LIVE POLIO IRUS VACCINES

Application of Genetic Markers to Development and Control of Vaccine 57
TABLE 6. MARKERS AS DETECTIVE AGENTS. TEMPERATURE MARKERS OF TYPE 1 STRAINS ISOLATED
FRoM HEALTHY INFANTS AND CHILDREN VACCINATED WITH CHAT VIRUS IN NEW JERSEY AND
PHILADELPHIA
LOCATION NUMBER OF PASSAGES MARKER
THROUGH MAN
TOTAL COLD HOT
TESTED
MOORESTOCN 1 6 6
2 2 1 1(?)
3 1 1 0
PGH * 1 9 9 0
TOTAL 18 17 1(?)
· Premature infants in Philadelphia General Hospital.
of 40 ° C. and the results were therefore classified
as intermediate.
In view of this remarkable stability of the
CHAT strain in relation to the temperature
marker, similar studies were undertaken with
Type 1 strains isolated in Leopoldville and
Poland during large-scale vaccination campaigns
with CHAT virus. The results of these investigations
are shown in Table 7. Type 1 virus isolated
from two symptom-free, vaccinated children
in the Leopoldville area retained the cold character.
In contrast, none of the remaining 11
strains isolated from vaccinated and non-vaccinated
infants in Leopoldville, and none of the
eight strains isolated from similar subjects in
Poland, showed the cold character. Except for
one Leopoldville strain, the reproductive capacity
of these viruses was not inhibited by the temperature
of 40 ° C. Results obtained with one
strain seemed to classify its character as intermediate.
Development of New Attenuated Strains
through Cultivation at Low Temperature. The attenuated
strains of poliovirus now available can
TABLE 7. MARKERS AS DETECTIVE AGENTS. TEMPERATURE MARKER OF TYPE 1 STRAINS ISOLATED
FROM HUMAN SUBJECTS DURING VACCINATION CAMPAIGN WITH CHAT ViRus IN LEOPOLDVILLE
AND POLAND
LOCATION SUBJECTS MARKEP OF STRAINS
V or N CONDITION TOTAL NUMBER NUMBER
TESTED COLD HOT
LEOPOLDVILLE V HEALTHY 2 2 0
V SICK 3 0 3
N SICK 8 0 8*
POLAND V SICK 3 0 3
N SICK 5 0 5
* One strain showed more intermediate characteristic.