1872
However , serial passages of fetal lamb kidney ( FLK ) cells , which are sensitive to infection with BLV , after transient transfection revealed that mutation of a second tyrosine residue in the N - terminal motif completely prevented the propagation of the virus .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: GENE 
Text: {0} 
Answer:
 None