In vivo immunoimaging of interferon-gamma

1. A method for in vivo immunoimaging interferon gamma (IFN-γ) as a marker of active T cells in a subject with cancer, comprising:

administering a labeled-antibody conjugate to a subject, wherein the labeled-antibody conjugate comprises:

an antibody that specifically binds to IFN-γ, and

a detection label conjugated to the antibody, wherein the detection label is a radionuclide tracer selected from 11 C, 13 N, 15 O, 18 F, 44 Sc, 45 Ti, 52 Mn, 64 Cu, 68 Ga, 76 Br, 82 Rb, 86 Y, 89 Zr, 111 In, 124 I, 43 K, 52 Fe, 57 Co, 67 Cu, 67 Ga, 77 Br, 81 Rb, 81m Kr, 87m Sr, 113m In, 123 I, 127 Cs, 129 Cs, 132 I, 197 Hg, 203 Pb, 206 Bi, or a combination of any two or more thereof; and

detecting the presence of the labeled-antibody conjugate in the subject in vivo by imaging, wherein specific binding of the labeled-antibody conjugate to IFN-γ indicates the presence of activated T cells.

2. The method of claim 1 , wherein the subject received an immunotherapy prior to administering and detecting the presence of the labeled-antibody conjugate, and wherein the mechanism of action of the immunotherapy results in an increased number of tumor-infiltrating lymphocytes in the subject and/or an increased activation state of a tumor-infiltrating lymphocyte population in the subject; or wherein administering and detecting the presence of the labeled-antibody conjugate is performed prior to administration of a therapy to determine the state of active immunity in the subject.

3. The method of claim 2 , wherein the subject received an immunotherapy prior to administering and detecting the presence of the labeled-antibody conjugate, and wherein the mechanism of action of the immunotherapy results in an increased number of tumor-infiltrating lymphocytes in the subject and/or an increased activation state of a tumor-infiltrating lymphocyte population in the subject; and wherein the immunotherapy is an immune checkpoint inhibitor, a cytokine, a vaccine, or an adoptive cell transfer therapy.

4. The method of claim 1 , wherein the subject is human and the antibody specifically binds to human IFN-γ.

5. The method of claim 1 , wherein the antibody is selected from a monoclonal antibody, an antibody fragment, or combination thereof.

6. The method of claim 5 , wherein the antibody is an antibody fragment, and wherein the antibody fragment is a Fab fragment or a diabody.

7. The method of claim 1 , wherein the imaging comprises positron emission tomography (PET) imaging, single photon emission computed tomography (SPECT) imaging, or a both PET and SPECT.

8. The method of claim 1 , wherein the presence of the labeled-antibody conjugate is detected in real time.

9. The method of claim 1 , wherein the radionuclide tracer is conjugated to the antibody with a bifunctional chelator or linker.

10. The method of claim 9 , wherein the radionuclide tracer is conjugated to the antibody with a bifunctional chelator, and wherein the bifunctional chelator comprises a chelator selected from N′-{5-[Acetyl(hydroxy)amino]pentyl}-N-[5-({4-[(5-aminopentyl)(hydroxy)amino]-4-oxobutanoyl}amino)pentyl]-N-hydroxysuccinamide (DFO), 1,4,7-triazacyclononane-N,N′,N′-triacetic acid (NOTA), 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), ethylenediaminetetraacetic acid (EDTA), 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOPA), diethylenetriaminepentaacetic acid (DTPA), 2,2′-(7-(1-carboxy-4-((2,5-dioxopyrrolidin-1-yl)oxy)-4-oxobutyl)-1,4,7-triazonane-1,4-diyl)diacetic acid (NODA), or a combination of any two or more thereof.

11. The method of claim 9 , wherein the radionuclide tracer is conjugated to the antibody with a bifunctional chelator, and wherein the bifunctional chelator is p-SCN-Bn-DFO or NOTA.