TABLE 1.

Antibody isotype titers specific to influenza virus A/PR8 at different time pointsa

Time (immune sera)Antibody isotype titer (103)
IgG1IgG2aIgG2bIgG3
0 wk (preimmune)0.5 ± 0.10.05 ± 0.10.05 ± 0.020.05 ± 0.01
2 wk (primary)2 ± 0.52 ± 0.51 ± 0.30.05 ± 0.01
5 wk (first boost)16 ± 2.416 ± 1.82 ± 0.50.5 ± 0.01
8 wk (second boost)32 ± 2.532 ± 2.232 ± 3.61 ± 0.1
5 mo postimmunization64 ± 4.264 ± 3.432 ± 3.21 ± 0.1
  • a IgG subclass serum antibodies specific to influenza virus PR8 were determined at week 0, 2, 5, 8, and 5 month postimmunization (at week 27) in the group of mice that were intranasally immunized with 10 μg of HA VLPs. Titers are expressed as the highest dilution of serum having a mean optical density at 450 nm greater than the mean plus 2 standard deviations of similarly diluted naïve serum samples.