How much does the lentiviral vector titer drop with freeze-thaw cycles?

The titer of lentiviral vectors will drop with freeze-thaw cycles. In-house studies have shown that the titer drops approximately 50% with each freeze-thaw cycle, though this number will vary. We recommend avoiding freeze-thaw cycles. If it is necessary to re-freeze lentiviral vectors for future use, the lentiviral vectors should be aliquoted into single-use aliquots.