TABLE 2.

Viability of SL5 loop mutants^a

Mutant	IFA at the indicated time points posttransfection			Titer (PFU/ml) at 24 h posttransfection
	14 h	24 h	40 h
wt	++	+++	X	2 × 107
Loop1	+	++	+++	5 × 105
Loop2	−	−	−	ND
Loop3	−	−	−	ND
Open	++	+++	X	5 × 106
Stable	−	−	−	ND

^aX, cells were detached and dying from infection. ND, not determined.