The immunogenicity of intranasal adjuvanted pandemic avian influenza vaccine in murine model

Influenza vaccination remains the primary method for the prevention of influenza and the severe complications related to the disease. Development of an intranasal vaccination strategy will not only prevent the disease but also block the viral entry to the host and the horizontal transmission. Thus, intranasal pandemic vaccines may induce of humoral and cellular immune responses at the both systemic and mucosal levels. In this study, we investigated and compared the mucosal, humoral and cytokine immune responses induced in mice after intranasal vaccination with subunit influenza vaccine formulated with or without a novel c-di-GMP" adjuvant. Forty BALB/c mice were divided into two equally sized groups. Mice were vaccinated intranasally with two doses at three week interval of 15 µg of A/Vietnam/1194/2004 (H5N1) non-adjuvanted subunit vaccine or c-di-GMP adjuvanted antigen. Nasal wash and serum samples were collected at various time points after vaccination and used in the ELISA, whilst sera was in addition used in the HI assay. Supernatants from in vitro activated splenocytes were used to determine the concentration of IFN-γ, IL-2, IL-4, IL-5, IL-10 and IL-17 by Bio-plex bead immunoassay. In this study, we showed that intranasal immunisation of subunit vaccine formulated with c-di-GMP adjuvant induced a more rapid mucosal and humoral immune response than the subunit vaccine administered alone. Additionally, the study showed that the presence of the mucosal adjuvant elicited a Th1 profile, which suggests promotion of cell-mediated immune response. On the other hand, immunization with subunit vaccine alone induced low antibody responses and a Th2-type immune response. The results obtained in this study indicate that c-di-GMP is a promising adjuvant for the future development of intranasal pandemic influenza vaccines