M Lutterbeck

Concomitant Interferon Alpha Stimulation and TLR3 Activation Induces Neuronal Expression of Depression-Related Genes That Are Elevated in the Brain of Suicidal Persons

We have previously identified 15 genes that are associated with the development of severe depressive side effects during the standard therapy with interferon alpha and ribavirin in the peripheral blood of hepatitis C virus infected patients. An enhanced expression of these genes was also found in the blood of psychiatric patients suffering severe depressive episode. Herein, we demonstrate that the same depression-related interferon-inducible genes (DRIIs) are also upregulated in post-mortem brains of suicidal individuals. Using cultured mouse hippocampal and prefrontal neurons we show that costimulation with murine IFN (mIFN) and the TLR3 agonist poly(I:C) promotes the expression of the described DRIIs, at the same time inducing pro-inflammatory cytokine expression through Stat1 and Stat3 activation, promoting neuronal apoptosis. Consequently, the upregulation of selective DRIIs, production of inflammatory cytokines and inhibition of neuronal plasticity may be involved in the pathogenesis of IFN-associated depression.

Long-term stimulation of Toll-like receptor 3 in primary human hepatocytes leads to sensitization for antiviral responses induced by poly I:C treatment

Chronic hepatitis C infection is associated with increased expression of interferon‐sensitive genes (ISGs) in the liver, which is, paradoxically, correlated with the nonresponse to interferon (IFN)‐based therapies. In the present study PHHs were isolated from HCV‐infected or uninfected patients and stimulated with the TLR1‐9 ligands for 6–24 h. Expression of cytokines and ISGs was determined by ELISA and qRT‐PCR. A comparative analysis was performed for TLR3 signalling, which was also correlated with single nucleotide polymorphisms (SNPs) related to HCV pathogenesis. TLR‐activated PHHs produced pro‐inflammatory and anti‐inflammatory cytokines, whereas IFNs were exclusively induced by TLR3 stimulation. Here, IL‐29 and IL‐28A were significantly highly expressed than IFN‐α and IFN‐β. TLR3‐induced IFN response was enhanced in hepatocytes isolated from patients with HCV infection. This hyper‐responsiveness could be mimicked in naïve PHHs consistently stimulated with low dose of poly I:C, but not Guardiquimod. The higher responsiveness in PHH isolated from HCV‐infected patients could be partially explained by higher frequencies of unfavourable SNP alleles of different SNPs associated with HCV progression and treatment outcome. These data suggest that durable activation of TLR3 but not TLR7, by low doses of viral replicative intermediates, increases the sensitivity to viral invasion. These findings shed new light on the relevance of TLR3 in the pathogenesis of HCV and may provide a possible explanation for the increased ISG expression during chronic HCV infection, the so‐called IFN paradox.

Intrahepatic B‐cell follicles of chronically hepatitis C virus‐infected individuals lack signs of an ectopic germinal center reaction

Chronic infection with hepatitis C virus (HCV) often affects the B‐cell compartment, leading to the occurrence of autoimmunity and B‐cell lymphoproliferation, in particular mixed cryoglobulinemia and B‐cell lymphomas. HCV presumably causes these lymphoproliferations by chronic antigenic stimulation and/or direct mutagenic effects on B cells. It has been speculated that the interaction of HCV with B cells and the expansion of antigen‐triggered B cells happens in germinal center‐like structures in the livers of HCV carriers. We studied rearranged immunoglobulin VH genes from seven B‐cell follicles microdissected from the livers of three unselected chronic HCV patients. The follicles consisted of polyclonal naive and memory B‐cell populations with only rare indication of minor clonal expansions and no evidence for active somatic hypermutation. Frequent detection of VH rearrangements using the VH1‐69 gene segment nevertheless indicated that at least a fraction of the B cells is HCV‐specific and/or autoreactive. Thus, the typical intrahepatic B‐cell follicles in chronic HCV carriers do not function as ectopic germinal centers for clonal expansion and affinity maturation of B cells. Hence, autoreactive and HCV‐specific B‐cell clones might either develop in secondary lymphoid organs or in intrahepatic follicles only under particular, yet undefined, circumstances.

348 TOLL-LIKE RECEPTOR 3 STIMULATED PRIMARY HUMAN NON-PARENCHYMAL LIVER CELLS ARE POTENT SUPPRESSORS OF HEPATITIS C VIRUS REPLICATION

Conclusions: In contrast to data obtained from cell lines, TLRinduced expression of IFNs and ISGs is higher in patients infected with HCV. This situation could be mimicked in vitro during longterm poly I:C treatment. These findings shed new light on the relevance of TLR3 in the pathogenesis of HCV and may provide a possible explanation for the elevated ISG expression during chronic HCV infection, the so called “IFN-paradox”.