Table 4.

Effect of synonymous mutations in the NA-coding region on segment 6 packaging

vRNAa	Mutation	MPD score	Relative packaging efficiency (on a 0.1–100 scale)b	vRNA expression levels (% of CAT35)b
CAT35	n/a	n/a	0.1	100
CAT38	n/a	n/a	100	111 ± 5
mut 461	GCU -> GCA	0.364	15.0 ± 4.5	94 ± 19
mut 464	CCG -> CCC	0.393	9.5 ± 1.5	44 ± 9
mut 463a	UUG -> UUA	0.098	0.5 ± 0.1	103 ± 17
mut 463b	UUG -> CUG	0.098	11.9 ± 4.3	44 ± 7
mut 466	ACC -> ACG	0.065	35.5 ± 1.0	55 ± 7
mut 467	AAU -> AAA	0.047	64.2 ± 6.7	91 ± 12
mut 468	GAC -> GAU	0	2.4 ± 0.4	333 ± 91
mut 469	AAG -> AAA	0.061	6.6 ± 1.2	235 ± 43

^aCAT38 denotes vRNAs containing NA codons 456–469 required for efficient packaging, while CAT35 refers to a vRNA lacking all 3′-NA-coding region. Synonymous mutations were introduced into the CAT38 vRNA as indicated.

^bMean ± standard deviation of four measurements from two independent clones as determined by CAT ELISA. n/a, not applicable.