Abstract
Hemagglutinin (HA) is the main surface glycoprotein of influenza B virus. The B/Ibaraki/2/85 virus HA gene is 1758 bp in length, including signal peptide sequence, HA1 sequence, and HA2 sequence. We previously proved that B/Ibaraki/2/85 HA DNA induced immune response and provided effective protection in mice against challenge with homologous virus. In this study, a series of recombinant plasmids encoding truncated HA gene were constructed by PCR. BALB/c mice were immunized with the plasmids and challenged with a lethal dose of homologous virus. The essential sequence of HA DNA against influenza virus was explored by evaluation of survival rate, lung virus titer, bodyweight change, and serum anti-HA antibody titer of mice. The result showed that serial deletion did not deprive HA DNA of its protective ability until 885 nucleotides (295 amino acids) at 3′-terminal or 9 nucleotides of the signal peptide sequence at 5′-terminal were deleted. When the signal peptide sequence was kept intact and the 5′-terminal deletion started at the beginning of the HA1 sequence, deletion of 51 nucleotides (17 amino acids) made HA DNA lose its protective ability. This suggests that the sequence nt94–876 of B/Ibaraki/2/85 virus HA DNA played an important role in protection against infection.
Get full access to this article
View all access options for this article.