Increased immunostimulatory activity conferred to antigen-presenting cells by exposure to antigen extract from hepatocellular carcinoma after radiofrequency thermal ablation.

Radiofrequency thermal ablation represents an effective treatment for hepatocellular carcinoma (HCC) and it can also exert an "adjuvant" effect on spontaneous antitumor T-cell responses, as suggested by human and animal studies. The adjuvant effect is thought to depend on the huge amount of necrotic tumor antigen made available to the immune system by HCC thermal ablation. In addition, radiofrequency thermal ablation may result in the release of local stimuli responsible for activation and maturation of antigen-presenting cells (APCs). To test this hypothesis, we studied APC maturation and function in 19 patients undergoing thermal ablation for HCC. Patients' monocytes induced to differentiate with granulocyte macrophage colony-stimulating factor (GM-CSF), or GM-CSF plus IL-4, were cocultured in vitro with tumor debris generated by radiofrequency thermal ablation. Expression of costimulatory molecules, lymphnode homing chemokine receptor, antigen presentation, and cytokine secretion were enhanced by incubation with HCC treated tissue as compared with untreated HCC and nontumor liver tissue. Moreover, HCC-specific T-cell responses could be induced by monocytes activated with GM-CSF and incubated with thermally ablated HCC tissue. HCC thermal ablation can create an antigenic source along with stimuli appropriate for maturation of APCs to induce HCC-specific T-cell responses. These results contribute to explain at least in part the adjuvant effect of HCC thermal ablation and suggest a novel strategy to induce maturation of APCs and their loading with HCC antigens for active immunotherapy protocols aimed at reducing HCC recurrence after thermal ablation.

Ex vivo characterization of tumor-derived melanoma antigen encoding gene-specific CD8+cells in patients with hepatocellular carcinoma.

BACKGROUND/AIMS: Members of the melanoma antigen encoding gene family are expressed in tumors of different histological types but not in normal tissue. For this reason, they are attractive targets for cancer immunotherapy. METHODS: In the present study, we analyzed the expression of MAGE-1 and -3 genes in the hepatocellular carcinoma (HCC) tissue as well as frequency, phenotype and function of circulating and tumor infiltrating CD8+ cells specific for HLA-A1 and -A2 restricted epitopes of MAGE-1 and -3. RESULTS: Our study shows for the first time the presence of MAGE/tetramer+ CD8 cells in the tumor tissue of patients with HCC. These cells are able to recognize the MAGE-1 sequence 161-169 and the MAGE-3 sequence 271-279. In a patient with a particularly high frequency of MAGE-1 sequence 161-169-specific T cells, phenotypic and functional analysis was performed showing a phenotype of recently-primed CD8 cells (CD28+CD27+CD45RA-CCR7). CONCLUSIONS: The observation of a spontaneous in vivo priming of a MAGE-specific T cell response in patients with HCC and the high frequency of MAGE antigens expression in this tumor, makes this antigen a potential candidate for a MAGE-specific immunotherapy in hepatocellular carcinoma.

Virus-specific CD8+ lymphocytes share the same effector-memory phenotype but exhibit functional differences in acute hepatitis B and C.

Hepatitis B and hepatitis C viruses (HBV and HCV) are both noncytopathic and can cause acute and chronic infections of the liver. Although they share tropism for the same organ, development of chronic hepatitis is much more frequent following HCV infection, suggesting different mechanisms of viral persistence. In this study, we show that circulating HBV- and HCV-specific tetramer-positive CD8 cells during the acute phase of hepatitis B and C belong almost entirely to an effector-memory subset (CCR7(-) CD45RA(-)). Despite this phenotypic similarity, HBV- and HCV-specific CD8 cells show striking functional differences. HBV-specific tetramer-positive CD8 cells express high perforin content ex vivo, expand vigorously, and display efficient cytotoxic activity and gamma interferon (IFN-gamma) production upon peptide stimulation. A comparable degree of functional efficiency is maintained after the resolution of hepatitis B. In contrast, HCV-specific CD8 cells in the acute phase of hepatitis C express significantly lower levels of perforin molecules ex vivo and show depressed CD8 function in terms of proliferation, lytic activity, and IFN-gamma production, irrespective of the final outcome of the disease. This defect is transient, because HCV-specific CD8 cells can progressively improve their function in patients with self-limited hepatitis C, while the CD8 function remains persistently depressed in subjects with a chronic evolution.