TABLE 1.

Replication of the ΔNS1-B virus is attenuated in MDCK and Vero cells^a

Cell type and expt no. (MOI)	Virus titer
	Recombinant wild type	ΔNS1-B
MDCK cells
1 (0.1)	3.1 × 108	3.2 × 102
2 (0.1)	3.1 × 108	1.7 × 102
3 (0.1)	1.4 × 107	6.8 × 101
4 (0.1)	3.1 × 107	6.8 × 101
5 (0.01)	2.7 × 108	<1.7 × 101
6 (0.01)	3.3 × 108	<1.7 × 101
Vero cells
1 (0.1)	5.9 × 106	2.5 × 102
2 (0.1)	6.6 × 106	1.7 × 102
3 (0.1)	1.2 × 105	2.2 × 102
4 (0.1)	2.0 × 105	1.7 × 102
5 (0.01)	3.5 × 106	<1.7 × 101
6 (0.01)	4.4 × 106	<1.7 × 101

^aConfluent monolayer cultures were infected at the indicated MOIs and incubated for 3 days at 33°C. Virus titers were determined as described in Materials and Methods.