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Virology journal2014; 11; 159; doi: 10.1186/1743-422X-11-159

An efficient genome sequencing method for equine influenza [H3N8] virus reveals a new polymorphism in the PA-X protein.

Abstract: H3N8 equine influenza virus (EIV) has caused disease outbreaks in horses across the world since its first isolation in 1963. However, unlike human, swine and avian influenza, there is relatively little sequence data available for this virus. The majority of published sequences are for the segment encoding haemagglutinin (HA), one of the two surface glycoproteins, making it difficult to study the evolution of the other gene segments and determine the level of reassortment occurring between sub-lineages. Methods: To facilitate the generation of full genome sequences for EIV, we developed a simple, cost-effective and efficient method. M13-tagged primers were used to amplify short, overlapping RT-PCR products, which were then sequenced using Sanger dideoxynucleotide sequencing technology. We also modified a previously published method, developed for human H3N2 and avian H5N1 influenza viruses, which was based on the ligation of viral RNA and subsequent amplification by RT-PCR, to sequence the non-coding termini (NCRs). This necessitated the design of novel primers for an N8 neuraminidase segment. Results: Two field isolates were sequenced successfully, A/equine/Lincolnshire/1/07 and A/equine/Richmond/1/07, representative of the Florida sublineage clades 1 and 2 respectively. A total of 26 PCR products varying in length from 400-600 nucleotides allowed full coverage of the coding sequences of the eight segments, with sufficient overlap to allow sequence assembly with no primer-derived sequences. Sequences were also determined for the non-coding regions and revealed cytosine at nucleotide 4 in the polymerase segments. Analysis of EIV genomes sequenced using these methods revealed a novel polymorphism in the PA-X protein in some isolates. Conclusions: These methods can be used to determine the genome sequences of EIV, including the NCRs, from both clade 1 and clade 2 of the Florida sublineage. Full genomes were covered efficiently using fewer PCR products than previously reported methods for influenza A viruses, the techniques used are affordable and the equipment required is available in most research laboratories. The adoption of these methods will hopefully allow for an increase in the number of full genomes available for EIV, leading to improved surveillance and a better understanding of EIV evolution.
Publication Date: 2014-09-02 PubMed ID: 25183201PubMed Central: PMC4161859DOI: 10.1186/1743-422X-11-159Google Scholar: Lookup
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  • Journal Article
  • Research Support
  • Non-U.S. Gov't

Summary

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This research presents an efficient and cost-effective method for genome sequencing of Equine Influenza Virus (EIV), and indicates the discovery of a new polymorphism in the PA-X protein of some virus isolates.

Introduction and Methodology

This study was designed to unravel the full genome sequence of the equine influenza virus (EIV), a rampant disease among horses globally. The researchers note a lack of extensive sequence data for this virus compared to its counterparts in humans, swine, and birds. The newly developed method involves the use of M13-tagged primers to amplify relatively short and overlapping RT-PCR products, which are then analysed using Sanger dideoxynucleotide sequencing technology.

  • The researchers modified an existing method, previously used for human H3N2 and avian H5N1 influenza viruses, to sequence the non-coding parts of the EIV genome; an essential feature in determining the overall action and reproduction patterns of the virus in the host.
  • New primers were created for the N8 neuraminidase segment to expedite genome sequencing.

Results

Two virus samples were successfully sequenced with this method: A/equine/Lincolnshire/1/07 and A/equine/Richmond/1/07. These samples represented clades 1 and 2 of the Florida sub-lineage respectively.

  • By sequencing 26 PCR products varying in length from 400 to 600 nucleotides, the researchers covered the full coding sequences of the eight segments of the virus genome with sufficient overlap for sequence assembly without primer-derived sequences.
  • Sequences of the non-coding regions revealed a cytosine at nucleotide 4 in the polymerase segments.
  • In some isolates, the researchers discovered a novel polymorphism in the PA-X protein, an important find which could potentially inform better strategies for disease control and management.

Conclusion

This research methodology proves a salient tool for genome sequencing of EIV and could potentially be replicated on other virus genomes. The method is both cost-effective and efficient, requiring fewer PCR products than previously reported techniques. Embracing this approach could lead to an increase in the number of full EIV genomes available for study, which in turn might result in an improved understanding of the virus evolution and inform better strategies for disease surveillance and management.

Cite This Article

APA
Rash A, Woodward A, Bryant N, McCauley J, Elton D. (2014). An efficient genome sequencing method for equine influenza [H3N8] virus reveals a new polymorphism in the PA-X protein. Virol J, 11, 159. https://doi.org/10.1186/1743-422X-11-159

Publication

ISSN: 1743-422X
NlmUniqueID: 101231645
Country: England
Language: English
Volume: 11
Pages: 159
PII: 159

Researcher Affiliations

Rash, Adam
  • Animal Health Trust, Lanwades Park, Kentford, Newmarket CB8 7UU, UK. adam.rash@aht.org.uk.
Woodward, Alana
    Bryant, Neil
      McCauley, John
        Elton, Debra

          MeSH Terms

          • Animals
          • DNA, Complementary
          • Genome, Viral
          • Horse Diseases / virology
          • Horses
          • Influenza A Virus, H3N8 Subtype / genetics
          • Orthomyxoviridae Infections / veterinary
          • Orthomyxoviridae Infections / virology
          • Polymerase Chain Reaction
          • Polymorphism, Genetic
          • RNA, Untranslated / genetics
          • RNA, Viral

          Grant Funding

          • MC_U117512723 / Medical Research Council
          • MC_U117585868 / Medical Research Council

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