The Cytoplasmic Tail of Ovine Herpesvirus 2 Glycoprotein B Affects Cell Surface Expression and Is Required for Membrane Fusion

TL;DR

This study investigates how a specific protein from a deadly animal virus affects cell fusion, which is important for developing vaccines.

Contribution

The study identifies the role of the cytoplasmic tail of OvHV-2 glycoprotein B in cell fusion and proposes a mutant version for improved assays.

Findings

The cytoplasmic tail of OvHV-2 gB is essential for cell–cell membrane fusion.

A truncated gB mutant (gB847) shows increased surface expression and fusion activity.

gB847 can replace wild-type gB in a more robust fusion assay.

Abstract

Ovine herpesvirus 2 (OvHV-2) causes the fatal veterinary disease malignant catarrhal fever (MCF). Fusion is an essential step in the host cell entry of enveloped viruses and is an important target for vaccine development. OvHV-2 cannot be propagated in vitro, so a robust virus-free cell–cell membrane fusion assay is necessary to elucidate its entry mechanism. OvHV-2 cell–cell fusion requires three conserved herpesviral envelope glycoproteins: gB, gH, and gL. OvHV-2 fusion activity is detectable but low. We hypothesize that enhancing the cell surface expression of gB, which is the core herpesviral fusogen, will increase cell–cell fusion. We generated C-terminal truncation mutants of gB and determined their cell surface expression, subcellular distribution, and fusion activity. Two mutants, including one that lacked the entire cytoplasmic tail domain, failed to function in the cell–cell fusion assay, despite wild-type levels of surface expression. This suggests that the OvHV-2 gB cytoplasmic tail is critical for fusion. A gB mutant truncated at amino acid 847 showed increased surface expression and fusion relative to the wild type. This suggests that the robust fusion activity of gB847 is the result of increased surface expression. gB847 may be used in place of wild-type gB in an improved, more robust OvHV-2 fusion assay.

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