. 2010 Jul 27;22(1):107–115. doi: 10.1089/hum.2010.064

Table 1.

Validation of Cell Removal by Step-Filtration and Modified Step-Filtration

Facility	Cell line	Volume assayed (ml)	Total cell challenge^a	Colonies detected post-filtration^b	LRV^c	Ref.
IUVPF	PG13	2,100	2.78 × 10⁹^d	0/4	9.4	Reeves and Cornetta (2000)
Sloan-Kettering Gene	PG13	2,600	(1.02–1.18) × 10⁹^e	0/3	8.57 ± 0.50	Przybylowski et al. (2006)
Transfer and Somatic			(1.30–2.22) × 10⁹^e	0/3	8.66 ± 0.55
Cell Therapy Facility			(1.08–1.16) × 10⁹^e	0/3	8.57 ± 0.49
SBVPF	PG13	1,000	2.0 × 10⁹^f	0/3^g	9.3
		1,000	2.78 × 10⁹^f	0/3^g	9.4
	293T	1,000	2.0 × 10⁹^f	0/3	9.3

^{^a}

PG13 or 293T packaging cells were expanded, and cell suspensions were prepared in D10 medium.

^{^b}

Following filtration, the filtrate was divided into aliquots and subjected to the centrifugation RCDA. Cells were allowed to grow for 7–14 days before being inspected visually for colonies or fixed with methanol and stained with crystal violet before being scored.

^{^c}

Log-removal value; inverse log₁₀ of the total cells removed during filtration. Colony detection was based on the detection assay sensitivity of three to five cells.

^{^d}

Individual filter units were sequentially challenged with 250 ml of D10 medium containing increasing concentration of cells ranging from 10⁴ to 10⁷ cells/ml (total cell challenge per filter was 2.78 × 10⁹).

^{^e}

Individual filters were challenged with the indicated number of PG13 cells in D10 medium.

^{^f}

Three separate filters were challenged with PG13 or 293T cells at a concentration of 2 × 10⁶ cell/mL in 1,000 ml of D10 medium.

^{^g}

For each series of experiments, cell challenges were carried out using three individual filter setups (n = 3). Aliquots (250 ml) for each post-filtration spiked medium were tested by RCDA. Results are presented as total colonies detected per filter unit.