TABLE 3.

Levels of replication in the upper and lower respiratory tracts of hamsters of rPIV3 bearing one, two, or three cp45 L protein amino acid substitutions and of wt rPIV3 (JS strain) and cp45^a

Virusb	Virus titer (log10 TCID50c/g [mean ± SE]) in:
	Nasal turbinates		Lungs
	Expt 1	Expt 2	Expt 1	Expt 2
rPIV3 wt	7.4 ± 0.16	6.4 ± 0.11	5.1 ± 0.49	5.8 ± 0.38
r942	6.6 ± 0.17	5.6 ± 0.19	3.0 ± 0.78	4.7 ± 0.96
r992	4.4 ± 0.16		3.1 ± 0.11
r1558	3.8 ± 0.40		4.3 ± 0.34
r942/992	<1.5 ± 0	<1.5 ± 0	<1.5 ± 0	<1.5 ± 0
r942/1558	2.9 ± 0.23		1.8 ± 0.17
r992/1558	5.7 ± 0.16	4.8 ± 0.18	3.2 ± 0.57	4.2 ± 0.46
r942/992/1558	3.9 ± 0.15	4.6 ± 0.24	<1.5 ± 0	1.8 ± 0.20
cp45	4.1 ± 0.27	5.1 ± 0.17	1.6 ± 0.08	2.5 ± 0.46

^aGroups of six hamsters each were intranasally administered 10^5.5 PFU of virus in a 0.1-ml inoculum, and the lungs and nasal turbinates were harvested 4 days later. 

^bcp45 is a biologically derived virus; the other viruses are recombinants. 

^cTCID₅₀, 50% tissue culture infectious dose.