Influenza Neuraminidase DNA: Essential Sequence Of Providing Protection Against Lethal Viral Infection And Crucial Sequence In Keeping Neuraminidase Activity

Neuraminidase (NA) is one of the surface glycoproteins of influenza virus. The immune response induced by NA DNA in mouse model has been proved to be able to provide a complete protection against the challenge with homologous virus and a cross protection against the challenge with heterologous virus of the same subtype. In this paper, we tried to determine the essential sequence relating to providing protection within the NA gene. A series of NA plasmid truncates, with the nucleotides at 5' or 3' - terminal of A/PR/8/34 (H1N1) NA deleted serially, were constructed by PCR. BALB/c mice were immunized with the plasmid truncates and challenged with homologous virus at a lethal dosage. The essential sequence of NA DNA to provide protection against influenza virus was explored by observing the survival rates, serum NA antibody titers and lung virus titer of the mice. The result showed that, along with the increasing number of nucleotides deleted serially at 5' or 3' -terminal of NA DNA, the antibody titer induced by NA-DNA decreased. NA-DNA did not lost its protection against influenza virus until 60 serial...