Abstract
1) In comparative experiments with Enders strain adapted to the chorio-allantoic cavity of the developing chick embryo and the newly isolated Towata strain of mumps virus, it was noticed that Enders strain was considerably attenuated. Towata strain showed a wide host range of tissue culture cells, mild virus growth in suckling mouse brains and high pathogenicity for the parotid glands of monkeys.
2) Attenuated Enders Strain was used for an inhalation test with monkeys as the live mumps vaccine. All monkeys showed good antibody responses without clinical manifestations.
3) Passage of the virulent Towata strain in the chorio-allantoic cavity of the embryonated egg was successful. During many passages, Towata strain lost the infectivity to various cells, acquiring biological characteristics similar to Enders strain.
