Glypican-3 is a promising target for immunotherapy for hepatocellular carcinoma, but limited data exist regarding its immunogenicity in patients with diverse HLA types, immunogenicity for CD4+ T-cells, and the impact of inhibitory co-stimulation on glypican-3-specific T-cells. Using a 15mer overlapping peptide library for glypican-3, PBMC from patients with HCC were assessed ex vivo and after short-term in vitro expansion for tumor antigen-specific T-cell responses with and without blockade of PD-1/PD-L1 and CTLA-4 signaling. Glypican-3-specific T-cells were undetectable ex vivo, but primarily IFNγ+ TNFα+ CD4+ T-cells expanded with short-term in vitro stimulation in 10/19 (52%) patients. Glypican-3-specific CD8+ T-cells predominantly produced TNFα, but did not secrete IFNγ nor degranulate. CTLA-4 and PD-1 blockade minimally impacted the cytokine secretion and proliferation of glypican-3-specific T-cells. These data suggest that CD8+ T-cell-directed tumor vaccines in HCC may have limited potential for efficacy unless optimal co-stimulation conditions can be identified but CD4+-directed vaccines merit consideration.

Silymarin displays anti-inflammatory effects on T-lymphocytes in vitro. The immunomodulatory properties of oral silymarin in vivo in humans with chronic hepatitis C have not previously been characterized. We hypothesized that silymarin would suppress T-cell proliferation and pro-inflammatory cytokine production of virus- and non-virus-specific T-cells while increasing anti-inflammatory IL-10 production in vivo. Patients from one site of the SyNCH-HCV double-masked, placebo-controlled study of oral silymarin in prior interferon non-responders with chronic hepatitis C provided blood samples at baseline and treatment week 20. Mononuclear cells were stimulated with recombinant HCV proteins and controls in 3H-thymidine proliferation assays, IFNγ Elispot and IL-10 Elispot. The frequency of CD4+CD25hi and CD4+foxp3+ regulatory T-cells, serum cytokine levels, serum IP-10 and lymphocyte interferon-stimulated gene expression were also quantified at baseline and week 20. Thirty-two patients were recruited (10; placebo, 11; 420mg three times a day, 11; 700mg three times a day). Serum ALT and HCV RNA titers did not change in any group. HCV-specific CD4+ T-cell proliferation and the frequency of IFNγ– and IL-10-producing T-cells were not significantly changed in silymarin-treated subjects. However, C. albicans-induced T-cell IFNγ and phytohemagglutinin-induced T-cell proliferation were suppressed by silymarin therapy. A trend towards augmentation of interferon-induced ISG15 expression was present in the high-dose silymarin group. While no effect on HCV-specific T-cells was identified, these data confirm that high-dose oral silymarin exerts modest non-specific immunomodulatory effects in vivo. The impact of this anti-inflammatory effect on long-term liver health in chronic hepatitis C merits future clinical investigation.

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