Live attenuated rabies virus vaccine and process therefor

Claim 2

A process as defined in claim 2 wherein the rabies seed virus is grown alternately in mouse brain and duck embryo tissue cultures until the virus has grown in each system at least five times, followed by continued growth of the rabies virus in duck embryo tissue cultures for from six to seven duck embryo tissue culture growth cycles, before it is used in the production lots of rabies virus vaccine.

Claim 3

A process for preparing a live attenuated rabies virus vaccine which comprises (1) infecting fertile duck eggs with a modified fixed rabies virus which has been grown alternately in a suckling rat brain and then in a duck embryo tissue culture until the virus has grown in each system at least five times followed by continued growth of the virus in duck embryo tissue cultures for at least 6 to 12 passages, (2) incubating the duck embryos for 6 to 10 days, (3) separating the rabies-infected duck embryos from their shells, (4) trypsinizing the rabies-infected duck embryo cell tissues, (5) seeding a duck embryo tissue cell growth medium with a trypsinized, rabies infected cells from step (4), (6) growing the rabies infected cells in the cell growth medium for from about 3 to about 8 days, (7) separating at least a portion of the rabies virus-containing growth medium from the growing rabies-infected duck embryo cells, (8) mixing the separated rabies virus-containing growth medium with from 3 to about 5 percent stabilizing bulk agent and (9) freezing and drying the rabies virus composition from step 8 to less than about 5 percent by weight of moisture as measured by the Karl Fischer method.

Claim 4

A process as defined in claim 4 wherein in step (1) the fixed rabies virus is grown alternately in (a) suckling rat brain and (b) duck embryo tissue cultures until the virus titer has reached a minimum of 10 4.0 MLD50/0.03 ml. of virus fluid, and then the rabies virus is grown in duck embryo tissue cultures for from 6 to 13 passages, before it is used as rabies virus seed in the production of rabies virus vaccine.