Hepatitis E virus enters liver cells through a dynamin-2, clathrin and membrane cholesterol-dependent pathway.

The hepatitis E virus (HEV) causes large outbreaks and sporadic cases of acute viral hepatitis in developing countries. In the developed world, HEV occurrence has increased as a result of zoonotic transmission from swine. The cellular aspects of HEV infection, especially the determinants of entry, are poorly understood. In the absence of a robust in vitro culture system for HEV, it is not possible to produce high titre infectious virus that can be labeled for tracking its internalization. We have therefore used an Escherichia coli expressed HEV-like particle (HEV-LP) to study HEV entry. Following internalization, the HEV-LP initially trafficks to Rab5-positive compartments en route to acidic lysosomal compartments where it is degraded. Using pharmacological inhibitors, dominant negative and constitutively active mutants, and siRNA-mediated perturbations, we show that HEV entry requires dynamin-2, clathrin, membrane cholesterol and actin, but is independent of factors associated with macropinocytosis. The HEV-LP results were further validated through infection of liver cells with virus from the stool of an infected patient. The comparative analysis also showed involvement of the phosphatidylinositol-3-kinase/Akt pathway in an early post-entry step of viral replication. This report provides a detailed description of endocytic processes associated with HEV infection.

The cell death regulator GRIM-19 is involved in HIV-1 induced T-cell apoptosis.

One of the hallmarks of Human Immunodeficiency Virus-1 (HIV-1) infection is progressive depletion of the infected and bystander CD4+ T-cells by apoptosis. Different mitochondrial proteins have been implicated in this apoptotic process; however, the role of different subunits of mitochondrial oxidative phosphorylation (OXPHOS) complexes in apoptosis is not clearly understood. Some of the OXPHOS complex subunits seem to perform other functions in addition to their primary role in energy generating process. GRIM-19 (gene associated with retinoid-interferon-induced-mortality-19), a subunit of mitochondrial complex-I was previously implicated in Interferon-ß and retionoic acid induced apoptosis in many tumor cells. In this study we report, using differential gene expression analysis, that GRIM-19 is up-regulated in HIV-1 infected apoptotic T-cells. A temporal up regulation of this subunit was observed in different HIV-1 infected T-cell lines and human PBMC and the extent of increase correlated to increasing apoptosis and virus production. Moreover, silencing GRIM-19 in HIV-1 infected cells reduced apoptosis, indicating its involvement in HIV-1 induced T-cell death.