Intranasal interleukin-12 is a powerful adjuvant for protective mucosal immunity

The use of interleukin (IL)-12 as a new vaccine adjuvant for stimulating pr otective antiviral mucosal immunity has been examined, Mice were immunized intranasally (in) with an influenza vaccine consisting of soluble hemagglut inin (H1) and neuraminidase (N1) plus IL-12. This treatment resulted in ele vated levels of lung and splenic interferon-gamma and IL-10 mRNA, Total and IgG2a anti-H1N1 antibody levels in serum were significantly elevated, as w ere total, IgG1, IgG2a, and secretory IgA antibody levels in bronchoalveola r lavage (BAL) fluids compared with animals receiving vaccine alone. Mice i mmunized in with vaccine and IL-12 also exhibited decreased weight loss and dramatically enhanced survival after lethal challenge with infectious infl uenza virus. Protection was dependent upon the presence of B cells and coul d be transferred to naive mice by inoculation of either serum or BAL fluid from IL-12-treated mice. These findings show for the first time that solubl e IL-12 delivered in serves as a powerful respiratory adjuvant for protecti ve antiviral immunity.