FIG. 2.

Replication of rRSV/mIL-2, rRSV/CAT, and wt rRSV in the upper (nasal turbinates) and lower (lungs) respiratory tracts of BALB/c mice. Each animal was infected intranasally with 10⁶ PFU of the indicated virus. Five animals per group were sacrificed on the indicated days, the nasal turbinates and lungs were harvested, and viral titers were determined by plaque assay. The data are given as average concentrations of the virus (log₁₀ PFU/gram of tissue) and standard deviations. Statistical significance of the reduced titer of rRSV/mIL-2 compared to wt rRSV by Student's t test: for nasal turbinates, day 3, P < 0.01; day 4, P < 0.02; and day 5, P < 0.1; for lungs, day 3, P < 0.05; day 4, P < 0.05; and day 5, P < 0.001.