An improved poultry influenza vaccine has been developed by researchers from The Pirbright Institute. The potential vaccine triggers a rapid immune response which protects chickens against signs of disease and reduces the level of virus that they could pass on, a key element to halting the spread of bird flu through flocks. The vaccine would also be easier and less costly to produce than the traditional flu vaccines made in chicken eggs.
Many poultry flu vaccines protect birds from serious illness and death, but do not prevent them from transmitting the virus. In recent years, new methods have been developed to enhance the immune responses that vaccines produce and reduce the amount of virus shed by birds into the environment.
One of these techniques involves tagging flu virus proteins with a marker that makes them easier for Antigen Presenting Cells (APCs) to capture. These immune cells can efficiently process the tagged proteins resulting in robust and long-lasting antiviral responses in chickens.
For the first time, researchers at Pirbright have shown that tagging the flu virus haemagglutinin (HA) protein and directing it to target a specific protein on the chicken APCs, called CD83, generates faster and stronger immune responses against the H9N2 bird flu strain compared to the current industry standard inactivated virus vaccine.
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.
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.
“By targeting HA to chicken immune cells, we have generated a powerful addition to the armory of poultry vaccines,” said Professor Munir Iqbal, head of Pirbright’s Avian Influenza Virus group. 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.”