Adjuvant effect of liposome in chicken result from induction of nitric oxide

Intranasal delivery of liposome-encapsulated inactivated Newcastle Disease virus (NDV) is known to be an effective vaccine for inducing immunity in the respiratory tract from our previous reports. Four-week-old specific pathogen-free chickens were intranasally immunized with NDV entrapped in phosphatidylcholine-liposomes (PC-Lip). The mucosal levels of anti-NDV s-immunoglobulin A (IgA), serum IgG, a high hemagglutination inhibition titer (1:640), and the high survival rate with the PC-Lip vaccine were comparable to those of our previous report. The immune mechanisms of the PC-Lip adjuvant were determined by in vitro cellular experiments using the NO production of chicken spleen macrophages. The most important finding of this study was proving that macrophages were stimulated by PC-Lip via the extracellular regulated kinase (ERK) 1/2 and nuclear factor (NF)-κB activation pathways. This finding may be useful for developing potent mucosal vaccine delivery systems in the future.