Poor Sakura Vol 6 2
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Figure 4. The HA stem of wild-type and H9N2 is almost identical. We next performed a differential epitope mapping using three mutants of HA: HA-A, HA-A-HM, and HA-TM. The ratios of the HA-A titer (HA-FL/HA-A) are shown. HA-A-HM retained a stem-specific epitope. However, the binding of HA-GFC epitopes was reduced (lanes 1–4). HA-TM is a mutant with a large deletion under the transmembrane domain. HA-TM was shown to be a mutant of HA-A-HM. HA-A and its active site-mutated HA-A-HM differ markedly in their HA stem-specific epitopes. Furthermore, even HA head-modified HA (HA-GFC) exhibited HA stem-specific antibodies in sera from the H9N2 vaccinees. This result indicates that the region that is not involved in the HA head does not confer HA stem-specific epitopes. We found that the adjuvant PE promotes cell-mediated immunity and that a cytotoxic T-cell response develops as a common after-effect even without influenza virus infection. A clonal selection assay also indicated that the T-cell receptor variable region grafted with a VJ gene pair of Vα2.11 and Vβ17.2 was preferentially selected in sera from immunized mice, with the biased product shown by expansion. These clonally selected T-cells predominantly recognized a peptide derived from HA stem. In conclusion, immunization with our chimeric HA vaccine adjuvanted with the ASAI polymer induced not only antibodies against HA stem but also CTL that recognize a epitope located in the HA stem. Here, the HA stem of H9N2 is almost identical to that of the wild-type H9N2 virus. It is also predicted that the present strategy could be effective in the vaccine against the different subtypes of H5N1 which are currently circulating worldwide. Because Group 1 HA-FL and Group 2 HA-FL are antigenically similar and because H9N2 is one of the subtypes of H5N1, the epitope recognized by cHA-FL would also be shared by the Group 2 HA-FL. d2c66b5586