Similarly, the ratio of env to transgene signal in cells infected with vector Akv4070AeGFP or AkvB4070AeGFP also increases in each cell line, albeit slightly later, from infection cycles 12, 19, and 12 onwards, in NIH-3T3, HEK293, and U87-MG cells, respectively (Fig. 2). Here, ERVW-1 is linked to infection.