Foreign gene expression and induction of antibody response by recombinant fowl adenovirus-9-based vectors with exogenous promoters.

Fowl adenoviruses (FAdVs) are promising vectors for poultry vaccines and gene therapy. The commonly used human cytomegalovirus (CMV) promoter in recombinant FAdV-9 viruses (recFAdV-9s) leads to foreign gene expression that elicits an antibody response. Despite its strength, studies have shown that the CMV promoter is prone to silencing by methylation hampering the in vivo application of vectors containing this promoter. Therefore, to improve our virus vector system and circumvent potential limitations of silencing, we engineered recFAdV-9s with foreign gene expression cassettes carrying the CMV enhancer/chicken ß-actin (CAG) or the human elongation factor 1 alpha (EF1α) promoters with or without the posttranscriptional regulatory element of woodchuck hepatitis virus (WPRE). Chicken hepatoma cells (CH-SAH) infected with recFAdV-9s carrying either CAG or EF1α promoters expressed higher levels of foreign protein than those infected with recFAdV-9 carrying the CMV promoter. Incorporation of the WPRE element rendered lower gene expression regardless of promoter type. Surprisingly, most chickens inoculated with recFAdV-9 containing the CMV promoter had the highest antibody response to foreign protein compared to other promoters. Our findings suggest the importance of promoter selection for candidate virus vector vaccines based on humoral immune response rather than foreign protein expression levels in vitro.

Molecular characterization of pathogenic and nonpathogenic fowl aviadenovirus serotype 11 isolates.

Fowl aviadenoviruses, many of which are of importance in veterinary medicine, are classified into 5 species. In this study, a pathogenic isolate and a nonpathogenic isolate of fowl aviadenovirus serotype 11 (FAdV-11) of species Fowl aviadenovirus D were characterized. Growth rates were analyzed for the 2 isolates, showing notable differences. The complete genomic sequences of the viruses were fully determined and were analyzed. The genomes of the 2 isolates showed 98.1% sequence identity and revealed 6 nonsynonymous mutations between the Ontario isolates. Two of the 6 mutations were also found in the sequences of recently published pathogenic Chinese fowl aviadenovirus 11 isolates, suggesting potential molecular markers that could be associated with pathogenesis. Deletions were found in the L5 region within the overlapping coding sequences for the 100, 22, and 33 kDa proteins, and these were found in only the nonpathogenic isolates. This molecular pattern was identified in FAdV-9, another nonpathogenic FAdV-D species virus. Furthermore, the tandem repeat regions varied dramatically; the pathogenic isolates contained a reduced number of tandem repeats compared with the nonpathogenic isolates. Lastly, a protein produced early in infection was analyzed using bioinformatics to determine its role in disease. This study highlights several candidate molecular determinants of avian adenovirus genomes related to pathogenicity.

Characterization of a novel adenovirus isolated from a skunk.

Adenoviruses are a ubiquitous group of viruses that have been found in a wide range of hosts. A novel adenovirus from a skunk suffering from acute hepatitis was isolated and its DNA genome sequenced. The analysis revealed this virus to be a new member of the genus Mastadenovirus, with a genome of 31,848 bp in length containing 30 genes predicted to encode proteins, and with a G+C content of 49.0%. Global genomic organization indicated SkAdV-1 was similar in organization to bat and canine adenoviruses, and phylogenetic comparison suggested these viruses shared a common ancestor. SkAdV-1 demonstrated an ability to replicate in several mammalian liver cell lines suggesting a potential tropism for this virus.