Immunogenic cross-reactivity between different serotypes novel duck reoviruses: Evaluation of cross-protection provided by mono or bivalent vaccine.

To investigate the immunogenic cross-reactivity among different novel duck reovirus isolates, animals immunized with monovalent inactivated duck reovirus were challenged with homologous and heterologous viruses, and serum samples were collected after immunization for cross-neutralization test. The results showed that the virus neutralizing titer against homologous virus was significantly higher than that against heterologous virus(p < 0.000001), which indicated that there was an important difference in antigenicity between DE13 and WL01 strains, which affected the specificity of protective virus neutralizing antibodies induced. This was further confirmed by cross-protection studies in ducks immunized at 2 d of age with whole-virus inactivated oil emulsion vaccines containing DE13 strain or WL01 strain as monovalent vaccine or both strains as bivalent vaccine. Protection against clinical disease with the monovalent vaccine was fully effective against homologous virus challenge at 2 weeks after vaccination, whereas protection against heterologous virus challenge was significantly lower (p < 0.001). Only the bivalent inactivated vaccine containing both strains protected birds against the two novel duck reovirus that cause disease in ducks. The results showed that vaccination of the inactivated vaccine at 2 day of age induced rapid immunity (within 2 weeks after vaccination) with complete clinical protection in ducks, the high level of neutralizing antibody could be maintained until 60 days-old. Pre-laying ducks immunization with two doses of bivalent inactivated vaccine could induce passive immunity in offspring ducks, and 100 % protection could be obtained through maternal antibody, which could be maintained until 21 days of age.