FIG 3.
rHRSV vaccine-induced serum IgG. Cotton rats at the age of 2 months (white bars) or 9 months (black bars) (n = 6/group) were immunized with an rHRSV vaccine dose of 105 TCID50, and HRSV-specific IgG was analyzed in serum weekly. Animals were challenged with wild-type HRSV (3 × 105 TCID50) at day 28. This graph shows data from one experiment representing lower levels of rHRSV-induced antibodies in old cotton rats found in three independent experiments. *, P < 0.05 for differences between the 2-month and 9-month age groups, as determined by a t test. OD, optical density.