LIVE POLIO IRUS VACCINES

42
Safety-Laboratory Evidence of Attenuation and Safety
2ab strain, which had not been through human
beings. The elution pattern of this virus of
strain was quite different from that of the Mahoney
strain.
Dr. Sabin then sent us two additional strains.
obtained from a child which he had fed the LSc,
2ab strain. He recovered the first strain seven
days after the child had been fed the vaccine
virus, and the second strain he sent us had been
recovered 19 days after feeding of the strain of
the vaccine material.
The seven-day strain proved to have exactly
the same elution pattern as that of the vaccine
strain, but the 19-day pattern had an intermediate
sort of pattern.
At this point, I would like to explain the
method we used in more detail.
Your attention is called to the left-hand part
of Figure 1. The method we follow is to grow
virus in tissue culture. With this work the monkey-kidney
tissue cultures are used, 30 cc. of
virus are obtained, and centrifuged at 100,000
G. This centrifugate is made up in 2 ml. of
0.02 M phosphate buffer. This material is
loaded onto a cellulose ion-exchange column, the
column being 8 centimeters long and 2 centimeters
in diameter.
Before the virus is put on, this column has
been equilibrated with the 0.02 M phosphate
buffer. In other words, the virus pellet is suspended
in 2 ml. of the buffer, then put on the
column and eluted off with 2 cc. amounts of
a-
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