LIVE POLIO IRUS VACCINES

Minnesota Studies with Oral Poliomyelitis Vaccines
359
could not be bias in the interpretation of the
symptoms that were reported or in the evaluation
of laboratory findings by laboratory personnel.
Blood specimens, throat swabs, and stool specimens
were coded before being sent to the laboratory
for testing. The blood specimens for antibody
titrations were assigned numbers from a
table of random numbers, and it was impossible
for the testing personnel to identify any one
specimen as to its individual origin, its set
origin or sequence within any given set. However,
the blood specimens were so arranged that
all specimens from the same person were tested
on the same day and in the same test run.
LABORATORY METHODS
Except for antibody titrations, detection of
virus in blood and pharynx, the laboratory procedures,
and materials used for virus isolation
and identification were the same as those described
in a previous publication.l To determine
the antibody titer, six four-fold dilutions of serum
and five tissue-culture tubes per dilution were
used. Accordingly, a fourfold rise in antibody
titer by this procedure was significant. Pharyngeal
swabs (cotton tipped) supplied in 0.5 ml. of
tissue-culture maintenance medium were used to
collect specimens from the pharynx of the participants.
The swabs were returned to the laboratory
in the original tube on the day collected.
Upon receipt in the laboratory, the swabs were
immersed in 2 ml. of tissue-culture maintenance
medium and allowed to stand at room temperature
for one hour. The swabs were then withdrawn
from the fluid and pressed against the side
of the tube to express as much fluid as possible.
Two monkey-tissue culture tubes from which
growth medium had been removed were inoculated
with 1 ml. each of the maintenance medium
in which the pharyngeal swabs had been immersed.
Whole blood specimens for viremia
studies were collected by venipuncture and
brought to the laboratory on the day of collection.
The serum was drawn off of the clot and stored
at -20 ° C. Attempts to isolate virus from all
specimens were made by inoculating 0.2 ml. of
serum into each of two monkey-kidney tissue
culture tubes. A passage of tissue-culture fluid
to fresh tissue-culture tubes was made from all
inoculated tissue-culture thbes which showed
cytopathogenic effect and also from those which
showed no cytopathogenic effect on the seventh
day. In an effort to increase the number of virus
isolations, serum specimens from sixty-six persons
lacking antibody to one or more types of
poliovirus were retested by inoculating 2.0 ml. of
serum onto a HeLa cell sheet in a 200 ml. donor
bottle containing approximately 7,000,000 HeLa
cells. An adsorption period of one hour at room
temperature was allowed. The bottles were
tilted at 10-minute intervals to distribute the
serum over the cell sheet. Following the adsorption
period, the serum was removed and 10 ml. of
maintenance medium was added. The bottles
were incubated at 37 ° C. for seven days. Microscopic
examination of the cell sheet for cytopathogenic
effect was made daily. The tissueculture
fluid was removed from the bottle for
transfer to HeLa cell tubes when cytopathogenic
effect was observed. If no cytopathogenic effect
was observed at the end of the seventh day of
incubation, the tissue-culture fluid was also
transferred.
EVALUATION OF SYMPTOMS DURING
THE CONTROL PERIOD
The recording and evaluating of illnesses and
complaints during the control period was done by
the institution's medical staff. There was neither
an increase in the frequency of visits to the infirmary
nor were visits made for qualitatively
different reasons than usual.
LABORATORY RESULTS
The initial antibody status of participants in
the various groups under study are shown in
Table 3. An analysis of the data shows that
there is no marked variation in the proportion of
individuals with single and double antibody titers
of less than four. Accordingly, it is considered
justifiable to use these groups to study the effect
of dosage form on the antibody response. Table
4 shows the number of blanks filled in and the
number of persons who converted to triple positives
by groups. The per cent of blanks filled
in varied from 57.9 to 81.2 per cent. No correlation
could be found between type and time of
feeding and antibody response. Seventy-three
per cent of the Type 1 blanks were filled in, 62