Abstract
Summary
A method has been presented for the removal from rabies vaccine of the factor which causes allergic encephalomyelitis. This factor is not removed by extraction with benzene and ether, but preliminary treatment of the vaccine with these solvents facilitates separation by subsequent treatment. The presence of calcium acetate prevents the loss of antigen when the vaccine is washed. It does not prevent removal of the encephalitic factor which appears to be water soluble. About one-half of the total nitrogen of the vaccine is removed by this washing process. The technic may be briefly summarized as follows:
1. A suspension of infected brain in water is dried from the frozen state.
2. The dried brain is extracted with benzene followed by ether (Live virus may be killed in this stage by heating in benzene).
3. After removal of the ether the dried brain is suspended in distilled water.
4. Sufficient solution of calcium acetate is added to make final concentration of M/10 calcium acetate, and the suspension is permitted to stand in the cold for an hour or two.
5. The calcium acetate solution is removed by centrifugation or filtration and the sediment is resuspended in distilled water to the original volume with agitation (clumps of sediment must be broken up).
6. The distilled water is removed by centrifugation or filtration.
7. The sediment is resuspended in distilled water or saline and homogenized. This is the washed vaccine.
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