Objectives: The H5 influenza virus constantly evolves by mutation and re-assortment and results in the emergence of new subtypes. The DNA vaccine may be an ideal candidate vac- cine for influenza virus because it can be developed rapidly in response to the new subtypes of influenza viral genes. As, finding an efficient H5 influenza DNA vaccine is still challeng- ing, we aimed to review the articles which have reported the effects of an adjuvant on the H5 influenza DNA vaccines. Results: Different types of adjuvants have been co-administered with the H5 influenza DNA vaccines. These adjuvants are generally divided into two types: ‘genetic adjuvants’ and ‘chemical adjuvants’. Among the genetic adjuvants, the Esat-6 gene of Mycobacterium tuber- culosis was found to induce the highest humoral response. Both Lipofectin® and silver nanoparticle (AgNP) were potent chemical adjuvants for DNA vaccine in chickens via IM and oral administration routes, respectively. Conclusion: It could be concluded that the formulation of an H5 DNA vaccine with both Lipofectin® as the most potent chemical adjuvant and Esat-6 gene of Mycobacterium tubercu- losis as the best genetic adjuvant is proposed for chicken immunization against H5 influenza virus. Also, the cationic derivatives of the polyprenols (PTAI) can be formulated in DNA vac- cine instead of Lipofectin® to make the adjuvant more affordable. Additionally, it seems that AgNP could be a potent candidate adjuvant for the oral H5 influenza DNA vaccine. Finally, more research is needed to find better adjuvants to include DNA vaccines as an applied vaccine type.

Keywords