The role of hepatocytes and sinusoidal cells in the pathogenesis of viral hepatitis

A study of susceptibility of primary human Kupffer cells to hepatitis C virus

BACKGROUND/AIMS

Histological examination of a liver-biopsy from a patient with chronic hepatitis C shows activated Kupffer cells. In vitro infection of human Kupffer cells (KC) was performed to study their interaction with hepatitis C virus (HCV).

METHODS

KC, isolated by collagenase perfusion and centrifugal elutriation, were infected with various HCV positive sera. The presence of the viral genome was followed, at different times, quantitatively by a branched-DNA assay and qualitatively by reverse transcriptase-nested polymerase chain reaction. A strand-specific assay performed with the thermostable enzyme rTth was used to detect the synthesis of a negative replicative intermediate. Cytopathic effect was examined by electron microscopy. Production of cytokines and inducible nitric oxide synthase was evaluated in the supernatants.

RESULTS

Quantification of HCV-RNA showed that the level of viral RNA associated with KC after adsorption decreased rapidly. Genomic viral RNA disappeared within 5 days of infection. Negative-strand RNA was never detected in any of these experiments. No cytopathic effects could be detected at any time. KC did not produce inflammatory nor antiviral cytokines.

CONCLUSIONS

Our results strongly suggest that primary cultures of KC are not permissive for HCV in vitro.

Infection of primary cultures of human Kupffer cells by Dengue virus: no viral progeny synthesis, but cytokine production is evident

We investigated the ability of dengue virus to invade human primary Kupffer cells and to complete its life cycle. The virus effectively penetrated Kupffer cells, but the infection did not result in any viral progeny. Dengue virus-replicating Kupffer cells underwent apoptosis and were cleared by phagocytosis. Infected Kupffer cells produced soluble mediators that could intervene in dengue virus pathogenesis.

Effect of macrophage source and activation on susceptibility in an age-dependent model of murine hepatitis caused by a phlebovirus, Punta Toro

The Adames strain of a bunyavirus, Punta Toro virus (PTV), is an hepatotrophic virus that has been described to produce an age-dependent lethal hepatic necrosis in 3-4 week old C57BL/6 mice, but 8 week old mice survive with minimal necrosis. The course of PTV infection in vitro in macrophages derived from these mice served as a model to study the pathogenesis of phlebovirus infection. Peripheral blood monocytes, resident or elicited peritoneal macrophages, and Kupffer cell liver macrophages, as well as hepatocytes, were able to support replication of PTV in vitro to a variable extent. Kupffer cells were the only population of macrophages, however, that expressed an age-related ability to affect viral infection and replication in vitro, suggesting that liver macrophages may have a unique modulatory effect on the occurrence and severity of PTV-induced hepatitis in mice. Whereas PTV showed minimal replication in resident peritoneal macrophages, the virus could replicate effectively in peritoneal macrophages elicited by thioglycolate. Activation of peritoneal macrophages with endotoxin resulted in a significant inhibition of intrinsic PTV replication (p less than 0.001), and a modest extrinsic inhibitory effect on PTV replication in cocultured hepatocytes. Both effects persisted in the presence of anti-interferon. These results indicate that the source and state of activation of macrophage/monocyte populations can influence the course of infection in vitro by the phlebovirus, Punta Toro, and can modulate infection in cocultured target cells.

Role of hepatocytes and Kupffer cells in age-dependent murine hepatitis caused by a phlebovirus, Punta Toro

Punta Toro virus (PTV) infection of C57BL/6 mice results in fulminant hepatic necrosis and death in 3-week-old susceptible mice, but survival with minimal hepatocellular necrosis in 8-week-old resistant mice. Susceptibility in 3-week-old mice is associated with an earlier rise of viral titers in liver and serum than that occurring in 8-week-old resistant mice. There is also an earlier and more rapid accumulation of infectious progeny in serum vs. liver after PTV infection in both age groups, suggesting that the virus may replicate in extrahepatic sites as well as the liver. PTV infection of isolated hepatocytes and Kupffer cells from 3- and 8-week-old mice demonstrates a significant age-related difference in the ability of these cells to support replication of PTV in vitro (P less than 0.05). The age-related difference in liver cell-PTV interaction appears to be an inherent difference in the liver cells themselves, since there are no age-related differences in viral adsorption, morphogenesis, cytopathic effect, or interferon action within these cells. Thus, age-related differences in PTV replication or dissemination at extrahepatic sites, and the ability of the virus to replicate in intrahepatic sites, may be additive factors in the expression of age-related susceptibility to PTV in C57BL/6 mice.