TABLE 5.

The 1030 mutation increases the ts and att phenotypes of rA2cp248/404

Virusa	Virus titer (log10 PFU/ml) at temp (°C) ofb:						Shutoff temp (°C)c	No. of mice with virus ind:		Mean ± SE titer (log10 PFU/g) ind:
	32	35	36	37	38	39		Nasal turbinates	Lungs	Nasal turbinates	Lungs
A2 (wt) (HEK-7)	5.8	5.6	5.7	5.6	5.6	5.4	>40	6	6	4.8 ± 0.07	4.7 ± 0.08
cpts248/404	5.4	5.1	4.6e	<0.7	<0.7	<0.7	37	4	6	2.2 ± 0.13	2.2 ± 0.09
rA2cp248/404	5.2	4.8	4.1e	<0.7	<0.7	<0.7	37	4	4	2.0 ± 0.02	1.8 ± 0.12
rA2cp248/404/1030	5.5f	4.0e	<0.7	<0.7	<0.7	<0.7	36	0	0	<2.0 ± 0.00	<1.7 ± 0.00

^aRecombinant (r) viruses each contained the “HEK” F gene mutations and the L gene “sites” mutations (26). A2 (wt) (HEK-7) and cpts248/404 were biologically derived viruses. 

^bBoldfacing indicates virus titer at the shutoff temperature. 

^cDefined as the lowest restrictive temperature at which a 100-fold or greater reduction of titer was observed. 

^dMice in groups of six were administered 10⁶ PFU of virus intranasally under light anesthesia on day 0 and sacrificed on day 4. 

^ePinpoint plaque size. 

^fSmall plaque size.