Journal of Virology, March 2006, p. 2587-2588, Vol. 80, No. 6
0022-538X/06/$08.00+0 doi:10.1128/JVI.80.6.2587-2588.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
| SPOTLIGHT |
Articles of Significant Interest Selected from This Issue by the Editors
A Cell-Cell Fusion Assay for Ebola Virus GlycoproteinsEbola virus enters cells by an acid-dependent pathway. However, unlike other acid-activated viral fusion proteins, expression of the Ebola virus glycoproteins on the cell surface does not lead to cell-cell fusion after acid treatment. Bär et al. (p. 2815-2822) show that cells expressing Ebola virus glycoproteins mediate fusion if acid treatment occurs before but not after mixing with target cells. This new approach will allow functional studies of Ebola virus glycoproteins without the use of replication-competent virus. Moreover, this work suggests that an Ebola virus entry mediator, perhaps a viral receptor, is acid sensitive.
Picornaviruses Exploit Different Proteins To Permeabilize the Nuclear Envelope
Enteroviruses induce leakiness of the nuclear envelope by the viral protease 2Apro-dependent degradation of certain nucleoporins and the resultant "opening" of nuclear pores. Lidsky et al. (p. 2705-2717) show that during similar permeabilization of the nuclear envelope caused by 2Apro-lacking cardioviruses, the nuclear pores also are damaged, but the nucleoporins, which are cleaved upon poliovirus infection, are not. Permeabilization is triggered by the enzymatically inactive viral leader protein. Thus, members of two picornavirus genera, enteroviruses and cardioviruses, similarly alter intracellular trafficking but achieve this effect by strikingly different mechanisms.
A Host Protein Is a Suppressor of Viral RNA Recombination
RNA recombination can facilitate RNA virus interspecies transmission, escape from natural resistance mechanisms, and the development of antiviral drug resistance. To examine the role of host proteins in viral RNA recombination, Cheng et al. (p. 2631-2640) identified recombination intermediates in xrn1
yeast cells, which support efficient recombination of a tombusvirus replicon RNA. The authors propose that Xrn1p 5'-3' exoribonuclease can suppress tombusvirus RNA recombination by rapidly removing 5'-truncated viral RNAs, which are the substrates of recombination. This report establishes that host-mediated viral RNA turnover plays a major role in RNA virus recombination and evolution.
NSP4 Interaction with Caveolin-1 Suggests a Novel Function for the Viral Enterotoxin
Rotavirus NSP4, the first described viral enterotoxin, is a multifunctional glycoprotein with established roles in viral pathogenesis, transcription, and morphogenesis. NSP4 and the enterotoxic peptide, NSP4114-135, preferentially interact with caveola-like model membranes. Parr et al. (p. 2842-2854) now show both colocalization of NSP4 and caveolin-1 at multiple sites in the cell and a direct protein-protein interaction of NSP4 residues 114 to 135 and caveolin-1. These data indicate that endogenous NPS4 interacts with caveola membranes, which may influence NSP4 intracellular trafficking and signaling events.
Anti-Simian Immunodeficiency Virus (SIV) T-Cell Responses Are Not Attenuated in a Natural Host of SIV with Nonpathogenic Infection
Sooty mangabeys, a natural host for simian immunodeficiency virus (SIV), usually do not develop AIDS and show no evidence of increased immune activation or AIDS-related immunopathology despite sustained SIV viremia. Wang et al. (p. 2771-2783) show that the cellular immune response to natural SIV infection in sooty mangabeys consists of Th1-type effector memory, SIV-specific, cytotoxic CD8+ T cells that secrete IFN-
, TNF-
, and MIP1ß comparable in magnitude to that of SIV-infected rhesus macaques. These data suggest that virus-specific CD8+ T lymphocytes do not contribute to immunopathology in AIDS. Furthermore, immune attenuation does not appear to be required for maintaining nonpathogenic lentivirus infection in its natural host.
Hematogenous Vertical Transmission of Herpes Simplex Virus Type 1
Herpes simplex virus type 1 (HSV-1) causes severe disease and death in newborns. However, the mechanisms underlying maternal-fetal transmission of HSV-1 are not clear. Using a mouse model of HSV-1 disease, Burgos et al. (p. 2823-2831) show that HSV-1 is transmitted from latently infected dams to their offspring. Moreover, examination of embryos confirmed that transmission occurred in utero. HSV-1 was detected in the hippocampal neurons, and immunofluorescence studies showed that these viruses can reactivate after hyperthermia. Finally, prenatal antiviral treatment reduced or eliminated HSV-1 in the offspring. This study represents the first demonstration of vertical transmission of HSV-1 to the fetal nervous system.
Journal of Virology, March 2006, p. 2587-2588, Vol. 80, No. 6
0022-538X/06/$08.00+0 doi:10.1128/JVI.80.6.2587-2588.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
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