STRAINS)
H. PETTE, H. LENNARTZ, G. MAASS, L. VALENCIANO, AND K. MANNWEILER
Institute for the Research of Poliomyelitis and Multiple Sclerosis,
Hamburg, Germany
DR. PETTE (presenting the paper) : Conflicting
reports on the extent of pathogenicity of attenuated
strains of poliovirus suggested this investigation
on the results of the experimental
infection of monkeys with such strains. The
polio strains of Sabin* and Cox* were used;
external circumstances did not permit the inclusion
of Koprowski's strains in this study.
Material and methods. Rhesus monkeys
weighing 1500 to 3000 g. were divided into
groups of 4 to 5 animals and subjected to. intraspinal
and intracerebral inoculation with virus
strains (undiluted and dilutions 1:10 and
1:100). At the beginning of the experiments the
animals received aureomycin daily for 10 days
(in the examination of Type 1 strain of Cox terramycin
was used) to prevent enteritis.
Technique of inoculation. The technique described
by Murray was employed, i.e., the intraspinal
injection of 0.2 ml. between the first
and second lumbar vertebra into the lumbar intumescence,
or the bilateral intrathalamic injection
of 0.5 ml. The injections were made
under ether anesthesia.
The strains used including the virus concentrations
found by us, are recorded below.
* We are grateful to Prof. Verlinde of the University
of Leiden, for supplying us with the virus strains
of Sabin, and to Dr. Cox of Lederle Laboratories,
Pearl River, N.Y., for the Cox strains.
For the dilution of the virus strains examined
TCM 199 was used. Following a 21-day period
of observation the monkeys were sacrificed.
Virus isolation.
(a) From feces: Before the beginning of the
experiment and thereafter weekly stools
were taken by rectal swabs, prepared in
usual manner and inoculated into cultures
of monkey-kidney tissue.
(b) Central nervous system: At autopsy material
was taken from the lumbar and
cervical cord, brain stem and precentral
gyrus. A 10 per cent suspension was
examined for poliovirus in monkey-kidney
tissue cultures.
Virus titration. Tenfold dilution series, inoculation
dose per tube 0.1 ml.; in general five
test tubes per dilution were used. Calculations
of virus titer were made according to Reed and
Muench. The determination of plaque-forming
units was carried out in bottles according to the
technique of Hsiung and Melnick.
Antibody determination. Blood was drawn for
serological examination at the beginning and
thereafter once weekly during the experiment.
Neutralizing antibodies were determined with
the color test according to the method of Salk
et al.
Observation of the animals.
The animals
TYPE
STRAIN
PFU/I .0
TCID 5 o/1.0
Sabin
1
2
3
L Sc, 2 ab
P 712, Ch, 2 ab
Leon 12 alb
106.7
107.7
10o.7
10605
107.0
106.3
Cox
1
2
3
7 - 1231 - 166
7 - 1232 - 243
7 - 1233 - 344
106'5
106.2
107.0
106.2
106.0
1073
68