Adenovirus type D and type E infection in broiler chickens: the effect on CD4 and CD8 T cell response, cytokines expression and their immunopathology

ABSTRACT

1. A total of 150-day-old chicks were divided into three groups of 50 birds (G1-G3); G1 and G2 were orally inoculated at 1-day old with 0.5 ml of 10⁷ TCID50/ml FAdV-D serotype 2 (MT386509.1) and FAdV-E serotype 8a (MW847902), respectively, and G3 was blank control group.

2. Cell-mediated immune response was evaluated by detection of CD4, CD8 T lymphocytes and the mRNA expression of IL6 and IL8 in the chicken spleen using q-PCR. Additionally, immunopathology was performed at 3, 5 and 7 day post infection (dpi) and weekly until the end of the experiment.

3. Results revealed that transcription of inflammatory cytokines (IL6, IL8) was up regulated in the spleen of FAdV type D and type E infected chickens at various time points relative to the control group. A marked decrease in the number of CD4 and CD8 T lymphocytes at 5 and 7 dpi in G1 of chickens infected with FAdV type D. Whereas, in chickens infected with FAdV type E, the CD4 and CD8 T lymphocytes were markedly decreased at 7 dpi.

4. In contrast, there were no significant differences in humoral immune responses against NDV vaccine in (G1 and G2) at different intervals post-vaccination compared to the control group. The histopathology of the bursa, thymus, and spleen in the infected groups showed lymphocytolysis with severe reticular cells hyperplasia and lymphoid depletion.

5. In conclusion, fowl adenovirus types D and E have an immunosuppressive effect in broilers which may be considered one of the main causes of the continuous co-infections with other viruses reported in the field during the last 10 years.

KEYWORDS:

• Broilers
• adenovirus
• hepatitis
• immunosuppression
• infections
• challenge

Acknowledgments

The authors would like to thank Poultry Diseases Department, Faculty of Veterinary Medicine, Cairo University for their help and support to perform the experiment.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributiors

G.A.A. and S.M.A. conceived and designed this study. G.A.A., E.A.M. and M.G.N. performed the experiment. H.A.H. and E.A.M. wrote the first draft of the manuscript and reviewed all the results. M. S. K. performed the pathological studies. T. M. A. shared data collection. A. M. B. and Sh. M. A. carried out the statistical and data analysis and performed the molecular study. All authors wrote, read, revised, and approved the final manuscript.

Compliance with ethics requirements

All Institutional and National Guidelines for the care and use of animals were followed.

Additional information

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.