The overall prognosis for hepatocellular carcinoma (HCC) patients is poor but immunotherapeutic strategies may represent a novel and effective tool for HCC. However, the prediction of the early response for the immunotherapeutic effect of HCC remains a big challenge. We developed a novel near-infrared fluorescence (NIRF) probe (IRDye800-AbOX40) for OX40-targeted imaging. The H22 dual-tumor-bearing mice models were established and treated with CpG ODN intratumoral vaccination. Sixteen hours after vaccination, the mice were injected with the probe via the tail vein and conducted with NIRF imaging. The uptake of this probe in HCC tumors was greatly increased as early as 40 h post vaccination and reached a plateau between 54 and 112 h, while the untreated tumors showed a lower uptake, which was further confirmed by ex vivo imaging and flow cytometry. Immunofluorescence staining identified the colocalization of CD3 and OX40 in the tumor microenvironment. Moreover, immunohistochemistry analysis showed that OX40 expression level on tumor infiltrating lymphocytes (TILs) was associated with the fluorescence signal of the H22 tumors. IRDye800-AbOX40 could be used as a specific NIRF probe for noninvasive imaging of OX40 expression on TILs, which may aid in predicting the early response to immunotherapy of HCC.
Keywords: CpG ODN; OX40; antibody; near-infrared fluorescence (NIRF) imaging; tumor.