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. 2018 Oct 9;9:2312. doi: 10.3389/fimmu.2018.02312

Figure 2.

Figure 2

Cross-reactive antibody responses induced by sequential infection or immunization. On day 28 (the day of the second infection or immunization; A) and on day 56 (the day of sacrifice or challenge; B–F), serum samples and nasal washes were collected from the mice described in the legend to Figure 1. Anti-PR8 (HA/NA) IgG antibodies (A; n = 7) and Anti-X-31(HA/NA) IgG antibodies (B; n = 7) in serum samples were detected by ELISA using PR8 SU and X-31 SU for coating. Anti-H1N1pdm09-specific IgG (C; n = 15), IgG2a and IgG1 (D; n = 5) antibodies in serum samples were detected by ELISA. Microneutralization assay was used to determine the neutralizing ability of these antibodies toward A(H1N1)pdm09 virus (E; n = 5). Anti-H1N1pdm09 IgA antibody levels in nasal washes were determined by ELISA (F; n = 5). Data of individual animals (A–E) are depicted or mean values ± SEM (F) are given, **p < 0.01, ***p < 0.001. Mann-Whitney U-test. The dashed line represents the limit of detection.