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A liver-fluke-associated cholangiocarcinoma (CCA), comparable to that occurring in humans, was induced by exposing Opisthorchis viverrini-infected hamsters to dimethylnitrosamine (DMN). Tumor masses were removed and histopathologically identified, then one portion was extracted for antigens used in the production of monoclonal antibodies (MAbs). The remaining portions were used to establish CCA cell lines. The antigens produced and secreted by these cell lines, as well as those originally present in the tissue extracts, possessed a 200-kDa glycoprotein that appeared to be immunologically distinct from other tumor markers. A specific MAb called 6E5 was used to set up a sandwich ELISA for the quantification of this antigen in the serum and bile of tumor-bearing animals. The assay system was sensitive enough to detect the antigen at concentrations below 10 ng/ml. The serum and biliary levels of this antigen were markedly elevated in animals with progressive tumors when compared with untreated controls. The serum taken serially from each animal that subsequently developed CCA showed a gradual but significant elevation of the antigen as carcinogenesis progressed. A few isolated animals exhibited a slight elevation of the antigen at a time as early as the end of DMN treatment, when the CCA should not yet have developed, judging from microscopic examination. The data from this animal model suggested that the CCA-associated soluble antigen defined by MAb 6E5 was a useful marker for the detection of tumors at an early stage of development.

To elucidate the host cell defense mechanisms in response to Sindbis viral infection, we have started to characterize interferon (IFN)-stimulated response element (ISRE)-binding proteins activated in infected cells that are involved in the transcriptional induction of IFN type I-inducible genes. Using electromobility shift assays (EMSA), we detected several protein complexes with a human IFN-stimulated gene 15 (ISG15) ISRE in extracts from virus-infected L929 cells that were absent in extracts from uninfected cells. Comigration with Newcastle disease virus-activated ISRE-binding complexes, ISRE-binding specificity, supershift experiments, and conditions of formation indicate that the complexes activated by Sindbis viral infection in L929 cells correspond to DRAF1 and ISG factor 3 (ISGF3). Transfection of L929 cells with poly rI:rC induced only ISGF3. DRAF1 could be detected in Sindbis virus-infected mouse embryo fibroblasts derived from IFNR type I and type II KO mice. Viral RNA synthesis is required for activation of DRAF1.

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