shRNA expressing lentivector - low titer (Apr/20/2008 )

Hello everyone,
I cloned several shRNA into lentiviral vector. Some of them produce very low titer lentivirus. What might cause the problem?

I initially had the same worries too. After consulting members of the virus facility here, the general consensus is that the shRNA can lead to the degradation of the viral RNA genome inside the packaging cell line, thus preventing genome packaging/virus production. It should be expected to see less than optimal titers when making shRNA lenti. I have made many shRNA lentivirus and my typical titer is 10^7 to 10^8 after concentration, sometimes even as low as 10^6.

cheers