Each lot of virus produced by viral service is titered before being shipped to customers.
Lentiviral titers are reported as TU/mL, where TU is transducing units and generally represents the number of infective viral particles. Lentiviral titering is performed on viral preparations that have been stored at -80°C and thawed.
AAV titers are reported as GC/mL, where GC is genome copies and generally represents the physical number of viral particles. AAV titering is performed prior to freezing, because we have seen that physical AAV titer values are not substantially affected by freeze-thaw.
A complete explanation of the titering protocols we use can be found on our Viral Production page.