Genetically Modified H3N1 Reduces Virulence of Avian Influenza

Researchers from the National Veterinary Research Institute, the University of Edinburgh, and partner institutions have developed a genetically modified (GM) strain of the H3N1 (mH3N1) avian influenza virus to understand how specific genetic changes affect disease severity in chickens. The modified virus was designed to weaken key mechanisms linked to viral spread and tissue damage and was compared with a wild-type H3N1 (wH3N1) strain associated with a disease outbreak in Belgium.

The results showed that adult hens exposed to wH3N1 experienced severe effects, including a complete halt in egg production, widespread viral replication, and tissue damage in the reproductive tract, brain, and kidneys. In contrast, hens infected with the mH3N1 strain showed only mild and temporary drops in egg production, along with minimal viral presence in tissues. No mortality was recorded in either group, and younger chickens developed only subclinical infections.

The findings show that targeted genetic modification can significantly reduce the virulence of avian influenza viruses. The study points to the loss of a specific neuraminidase (NA) glycosylation site linked to plasminogen binding and haemagglutinin (HA) cleavage as a key factor in weakening the virus. Researchers say this method could improve risk assessment, detection, and avian influenza control strategies in poultry.

For more information, read the abstract from Avian Pathology.