Essential Sequences Of Influenza A And B Virus Hemagglutinin DNA To Provide Protection Against Lethal Viral Infection

The hemagglutinin (HA) is the major surface glycoprotein of influenza virus that mediates the attachment and penetration of the virus into host cells. The HA is the major surface antigen of influenza virus, which can induce the production of neutralizing antibodies to neutralize the infectivity of the virus. And there are five antigenic sites mapped on the HA. Antigenic changes of HA play an important role in influenza virus variation. The immune response induced by HA DNA in mouse model has been proved to be able to provide a complete protection against the challenge with homologous virus. To determine the essential sequence relating to providing protection within the HA gene, we constructed a series of HA plasmid truncates by PCR, with the nucleotides at 5' or 3' - terminal of A/PR/8/34 (H1N1) HA (1701bp full length) and B/Ibaraki/2/85 HA (1758bp full length) deleted serially. BALB/c mice were immunized with the plasmid truncates by intramuscular injection and challenged with homologous virus at a lethal dosage. The essential sequence of HA DNA to provide protection against influenza virus was explored by observing the survival rates, serum HA antibody titers and lung virus titer of the mice.The data showed that (1) HA-DNA of influenza A virus didn' t lost its protection against influenza virus when 6 nucleotides at 5' -terminal or 876 nucleotides at 3' -terminal were deleted serially. But HA-DNA of influenza A virus lost its protection when 12 nucleotides at 5' -terminal or 882 nucleotides at 3' -terminal were deleted...