WORLD HEALTH ORGANIZATION EXPERT COMMITTEE ON YELLOW PEVER VACCINATION Geneva, 8-13 A p r i l I957
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ORGANISATION MONDIALE DE LA SANTÉ W H O A F V / 5 8 March 1957
O R I G I N A L : FRENCH
P r o v i s i o n a l agenda item 4
MAINTENANCE OF STRAIN 17D by Dr R. Panthier
In the past we encountered serious d i f f i c u l t i e s i n our attempts to maintain (under conditions which were then unsatisfactory) s t r a i n I7D and ever since we have been able to do so we liave preferred to use ampoules of secondary seed-lot derived d i r e c t l y from ampoules of primary ^eed-lot, the l a t t e r being prepared i n another laboratory. I t seems to us that the f a l l observed at the time In the q u a l i t y of the vaccine was due, at l e a s t i n part, to the temperature of our incubators being too high. This opinion i s of course open to discussion, nevertheless POX has
c l e a r l y shown the influence of temperature on the growth curve of v i r u s 17D i n the chick embryo. We v>/orked with P. GIROUD f o r a considerable period on the growth of R i c k e t t s i a i n the mouse lung, and were l e d to put forward the above hypothesis from a comparison of the phenomena observed under the microscope with what might happen during the c u l t u r e of an ultramicroscoplc v i r u s , which one i s obliged to study through the more or l e s s d i s t o r t i n g mirror represented by i t s pathogenic e f f e c t on animals. In the preparation of typhus fever vaccine we had to make
a sharp separation between lungs reserved f o r seeding and lungs used f o r the vaccine. The few t r i a l s we c a r r i e d out (naturally without using the vaccine) with s t r a i n I7D seem to confirm t h i s point. The properties the vaccine i s required
to have are, i n f a c t , not required of the seed v i r u s , and v i c e versa.
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1.
P r o p e r t i e s o f t h e Va c e i n e (a) (b) The v a c c i n e s h o u l d c o n t a i n a l a r g e amount o f v i r u s . sessions,
I t s h e u l d be e a s i l y l'chydrated, so t h a t d u r i n g v a c c i n a t i o n
each vaccinée w i l l r e c e i v e a n e q u a l amount o f t h e p r o d u c t . T h i s i s why: (a) we endeavour n o t t o cJiai-i^c any of the c u l t u r e c c n d i t l o r o , so as t o be
as n e a r as p o s s i b l e t o t h e h i g h e s t p o i n t o f t h e grov/th c u r v e o f t h e v i r u s on harvesting; (b) we a l s o endeavour d u r i n g f r e e ^ ^--drying t o o b t a i n a p r o d u c t w h i c h ,
a.lthough s u f f i c i e n t l y d e s i c c a t e d , i s easy t o réhydrate (Ann. I n s t ^ ^ P a s t e u r , March 1 9 5 7 ) . The v a c c i n e i s n o t inuended t o r e m a i n v i r u l e n t i n d e f i n i t e l y ,
but must o n l y be k e p t f o r two 3''ears i n t h e d r y s t a t e , 2, F r o p e r t i e s _ of __the_Seed_yiru3 The p r o p e r t i e s r e q u i r e d i n t h e c a s e o f t h e seed v i r u s a r e , however, q u i t e
different: (a) The v i r u s s h o u l d be c a p a b l e o f r e p r o d u c t i o n (and n o t be v e r y abundant t h e v i r u s perhaps
at the outset). before
I t w o u l d appear p r e f e r a b l e t o h a r v e s t
i t has r e a c h e d t h e peak o f t h e growth c u r v e , and c e r t a i n l y b e f o r e i t We a r e c e r t a i n o f t h i s f a c t i n t h e case o f R i c k e t t s i a and
has p a s s e d i t .
we have been a b l e t o c o n f i r m w i t h 17D t h a t a v e r y r i c h v a c c i n e does n o t g i v e good r e s u l t s when s u b c u l t u r e d i n t h e c h i c k embryo ( i t was p e r h a p s by shortening degradation
the g r o w t h c u r v e o f t h e v i r u s t h a t we b r o u g h t a b o u t t h e p r o g r e s s i v e
of t h e s t r a i n , t h e v i r u s was p o e s i b l y i ^ a r v e s t e d t o o l a t e a.id i t i s perhaps i n t h i s way t h a t t h e t e m p e r a t u r e o f t h e i n c u b a t o r c a n p l a y a p a r t ) . (b) The v i r u s must keep f o r a l o n g t i m e , so t h a t d r y i n g s h o u l d be c a r r i e d The p h y s i c a l d i s p e r s i o n o f t h e v i r u s on r e h y d r a t i o n i s change. For this
cut d i f f e r e n t l y .
leer; i m p o r t a n t t h a n t h e c o n s e r v a t i o n o f tho s t r a i n w i t h o u t
r e a s o n , i t i c n e c e s s a r y t o c a r r y d e s i c c a t i o n as f a r as p o s s i b l e by means o f a second s t a g e o v e r phosphorus p e n t o x i d e i n a h i g h vacuum.
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These f a c t s a r e d o u b t l e s s w e l l Imown t o t h e e x p e r t s , b u t I have n o t found them mentioned i n t h e s c i e n t i f i c c o u r s e , no q u e s t i o n o f m u t a n t s i experiment l i t e r a t u r e on 17D. I n a l l t h i s there i s , of
t h e l a t t e - by i t s e l f f u l l y j u s t i f i e s t h e
w i t h rhesus nonlceys, c e r t a i n l y t h e o n l y p r a c t i c a l method o f d e t e c t i n g
t h e s e changes. A n o t h e r q u e s t i o n may be r a i s e d . s h o u l d t h e secondary (1) The p r i m a r y s e e d - l o t s h o u l d be d r i e d , b u t
s e e d - l o t be d r i e d o r n o t ?
A d r i e d s e c o r x i a r y s e e d - l o t has t h e d e f i n i t e a d v a n t a g e o f b e i n g more e a s i l y This i s
c o n s e r v e d , b u t t h e v a c c i n e b a t c h e s p r o p e r e d w i t h i t seem more v a r i a b l e . n o r m a l , moreover, t a k i n g i n t o (a) (b) account:
t h e p h y s i c a l changes d e f i r d t e l y b r o u g h t about by d r y i n g ; r e h y d r a t i o n . , w h i c h i s c e r t a i n l y d i f f e r e n t f o r each o f t h e p a r t i c l e s
( t h i s was shown v e r y c l e a r l y w i t h BCG v a c c i n e w h i c h was d r i e d and t h e n r e h y d r a t e d and c o u n t e d a f t e r c u l t u r e i n hundd, d r y , and s o m i - s o l i d These f a c t s a r e d o u b t l e s s t h e cause o f t h e changes found v i r u l e n c e curve, (2) i.e.: media).
i n t h e SVEN GARD
a narrow S c u r v e w i t h t h e f r e s h p r o d u c t s a much more e l o n g a t e d S c u r v e w i t h t h e d r y p r o d u c t . s e e d - l o t s u c h a s t h ^ one we u s e d , w h i c h h a d been
An u n d r i e d secondary
p r e p a r e d a t H a r r i l t o n (Montana) by H'J^KJBS, i s c e r t a i n l y more d i f f i c u l t t o c o n s e r v e , but a f t e r a l l i t corresponds fermentation laboratories. t o t h e ferment used f c r t h e next b a t c h i n I t has i n d i s p u - ^ a b l e a d v a n t a g e s because o f t h e g r e a t e r As we s h a l l see l a t e r on, we employ t h i s
u n i f o r m i t y o f the r e s u l t s i t g i v e s .
t e c h n i q u e w i t h t h e D a k a r v i r u s u s e d f o r t h e mouse p r o t e c t i o n t e s t s w i t h e x c e l l e n t results.