Antibody Response and Virus Shedding of Chickens Inoculated with Left End Deleted Fowl Adenovirus 9-Based Recombinant Viruses

The nonpathogenic fowl adenoviruses (FAdVs) are suitable recombinant virus vectors. Two different replication-competent FAdV-9-based recombinant viruses carrying the enhanced green fluorescent protein (EGFP) gene within a nonessential DNA sequence at the left end genomic region were tested in chickens to study the antibody response by enzyme-linked immunosorbent assay to both the foreign proteins, EGFP and FAdV-9, and virus shedding through the feces. All inoculations were done intramuscularly: groups 1 and 2 with the recombinant viruses and group 3 with the wild-type FAdV-9 virus. Group 4 was mock inoculated. Sentinel birds also were included in groups 1-3 to study virus transmission. Boosting inoculations were done in all groups at 2, 3, and 4 wk after the first inoculation. Antibodies to EGFP were detected at 3-7 wk postinoculation in groups 1 and 2 only. Antibody response to FAdV-9 in groups 1-3 did not differ significantly (P > 0.06). Virus was not detected in the feces of chickens in groups 1 and 2, including the sentinel birds, but virus was present in the feces of chickens in group 3, including the sentinel birds. These results further supported our previous findings regarding the suitability of the nonessential region at the left end of the viral genome as an insertion site for foreign genes and its importance in in vivo replication. In this work, we demonstrated the potential of FAdV-9-based recombinant viruses as vaccines for poultry.