Table 1.

Viral Titers in the Respiratory Tract of PR8/PB2-PspA Virus–Immunized Mice Challenged With PR8 Virus^a

Immunization	Time After Challenge, d	Viral Titer, Mean (SD) log10 PFUs/g
		Nasal Turbinates	Lungs
Medium	3	7.4 (0.2)	8.5 (0.4)
	6	7.0, NA, NAb	7.1, NA, NAb
PR8/PB2-GFP virus	3	6.9 (0.2)	7.8 (0.9)
	6	5.8 (0.3)	6.4, 4.5
PR8/PB2-PspA virus	3	7.8, 7.9	8.5
	6	NDc	ND

Abbreviations: GFP, green fluorescent protein; NA, not applicable; ND, not detected; PFUs, plaque-forming units; PspA, pneumococcal surface protein A; SD, standard deviation.

^a Mice were intranasally immunized with the indicated agents (50 µL) 3 times at 2-week intervals. Two weeks after the final vaccination, the immunized mice were challenged with 10-fold 50% mouse lethal dose of PR8 virus (50 µL). Nasal turbinates and lungs were harvested from the challenged mice (n = 3) on days 3 and 6 after challenge and subjected to virus titration by plaque assays in AX4/PB2 cells. When virus was not recovered from all 3 mice, individual titers are provided.

^b NA because the mice died.

^c The detection limit was 1.5 log₁₀ PFUs/g.