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Recombinant Listeria monocytogenes mutants carrying Newcastle disease virus (NDV) fusionprotein gene F were constructed by homologous recombination.NDV F or its truncated fragment Fa wasused as the model heterologous gene to be integrated into actA or plcB downstream of their signal sequences.Correct orientation of the inserted genes was verified by polymerase chain reaction amplification of F or Fa.The inserted F and Fa were expressed in the two recombinants Lm-AactA-F and Lm-AplcB-Fa as shown bysodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot.Both recombinantsexhibited reduced virulence to embryonated eggs and mice by about 1.5-2.5 logs as compared with theparent wild strain 10403S. They were also less invasive than strain 10403S (P<0.05). Chickens receiving therecombinant strains orally or intraperitoneally were partially protected from virulent NDV challenge possiblydue to enhancement of non-specific immunity because the antibody titers against the homologous virus strainor the recombinant truncated fusion protein were marginal. Further research is needed in other animal modelsto see if the low antibody response results from insufficient expression of the heterologous genes as a resultof failure of L. monocytogenes or its recombinants to persist or replicate in chickens.
Recombinant Listeria monocytogenes mutants carrying Newcastle disease virus (NDV) fusion protein gene F were constructed by homologous recombination. NDV F or its truncated fragment Fa was used as the model heterologous gene to be integrated into act A or plcB downstream of their signal sequences. Correct orientation of the inserted genes were verified by polymerase chain reaction amplification of F or Fa. The inserted F and Fa were expressed in the two recombinants Lm-AactA-F and Lm-AplcB-Fa as shown by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot. Rabbit reduced virulence to embryonated eggs and mice by about 1.5-2.5 logs as compared with the wild type strain 10403S. They were also less invasive than strain 10403S (P <0.05). Chickens receiving therecombinant were orally or intraperitoneally were partially protected from virulent NDV challenge possibly able to enhance non-specific immunity because the antibody titers against t he homologous virus strainor the recombinant truncated fusion protein were marginal. Further research is needed in other animal model sto see if the low antibody response results from insufficient expression of the heterologous genes as a result of failure of L. monocytogenes or its recombinants to persist or replicate in chickens.