Membrane-bound immunomodulators as adjuvants in a cell culture-based avian influenza vaccine.

摘要

Inactivated viral vaccines often generate suboptimal immune responses. Adjuvants are incorporated into vaccines to increase their immunogenicity, however currently available adjuvants have shortcomings which have limited their use in human and veterinary medicine. This necessitates the development of new adjuvants and delivery systems. Cytokines have been extensively tested as adjuvants in vaccines but challenges such as diffusion from antigen, short half-lives and production costs have been encountered. To address this, we developed a technology that efficiently produces inactivated, whole-virus influenza vaccine bearing membrane-bound cytokines. Tethering the cytokine to the antigen of interest keeps the immunomodulator in close contact with the antigen ensuring that immune cells recruited or activated by the adjuvant react with the antigen as well. Influenza can be used to test this model since its surface proteins HA and NA contain conserved signal sequences that direct these proteins to the infected cell surface where they are picked up by budding virions. Plasmids containing cytokines fused to these signal sequences are introduced into MDCK cell lines and, upon expression, the fusion proteins are directed to the lipid islands on the cell membrane. When the cells are infected with influenza, new virus assembles at the lipid islands and incorporates the fusion proteins into the viral envelope. Furthermore, this mammalian cell culture-based production system bypasses many of the current limitations found in the egg-based influenza vaccine production system.;This model was tested in a chicken model using membrane-bound C3d, GMCSF, IL2 and IL4 as adjuvants. GMCSF adjuvanted vaccines delivered subcutaneously and C3d adjuvanted vaccines delivered subcutaneously and intranasally resulted in significantly higher antibody titers than vaccinating with inactivated virus alone. Vaccination with C3d adjuvanted virions by either route completely eliminated viral shedding after challenge with live virus and the GMCSF vaccine reduced the number of birds shedding virus.