Comparison of fiber gene sequences of inclusion body hepatitis (IBH) and non-IBH strains of serotype 8 and 11 fowl adenoviruses

Abstract

Fowl adenoviruses (FAdVs) are common in broiler operations, and the most frequently isolated FAdVs belong to serotypes 1, 8, and 11. Serotype 1 viruses are considered nonpathogenic. While some serotype 8 and 11 viruses cause inclusion body hepatitis (IBH), these virus serotypes can also be isolated from non-IBH cases. The fiber protein is one of the major constituents of the adenoviral capsid, involved in virus entry, and it has been implicated in the variation of virulence of FAdVs. The fiber gene sequences of four FAdV-8 and four FAdV-11 isolates from both IBH and non-IBH cases were determined and analyzed for a possible association of the fiber gene sequence in virulence. The fiber protein can be divided into tail, shaft, and head domains comprising some specific features. The conserved "RKRP" sequence motif (aa 17-aa 20) fit the consensus sequence predicted for the nuclear localization signal, while the "VYPF" motif (aa 53-aa 56), involved in the penton base interaction, was also found. Similar to mammalian adenoviruses, 17 pseudo-repeats with an average length of 16 aa were detected in the FAdV-8 fiber shaft region, while 20 pseudo-repeats with an average length of 18 aa were found in FAdV-11 fibers. There was a 144-147 nt difference between the fiber genes of the two FAdV serotypes. In the shaft region, the TLWT motif that marks the beginning of the fiber head domain of the mastadenovirus was not evident among examined FAdVs. The FAdV-11 isolates had 99.1 % aa sequence identity and 99.3 % similarity to each other, and there was no conserved aa substitution within the fibers. The FAdV-8 fiber proteins showed an overall lower, 89 % aa sequence identity and 93.4 % similarity, to each other and 22 nonsynonymous mutations were detected. Virulence markers were not detected in the analyzed fiber gene sequences of the different pathotypes of the two FAdV serotypes.

Pathogenicity and Complete Genome Characterization of Fowl Adenoviruses Isolated from Chickens Associated with Inclusion Body Hepatitis and Hydropericardium Syndrome in China

“…AF083975) and FAdV-E (1 strain, GenBank Accession No. GU734104) [ 26 – 30 ]. A wide range of phylogenetic analysis in the whole genome levels would be very necessary and far-reaching for the deep understanding of the evolutionary relationship of aviadenovirus isolates.…”

“…The pathogenicity of FAdV strains varied from subclinical infections to severe diseases [ 6 , 10 , 22 – 26 , 30 ]. The pathogenicity of HBQ12 and JSJ13 strains were determined by observing the clinical signs, gross and histological lesions in chickens.…”

Molecular characterization of pathogenic and nonpathogenic fowl aviadenovirus serotype 11 isolates

“…The isolates examined in this study contained only synonymous mutations in the fiber region, leading to no amino acid differences. While Grgic et al (2014) examined the fiber sequence of multiple FAdV serotypes as a determining factor of pathogenicity, no correlation was found.…”

“…The fiber is responsible for viral attachment to host cells, facilitating binding between the penton base and integrin leading to receptor mediated endocytosis (Zhang and Bergelson 2005). The fiber of FAdV-11 has a well-conserved nuclear localization signal at positions 17-20 (RKRP), along with the VYPF motif associated with the interaction between the fiber and the penton base (Grgic et al 2014). The isolates examined in this study contained only synonymous mutations in the fiber region, leading to no amino acid differences.…”

Outbreaks of serotype 4 fowl adenovirus with novel genotype, China

“…1 Although this virus has spread globally, FAdV infection typically causes only subclinical symptoms, and severe FAdV infection is associated with inclusion body hepatitis (IBH), hydropericardium syndrome (HPS) and gizzard erosion and ulceration. 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 Notably, severe FAdV cases with IBH and HPS in chicken flocks have been observed in China since 2013. 9 These outbreaks typically occurred in 3–5-week-old broiler flocks, as well as in 10–20-week-old layer flocks.…”