Table 3.

Titers of viruses lacking gK or pUL20 in complementing and non-complementing cell lines.

Virus	Virus Titre (PFU/mL)
	Non-Complementing Cell Line (Vero) *	Complementing Cell Lines (VK302/Fd20-1) **
KOS ΔgK	1.52 × 104	2.63 × 106
KOS ΔpUL20	3.40 × 103	9.70 × 105
KOS ΔgMΔgK	2.20 × 103	1.08 × 106
KOS ΔgMΔpUL20	2.70 × 102	1.53 × 105

Virus stocks, were prepared by infecting complementing cells (VK302 or Fd20-1) at low MOI (0.1–0.01 PFU/cell) for 1 h at 37 °C. After incubation for up to 4 days at 37 °C, the cells were harvested by scraping into the culture medium and centrifugation (4 °C, 1200× g, 10 min). The cells were lysed to release cell-associated virus by sonication for 20 s at 39% amplitude in a cup horn sonicator (Fisher Scientific) and virus stocks were stored at −80 °C. Viral titers were determined by plaque assays on Vero cells (*) or on the appropriate complementing cell line (**).