Abstract
Inflammatory bowel diseases (IBD) in humans are characterized in part by aberrant 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 anti-mouse CD4 antibody fragment derived from the GK1.5 hybridoma, was used as a positron emission tomography (PET) probe for CD4+ T cells in the dextran sulfate sodium (DSS) mouse model of IBD. METHODS: The DSS mouse model of IBD was validated by assessing changes in CD4+ T cells in the spleen and mesenteric lymph nodes (MLN) using flow cytometry. Furthermore, CD4+ T cell infiltration in the colons of colitic mice was evaluated using immunohistochemistry. 89Zr-labelled 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 (ROI) analysis was performed on specific regions of the gut to quantify probe uptake. Colons, ceca, and MLN were removed and imaged ex vivo by PET. Imaging results were confirmed by ex vivo biodistribution analysis. RESULTS: Increased number of CD4+ T cells in colons of colitic mice was confirmed by anti-CD4 immunohistochemistry. Increased uptake of 89Zr-malDFO-GK1.5 cDb in the distal colon of colitic mice was visible in vivo in PET scans, and ROI analysis of the distal colon confirmed increased activity in DSS mice. MLN 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 % injected dose (ID)/organ respectively), ceca (DSS: 1.1±0.38, control: 0.35±0.09 % ID/organ), and MLN (DSS: 1.1±0.58, control: 0.37±0.25 % ID/organ). CONCLUSION: 89Zr-malDFO-GK1.5 cDb detected CD4+ T cells in the colons, ceca, and MLN of colitic mice, and could 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.
- Copyright © 2018 by the Society of Nuclear Medicine and Molecular Imaging, Inc.