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Isolation of Fidelity Variants of RNA Viruses and Characterization of Virus Mutation Frequency
18:10

Isolation of Fidelity Variants of RNA Viruses and Characterization of Virus Mutation Frequency

Published on: June 16, 2011

A single polymerase (L) mutation in avian metapneumovirus increased virulence and partially maintained virus

Paul A Brown1, Caterina Lupini, Elena Catelli

  • 1Department of Infection Biology, University of Liverpool, Leahurst Campus, Neston, Cheshire CH64 7TE, UK.

The Journal of General Virology
|November 5, 2010
PubMed

Insights

Avian metapneumovirus virulence was studied by adding mutations from a virulent strain to a live vaccine. Three specific L gene mutations restored full virulence in turkeys.

Area of Science:

  • Virology
  • Avian Pathogen Research

Background:

  • A virulent avian metapneumovirus (farm isolate Italy 309/04) was previously identified as originating from a live vaccine strain.
  • Understanding the genetic basis of virulence reversion is crucial for vaccine safety and efficacy.

Purpose of the Study:

  • To investigate the specific nucleotide mutations responsible for the reversion to virulence in avian metapneumovirus.
  • To determine the contribution of individual mutations to the overall virulence of the virus.

Main Methods:

  • Reverse genetics was employed to introduce five specific nucleotide mutations from the virulent Italy 309/04 strain into the live vaccine strain genome.
  • Recombinant viruses were generated and their virulence assessed by infecting one-day-old turkeys.

Main Results:

  • Combined mutations in the matrix gene did not restore virulence compared to the vaccine strain.
  • Combined mutations in the L gene significantly increased disease severity, matching the virulent Italy 309/04 isolate.
  • A single L gene mutation (Asn to Asp substitution) was identified as the primary driver of increased virulence.
  • The virulent mutant exhibited enhanced viability at turkey core body temperatures compared to the vaccine strain.

Conclusions:

  • Specific mutations within the L gene are critical for the reversion of avian metapneumovirus to high virulence.
  • The identified mutation may enhance viral replication in host tissues at higher temperatures, contributing to pathogenesis.
  • Findings have implications for live attenuated vaccine design and safety monitoring.

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