Immuno-PET in Inflammatory Bowel Disease: Imaging CD4-Positive T Cells in a Murine Model of Colitis

Abstract

Inflammatory bowel diseases (IBDs) in humans are characterized in part by aberrant CD4-positive (CD4+) T-cell responses. Currently, identification of foci of inflammation within the gut requires invasive procedures such as colonoscopy and biopsy. Molecular imaging with antibody fragment probes could be used to noninvasively monitor cell subsets causing intestinal inflammation. Here, GK1.5 cys-diabody (cDb), an antimouse CD4 antibody fragment derived from the GK1.5 hybridoma, was used as a PET probe for CD4+ T cells in the dextran sulfate sodium (DSS) mouse model of IBD. The DSS mouse model of IBD was validated by assessing changes in CD4+ T cells in the spleen and mesenteric lymph nodes (MLNs) using flow cytometry. Furthermore, CD4+ T cell infiltration in the colons of colitic mice was evaluated using immunohistochemistry.Zr-labeled GK1.5 cDb was used to image distribution of CD4+ T cells in the abdominal region and lymphoid organs of mice with DSS-induced colitis. Region-of-interest analysis was performed on specific regions of the gut to quantify probe uptake. Colons, ceca, and MLNs were removed and imaged ex vivo by PET. Imaging results were confirmed by ex vivo biodistribution analysis. An increased number of CD4+ T cells in the colons of colitic mice was confirmed by anti-CD4 immunohistochemistry. Increased uptake ofZr-maleimide-deferoxamine (malDFO)-GK1.5 cDb in the distal colon of colitic mice was visible in vivo in PET scans, and region-of-interest analysis of the distal colon confirmed increased activity in DSS mice. MLNs from colitic mice were enlarged and visible in PET images. Ex vivo scans and biodistribution confirmed higher uptake in DSS-treated colons (DSS, 1.8 ± 0.40; control, 0.45 ± 0.12 percentage injected dose [%ID] per organ, respectively), ceca (DSS, 1.1 ± 0.38; control, 0.35 ± 0.09 %ID per organ), and MLNs (DSS, 1.1 ± 0.58; control, 0.37 ± 0.25 %ID per organ). Zr-malDFO-GK1.5 cDb detected CD4+ T cells in the colons, ceca, and MLNs of colitic mice and may prove useful for further investigations of CD4+ T cells in preclinical models of IBD, with potential to guide development of antibody-based imaging in human IBD.

CAR T cells for brain tumors: Lessons learned and road ahead

“…64 Cu) for visualizing cell‐antigen‐specific targeting with PET. This approach has been most commonly used for cancer cell detection and has been more recently applied to the tracking of endogenous T cells or cells with engineered antigen tags . To reduce signal background and circumvent issues with BBB permeability, these antibodies could be used for ex vivo pre‐labeling of cells to study initial trafficking as long as the antibody stays cell‐associated and radionuclide half‐life is permissible.…”

Antibody‐Based Tracers for PET/SPECT Imaging of Chronic Inflammatory Diseases

“…Freise et al . developed an anti‐CD4 Cys‐diabody (GK1.5cDb) probe for the immunoPET imaging of CD4 + T cells, and used it to detect DSS‐induced colitis in mice . 89 Zr‐malDFO‐GK1.5cDb was used to visualize and quantify CD4 + T cells in the colons and mesenteric lymph nodes of colitis mice with immunoPET.…”

“…In addition, even though the tracer enabled detection of CD4 + T cells, it is still hard to distinguish each subset of CD4 + T cells (i.e., T H 1, T H 17, etc. ), which might need further investigation …”

“…[93] Freise et al [94] developed an anti-CD4C ys-diabody (GK1.5cDb) probe for the immunoPET imagingo fC D4 + Tcells, and used it to detect DSS-inducedc olitis in mice. [95] 89 Zr-malDFO-GK1.5cDb was used to visualize and quantify CD4 + Tcells in the colons and mesenteric lymph nodes of colitis mice with immunoPET. The accumulation of the radiolabeled tracer in the colon of DSS-treated mice was significantly increased and confirmed by ex vivo results (DSS-treatedg roup:1 .8 AE 0.4 vs. controlg roup: 0.45 AE 0.12 %ID/organ, p < 0.0001, n = 8; Figure 3C).…”

“…C) CT (coronal) and PET/CT( coronal and sagittal) images in DSS and control mice 20 h.p.i. of89 Zr-malDFO-GK1.5 cDb [95]. ····:colon ROI, ALN:axillary lymphn ode, B: bone, CLN:c ervicallymph node, ILN:i nguinal lymph node, K: kidney,Li: liver,MLN:m esenteric lymph node,P LN:popliteal lymphn ode, Sp:s pleen.…”