Construction And Expression Of The Hemagglutinin Gene(NA) From Influenza A Virus

Nucleic acid vaccines are eukaryotic expression plasmid containing gene sequence encoding certain kind of antigen, which can be introduced into zooblast. It synthesizes antigen protein by transcription system in host cell and activate immunologic system, which can introduce host produce immunologic response against certain antigen to achieve immunity. Nucleic acid vaccine makes the body produce both humoral immunity and cellular immunity, moreover, the plasmid can be injected into the muscle directly and applied easily. Then muscle cells transfer antigenic message by MHC-â… and MHC-â…¡molecule without considering MHC restriction, and it will induce CTL effect that many subunit vaccine can't induce. After expression plasmas containing DNA encoding certain antigen being injected locally, they are absorbed by local histiocytes, APC (antigen presenting cells) and other cells, and the plasmas are transcribed and translated into protein in cytoplasm. These proteins are degraded into short peptide fragments by protein enzyme complex. Part of short peptides are transported into reticulum, combined with MHC-â… molecule and expressed on the surface of cell memebrane. They can be recognized by precursor cell CD8+T cell, assisted with interaction between CD28 on T cell and B7 on APCs, stimulated by lymphokine secreting by lymphocyte, precursor CD8+T cell can be activated to CTL to kill target tumor cells. The other part of short peptides may enter lysosome / endosome region, combined with MHC-â…¡molecule, which are transported on the surface of cell memebrane and recognized and activated by CD4+T cells, and they can activated CD8+T cell or CD4+T cells, at the same time the complex presents on B cells, assisted with CD4+T cells, they can stimulate B cell to produce neutralizing antibody, inducing humoral immunity. Traditional in-activited influenza vaccine can induce the bodies to produce IgG for anti-influenza virus infection , Antigenic drift and antigenic shift of influenza always lead to the un-effective inoculation of influenza vaccines and the spread of influenza. DNA vaccines can cause cellular immunity and humoral immunity to resist the influenza virus by the natural constructure immunization , So it is now a studying hot point of the influenza vaccines .This test successfully constructed the expression vector pVAX/NA of influenza DNA vaccine , It has made a foundation for the immunization protection system of DNA vaccine and novel influenza vaccine. It is continuing that mouse immunity test and protection test of DNA vaccine .