TABLE 2.

IgG and IgA antibody titers from the first or second immune seruma

Vaccine group (μg)bTiters (103) (±SD) of first immune serumTiters (103) (±SD) of second immune serum (fold increase)c
IgGIgAIgGIgA
HA (0.5)+ mLT26 ± 21.6 ± 0.2410 ± 50 (16)52 ± 6 (31)
HA (0.5)13 ± 10.4 ± 0.05102 ± 20 (8)3.2 ± 0.4 (8)
HA (0.1)+ mLT6.4 ± 0.50.4 ± 0.04154 ± 20 (24)20 ± 2 (47)
HA (0.1)1 ± 0.40.2 ± 0.026.4 ± 0.5 (6)0.4 ± 0.05 (2)
HA (0.02)+ mLT1.6 ± 0.10.6 ± 0.0351 ± 6 (32)3.2 ± 0.4 (5)
HA (0.02)0.4 ± 0.050.2 ± 0.026 ± 0.5 (16)0.4 ± 0.05 (2)
HA (0.5)+ CTB26 ± 30.8 ± 0.05205 ± 15 (8)25 ± 3 (31)
Naïve0.1 ± 0.020.2 ± 0.02
  • a IgG and IgA antibody titers specific to influenza virus A/PR8 were determined at week 2 after a single immunization and after two immunizations. Titers are expressed as the highest dilution of serum having a mean optical density at 450 nm greater than the mean plus two standard deviations of similarly diluted naïve serum samples.

  • b Groups of mice are as described in the legend of Fig. 1. mLT, mutant LT(R192G).

  • c Fold increase in antibody titers after the second immunization compared to that after the single-dose immunization.