FIG. 4.

Prechallenge antigen-specific humoral responses were enhanced by IFN-γ expression. Groups of F344 rats (five animals per group) were inoculated and boosted once with different constructs. Antibody titers 2 weeks after the boost were determined using recombinant SIVmac251 p27 Gag (corresponding to the first column for each group) produced in an E. coli expression system or SIVmac251 viral lysates (corresponding to the second column for each group) as coating antigens for ELISA. Results are shown as mean titers of individual samples assayed in duplicate and the geometric means for each group (bars). Comparative analysis was performed by using nonparametric ANOVA, followed by a multiple-comparison test. Statistically significant differences (P < 0.05) between pseudotyped SIV groups and the mock control are marked by *.