Vaccines delivered through mucosal surfaces are increasingly studied because of their properties to effectively induce mucosal immune responses, are cheap, easily administrable and suitable for mass vaccinations. The prospects of development of edible and intranasally administered (perhaps through nose drops or spray) vaccines are inciting a lot of interest and generating many studies. One major obstacle is to be able to induce systemic as well as mucosal responses to mucosal vaccines. Apart from immunizing with live viruses, this has proven to be a challenge and one way to overcome it is by using adjuvants. It is well established that toxins with little or no capacity to activate adenylate cyclase and thus lacking toxicity (CT or mutant Echerichia Coli labile toxin) improve performance of mucosal vaccines. Synthetic oligodeoxynucleotides containing immunostimulatory CpG motifs (CpG) have synergistic action with other adjuvants, such as alum and CT when delivered mucosally. There are several other important candidates for use as mucosal adjuvants. The proinflammatory cytokines IL-1α, IL-12, and IL-18 can replace CT as a mucosal adjuvant for antibody induction and induce an increase of mucosal CTLs. IL-15 also has the potential to increase antigen-specific CTL activity when used as an adjuvant while IL-5 and IL-6 were shown to be able to markedly increase IgA reactivity to co-expressed heterologous antigen. Chemokines such as MCP-1 could also be used as potential adjuvant for mucosally administered DNA vaccines as it significantly increases mucosal IgA secretion and CTL responses.
Keywords: adjuvants, mucosal, vaccine, cytokine, chemokine
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