TABLE 4.

Recovery of rHPIV1 bearing codon substitution mutations at amino acid position 992 in the L protein

Virus	Codona	No. of nucleotide changes needed to restore wild-type amino acid	rHPIV1 mutant recovered
rHPIV1 wild type	TTA, TTG, CTT, CTC, CTA, CTG	0	+
rHPIV1 L992Fcp45	TTT	1	+
rHPIV1 L992M	ATG	1	+
rHPIV1 L992H	CAC	1	+
rHPIV1 L992I	ATC	1	+
rHPIV1 L992W	TGG	1	+
rHPIV1 L992R	CGG	1	−b
rHPIV1 L992V	GTC	1	+
rHPIV1 L992Q	CAG	1	−b,c
rHPIV1 L992E	GAG	1	−d
rHPIV1 L992P	CCG	1	−b
rHPIV1 L992A	GCG	2	+
rHPIV1 L992Y	TAC	2	+
rHPIV1 L992C	TGC	2	+
rHPIV1 L992N	AAC	2	+
rHPIV1 L992D	GAC	2	−d
rHPIV1 L992T	ACC	2	−c
rHPIV1 L992G	GGG	2	−c
rHPIV1 L992K	AAG	2	+

^aIn the case of wild type, the six possible codons yielding the wild-type amino acid for leucine (L) are shown; for each mutant, the codon chosen for introduction into rHPIV1 is shown. A cDNA bearing an L992S mutation was not constructed.

^bMutant was recovered but reverted to wild type during passage at 32°C and was not further studied.

^cMutant recombined with wild-type pTML₁ and was not further studied.

^dVirus was recovered from transfection, but titer was low and virus was lost on subsequent passage.