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Improvement of the H5N1 influenza virus vaccine strain to decrease the pathogenicity in chicken embryos.

Norikazu Isoda¹, Yoshihiro Sakoda, Masatoshi Okamatsu

¹Laboratory of Microbiology, Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Kita-18 Nishi-9, Kita-ku, Sapporo, Hokkaido, Japan.

Archives of Virology

|January 5, 2011

Summary

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Avian influenza virus strain Vac-1 (H5N1) showed pathogenicity in chicken embryos. Reassortant viruses identified the PA protein as key to pathogenicity, leading to a potential improved vaccine candidate.

Area of Science:

Virology
Immunology
Molecular Biology

Background:

The avian influenza vaccine strain A/duck/Hokkaido/Vac-1/2004 (H5N1), designated Vac-1, exhibits pathogenicity in chicken embryos (CEs).
Reducing the pathogenicity of Vac-1 is crucial for developing safer and more effective influenza vaccines.

Purpose of the Study:

To decrease the pathogenicity of the Vac-1 (H5N1) strain in chicken embryos.
To identify the viral components responsible for Vac-1's pathogenicity.
To generate and evaluate reassortant viruses as potential vaccine candidates.

Main Methods:

Generation of reassortant viruses between Vac-1 (H5N1) and A/Puerto Rico/8/1934 (H1N1) (PR8).
Comparison of pathogenicity and growth potential of reassortant viruses in chicken embryos.

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Assessment of hemagglutinin (HA) titers in allantoic fluids.

Main Results:

The PB1 or PA protein was identified as responsible for Vac-1's pathogenicity in CEs.
Recombinant H5N1 viruses with reduced pathogenicity maintained equivalent HA titers compared to the original Vac-1.
The reassortant virus rg-PR8-PA/Vac-1 (H5N1), with a modified PA gene, showed comparable HA titers to Vac-1.

Conclusions:

The PA gene segment plays a significant role in the pathogenicity of the H5N1 Vac-1 strain in chicken embryos.
The rg-PR8-PA/Vac-1 (H5N1) reassortant virus is a promising candidate for an improved avian influenza vaccine due to its reduced pathogenicity and maintained viral yield.