LIVE POLIO IRUS VACCINES

470
Efficacy-Field Evidence
470 Efficacy-Field Evidence~~~~~~~~~~~~~~~~~~~~~~~~~~~
of guinea pigs, and then the use of this serum
to neutralize the virus against which it was prepared
and other viruses which one desires to
compare with the prototype strain. For example,
in a typical test, monkey-kidney monolayers in
Petri dishes are separately inoculated with approximately
10 plaque-forming units of CHAT,
Mahoney, and a virus to be tested for its
similarity to CHAT. After time is allowed for
adsorption, some of the monolayers are overlayed
with agar containing several dilutions of
CHAT antiserum. After incubation, the plates
are read for the number and size of the plaques
formed. The dilution which is used to read the
test is that which just neutralizes the CHAT virus
but allows Mahoney virus to form plaques. The
Mahoney virus plaques will generally be approximately
30 per cent -40 per cent of the diameter
of control Mahoney plaques. If the unknown
virus is similar to CHAT, it will be neutralized
to the same degree; if not, it will break through
as does the Mahoney virus.
Table 9 shows the results of these tests when
applied to known human intestinal passages of
the CHAT virus. To this date, none of the
viruses tested, which included up to three human
intestinal passages, has differed from CHAT
with respect to temperature, character or what
we would call its antigenic character. The 10
virulent viruses referred to were the Type 1
viruses isolated from cases in Leopoldville up
until April 1959.
Tests of Type 1 viruses isolated more recently
are shown in Table 10. Nos. 211 and 212 were
isolated from vaccinated infants. They are close
to CHAT in their temperature and serologic
characters. Viruses isolated from non-vaccinated
children are represented by Nos. 233, 235, 224,
and 229, whereas No. 220 was isolated from a
vaccinated child. All of these viruses are able
to grow at 40 ° C. and are capable of breaking
through the CHAT antiserum.
Virus 525 is of particular interest. The patient
from whom this was isolated was a 32-yearold
European woman who developed poliomyelitis
one month after coming to a village near Leopoldville.
In this village and in neighboring villages
during the latter part of 1959 there had been
TABLE 9. GENETIC AND SEROLOcIC MARKERS OF CHAT AND ITS HUMAN PASSAGE STRAINS
MARKERS
STRAIN
HUMAN
INTESTINAL
PASSAGE
TEMP.
MS
NEUT.*
IC
PATHOG.
PAR.
LESIONS
CHAT
Cold
MS
Yes
0/5
0/5
C-1
D-1
I-1
L-1
R-1
Q-1
0-5
Q-5
Q-2
1
2
2
3
Cold
Cold
Cold
Cold
Cold
Cold
Interm.
Cold
Cold
MS
MS
MS
MS
MS
MS
MS
MS
MS
Yes
Yes
N.T.
Yes
N.T.
Yes
Yes
Yes
Yes
0/4
0/3
0/7
0/4
1/3
0/7
Mahoney
Virulent
(10) t
Hot
Hot(6)
Interm.
(1)
N.T.(3)
MS+
MS + (10)
No
No(6)
N.T.(4)
* By anti-CHAT serum.
t Ten "wild" strains isolated from
paralytic patients during an epidemic.