Figure 5

Analysis of HA-antigen expression and in vivo immune response for recombinant Salmonella -HA strains. (A) Expression analysis of the HAOP antigen in the C-HAOP strain using SDS-PAGE with Commassie Blue staining and Western blot. SL7207 was used as negative control. (B) Western blot analysis of HAOP expression in the O-HAOP strain, using the HO strain as the negative control. (C) Results from ELISA experiments showing HA-specific IgG response raised by the O-HAOP strain using the HO strain as a negative control. 10 mice were used for each group. 1 × 10¹¹ bacteria were used to prime each mouse for 3 days, and two boosts were given on day 21 and 35; all by oral gavage. Blood sera from infected mice were collected on days 7, 28 and 42 for ELISA analysis. * underneath Day 42 indicates that the mean ELISA titer raised by the O-HAOP strain was significantly higher than that of the -HAOP strain (P < 0.05). (D) Results from HIA using blood sera taken from mice infected with O-HAOP strain on day 42. Blood sera from non-infected mice, and mice infected with the HO strain (taken on day 42) were also used a controls. * underneath O-HAOP indicates the mean HIA titer raised by O-HAOP strain was significantly different from those of HO and No-infection groups (P < 0.05). (E) T cell anti-HA IFN-γ responses provoked by the O-HAOP and C-HAOP strains, using the HO strain as a negative control. Asterisks indicate that the average ELISpot ratios provoked by O-HAOP were significantly different to those provoked by HO or C-HAOP (P < 0.05). In (C), (D) and (E), each ▴ represents one mouse. Red lines indicate the average titers in (C) and (D), and the average ELISpot ratios in (E).