FAQ

It is recommended that the sample volume of a single commissioned express delivery is not less than 50uL to avoid the effects of freezing and thawing, evaporation, and tube wall adhesion. The recommended sample delivery volume for genome titer, plasmid DNA residue, rcAAV, etc. is more than 10ul. The recommended sample delivery volume for infection titer is more than 20ul, and the sample delivery amount for empty shell rate testing is 5E+13vg.

The %RSD of general biochemical methods is usually 15%-25%, and the accepted standard of ddPCR is 10%. In most cases the %RSD for PackGene’s QC ddPCR verification data is lower than 5%, and the %RSD of TCID50 is lower than 10%.

The harvest liquid generated through PackGene’s AAV fast service will be broadly tested for exogenous viral elements as necessary following an evaluation of project characteristics. Both the original harvest liquid and final deliverables for the AAV Fast service will be devoid of such exogenous viral elements.

Yes.

The expected empty shell rate for our AAV Fast Services varies across AAV serotypes. As one example, the expected empty shell rate for AAV9 generated through our AAV Fast Service is lower than 10%.

Viral empty shell rate can be determined using several techniques including anion chromatography HPLC, Analytical Ultracentrifugation (AUC), Transmission Electron Microscopy (TEM), CyroTEM, or VG Titer/Capsid titer. AUC, TEM and CyroTEM are typically not suitable for quantitative quality control determinations and thus PackGene’s standard method for empty shell rate determination is anion chromatography HPLC. PackGene can provide additional CyroTEM and AUC analytical services to serve as a secondary verification of the results derived from anion chromatography HPLC.

Genome copies per ml (GC/ml) can be determined using primers directed at common vector elements during the early development stage, and thus we use common features such polyA segments or ITRs to determine GC/ml during this stage. However, it is recommended that specific primers targeted at AAV vector transgenes are used for testing the GC of GMP products. Our final fast service titer test is designed to use transgenes specific primers.

The terms genome copies per ml (GC/ml) and viral genomes per ml (vg/ml) are interchangeable and equal in most cases. At PackGene we may test GC by both qPCR and ddPCR. Testing by qPCR involves the use of a calibration standard while ddPCR may use optional reference products. Measurements by qPCR are more likely to be influenced by inter-lab and inter-operator variables, and ddPCR generally shows lower %RSD precision. Typically, GC is determined by qPCR during process exploration phase and for intermediate products while the GC of final products is more often determined by ddPCR.