Efficient cross-protection against serotype 4/8a fowl adenoviruses (FAdVs): recombinant FAdV-4 with FAdV-8a Fiber

Recently, the infection of fowl adenoviruses (FAdVs) in chicken flocks has caused huge economic losses to the poultry industry in China. Although immunization with Fiber protein can provide autogenous protection of FAdVs, no commercial multivalent vaccines are available for the prevention and control of FAdVs. In this study, a novel recombinant virus FAdV4-F/8a-rF2 expressing the Fiber of FAdV-8a was generated through CRISPR-Cas9 and Cre-LoxP system by using the template virus FA4-EGFP. FAdV4-F/8a-rF2 not only exhibited a similar replication capacity to the wild-type FAdV-4 in Leghorn male hepatoma (LMH) cells but was also highly attenuated to specific pathogen free (SPF) chickens. Moreover, the inoculation of FAdV4-F/8a-rF2 could induce high neutralizing antibodies and provide full protection against both FAdV-4 and FAdV-8a. All these data demonstrate that the recombinant virus FAdV4-F/8a-rF2 developed here can be used as an attenuated bivalent vaccine candidate for the prevention and control of both FAdV-4 and FAdV-8a.IMPORTANCEEpidemiological data reveal that FAdV-4 and FAdV-8a are the dominant serotypes of FAdVs in the poultry industry in China. Although three commercial inactivated vaccines against FAdV-4 have been licensed in China, the bivalent vaccine against both FAdV-4 and FAdV-8a is not available. Here, we used CRISPR-Cas9 and Cre-LoxP system to generate a recombinant virus FAdV4-F/8a-rF2 expressing the Fiber of FAdV-8a. Notably, FAdV4-F/8a-rF2 was highly attenuated and could provide efficient protection against both FAdV-4 and FAdV-8a in the chicken infection model, highlighting the applaudable application of FAdV4-F/8a-rF2 as a novel live-attenuated bivalent vaccine against the diseases caused by the infection of FAdV-4 and FAdV-8a. Epidemiological data reveal that FAdV-4 and FAdV-8a are the dominant serotypes of FAdVs in the poultry industry in China. Although three commercial inactivated vaccines against FAdV-4 have been licensed in China, the bivalent vaccine against both FAdV-4 and FAdV-8a is not available. Here, we used CRISPR-Cas9 and Cre-LoxP system to generate a recombinant virus FAdV4-F/8a-rF2 expressing the Fiber of FAdV-8a. Notably, FAdV4-F/8a-rF2 was highly attenuated and could provide efficient protection against both FAdV-4 and FAdV-8a in the chicken infection model, highlighting the applaudable application of FAdV4-F/8a-rF2 as a novel live-attenuated bivalent vaccine against the diseases caused by the infection of FAdV-4 and FAdV-8a.