Characterizing the immune response of chickens to Campylobacter jejuni (Strain A74C)

Authors: MORTADA, MOHAMAD - University Of Georgia; Cosby, Douglas; AKERELE, GABRIEL - University Of Georgia; RAMADAN, NOUR - University Of Georgia; OXFORD, JARRED - University Of Georgia; Shanmugasundaram, Revathi; NG, THEROS - University Of Georgia; SELVARAJ, RAMESH - University Of Georgia

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2021
Publication Date: 3/15/2021
Citation: Mortada, M., Cosby, D.E., Akerele, G., Ramadan, N., Oxford, J., Shanmugasundaram, R., Ng, T., Selvaraj, R.K. 2021. Characterizing the immune response of chickens to Campylobacter jejuni (Strain A74C). PLoS ONE. 16(3):e0247080. https://doi.org/10.1371/journal.pone.0247080.
DOI: https://doi.org/10.1371/journal.pone.0247080

Interpretive Summary: Campylobacter continues to be a major source of foodborne illnesses associated with poultry and poultry products worldwide. The immune response of poultry is not well defined and is still being researched. This study seeks to determine the immune response of chickens to colonization with Campylobacter jejuni. Day of hatch boilers were challenged with Campylobacter jejuni and raised under commercial conditions and sampled during grow-out. Campylobacter jejuni was detected in the ceca of the challenged birds. This study looked at the expression of immune components during grow-out. The immune responses appeared to be balanced with up-regulation of some immune components and down-regulation of other immune components. These balanced immune responses (Th1 and Th2) might explain the bacterial colonization of the ceca and the absence of pathology of chickens with Campylobacter colonization.

Technical Abstract: Campylobacter is one of the major foodborne pathogens causing bacterial gastroenteritis worldwide. The immune response of broiler chickens to C. jejuni is under-researched. This study aimed to characterize the immune response of chickens to Campylobacter jejuni colonization. Birds were challenged orally with 0.5 mL of 2.4 x 108 CFU/mL of Campylobacter jejuni or with 0.5 mL of 0.85% saline. Campylobacter jejuni persisted in the ceca of challenged birds with cecal colonization reaching 4.9 log10 CFU/g on 21 dpi. Campylobacter was disseminated to the spleen and liver on 7 dpi and was cleared on 21 dpi from both internal organs. Challenged birds had a significant increase in anti-Campylobacter serum IgY (14&21 dpi) and bile IgA (14 dpi). At 3 dpi, there was a significant suppression in T-lymphocytes derived from the cecal tonsils of birds in the challenge treatment when compared to the control treatment after 72 h of ex vivo stimulation with Con A or C. jejuni. The T-cell suppression on 3 dpi was accompanied by a significant decrease in TNF-a, K60, CLAU-2, IL-1ß, iNOS, and IL-6 mRNA levels in the ceca and an increase in nitric oxide production from adherent splenocytes of challenged birds. In addition, on 3 dpi, there was a significant increase in CD4+ and CD8+ T lymphocytes in the challenge treatment. On 14 dpi, both pro and anti-inflammatory cytokines were upregulated in the spleen, and a significant increase in CD8+ T lymphocytes in Campylobacter-challenged birds' ceca was observed. The persistence of C. jejuni in the ceca of challenged birds on 21 dpi was accompanied by an increase in IL-10 and TNF-a mRNA levels, an increase in MNC proliferation when stimulated ex-vivo with the diluted C. jejuni, an increase in serum specific IgY antibodies, an increase in both CD4+ and CD8+ cells, and a decrease in CD4+:CD8+cell ratio. The balanced Th1 and Th2 immune responses against C. jejuni might explain the ceca's bacterial colonization and the absence of pathology in Campylobacter-challenged birds. Future studies on T lymphocyte subpopulations should elucidate a pivotal role in the persistence of Campylobacter in the ceca.