Recombinant Newcastle disease virus nucleoprotein mutant as a marker vaccine

1. A viable Newcastle disease virus (NDV) mutant lacking an immunodominant epitope found on an unmodified NDV protein as a result of a mutation in a gene encoding the protein, said epitope that is lacking being located within a region of the nucleoprotein (NP) of an unmodified NDV and having the amino acid sequence (447–455) shown in SEQ ID No. 1.

2. The NDV mutant according to claim 1 , wherein the NDV mutant induces antiserum in poultry lacking antibodies that react with an immunodominant epitope located within the amino acid region (447–455) of the NP.

3. The NDV mutant according to claim 2 , wherein the antiserum induced in poultry tacks antibodies that react with an 18-mer peptide having the NP amino acid sequence (443–460) shown in SEQ ID No. 2.

4. The NDV mutant according to claim 1 , wherein the mutant comprises a deletion or substitution of one or more amino acids in a region of the NP protein having the amino acid sequence (447–455).

5. The NDV mutant according to claim 2 , wherein the amino acids 443+/−1–460+/−1are deleted.

6. The NDV mutant according to claim 5 , wherein the amino acids 443–460 are deleted.

7. The NDV mutant according to claim 4 , wherein nucleotides encoding one or more amino acids in the region are substituted by a heterologous nucleic acid sequence encoding an immunodominant epitope of a polypeptide.

8. The NDV mutant according to claim 1 , wherein the NDV mutant comprises additional attenuating mutations.

9. The NDV mutant according to claim 1 , wherein the NDV mutant additionally comprises a heterologous nucleic acid sequence encoding an antigen of another avian pathogen.

10. A vaccine against Newcastle disease in poultry, comprising an effective amount of the NDV mutant of claim 1 in a live or inactivated form, and a pharmaceutically acceptable carrier or diluent.

11. The vaccine according to claim 10 , wherein the vaccine additionally comprises at least one additional vaccine strain capable of inducing protection against ND or against another avian pathogen.

12. The vaccine according to claim 11 , wherein the additional vaccine strain is a rccombinant vaccine vector capable of expressing the F or HN protein of NDV.

13. The vaccine according to claim 12 , wherein the recombinant vaccine vector is HVT.

14. The vaccine according to claim 11 , wherein the additional vaccine strain is an embryo-safe vaccine strain.

15. A method for the protection of poultry against Newcastle disease comprising administering a vaccine according to claim 10 to the poultry.

16. The method according to claim 15 , wherein the vaccine is administered via the in ovo route to an embryo.

17. A method for detecting NDV infection in poultry comprising the steps of:

(i) incubating a sample suspected of containing anti-NDV antibodies; with a fragment of the NP region of NDV comprising an amino acid sequence selected from the group consisting of sequence (447–455) and sequence (443–460) as shown in SEQ. ID No. 2 as the sole epitope,

(ii) allowing the formation of antibody-antigen complexes, and

(iii) detecting the presence of the antibody-antigen complexes.

18. The method according to claim 17 , wherein the NP fragment is a 18-mer peptide having the amino acid sequence (443–460) as shown in SEQ ID NO. 2.

19. A diagnostic test kit suitable for carrying out a method according to claim 17 , comprising a NP fragment comprising the amino acid sequence (447–455) as shown in SEQ ID NO. 1.

20. A method for distinguishing vaccinated poultry from non-vaccinated poultry, wherein vaccinated poultry have been vaccinated with a vaccine according to claim 10 , comprising extracting serum from the poultry and determining the presence or absence of antibodies reactive with an amino acid sequence (447–455) as shown in SEQ ID NO. 1, wherein serum from vaccinated poultry will lack antibodies reactive with said amino acid sequence.