Impaired Antiviral Response in Human Hepatoma Cells

Abstract

Hepatitis B, C, and D viruses can infect liver cells and in some individuals establish a chronic phase of infection. Presently, relatively little information is available on the antiviral mechanisms in liver cells. Because no good in vitro model infection systems for hepatitis viruses are available, we have used influenza A, Sendai, and vesicular stomatitis (VSV) viruses to characterize interferon (IFN) responses and IFN-induced antiviral mechanisms in human hepatoma cell lines. HepG2 or HuH7 cells did not show any detectable IFN-alpha/beta production in response to influenza A or Sendai virus infections. Treatment of cells with IFN-alpha resulted in upregulation of IFN-alpha-inducible Mx, 2',5'-oligoadenylate synthetase (OAS) and HLA class I gene expression but only with exceptionally high levels of IFN-alpha (>/=100 IU/ml). Accordingly, high pretreatment levels of IFN-alpha, 1000 IU/ml for influenza A and VSV and 100 IU/ml for Sendai virus, were required before any detectable antiviral activity against these viruses was seen. IFN-gamma had some antiviral effect against influenza A virus but appeared to be ineffective against VSV and Sendai virus. IFN-gamma upregulated HLA class I protein expression, whereas Mx or OAS expression levels were not increased. There was a modest upregulation of HLA class I expression during Sendai virus infection, whereas influenza A virus infection resulted, after an initial weak upregulation, in a clear decrease in HLA class I expression at late times of infection. The results suggest that hepatoma cells may have intrinsically poor ability to produce and respond to type I IFNs, which may contribute to their inability to efficiently resist viral infections.

Enhanced expression of type I interferon and toll-like receptor-3 in primary biliary cirrhosis

“…Only a few report is available concerning the mRNA expression of IFN-b in hepatocytes in vivo or hepatocyte cell lines in vitro. 47,48 Therefore, the expression of IFN-b in hepatocytes at a protein level is, to our knowledge, the first definite demonstration by immunohistochemistry. The role of IFN-b signaling pathway via TLRs is now under investigation using primary human hepatocytes and ligands for TLRs including poly I:C and LPS.…”

Interferon type I gene expression in chronic hepatitis C

“…Type I IFNs are produced by many, if not all, virus-infected cells. However, there is evidence that some cell types such as hepatocytes are poor IFN producers, 8 whereas a certain blood leukocyte population, termed natural IFN-producing cells, is specialized for the production of high amounts of type I IFNs (reviewed in Colonna et al 9 ). In contrast to type I IFNs, the expression of IFN-g is restricted to activated T lymphocytes and natural killer cells.…”

Cellular models for the screening and development of anti-hepatitis C virus agents

“…Such drastic difference in phenotype, notably proliferating versus quiescent cells (but this is not the only difference) may clearly lead to false or unappropriated anti-viral responses that will not be observed in vivo. A further problem encountered with cultured hepatoma cells (including HepG2, Hep3B and Huh-7) is their impaired poly(I-C)-and virus-activated IFN responses and the considerable variations they exhibit in the IFN response, notably in different Huh7 cell lines originating from different laboratories (Keskinen et al, 1999;Lanford et al, 2003;. This suggests that studies carried out with these cells must be interpreted with caution.…”

“…In addition, these models offer wide possibilities £ To the best of their knowledge, authors have no real or perceived conflicts of interests. to investigate antiviral drugs: i) the cells can be maintained in a differentiated phenotype, ii) they can be cultured in such a way as to maintain their drug metabolizing capacities (PichardGarcia et al, 2002), iii) they can be infected with HCVser of any genotype (including HCVpp and HCVcc particles), iv) the innate immune response is fully preserved, in contrast to what is observed in Huh-7 cells and derivatives, and other hepatoma cell lines (Keskinen et al, 1999;Lanford et al, 2003;Sumpter et al, 2005) ; indeed, fetal and adult human hepatocytes produce IFNβ and ISGs in response to IFN and HCV infection (Buck, 2008;Castet et al, 2002;Lazaro et al, 2007) a process that is likely to account for the low level of viral infectivity in these cells ; iv) finally, hepatocytes can be prepared from different patients so that the contribution of the interindividual variability of the host biology to antiviral drug response can be evaluated, in contrast to hepatoma cell lines of immortalized hepatocytes that are issued from a single individual; indeed previous analysis show that such diversity exists in terms of natural anti-viral response, response to IFN, receptor expression, etc. (Chevaliez & Pawlotsky, 2007a).…”