I got some problems with growing a GFP recombinant adeno-virus in HEK-293T. I used the stock virus left by a previous lab member. The virus can infect 293T and express GFP, which can be detected as early as 24h. I let the infection last 3-4 days and harvest the virus when 90% cells showed CPE. Then I used the harvested virus to do the infection study again, however, the retrieved virus seems not be able to infect the cells. I think the problem may be caused by 293T. My labmate used HEK-293A, but currently we don't have that cell line. Any thoughts?