Laboratory investigations on neuroparalytic accidents associated with suckling mouse brain rabies vaccine. III. -- Preservation of vaccine potency after elimination of murine brain myelin by centrifugation.

Myelin, which has been found in nine day-old mouse brain, was eliminated from weanling mouse brain suspensions by centrifugation at 17,000 g for 10 min, as demonstrated by electron microscopy and guinea-pig inoculation tests for encephalitogenic activity. This centrifugation procedure did not affect the potency of seven batches of suckling mouse brain vaccine, when centrifuged and non-centrifuged samples of the same batches were compared by a modified NIH potency test (t = 0.17). The present results with weanling mouse brain preparations suggest that centrifugation at 17,000 g be used in the preparation of rabies suckling mouse brain vaccine instead of the 1,900 g currently employed, which does not eliminate myelin. This new procedure would be expected to reduce the number of postvaccinal reactions which are attributable to the small amount of myelin which remains in vaccines prepared with new-born animal brains following the current procedure.