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Using Reverse Genetics to Manipulate the NSs Gene of the Rift Valley Fever Virus MP-12 Strain to Improve Vaccine Safety and Efficacy
Published on: November 1, 2011
Functional analysis of Rift Valley fever virus NSs encoding a partial truncation
Jennifer A Head1, Birte Kalveram, Tetsuro Ikegami
1Department of Microbiology and Immunology, The University of Texas Medical Branch, Galveston, TX, USA.
Plos One
|October 3, 2012
Summary
Truncating Rift Valley fever virus NSs protein domains unexpectedly abolished its functions, including inhibiting interferon-beta mRNA synthesis and degrading protein kinase R. Truncated NSs lacked stability and dominant-negative effects, indicating conformational integrity is crucial for NSs function.
Area of Science:
- Virology
- Molecular Biology
- Immunology
Background:
- Rift Valley fever virus (RVFV) is a priority pathogen causing severe disease in humans and animals.
- The NSs protein of RVFV is a key virulence factor, inhibiting host transcription and promoting protein kinase R (PKR) degradation.
- Currently, no therapeutics exist for RVF, highlighting the need to understand RVFV pathogenesis.
Purpose of the Study:
- To investigate the role of specific domains within the RVFV NSs protein in its function.
- To determine if truncating these domains can abolish NSs virulence functions.
- To assess the potential for dominant-negative effects by co-expressing truncated NSs with intact NSs.
Main Methods:
- Truncation mutants of the RVFV NSs protein were generated.
- The functions of these truncated NSs proteins, including inhibition of interferon-beta (IFN-β) mRNA synthesis and PKR degradation, were assessed.
- Cellular stability and nuclear localization of truncated NSs were evaluated.
- Dominant-negative effects were tested by co-expressing truncated NSs with intact NSs in RVFV-infected cells.
- Protein-protein interactions between truncated and intact NSs were analyzed.
Main Results:
- All tested RVFV NSs truncations (aa. 6-265) failed to inhibit IFN-β mRNA synthesis or degrade PKR.
- Truncated NSs proteins exhibited reduced stability and impaired nuclear localization.
- Co-expression of truncated NSs did not produce significant dominant-negative effects on NSs-mediated suppression or PKR degradation.
- Truncated NSs, except for intact NSs, did not interact with RVFV NSs.
Conclusions:
- Conformational integrity of the RVFV NSs protein is essential for its stability, cellular localization, and biological functions.
- Truncation of specific domains abolishes NSs virulence functions.
- The dominant-negative strategy using truncated NSs is not effective for attenuating RVFV pathogenicity.
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