Table 1.
Immunoprotective Abilities of pXL1, -2, -3, and -4 Plasmids Administered via the Intramuscular Route
| Immunogen | S* | M* | Intron II* | After RSV challenge | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Mean virus lung titer‡ (Log10 PFU/g) | No. fully protected mice§/ No. immunized mice | |||||||||
| pXL1 | + | − | − | 0.72 ± 0.99 | 5/8 | |||||
| pXL2 | + | − | + | 0.00 ± 0.00 | 9/9 | |||||
| pXL3 | − | + | − | 2.77 ± 0.72 | 0/8 | |||||
| pXL4 | − | + | + | 0.66 ± 1.00 | 6/9 | |||||
| pXL0 | − | − | − | 3.93 ± 0.27 | 0/12 | |||||
Mice were immunized with 100 μg i.m. of either pXL1–pXL4 or pXL0 at 0 and 6 wk and challenged with 106 PFU i.n. of a clinical RSV strain of the A2 subtype 4 wk after the boost. Lungs were removed 4 d later to determine the RSV titer.
*
S, M, and intron II indicate that the F cDNA construct encodes either a secretory (S) or a membrane-anchored (M) form of the protein or contains the β-globin intron II sequence.
‡
Detection sensitivity: 101.96 PFU/g lung.
§
Fully protected mice refers to animals with no detectable RSV in lungs after RSV challenge.