Figure 6.

Humoral responses induced by the MDV A/AA/6/60 LAIVs: Four-to-six-week-old female C57BL/6 mice (n = 5) were infected i.n. with 1 × 10⁵ FFU with the WT MDV A/AA/6/60 LAIV (PA_WT⁺/NS1_WT⁺) or the mutant MDV A/AA/6/60 LAIVs (PA_WT⁺/NS1_MT⁻, PA_MT⁻/NS1_WT⁺, and PA_MT⁻/NS1_MT⁻) as indicated. At 21 days p.i., mice were bled, and sera were collected and evaluated for the presences of antibodies against recombinant pH1N1 HA (A) or total viral proteins using cell extracts from pH1N1 virus-infected MDCK cells (B) by ELISA. OD, optical density. (C) HAI titers were calculated from mouse serum. *, p < 0.05 (PA_WT⁺/NS1_WT⁺ vs. the other viruses) using a Student’s t test from Microsoft Excel.