Mycoplasma gallisepticum Infection Impaired the Structural Integrity and Immune Function of Bursa of Fabricius in Chicken: Implication of Oxidative Stress and Apoptosis

Abstract

Mycoplasma gallisepticum (MG) induces a dysregulated immune response in the lungs and air ways of poultry. However, the mechanism of MG-induced immune dysregulation is still not completely understood. In the present study, the effect of MG-infection on chicken bursa of fabricius (BOF) is investigated. Histopathology, electron microscopy, TUNEL assay, qRT-PCR and western blot were employed to examine the hallmarks of oxidative stress and apoptosis. The data revealed that MG-infection induced oxidative stress and decreased antioxidant responses in BOF tissues compared to control group. Histopathological study showed pathological changes including reduction in lymphocytes and increased inflammatory cell infiltration in MG-infection group. Ultrastructural assessment represents obvious signs of apoptosis such as mitochondrial swelling, shrinkage of nuclear membrane and fragmentation of nucleus. Increased cytokine activities were observed in MG-infection group compared to control group. Meanwhile, the mRNA and protein expression level of apoptosis-related genes were significantly (p < 0.05) upregulated in MG-infection group. Terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay further confirmed that MG induced apoptosis in BOF tissues as TUNEL-stained positive nuclei were remarkably increased in MG-infection group. In addition, MG-infection significantly reduced the number of CD8 + lymphocytes in chicken BOF at day 7. Moreover, bacterial load significantly increased at day 3 and day 7 in MG-infection group compared to control group. These results suggested that MG-infection impaired the structural integrity, induced oxidative stress and apoptosis in chicken BOF tissues, which could be the possible causes of damage to immune function in chicken BOF.

Baicalin attenuated Mycoplasma gallisepticum‐induced immune impairment in chicken bursa of fabricius through modulation of autophagy and inhibited inflammation and apoptosis

“…Previous studies demonstrated that BF is composed of lymphocytes that secrete antibodies, present antigens by producing cytokines and regulate the magnitude and quality of cellular and humoral immune responses, 55 and these elicited immune responses are vital for the protection of a host 56,57 . These cytokines not only induce inflammation and apoptosis but also cause immune impairment which could lead to immune disorders 13,58 . In the present study, we found that NF‐ κ B and the level of proinflammatory cytokines were significantly enhanced in the model group compared to the control group.…”

Absorption of N-acetylcysteine in Healthy and Mycoplasma gallisepticum-Infected Chickens

“…Mycoplasmosis, caused by Mycoplasma gallisepticum (MG), is a global respiratory disease that affects poultry and leads to a reduction in the laying capacity and growth of chickens [18]. MG provokes chronic inflammation of the airways and lungs, respiratory distress, severe inflammation of the mucous membranes, and lesions of the trachea and air sacs of varying severities [19,20]. MG evades the host immune system of chickens and causes immune dysregulation, which allows other infectious diseases to develop [20,21].…”

Current status of vaccine research, development, and challenges of vaccines for Mycoplasma gallisepticum

“…Various inflammation and immune-related signaling pathways including TLR, mitogen-activated protein kinase, Jak-STAT, and the nucleotide oligomerization domain-like receptor pathways were differentially expressed, depicting the complex inflammatory response during MG infection ( Beaudet et al., 2017 ). Some other in vivo and in vitro studies examined inflammatory response, induction of apoptosis, and triggering of autophagy following MG infection ( Majumder and Silbart, 2016 ; Tian et al., 2016 ; Wu et al., 2019 ; Bao et al., 2020 ; Zhang et al., 2020 ). The interaction and modulation of host immune responses is of major importance in the preparation of effective vaccine against MG infection.…”