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Single amino acid codon changes detected in louping ill virus antibody-resistant mutants with reduced neurovirulence

W R Jiang1, A Lowe, S Higgs

  • 1NERC Institute of Virology and Environmental Microbiology, Oxford, U.K.

The Journal of General Virology
|May 1, 1993
PubMed

Insights

Seven louping ill virus mutants were created. Critical changes in the envelope glycoprotein reduced virus neurovirulence and immune protection, highlighting key sites for virulence.

Area of Science:

  • Virology
  • Immunology
  • Molecular Biology

Background:

  • Louping ill virus (LIV) is a tick-borne flavivirus with significant neurovirulence.
  • Understanding the molecular basis of LIV virulence is crucial for developing effective countermeasures.
  • Envelope glycoproteins play a key role in flavivirus entry and immune evasion.

Purpose of the Study:

  • To generate and characterize LIV mutants with altered properties using a neutralizing monoclonal antibody.
  • To investigate the role of specific envelope glycoprotein regions in LIV neurovirulence and immunogenicity.
  • To identify critical amino acid substitutions affecting viral virulence.

Main Methods:

  • Generation of seven LIV mutants using a neutralizing monoclonal antibody.
  • Assessment of viral neutralization, antibody binding, and immunofluorescence microscopy.
  • Determination of mouse neurovirulence and protective immune responses against tick-borne encephalitis virus (TBEV).
  • Nucleotide and amino acid sequencing of the LIV envelope glycoprotein gene.

Main Results:

  • Mutants exhibited resistance to antibody neutralization and failed to bind the specific monoclonal antibody.
  • Four mutants displayed reduced mouse neurovirulence; two induced inadequate protective immunity against TBEV.
  • Mutants with lowest virulence showed poor or absent haemagglutinating activity.
  • Single amino acid substitutions (positions 308-311) were identified in all mutants.
  • Aspartate to asparagine substitution at position 308, a potential glycosylation site, most effectively reduced neurovirulence.

Conclusions:

  • Specific sites within the LIV envelope glycoprotein are critical determinants of viral virulence.
  • Amino acid substitutions, particularly at position 308, significantly impact neurovirulence and immunogenicity.
  • Targeting these critical sites offers potential strategies for developing attenuated vaccines or antiviral therapies.

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