Table 1. Inhibition of virus production in the lungs of influenza-infected mice by delivering influenza nucleoprotein siRNA mediated by linear, hydrolytically pure PEI87.

Challenge	Mean virus titer in the lung*	Decrease in viral titer	P value
5% glucose (control)	3.08 ± 0.4	—	—
PEI87/GFP-siRNA	3.00 ± 0.0	1.2	0.64
PEI87 alone	3.00 ± 0.0	1.2	0.64
PEI87/NP-siRNA	1.86 ± 0.5	16.6	0.002

—, not applicable.

^*Expressed as logarithm of the tissue culture 50% infective dose; see Materials and Methods for details.