A set of ten different chitosan-coated alginate microspheres (MS1-10), containing hen-egg white lysozyme (LZ) as immunostimulant, was developed for the oral delivery of antigens. MS10, the formulation chosen for in vivo studies, charged with heat-inactivated Vibrio anguillarum (VA), presents mean dry and swollen diameter, zetapotential value, LZ and VA encapsulation efficiency of 2.7 ± 1.1 pm, 3.2 ± 1.2 pm, 2.1 ± 0.6 mV, 45.5% and 65.0%, respectively. The immunomodulating properties of the system were preliminarily tested on CBA mice model. A 6 consecutive-day oral immunization with microencapsulated VA induces a significant humoral immune response. The presence of LZ in the system contributes to increase the immune response against co-encapsulated VA vs. VA loaded MSs (IgM and IgG) or non encapsulated VA (IgM). The microencapsulation seems to improve the VA uptake by Peyer's patches (PP) vs. free particulate. These results provide useful insights into the suitability of this system for oral immunization with microencapsulated antigens.
