FIG 6.
Attenuation of rA4G and r2stop+A4G RSV in vitro and in BALB/c mice. (Left) Replication kinetics of recombinant viruses in BEAS-2B cells infected at an MOI of 0.01. Supernatant samples were collected at indicated time points. The t0 indicates the input titer, and the dotted line indicates the limit of detection of the assay. Data represent the means from three experimental replicates ± standard errors of the means (SEMs). *, P < 0.05 when comparing wild type to both mutants (rA4G and r2stop+A4G RSV) by two-way ANOVA and Bonferroni’s multiple-comparison test. FFU, fluorescent focus units. (Right) Lung viral load in BALB/c mice shown as FFU per gram of lung homogenate quantified on the indicated days postinfection. Groups of 5 BALB/c mice were infected intranasally with 105 PFU of wild-type (black), rA4G (blue), and r2stop+A4G (red). On the indicated days postinfection, the left lung was harvested and homogenized, and viral load was determined using a fluorescent focus assay. Data represent the means from two experimental replicates ± SEMs. *, P < 0.05 when comparing wild type (rRSV-A2-K-Line19F) to both mutants (rA4G and r2stop+A4G) by two-way ANOVA test with Bonferroni’s correction for multiple comparisons.