Identification of residues in West Nile virus pre-membrane protein that influence viral particle secretion and virulence
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Published on: December 21, 2019
Y X Setoh1, N A Prow1, J Hobson-Peters1
1Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, 4072, QLD, Australia.
Abstract:
The pre-membrane protein (prM) of West Nile virus (WNV) functions as a chaperone for correct folding of the envelope (E) protein, and prevents premature fusion during virus egress. However, little is known about its role in virulence. To investigate this, we compared the amino acid sequences of prM between a highly virulent North American strain (WNV(NY99)) and a weakly virulent Australian subtype (WNV(KUN)). Five amino acid differences occur in WNV(NY99) compared with WNV(KUN) (I22V, H43Y, L72S, S105A and A156V). When expressed in mammalian cells, recombinant WNV(NY99) prM retained native antigenic structure, and was partially exported to the cell surface. In contrast, WNV(KUN) prM (in the absence of the E protein) failed to express a conserved conformational epitope and was mostly retained at the pre-Golgi stage. Substitutions in residues 22 (Ile to Val) and 72 (Leu to Ser) restored the antigenic structure and cell surface expression of WNV(KUN) prM to the same level as that of WNV(NY99), and enhanced the secretion of WNV(KUN) prME particles when expressed in the presence of E. Introduction of the prM substitutions into a WNV(KUN) infectious clone (FLSDX) enhanced the secretion of infectious particles in Vero cells, and enhanced virulence in mice. These findings highlight the role of prM in viral particle secretion and virulence, and suggest the involvement of the L72S and I22V substitutions in modulating these activities.
Insights
The pre-membrane protein (prM) of West Nile virus (WNV) plays a key role in viral particle secretion and virulence. Specific amino acid changes in prM enhance WNV virulence and infectious particle release.
Area of Science:
- Virology
- Molecular Biology
- Immunology
Background:
- The West Nile virus (WNV) pre-membrane protein (prM) is crucial for the proper folding of the envelope (E) protein and prevents premature fusion during virus release.
- The specific role of WNV prM in viral virulence remains largely uncharacterized.
Purpose of the Study:
- To investigate the role of WNV prM in viral virulence by comparing highly virulent (WNV(NY99)) and weakly virulent (WNV(KUN)) strains.
- To identify specific amino acid differences in prM that contribute to WNV virulence and infectious particle secretion.
Main Methods:
- Comparative amino acid sequence analysis of prM between WNV(NY99) and WNV(KUN) strains.
- Expression of recombinant WNV prM proteins in mammalian cells to assess antigenic structure and cell surface expression.
- Introduction of specific prM mutations into a WNV(KUN) infectious clone and evaluation of viral particle secretion and mouse virulence.
Main Results:
- Five amino acid differences were identified in WNV(NY99) prM compared to WNV(KUN) prM.
- WNV(NY99) prM exhibited native antigenic structure and cell surface export, unlike WNV(KUN) prM which was retained intracellularly.
- Substitutions I22V and L72S in WNV(KUN) prM restored antigenic structure, enhanced cell surface expression, increased WNV prME particle secretion, and significantly increased mouse virulence.
Conclusions:
- The prM protein significantly influences West Nile virus particle secretion and virulence.
- Specific amino acid substitutions, notably I22V and L72S in prM, are critical modulators of WNV infectivity and pathogenicity.
- Understanding prM's role provides insights into WNV pathogenesis and potential therapeutic targets.
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