Retroviral vector having immune-stimulating activity

1. A recombinant replication competent retroviral vector comprising a sequence encoding at least one agent that down regulates an immune inhibitory agent, wherein the at least one agent is a sequence encoding an antibody to a programmed death ligand (PDL) wherein the replication competent retroviral vector has a genome of the general structure from 5′ to 3′ comprising a long terminal repeat (LTR)-gag sequence-pol sequence-env sequence-at least one expression cassette-LTR, wherein said recombinant retroviral vector comprises a first cassette comprising a polIII promoter operably linked to a first inhibitory nucleic acid sequence, and a second cassette comprising a mini-promoter operably linked to the sequence encoding the antibody to the PDL.

2. The recombinant retroviral vector of claim 1 , wherein the vector comprises a second sequence encoding at least one agent that down regulates an immune inhibitory agent.

3. The recombinant retroviral vector of claim 1 , wherein the antibody is a single-chain antibody and the first inhibitory nucleic acid sequence is a miRNA encoding sequence.

4. The recombinant retroviral vector of claim 1 , wherein the vector further comprises a polynucleotide encoding a polypeptide having cytosine deaminase activity.

5. The retroviral vector of claim 1 , wherein the vector further comprises a third agent selected from the group consisting of (i) a polynucleotide encoding a polypeptide that converts a prodrug to a cytotoxic drug, and (ii) a polynucleotide encoding a cytokine or chemokine.

6. The recombinant retroviral vector of claim 1 , wherein the vector comprises a retroviral polynucleotide sequence engineered from murine leukemia virus (MLV), Moloney murine leukemia virus (MoMLV), Feline leukemia virus (FeLV) or Gibbon ape leukemia virus (GALV).

7. The recombinant retroviral vector of claim 6 , wherein the MLV is an amphotropic MLV.

8. The recombinant retroviral vector of claim 1 , where the vector comprises:

a retroviral GAG protein;

a retroviral POL protein;

a retroviral envelope:

a retroviral polynucleotide comprising:

LTR sequences at the 3′ end of the retroviral polynucleotide sequence;

a promoter sequence at the 5′ end of the retroviral polynucleotide sequence, said promoter being suitable for expression in a mammalian cell,

a gag nucleic acid domain;

a pol nucleic acid domain; and

an env nucleic acid domain;

Wherein the first cassette and the second cassette are positioned 5′ of the 3′ LTR and 3′ to the env nucleic acid domain; and

cis-acting sequences necessary for reverse transcription, packaging, and integration in a target cell.

9. The recombinant retroviral vector of claim 8 , wherein the env domain encodes an amphotropic env protein.

10. The recombinant retroviral vector of claim 1 , wherein the second cassette comprises an RSV promoter operably linked to the sequence encoding the antibody.

11. The recombinant retroviral vector of claim 1 , wherein the polIII promoter comprises an H1 or U6.