Methods to produce bunyavirus replicon particles

1. A method for generating a recombinant, non-spreading bunyavirus replicon particle, the method comprising:

A) culturing a eukaryotic cell with growth medium;

B1) expressing T7 polymerase in the eukaryotic cell;

B2) expressing bunyavirus Gn protein and bunyavirus Gc proteins, and optionally bunyavirus NSm protein, in the eukaryotic cell, wherein said Gn and Gc proteins may form a heterodimeric polyprotein (GnGc); and wherein upon the optional expression of NSm protein, a heterotrimeric polyprotein (NSmGnGc) may form;

B3) transforming or transducing the eukaryotic cell with a vector comprising cDNA that encodes a bunyavirus L genome segment, wherein said L genome segment cDNA is flanked by a T7 promoter and cDNA of a ribozyme sequence;

B4) transforming or transducing the eukaryotic cell with a vector comprising cDNA that encodes at least part of a bunyavirus S genome segment, wherein said S genome segment cDNA comprises at least the N-gene and the 3′ and 5′ UTRs, wherein said S genome segment cDNA is flanked by a T7 promoter and cDNA of a ribozyme sequence; and, optionally,

B5) transforming or transducing the eukaryotic cell with a vector comprising cDNA that encodes a bunyavirus M genome segment from which the GnGc coding region has been functionally inactivated, wherein said M genome segment cDNA is flanked by a T7 promoter and cDNA of a ribozyme sequence;

C) following steps B1-B5, the eukaryotic cell is maintained in the growth medium and recombinant, non-spreading bunyavirus replicon particles are generated and isolated from the growth medium;

wherein the sequence of steps B1, B2, B3, B4, B5 is random and all or part of these steps may be performed simultaneously.

2. The method according to claim 1 , wherein the T7 polymerase is provided to the eukaryotic cell by transfected the eukaryotic cell with a recombinant fowlpox virus expressing said T7 polymerase.

3. The method according to claim 1 , wherein the eukaryotic cell is provided with the bunyavirus proteins of step B2) through transfection of the eukaryotic cell with a recombinant non-replicative and/or non-spreading paramyxovirus expressing said bunyavirus Gn, Gc, and/or NSm proteins.

4. The method according to claim 3 , wherein the eukaryotic cell is stably transfected or wherein the recombinant non-replicative and/or non-spreading paramyxovirus is persistently present.

5. The method according to claim 1 , wherein the eukaryotic cell is provided with the bunyavirus proteins of step B2) through transfection of the eukaryotic cell with an expression vector conditionally expressing said bunyavirus Gn, Gc, and optionally NSm proteins.

6. The method according to claim 1 , wherein the bunyavirus L genome segment and/or the S genome segment, and/or, when present, the M genome segment comprises a foreign gene.

7. The method according to claim 1 , further comprising a M, L, or S minigenome, wherein a foreign gene is present in said M, L or S-minigenome.

8. The method according to claim 1 , wherein the eukaryotic cell is a mammalian cell.

9. The method according to claim 1 , wherein the bunyavirus is Rift Valley fever virus.

10. A recombinant, non-spreading bunyavirus replicon particle produced by the method according to claim 1 .

11. The recombinant, non-spreading bunyavirus replicon particle according to claim 10 , wherein the bunyavirus L genome segment and or the S genome segment and/or, when present, the M genome segment, comprises a foreign gene.

12. The recombinant, non-spreading bunyavirus replicon particle according claim 10 , wherein the bunyavirus is Rift Valley fever virus.

13. A method for producing a bunyavirus replicon particle, the method comprising:

A) culturing a eukaryotic cell with growth medium;

B) transfecting, transforming, or transducing said eukaryotic cell with vectors expressing the bunyavirus NSm, Gn, and Gc proteins;

C) transfecting the eukaryotic cell with the recombinant, non-spreading bunyavirus replicon particle according to claim 10 .

14. A medicament or an immunogenic composition comprising the recombinant, non-spreading bunyavirus replicon particle according to claim 10 .

15. method according to claim 8 , wherein the mammalian cell is BHK-21.

16. The method according to claim 8 , wherein the mammalian cell is BSR-T7/5.