Table 1.

Single-cycle growth of recombinant mutant viruses in mouse cells

Virus	Yield on mouse 3T3 cells, pfu
	At 2 h	At 18 h
wt	1.1  ×  104	6.8  ×  105
dl5	4.5  ×  103	1.1  ×  103
dl29	5.2  ×  103	4.2  ×  102
dl5-29	9.3  ×  103	1.4  ×  103

BALB/c 3T3 cells were infected with the indicated virus (multiplicity of infection = 5), and total intracellular and extracellular virus was harvested at the times indicated. Virus titers were then determined by plaque assay on V5-29 cells that complement growth of UL5 and UL29 mutant viruses. pfu, plaque-forming unit.