All lentivirus titering is performed on viral preparations that have been stored at -80°C and thawed. This ensures that any loss of titer associated with the recipient's initial thaw will be accounted for in our reported titers.
AAV titering is performed prior to freezing, and we have observed that physical titer values are not affected by freeze-thaw.
For a complete explanation of our viral service titering protocols, see our Viral Production page. Briefly, most lentivirus preparations are titered using the standard colony formation assay. Some lentivirus preparations are titered using microscopy to quantitate transduced cells. Additional titering is performed on some viruses.