FIG. 3.

Geometric mean titers of nasal viral shedding profiles after challenge with Sw/IN. The pigs were immunized by priming and booster administrations of a control plasmid DNA (open squares) (n = 12), an expression plasmid encoding the HA of Sw/IN into the epidermis (diamond) (n = 4) or into the tongue (triangles) (n = 4), or DNA encoding NP of A/PR/8/34 into the epidermis (circles) (n = 3) or by intramuscular injection of a commercial vaccine (crosshatched squares) (n = 4). The pigs were challenged 2 weeks after the booster immunization. None of the convalescent animals exhibited detectable nasal virus following rechallenge. The bars above day 1 and 5 titers represent the LSDs for comparisons between treated pig cohorts (n = 4) at α = 0.05. LSD values for comparison of immunized cohorts to the negative-control group are smaller; thus, the bars shown are conservative for these comparisons.