18F-3′-Deoxy-3′-Fluorothymidine Positron Emission Tomography Imaging for the Prediction of Acute Graft-Versus-Host Disease in Mouse Hematopoietic Stem Cell Transplant Models

Abstract

Acute graft-versus-host disease (aGVHD) remains a barrier to the success of allogeneic hematopoietic stem cell transplantation. In mice, studies have demonstrated that donor conventional T cells traffic into host secondary lymphoid tissues early after transplant, and that this process is critical for the development of disease. As a result, the measurement of cellular proliferation within lymphoid sites early after transplant might be a useful approach for predicting aGVHD in humans. 18F-3′-deoxy-3′-fluorothymidine (FLT) positron emission tomography (PET) imaging has recently emerged as a functional imaging modality in oncology patients. FLT, a thymidine analog, is incorporated into replicating DNA and is thus an indirect marker of cellular proliferation. Here we report that FLT PET imaging can differentiate mice receiving alloreactive T cells and destined to develop lethal aGVHD from control mice. Mice receiving allogeneic T cells demonstrated a stronger FLT signal within the peripheral lymph nodes compared with control mice at all time points after transplant. In addition, allogeneic T cell recipients transiently demonstrated stronger FLT uptake within the spleen. Importantly, these differences were apparent before the development of clinical disease. In contrast, the FLT signal within the host bowel, an important aGVHD target organ, was more variable after transplant and was not consistently different between aGVHD mice and control mice. Collectively, these findings suggest that the imaging of patient lymphoid sites using existing FLT PET technology might be useful for predicting aGVHD in the clinical setting.