Table 2.

Product-related impurities encountered in AAV vector manufacturing.

Product related impurity	Method for measurement	Potential toxicity
AAV empty capsids	Ultracentrifugation; electron microscopy; spectrophotometry [32]; ion exchange chromatography [33]	Immunotoxicity
Encapsidated host cell nucleic acids (nuclease-resistant)	qPCR using amplicons to generic host cell genome sequences	Genotoxicity, Immunotoxicity
	qPCR using amplicons to specific sequences of concern (e.g., E1A)
Encapsidated helper component DNA (nuclease-resistant)	qPCR using amplicons for helper backbone sequences	Genotoxicity, Immunotoxicity
Replication-competent AAV	Ad-dependent amplification	Immunotoxicity
Noninfectious AAV particles	Ad-dependent infectivity in susceptible cells	Immunotoxicity
Other, including aggregated, degraded, and oxidized AAV vectors	Various, including size exclusion chromatography; dynamic light scattering; electrophoresis, etc.	Immunotoxicity