Induction of mucosal immune responses by administration of liposome-antigen formulations and interleukin-12.

We examined the effect of interleukin-12 (IL-12) on the induction of mucosal immune responses following intranasal immunization with liposome-antigen formulations. We assessed the immune response to two recombinant glycoproteins (gD and gB) from bovine herpesvirus type 1 (BHV-1). Positively charged liposomes induced significantly higher gD-specific IgA titers than did immunization with antigen alone. This liposome formulation was selected to further assess the ability of IL-12 to influence mucosal immune responses. Intranasal immunization with IL-12 gD-liposome formulations did not alter the induction of mucosal immune responses. However, a significant increase in anti-gD antibody responses was induced in serum after intranasal immunization with IL-12 gD-liposome when compared with animals immunized with gD-liposomes. Mucosal antibody responses induced by a subcutaneous priming followed by an intranasal boost were significantly higher than those induced by two intranasal immunizations with the same IL-12 liposome-gD formulations. Furthermore, this immunization protocol resulted in the induction of high levels of interferon-gamma (IFN-gamma) in the lungs of subcutaneously primed mice. These findings indicate that the immunomodulatory effects of IL-12 influenced immune responses to a vaccine antigen when delivered intranasally and that these responses can be further enhanced by subcutaneous priming.