Fowl Adenovirus Serotype 4 SD0828 Infections Causes High Mortality Rate and Cytokine Levels in Specific Pathogen-Free Chickens Compared to Ducks

Abstract

Hydropericardium syndrome and inclusion body hepatitis, together called hydropericardium-hepatitis syndrome, are acute infectious diseases found in chickens. These diseases are caused primarily by fowl adenovirus serotype 4 (FAdV-4) strains. In this study, we isolated a FAdV-4 strain (SD0828) from clinically diseased chickens and phylogenetically analyzed the L1 loops of the hexon protein sequences in 3-weekold specific pathogen-free chickens and ducks infected intramuscularly and orally, determining differences in the pathogenicity by observing clinical signs and gross and histological lesions. We also detected the viral load in tissue samples. Postinfection necropsy showed that all chickens but no ducks exhibited typical necropsy lesions. Additionally, all chickens infected intramuscularly died within 2 days postinfection (dpi), and all those infected orally died within 5 dpi, whereas no infected ducks died before 28 dpi. Quantitative real-time polymerase chain reaction analysis was used to determine the viral load in the tissues of hearts, livers, spleens, lungs, and kidneys and in cloacal cotton swabs from infected chickens and ducks at 1, 2, 3, 5, 7, 14, 21, and 28 dpi. The greatest number of viral DNA copies was found in the livers of infected chickens, yet no virus was found in any samples from infected ducks. In addition, the viral load increased over time in both chicken and duck embryo fibroblasts (CEFs and DEFs, respectively); in the former, replication speed was significantly greater than in the latter. Innate immune responses were also studied, both in vivo and in vitro. In CEFs, DEFs, and chickens infected intramuscularly, but not in infected ducks, mRNA expression levels of proinflammatory cytokines (interleukin-6 and -8) and interferon-stimulated genes (Mx and OAS) were significantly upregulated. Although some cytokines showed significant upregulation in the oral chickens, most did not change significantly. Finally, the duck retinoic acid-inducible gene I and its caspase activation and recruitment domain both had significant antiviral functions in CEFs, particularly after 24 h postinfection. Taken together, this research provides new insights into the interactions between FAdV-4 and the innate immune systems of studied hosts (chickens and ducks).

Research Note: Molecular and pathologic characterization of avian adenovirus isolated from the oviducts of laying hens in eastern Japan

“…In the case of the IV-infected hens, the viruses were detectable from pooled duodenum, jejunum, and cecum samples only. Fowl adenoviruses show affinity for organs in the GIT such as the pancreas ( Nakamura et al., 2002 ); also, viral loads are highest in the liver ( Li et al., 2018 ), proventriculus, caecum, and ileum ( Okuda et al., 2006 ; Hess, 2017 ; Matczuk et al., 2017 ). In the present study, the pancreas and proventriculus were PCR-negative.…”

Identification, Pathogenicity of Novel Fowl Adenovirus Serotype 4 SDJN0105 in Shandong, China and Immunoprotective Evaluation of the Newly Developed Inactivated Oil-emulsion FAdV-4 Vaccine

“…Although the vaccine could provide broad cross-protection against various serotypes of fowl Adenovirus, the protection rate against FAdV-4 was only 80%. It was reported that the novel FAdV-4 has the specificity of continuous infection and cross-transmission between chickens and ducks [22,27]. It is not known whether the FAdV-4 strain SDJN0105 has pathogenicity to ducks.…”

“…Total RNAs of the samples (i.e., heart, liver, and spleen) were extracted, treated, quality determined, stored and reverse-transcribed to cDNA according to a previous report [27]. The primers for chicken β-actin, TLR3, TLR7, MDA5, IFN-α, IFN-β, IFN-γ, TNF-α, IL-1β, IL-2, IL-4, IL-6, IL-8, Mx and OASL genes were designed by Primer 5.0 software ().…”

Pathogenesis of Hypervirulent Fowl Adenovirus Serotype 4: The Contributions of Viral and Host Factors

“…Prompt activation of sensing mechanisms in the host targets each step of infection to detect and eliminate the pathogen. Hypervirulent FAdV-4 infection is initially recognized via pattern recognition receptors (PRRs) [46]. Downstream signaling cascades further elicit the release of pro-inflammatory cytokines into blood to recruit antiviral cells.…”

“…Recent studies have demonstrated that most of the hypervirulent FAdV-4 strains isolated in China are fatal to chickens but not ducks. After infected with HLJDAd15 (duck-isolated strain) [12] or SD0828 (chicken-isolated strain) [46], SPF chickens, but not ducks, exhibited HHS-typical clinical signs and histopathological lesion when exposed at the same doses of virus. By examining the mRNA expression of PRRs, duck retinoic acid-inducible gene I (RIG-I)-like receptors were dramatically upregulated; moreover, virus titers in duck RIG-I transfected chicken embryo fibroblast (CEF) cells were significantly lower than that in empty vector-transfected cells [46].…”