The vaccine strain of Ranikhet disease virus (RDF) was encapsulated in biodegradable poly-lactide-coglycolide (PLG) microspheres by double emulsion solvent evaporation technique. Immunogenicity of the microencapsulated RDF vaccine virus was evaluated in broiler chickens after intranasal delivery. A single dose of the experimental microsphere vaccine containing 75 μg of viral antigen was able to induce both humoral as well as cell mediated immunity in poultry. The serum samples of the immunized chicks showed significantly higher levels of circulating IgG and HI-antibodies against the viral antigens as compared to unvaccinated control chicks up to 6-week post immunization with the peak HI-titre of (log2) 6.0 and virus specific IgG level of (log10) 3.84 at 3rd wk PI. The levels of IgG and HI-antibodies induced by the microencapsulated RDF vaccine were comparable to that obtained with the conventional RDF vaccine. The intranasal delivery of microsphere vaccine formulation could also induce cellmediated immunity showing the peak blastogenic response of peripheral blood lymphocytes with mean stimulation index (S.I.) value of (1.416±0.034) at 3rd wk PI, which was significantly (P<0.05) higher than that of the control group.
PLG microspheres, microencapsulation, Ranikhet disease, intranasal immunization.
