Folate receptor-alpha is a cofactor for cellular entry by Marburg and Ebola viruses

Targeted transduction patterns in the mouse brain by lentivirus vectors pseudotyped with VSV, Ebola, Mokola, LCMV, or MuLV envelope proteins

Lentiviral vectors have proven to be promising tools for transduction of central nervous system (CNS) cells in vivo and in vitro. In this study, CNS transduction patterns of lentiviral vectors pseudotyped with envelope glycoproteins from Ebola virus, murine leukemia virus (MuLV), lymphocytic choriomeningitis virus (LCMV), or the rabies-related Mokola virus were compared to a vector pseudotyped with the vesicular stomatitis virus glycoprotein (VSV-G). Mokola-, LCMV-, and VSV-G-pseudotyped vectors transduced similar populations, including striatum, thalamus, and white matter. Mokola-pseudotyped vectors were the most efficient of the three. MuLV-pseudotyped lentivirus efficiently transduced striatum and hippocampal dentate gyrus. In contrast, no transduction resulted from injection of Ebola-pseudotyped virus in the CNS. The same pattern was observed in vitro with primary cultured oligodendrocytes. LCMV, MuLV, and Ebola pseudotypes were the most stable. These results demonstrate that targeted transduction in the CNS can be achieved using specific envelope glycoproteins to pseudotype lentiviral vectors, and support the use of Mokola-pseudotyped and MuLV-pseudotyped lentiviral vectors as efficient and stable alternatives to VSV-G-pseudotyped vectors for experiments in the mouse CNS.

GPI-anchored proteins are delivered to recycling endosomes via a distinct cdc42-regulated, clathrin-independent pinocytic pathway

Endocytosis of cell-surface proteins via specific pathways is critical for their function. We show that multiple glycosylphosphatidylinositol-anchored proteins (GPI-APs) are endocytosed to the recycling endosomal compartment but not to the Golgi via a nonclathrin, noncaveolae mediated pathway. GPI anchoring is a positive signal for internalization into rab5-independent tubular-vesicular endosomes also responsible for a major fraction of fluid-phase uptake; molecules merely lacking cytoplasmic extensions are not included. Unlike the internalization of detergent-resistant membrane (DRM)-associated interleukin 2 receptor, endocytosis of DRM-associated GPI-APs is unaffected by inhibition of RhoA or dynamin 2 activity. Inhibition of Rho family GTPase cdc42, but not Rac1, reduces fluid-phase uptake and redistributes GPI-APs to the clathrin-mediated pathway. These results describe a distinct constitutive pinocytic pathway, specifically regulated by cdc42.

Lipid raft microdomains: a gateway for compartmentalized trafficking of Ebola and Marburg viruses

Spatiotemporal aspects of filovirus entry and release are poorly understood. Lipid rafts act as functional platforms for multiple cellular signaling and trafficking processes. Here, we report the compartmentalization of Ebola and Marburg viral proteins within lipid rafts during viral assembly and budding. Filoviruses released from infected cells incorporated raft-associated molecules, suggesting that viral exit occurs at the rafts. Ectopic expression of Ebola matrix protein and glycoprotein supported raft-dependent release of filamentous, virus-like particles (VLPs), strikingly similar to live virus as revealed by electron microscopy. Our findings also revealed that the entry of filoviruses requires functional rafts, identifying rafts as the site of virus attack. The identification of rafts as the gateway for the entry and exit of filoviruses and raft-dependent generation of VLPs have important implications for development of therapeutics and vaccination strategies against infections with Ebola and Marburg viruses.

The pathogenesis of Ebola hemorrhagic fever

Ebola virus causes lethal hemorrhagic disease in humans, yet there are still no satisfactory biological explanations to account for its extreme virulence. This review focuses on recent findings relevant to understanding the pathogenesis of Ebola virus infection and developing vaccines and effective therapy. The available data suggest that the envelope glycoprotein and the interaction of some viral proteins with the immune system are likely to play important roles in the extraordinary pathogenicity of this virus. There are also indications that genetically engineered vaccines, including plasmid DNA and viral vectors expressing Ebola virus proteins, and passive transfer of neutralizing antibodies could be feasible options for the control of Ebola virus-associated disease.