Safety and efficacy of water-in-oil-in-water emulsion vaccines containing Newcastle disease virus haemagglutinin-neuraminidase glycoprotein

Subunit vaccines containing haemagglutinin-neuraminidase (HN) glycoprotein of Newcastle disease virus (NDV), formulated as water-in-oil-in-water (W/O/ W) emulsions, were prepared. First, the suitable constituents of a W/O/W em ulsion adjuvant were investigated with polyvalent vaccines using NDV, infec tious bronchitis virus and Haemophilus paragallinarum. The W/O/W emulsion a djuvant, composed of the antigen in phosphate-buffered saline (PBS), liquid paraffin, squalene, diglyceryl monooleate, polysorbate 80 and PBS in a 30: 25:10:5:2:28 ratio, induced a good antibody response with less adverse loca l reactions. HN protein of NDV was expressed by an improved baculovirus exp ression vector, a hybrid nucleopolyhedrovirus ( HyNPV) between Autographa c alifornica NPV and Bombyx mori NPV, and was prepared from silkworm pupae in fected with the recombinant baculovirus, HyNPV-HN. Then, the W/O/W emulsion vaccine containing HN protein was prepared using the aforementioned consti tuents. Chickens showed 100, 100 and 80% protection against challenge expos ure to virulent NDV at 4 weeks after vaccination with W/O/W emulsion vaccin es containing 30, 6 and 3% of HyHPV-HN-infected pupae, respectively. The va ccines containing HN protein did not induce adverse local reactions at the site of injection. The subunit vaccine for NDV containing HN protein expres sed in the recombinant baculovirus-infected pupae, formulated as a W/O/W em ulsion vaccine composed of the antigen in PBS, liquid paraffin, squalene, d iglyceryl monooleate, polysorbate 80 and PBS in a 30: 25: 10: 5: 2: 28 rati o, was therefore found to be safe and effective.