Intranasal delivery of mannan-coated liposomes enhances antibody responses to a newcastle disease virus vaccine

The polysaccharide, mannan, has been shown to be an effective immunoprotective agent and vaccine adjuvant in a variety of bacterial and viral diseases in different animal species. The objective of this study was to evaluate the immune response of chickens after being intranasal (i.n.) immunized using the Newcastle disease virus (NDV) encapsulated in liposomes and coated with mannan. Groups of chickens were vaccinated once intranasally with virus alone, then with uncoated liposome-encapsulated NDV (NC-lip), or mannan-coated liposome-encapsulated NDV (Man-lip). On day 14, velogenic viral challenge was carried out on vaccinated chickens. Chickens receiving virus alone had a 20% survival rate. In contrast, groups that received Man-lip had a higher survival rate of 70% (P <0.01). The titers of mucosal secretary immunoglobulin A (s-IgA) was the highest in the group for the birds that received Man-lip as mucosal adjuvant (P <0.01). These results suggest that liposomes coated with mannan may thus be used as a potential adjuvant for mucosal vaccination against NDV. This is the first study in which mannan has been demonstrated to enhance an adaptive immune response against ND virus infection in chickens.