The mortality rate decreased significantly compared to the control group from 76% to 40%. Virus image: Thomas Splettstoesser.

Virus a candidate for furunculosis vaccine

Scientists in China have created a recombinant adenovirus capable of inducing immunity against Aeromonas salmonicida, the bacteria that causes furunculosis.

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The recombinant adenovirus can be stably transferred between the cells, stimulating an immune response in the fish, because its genome is generally not integrated into the infected cell.

However, when used in vaccines, its immunological effects are closely related to the associated protective antigens.

Protective antigen

Previous studies have found that the A-layer protein of A. salmonicida is an important protective antigen against infection. The loss of this protein leads to losses in bacterial virulence, making it a candidate for recombinant vaccines.

In a newly-published study, scientists from the College of Veterinary Medicine at Gansu Agricultural University in Lanzhou designed a recombinant adenovirus carrying the “Vapa” gene that encodes the protein of layer A, with the aim of granting immunity to rainbow trout against A. salmonicida when administered as a vaccine.

Mortality almost halved

After vaccinating the fish and infecting them with A. salmonicida, the researchers showed that after 28 days the mortality rate of the vaccinated fish was 40% compared to 76% for the unvaccinated control group.

“This also led to an increase in specific antibodies in peripheral serum. In addition, the levels of IgM and IgT in the anterior kidney and the hindgut increased to varying degrees,” the authors noted with respect to serological evaluations performed on fish.

“In conclusion, our research provides a candidate vaccine for the prevention of A. salmonicida A450 infection in rainbow trout and lays the foundation for future research on adaptive immune mechanisms associated with rainbow trout antibodies.”

Read the abstract of the article entitled A recombinant adenovirus targeting typical Aeromonas salmonicida induces an antibody-mediated adaptive immune response after immunization of rainbow trout here .