Immunopotentiating of mucosal and systemic antibody responses in mice by intranasal immunization with HLT-combined influenza virosomal vaccine.

The mucosal vaccination strategy against influenza has been investigated by using influenza virosomal vaccine (IRIV) combined with two different adjuvants: the procholeragenoid (PCG) and the Escherichia coli heat labile toxin (HLT). A comparative study has been carried out on mice administered intranasally with these different formulations of influenza vaccine. PCG appears less effective than HLT in inducing an IgG response, but both the adjuvants elicit mucosal adjuvant activity inducing s-IgA in the upper respiratory tract. On the contrary, only HLT when administered intranasally to mice with influenza virosomes stimulates the production of s-IgA in the lower respiratory tract thereby providing a better protection against primary infection of the respiratory system. Both HLT and PCG enhance the production of IFN-gamma in the respiratory tract, nevertheless HLT appears more efficacious as a mucosal adjuvant.