Pathogenicity and genome changes in QX-like infectious bronchitis virus during continuous passaging in embryonated...

Area of Science:

• Veterinary Virology
• Poultry Disease Research
• Vaccine Development

Background:

• Infectious bronchitis (IB) significantly impacts the global poultry industry.
• Live attenuated vaccines are crucial for IB prevention, often produced via serial passaging in embryonated eggs.

Purpose of the Study:

• To evaluate the pathogenicity of a QX-like infectious bronchitis virus (IBV) strain (SZ) after extensive passaging in chicken embryos.
• To understand the attenuation process and genomic changes of IBV during serial passaging.

Main Methods:

• Continuous passaging of the SZ isolate of IBV in chicken embryos for 250 generations.
• Assessment of pathogenicity through clinical signs, gross lesions, viral load, tissue tropism, weight gain, and tracheal ciliary activity.
• Whole-genome sequencing to identify genomic variations.

Main Results:

• Increased passaging led to a significant decrease in viral pathogenicity and the ability to infect multiple organs.
• The attenuated SZ strain showed reduced virulence compared to earlier passages.
• Twenty-three genomic variations were identified in the passaged SZ strain.

Conclusions:

• Serial passaging in chicken embryos effectively attenuates QX-like IBV (SZ strain).
• The study offers valuable data for developing novel IBV vaccines.
• Findings contribute to understanding IBV attenuation mechanisms.