Whole yeast expressing recombinant fiber 2 protein vaccine candidate protects chicken against fowl adenovirus serotype 4 infection

Abstract

Fowl adenoviruses (FAdVs) are prevalent infectious agents in a variety of avian species including chickens worldwide. Among several serotypes, fowl adenovirus serotype 4 (FAdV-4) is known to cause mass economic damages to chicken farms in Korea as a pathogen for the hepatitis-hydropericardium syndrome (HHS). The encoding portions of hexon and fiber genes of FAdV-4 field strain ADL15 0401 were fully sequenced and three constructs, Hexon-L1-His and two constructs of fiber genes Fiber-1-His and Fiber-2-His were ligated with the pYEGa-HIR525α which was optimized for producing complex proteins in Saccharomyces cerevisiae yeast systems. The yeast cell containing these recombinant proteins were inoculated in specific pathogen-free (SPF) chickens. Antibodies against FAdVs were identified from all immunized chicken groups by commercial ELISA as early as 1 week post inoculation and better virus neutralization in Fiber-2 group with 2 logs neutralizing ability. Finally, the protective efficacy result showed the full protection after challenge with virulent FadV-4 virus in the SPF chicken from Fiber-1 and Fiber-2 groups. These results suggest that the whole yeast expressing recombinant fiber-2 protein can be a candidate for vaccines against the FAdV-4 infection.