TABLE 4.

Characteristics of and virus production by cells derived from transformed 208F foci^a

208F focus	Presence of hXpr1	Infecting XMRV virus	Virus production level (FFU/ml)
			S+L− foci	AP+ foci	Transforming virus
1	Yes	22Rv1	4 × 103	2 × 104	<1
2	No	VP62	600	104	<1
3	No	22Rv1	2.5 × 104	9 × 105	3 × 104

^aMedium was harvested 12 to 24 h after feeding of confluent layers of cells obtained from transformed foci of 208F cells (foci 2 and 3) or 208F/LhXpr1SN cells (focus 1) infected with the indicated viruses. The medium was assayed for replication-competent virus by an S⁺L⁻ assay. After the S⁺L⁻ foci were counted microscopically, the cells were stained for AP, and AP⁺ foci were counted in the same dishes. The presence of transforming virus in medium harvested from cells obtained from the transformed foci was measured by exposing 208F cells to 1 ml of virus and by checking for transformed foci for 1 month after infection. For focus 3, transformed foci were visible within 5 days of infection and were counted at 10 days after infection with diluted virus.