Table 2.

Infectivity assay results for pRCAS and mutant derivatives^a

Construct	Log TCID50/ml		Behavior in infectivity assayb	Relative −1 FS efficiency in DF1 cellsc
	Expt 1	Expt 2
pRCAS	−7.50	−7.83	++++	100
pRCAS-9	−2.50	−2.50	−	13
pRCAS-12	−3.50	−4.17	−	13
pRCAS-23	−6.83	−7.17	++	138
pRCAS-25	−6.38	−6.63	++	146
pRCAS-SRV	−7.83	−7.63	++++	151
pRCAS-12-SRV	−5.16	−5.20	−	19
pRCAS-25-SRV	−6.63	−6.56	+	229
pRCAS-IBV2	−7.25	−7.56	++++	225
pRCAS-12-IBV2	−6.50	−6.56	+	35
pRCAS-25-IBV2	−6.50	−6.63	+	306
pRCAS-11	−3.38	−3.17	−	ND
pRCAS-13	−3.17	−3.17	−	ND
pRCAS-14	−6.50	−6.63	++++	ND
pRCAS-15	−7.17	−7.50	++++	ND
pRCAS-16	−7.50	−6.83	++++	ND
pRCAS-17	−6.83	−7.25	++++	ND

^aValues are averages from the two data sets illustrated in Fig. 7. FS, frameshifting; ND, not determined.

^bQualitative estimate of the behavior of the viruses in multiple-passage infectivity assays.

^cShown for comparison, with the wild-type value set to 100.