Attenuated TGE virus

A process for the preparation of attenuated live TGE virus composition adapted for introduction into the body of swine in order to confer immunity against subsequent infection by virulent TGE swine virus comprising:

• a. inoculating a culture of pig colon organ cells in a maintenance culture medium solution with a virulent strain of TGE virus,
• b. allowing the virus to multiply in said culture for one or more days, and
• c. separating the culture medium infected with said virus from the colon organ culture,
• d. inoculating fresh colon organ cultures with virus from (b),
• e. repeating steps (b), (c) and (d) for at least five passages until a virus infected culture medium having an average titer of the virus of at least 10.sup.7.0 TCID.sub.50 per ml by a cytopathic effect test in tubes of fetal pig kidney cell cultures is obtained,
• f. separating the colon organ cells from the culture medium and harvesting the resulting virus-containing culture medium.