Experimental selection of virus derivatives with variations in virulence from a single low-pathogenicity H6N1 avian
Ching-Wen Wang1, Ching-Ho Wang
1Department of Veterinary Medicine, National Taiwan University, Taipei 106, Taiwan.
Abstract:
A mixture of viruses with variations in virulence is likely present within a low-pathogenicity avian influenza virus (LPAIV) population. An H6N1 AIV was isolated from a field case showing 3.8% weekly mortality and a 33% egg production drop in Taiwan. The pathologic lesions included proventricular hemorrhage and urate deposition in the kidneys and on visceral organs. From the field isolate, a done (2838N) that caused no lesions or death was obtained using limit dilution in chicken embryos and a done (2838V) that caused renal lesions and death was obtained using contact infection in chicks. Both clones were inoculated intranasally in 4-week-old specific pathogen free (SPF) chickens to test their virulence. Renal urate deposition was found in chickens inoculated with 2838V but not in chickens inoculated with 2838N. In situ hybridization, polymerase chain reaction, and virus isolation were used to confirm the spread of 2838V from the respiratory tract to the renal tissue. We found that contact infection in chickens is a good method to obtain a more virulent done from a heterogeneous virus population.
Insights
This study isolated a low-pathogenicity avian influenza virus (LPAIV) and developed a method to obtain more virulent strains. Contact infection in chickens effectively isolated a pathogenic clone from a mixed virus population.
Area of Science:
- Veterinary Virology
- Avian Pathology
Background:
- Low-pathogenicity avian influenza virus (LPAIV) populations can harbor strains with varying virulence.
- An H6N1 AIV outbreak in Taiwan caused significant mortality and egg production loss.
Purpose of the Study:
- To investigate the virulence of an H6N1 AIV isolate.
- To develop a method for isolating more virulent clones from a heterogeneous LPAIV population.
Main Methods:
- Isolation of H6N1 AIV from a field case.
- Cloning of virus variants using limit dilution in chicken embryos and contact infection in chicks.
- Intranasal inoculation of specific pathogen-free (SPF) chickens with cloned viruses.
- Pathological examination and molecular detection (in situ hybridization, PCR, virus isolation) to assess virulence and tissue tropism.
Main Results:
- Two clones were obtained: 2838N (non-pathogenic) and 2838V (pathogenic).
- Chickens inoculated with 2838V exhibited renal lesions and mortality, unlike those with 2838N.
- Molecular methods confirmed 2838V spread from the respiratory tract to renal tissues.
Conclusions:
- Contact infection in chickens is an effective method for isolating more virulent clones from heterogeneous LPAIV populations.
- The H6N1 AIV isolate demonstrated the potential to generate pathogenic variants with renal tropism.
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