TI—ŒRMAL DEGRADA‘T‘ION or vnwsas
_
113
TABLE 4. PREDICTED STABILITY DATA USED To EVALUATEΑHE ACCELERATED STORAGE TEST
FOR DRIED SUSPENSIONS OF MEASLES VIRUS
Temperature (° C)
_
+ 20
+ 15
+ 4
——20
[cl value (Fig. 2) . . . . . . . . .
_.
.
0.060
0.035
0.018
0.0014
Predicted time to lose 1 log of titer (Fig. 3).
12 days
24 days
56 days
1,200 days
Actual loss in titer (PEU/ml) . . . . . .
101-06
100-96
100-97
100-061
.
—————————————___—_—__
.
1. The predicted time
for samples kept at —— 20 °C (1,200 days) was too long for testing experimentay. The
actual loss in titer was that found after 90 days of storage; 100-075 PFU/ml.
‘
___—____——_
dried suspensions of measles virus to lose one log of titerat these temperatures is shown
below :
_
_
Time required to lose 1 log of titer'
‘
Temperature
of storage
_
_
_
_
L1qurd suspens1on
Dried suspension
'
10days.
_
‘
—20 °C
.
.
.
.
.
-.
60 days
3.3 years
Thus the advantages of using freeze—drying and”àdditiveS to'preserve’vnuses lies not in
'
;
the ability of this technique to produce dried suspensions that are unchanging under all
conditions of storage, but rather in its ability to produce suspensions that are extremely
_
stable when stored in low temperature‘faCitiës'that are readily available. Also, if one
starts With suspensions of viruses havinghightiters,degradation during storage at adverse
_
Î
temperatures will be retarded in preparations of- virus dried by sublimation
1
The assumption has been made frequently that biologie entities’ or materials of biologie
.
ÏÏ:
Origin, when dried to a low residual moisture Content (usuay'stated as less than 1 %),
lose little if any of their activity
{Wheneär}p‘dsed toeleVated;—temPeral
tures. This assumption has been used to justifygthe increased temperatures,
as 50 °C, used during the nal stages of dryingbiOlogicsby'ËÂsublimation
iïzï vàCu0wEXtrapola+
_
tion of our data indicates that'at the temperature
.
'
.
measles Virus in Medium 199
10%.0 PFU/ml during a 6—hour period; This declihéi‘m activity;îuidëæuhtedlyel101dsfor
other
_
biologie systems. Further. as our
less
than 1 %, exposure
content
is greater than I %-would be expecœ';toresultmgreaterlossesmaCtlVlty .It would "S°i°mâ
that drying
'th_° low?“
temperature
_°f
_
-
theorder of + 50 œœmœssarytoacceleratethdrymgpmœssfheyshouldbeuse
.