LIVE POLIO IRUS VACCINES

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230
Efficacy-Laboratory Evidence
TABLE 2.
THE MEAN TITERS OF POLIO ANTIBODIES ACHIEVED IN THE REPEATED INVESTIGATION OF A
REFERENCE SERUM BY DIFFERENT METHODS OF NEUTRALIZATION TEST
THE TITERS EXPRESSED AS LOG.,
TEST
CP/1
TYPE 1 TYPE 2 TYPE 3
7,37 -:0,195 11,41 - 0,340 4,83 - 0,259
CP/6
10,08 - 0,305
12,75 - 0,164
6,50 - 0,330
pH/1
9,27 - 0,243
12,63 - 0,420
8,00 - 0,302
pH/6 10,50 - 0,313 13,58 - 0,248 9,00 - 0,246
IIT
ND ND 9,08 - 0,268
The immuno-inactivation test was performed
according to the method recommended by S.
Gard. Ten tissue-culture tubes were used per
one dilution. The test was read repeatedly after
3, 5, and 7 days. Only Type 3 antibodies were
estimated by this technique.
The virus and antibody titers were computel
according to Karber's method.
2. The isolation and identification procedures
and the virus titrations were performed as described
previously.'
RESULTS
Results obtained in control virus and rejerence
serum titrations. Table 1 presents the results
achieved in repeated virus titrations. The mean
titers of three types of polioviruses were very
similar in all tests used, with only slight differences
which were in no one case significant.
These results suggest that only a very small proportion
of virus was inactivated during the sixhour
incubation period at 370 C.
The results obtained in repeated titrations of
standard human serum are shown in Table 2.
The mean titers, expressed as log2 of the initial
dilution of serum in the reaction mixture, show
marked differences between the antibody titers
estimated bv means of different methods. The
titers of antibodies to all three types are on the
lowest level in CP/1. The prolongation of the
incubation period of the virus-serum mixture
had a much greater influence on the antibody
titer in the CP than in the pH test.
Tables 1 and 2 show the results obtained from
O7
o,
1-.
1.
00
3
. 2 3 5 7 2
TIME AFTER INOCULATION IN DAYS
FiG. 1. The mean virus titers estimated in 2, 3, 5 and 7 day readings in repeated control titrations
included in CP/1 and CP/6 tests.