FIG. 4.

Vaccination induces a broad cross-neutralizing antibody response. Sera collected at 2.5 months postprime (preboost; white bars) or 1 month postboost (3.5 months postprime; gray bars) from vaccinated mice (n = 8) that were challenged with VN/1203 (described in the legend to Fig. 2B, D, and F) were subjected to microneutralization assays (39) against the indicated viruses (HK/156 [A] and INA/5 [B]). All mice vaccinated with the negative-control vectors (n = 8) had undetectable neutralizing activity, which corresponds to a titer of 10 in this assay (data not shown). Asterisks indicate sera from H5 HA-vaccinated animals with undetectable nAb.