At What Titer Does Adenovirus Begin to Aggregate?

Adenovirus aggregation does not occur at one exact titer, but the probability increases significantly as the viral concentration becomes higher.

Typical observations are as follows:

• ≤1 × 10¹² VP/mL → low aggregation risk
• 1–5 × 10¹² VP/mL → moderate aggregation risk
• ≥5 × 10¹² VP/mL → high aggregation risk
• ≥1 × 10¹³ VP/mL → very high aggregation risk

In practice, many adenovirus preparations begin showing noticeable aggregation when concentrated above approximately 5 × 10¹² VP/mL, especially under suboptimal formulation or handling conditions.

Several additional factors can strongly promote aggregation, including:

• Inappropriate storage buffer
• Low osmolarity or insufficient salt concentration
• Repeated freeze-thaw cycles
• Vortexing or harsh mechanical mixing
• Extended storage at 4°C
• Excessive concentration during ultracentrifugation

To minimize aggregation, adenovirus is commonly formulated at approximately 1–5 × 10¹² VP/mL in a stabilizing buffer such as A195 buffer or an equivalent formulation. Immediate aliquoting, storage at −80°C, and avoiding vortexing can further improve long-term viral stability and infectivity.