Researchers at The Pirbright Institute have developed a new vaccine that generates a faster and stronger immune response in chickens against the H9N2 bird flu strain, compared to the current industry standard inactivated virus vaccine.

Many poultry flu vaccines protect birds from serious illness and death, but do not prevent them from transmitting the virus, enabling the continued spread of disease through flocks. Pirbright scientists have used a new vaccination technique to enhance immune responses in birds and reduce the amount of virus shed into the environment.

The results published in npj Vaccines revealed that the vaccine was both fast acting and effective. Birds produced antibody responses as early as six days after vaccination and they shed significantly less flu virus when challenged with a natural flu strain, indicating the birds would be less likely to spread infection. High levels of protective antibodies were produced even when birds were given a reduced dose.

The vaccine works by tagging flu virus proteins with a marker that makes it easier for immune cells, called Antigen Presenting Cells (APCs), to efficiently capture and process the tagged proteins for triggering an immune response. The team specifically tagged the flu virus haemagglutinin (HA) protein and directed it to target CD83, a protein on the chicken APCs, showing for the first time that this can be used as an effective vaccine.

As well as providing enhanced protection, this vaccine will be easier and less costly to manufacture. The tagged flu virus HA protein can be produced in a laboratory culture of insect cells instead of using eggs to grow live vaccine viruses. This would enable the poultry industry to reduce its reliance on chicken eggs for vaccine production, increasing the availability of eggs for use as a food source.

The use of laboratory cells instead of eggs also highlights how Pirbright scientists actively develop animal health solutions that apply the principles of the 3Rs (Reduce, Refine, Replace) in animal research.

As the new vaccine does not contain live flu virus, biosafety risks are reduced, and no specialist high containment facilities would be required for production. These qualities make the vaccine very attractive for large scale manufacture. The Pirbright team is currently investigating the vaccine’s potential for commercial production and use in the field.

Professor Munir Iqbal, Head of Pirbright’s Avian Influenza Virus group, said: “By targeting HA to chicken immune cells, we have generated a powerful addition to the armoury of poultry vaccines. Our improved vaccine could help prevent the spread of flu amongst vaccinated birds, which is essential for protecting poultry welfare, increasing food production, and reducing the risk of avian influenza spreading to humans.”