Virulence of fowl adenovirus (FAdV) serotype 4 strains impacts cell proliferation and immune response of primary chicken-embryo intestinal epithelial cells

Title (eng)
Virulence of fowl adenovirus (FAdV) serotype 4 strains impacts cell proliferation and immune response of primary chicken-embryo intestinal epithelial cells
Author
Katharina Kau-Strebinger
Author
Ursula Reichart
Author
Taniya Mitra
Author
Beatrice Grafl
Author
Michael Hess
Author
Dieter Liebhart
Abstract (eng)
Fowl adenovirus serotype 4 (FAdV-4) causes hepatitis-hydropericardium syndrome (HHS) in chickens, leading to substantial economic losses. Following oral uptake, the virus infects intestinal epithelial cells (IEC) to overcome the first entrance barrier. The initial cellular interactions and intestinal immune responses are not well understood. This study uses a primary IEC culture model to investigate infection dynamics of virulent (AG234) and non-pathogenic (KR5) FAdV-4 strains and cellular defence mechanisms. Cell growth and viral propagation were assessed at 4, 12, 24, and 48 hours post-infection (hpi) using immunofluorescence and automated image analysis. The innate immune response was assessed by the mRNA expression of the Toll-like receptors (TLR1B, TLR2B, TLR3, TLR4, and TLR21) and the cytokines (IL-1β, IL-6, IL-10, IL-13, and IFN-γ). KR5 did not significantly reduce IEC growth; notable proliferation between 4 and 48 hpi was observed. Although IEC growth was initially similar, AG234 decreased cell numbers at 48 hpi. Compared to KR5, the abundance of AG234-infected cells was already higher at 4 hpi. Nevertheless, at 48 hpi, the number of IEC infected with the virulent strain was less than KR5, albeit without significance. The AG234 infection primarily activated the immune response at 48 hpi, characterised by a significant mRNA up-regulation of TLR3, TLR21, IL-1β and INF-γ compared to the negative control. KR5 induced a substantially higher expression of IL-13 mRNA compared to the control at 48 hpi. The results show that FAdV virulence significantly affects cell growth, viral augmentation, and the immune response. The chicken IEC culture system presented in this study effectively propagates FAdVs to examine the initial stage of intestinal infection.
Keywords (eng)
Intestinal Epithelial Cells (IEC)Fowl Adenovirus Serotype 4 (FAdV-4)Viral Infection DynamicsImmune ResponseToll-like Receptors (TLR)Cytokine ExpressionAutomated Imaging Analyses
Type (eng)
journal article
Language
[eng]
Persistent identifier
https://phaidra.vetmeduni.ac.at/o:4974
DOI
10.1186/s13567-025-01541-9
Is in series
Title (eng)
Veterinary Research
Volume
56
Issue
1
ISSN
1297-9716
Issued
2025
Number of pages
13
Publication
Springer
Version type (eng)
version of record (published version)
Date issued
2025
Access rights (eng)
open access
License
CC BY 4.0 International
Rights statement (eng)
© 2025, The Author(s)