|
DNA vaccination is a technique for protecting an animal against disease by injecting it with genetically engineered DNA so cells directly produce an antigen, resulting in a protective immunological response. Several DNA vaccines have been released for veterinary use, and there has been promising research using the vaccines for viral, bacterial and parasitic diseases, as well as to several tumour types. Although only one DNA vaccine has been approved for human use, DNA vaccines may have a number of potential advantages over conventional vaccines, including the ability to induce a wider range of immune response types. == History == Many believe vaccines are among the greatest achievements of modern medicine – in industrial nations, they have eliminated naturally occurring cases of smallpox, and nearly eliminated polio, while other diseases, such as typhus, rotavirus, hepatitis A and B and others are well controlled. Conventional vaccines, however, only cover a small number of diseases, and infections that lack effective vaccines kill millions of people every year, with AIDS, hepatitis C and malaria being particularly common. ''First generation'' vaccines are whole-organism vaccines – either live and weakened, or killed forms. Live, attenuated vaccines, such as smallpox and polio vaccines, are able to induce killer T-cell (TC or CTL) responses, helper T-cell (TH) responses and antibody immunity. However, there is a small risk that attenuated forms of a pathogen can revert to a dangerous form, and may still be able to cause disease in immunocompromised vaccine recipients (such as those with AIDS). While killed vaccines do not have this risk, they cannot generate specific killer T cell responses, and may not work at all for some diseases.〔 ''Second generation vaccines'' were developed to reduce the risks from live vaccines. These are subunit vaccines, consisting of defined protein antigens (such as tetanus or diphtheria toxoid) or recombinant protein components (such as the hepatitis B surface antigen). These, too, are able to generate TH and antibody responses, but not killer T cell responses. DNA vaccines are ''third generation vaccines'', and contain DNA coding specific proteins (antigens) from a pathogen. The vaccine DNA is injected into the cells of the body, where the "inner machinery" of the host cells "reads" the DNA and uses it to synthesize the pathogen's proteins. Because these proteins are recognised as foreign, when they are processed by the host cells and displayed on their surface, the immune system is alerted, which then triggers a range of immune responses.〔 Alternatively, the DNA maybe encapsulated in protein to facilitate entry into cells. If this capsid protein is also included in the DNA, the resulting vaccine hopes to combine the potency of a live vaccine without any reversion risks. In 1983, Enzo Paoletti and Dennis Panicali at the New York Department of Health devised a strategy to produce recombinant DNA vaccines by using genetic engineering techniques to transform ordinary smallpox vaccine into vaccines that may be able to prevent other diseases.〔Panicali, Dennis, Stephen W. Davis, Randall L. Weinberg, Enzo Paoletti (1983) "Construction of Live Vaccines by Using Genetically Engineered Poxviruses: Biological Activity of Recombinant Vaccinia Virus Expressing Influenza Virus Hemagglutinin" Proc. Natl. Acad. Sci. USA 80:5364-5368〕 They altered the DNA of cowpox virus by inserting a gene from other viruses (namely Herpes simplex virus, hepatitis B and influenza).〔Paoletti, Enzo, Bernard R. Lipinskas, Carol Samsonoff, Susan Mercer, and Dennis Panicali (1984) "Construction of Live Vaccines Using Genetically Engineered Poxviruses: Biological Activity of Vaccinia Virus Recombinants Expressing the Hepatitis B Virus Surface Antigen and the Herpes Simplex Virus Glycoprotein D" Proc. Natl. Acad. Sci. USA 81:193-197〕〔US Patent 4722848 - Method for immunizing animals with synthetically modified vaccinia virus〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「DNA vaccination」の詳細全文を読む スポンサード リンク
|