title: Glycoproteins required for entry are not necessary for egress of pseudorabies virus.
abstract: In the current perception of the herpesvirus replication cycle, two fusion processes are thought to occur during entry and nuclear egress. For penetration, glycoproteins gB and gH/gL have been shown to be essential, whereas a possible role of these glycoproteins in nuclear egress remains unclear. Viral envelope glycoproteins have been detected by immunolabeling in the nuclear membrane as well as in primary enveloped particles in several herpesviruses, indicating that they might be involved in the fusion process. Moreover, a herpes simplex virus type 1 mutant simultaneously lacking gB and gH was described to be deficient in nuclear egress (A. Farnsworth, T. W. Wisner, M. Webb, R. Roller, G. Cohen, R. Eisenberg, and D. C. Johnson, Proc. Natl. Acad. Sci. USA 104:10187-10192, 2007). To analyze the situation in the related alphaherpesvirus pseudorabies virus (PrV), mutants carrying single and double deletions of glycoproteins gB, gD, gH, and gL were constructed and characterized. We show here that the simultaneous deletion of gB and gD, gB and gH, gD and gH, or gH and gL has no detectable effect on PrV egress, implying that none of these glycoproteins either singly or in the tested combinations is required for nuclear egress. In addition, immunolabeling studies using different mono- or polyclonal sera raised against various PrV glycoproteins did not reveal the presence of viral glycoproteins in the inner nuclear membrane or in primary virions. Thus, our data strongly suggest that different fusion mechanisms are active during virus entry and egress.
authors.affiliation: Institute of Molecular Biology, Friedrich-Loeffler-Institut, Südufer 10, 17493 Greifswald-Insel Riems, Germany.
authors.forename: Barbara
authors.initials: B
authors.lastname: Klupp
authors.forename: Jan
authors.initials: J
authors.lastname: Altenschmidt
authors.forename: Harald
authors.initials: H
authors.lastname: Granzow
authors.forename: Walter
authors.initials: W
authors.lastname: Fuchs
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Mettenleiter
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D005455:Fluorescent Antibody Technique; D011558:Herpesvirus 1, Suid / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D008854:Microscopy, Electron; D009154:Mutation / Q000235:genetics; D011817:Rabbits; D034421:Sus scrofa; D014760:Viral Fusion Proteins / Q000235:genetics / Q000378:metabolism*; D053586:Virus Internalization
chemical_list: D017931:DNA Primers; D014760:Viral Fusion Proteins