LIVE POLIO IRUS VACCINES

Development and Persistence of Polio Antibodies in Young Adults 229
in this school was very high. None of the subjects
investigated had been vaccinated previously
by either Salk vaccine or by other attenuated
strains.
Just before the vaccination, a new blood sample
and a stool sample were taken. Further blood and
stool specimens were sampled on the fourth,
seventh, 10th, 14th, 21st, 28th, 35th, and 42nd
day after feeding the virus. An additional blood
sample was taken again on the 84th day.
The sera were inactivated at 56 ° C. for 30
minutes and antibiotics were added. Until investigation,
the serum and stool specimens were
kept at -20 ° C.
METHODS
1. The following methods of neutralization
test were used:
(a) the routine CP test with one hour incubation
of the virus-serum mixture at room temperature
(CP/1);
(b) the cytopathogenic test with six hours
incubation at 370 C. and overnight at +4 ° C.
(CP/6);
(c) the pH test with one hour incubation of
the virus-serum mixture at room temperature
(pH/1);
(d) the pH test with six hours incubation of
the virus-serum mixture at 37 ° C. and overnight
at +4 ° C. (CP/6); and
(e) the immunoinactivation test according to
S. Gard 5' 0 (IIT).
In tests (a) to (d), approximately 100 TCD.o
of the virus strains Brunhilde (Type 1), MEF-1
(Type 2), and Leon 12, ab (Type 3) were used.
The sera from each subject were investigated
simultaneously in all tests, using the same virus
and serum dilutions as in Parker's medium with
0.3 per cent of glucose. The sera were diluted in
fourfold steps from 1:4 to 1:1024, for IIT up to
4096. The same virus concentrations were used
in CP and pH tests. In the investigation of each
subject virus titrations were included, using per
dilution five tissue-culture tubes in CP tests, 10
tubes in IIT and eight cups in pH tests. A
standard human antiserum containing antibodies
to all three types of polioviruses was tested
simultaneously in all five tests performed.
Cytopathogenic tests. Tissue-culture tubes
from versenated monkey-kidney cells with 1.3
ml. of Earle-LAH (0.3 per cent) medium without
serum were inoculated with 0.2 ml. of the virusserum
mixture. Every dilution of serum was
assayed on three tubes; when testing the standard
serum four tubes were used. The results
were read repeatedly in all but two cases after
two, three, five, and seven days.
pH tests were carried out in polystyrene panels.
The 0.4 ml. amounts of the virus serum mixtures
were covered with paraffin oil, and 0.2 ml. of cell
suspension containing 25,000 versenated monkeykidney
cells in the above medium, enriched by
15 per cent of monkey serum previously tested
for the absence of polioviruses inhibitors, was
added. The final concentration of monkey-kidney
serum was then 5 per cent. Every dilution of
serum was tested against every type of virus in
two cups.
TABLE 1. THE MEAN TITERS ACHIEVED IN CONTROL VIRUS TITRATIONS PERFORMED
SIMULTANEOUSLY WITH DIFFERENT TESTS USED
THE TITERS EXPRESSED AS LOG 10
TEST
TYPE 1
TYPE 2
TYPE 3
CP/1
6,70 - 0,103
6,53 - 0,107
6,51 t- 0,088
CP/6
6,71 - 0,116
6,45 - 0,060
6,37 :- 0,081
PH/ 1 6,83 - 0,070 6,30 - 0,114 6,43 - 0,153
pH/6 6,65 - 0,109 6,33 - 0,117 6,31 - 0,164
IIT N D N D 6,47 - 0,097