This study evaluates the enhancement of immune response of birds to
Newcastle disease (ND)
vaccine encapsulated in 1,2-dioleoyl-3-trimethylammonium
propane (
DOTAP)-based
liposomes. The vesicles of the liposomal ND
vaccine were physically characterized for shape, particle size and zeta potential. The results of the analyses showed that vesicles of the liposomal ND
vaccine were spherical and tightly packed. The mean size distribution was below 100 nm. The mean zeta potential was 24 mV. Sixty experimental birds were then divided into an unvaccinated group, a liposomal ND
vaccine group and a live La Sota(®)
vaccine group. Both the liposomal ND
vaccine and live La Sota(®)
vaccine groups were vaccinated orally at 3 and 6 weeks of age. The mean antibody titres, total and differential white blood cell count, and blood chemistry, respectively, were assessed. Ten birds from each group were challenged by
oral administration of 0.2 ml virulent Herts 33 strain at 9 weeks of age. The log(2) mean antibody titre induced by the liposomal ND
vaccine after secondary immunization of the birds was 9.60±0.95 while that of the live La Sota( (®) )
vaccine was 6.00±0.63. Nine of the 10 challenged birds in the unvaccinated group died while none died from the liposomal ND
vaccine group or the live La Sota(®)
vaccine group. After the boost vaccination, the chickens vaccinated with the liposomal ND
vaccine had a higher mean antibody titre, indicating that encapsulating ND
vaccine in
DOTAP-based
liposome induced significantly higher immunity than the live La Sota(®)
vaccine.