Effects of T-2 Toxin on Turkey Herpesvirus-Induced Vaccinal Immunity Against Marek's Disease

Pathological consequences, metabolism and toxic effects of trichothecene T-2 toxin in poultry

Contamination of feed with mycotoxins has become a severe issue worldwide. Among the most prevalent trichothecene mycotoxins, T-2 toxin is of particular importance for livestock production, including poultry posing a significant threat to animal health and productivity. This review article aims to comprehensively analyze the pathological consequences, metabolism, and toxic effects of T-2 toxin in poultry. Trichothecene mycotoxins, primarily produced by Fusarium species, are notorious for their potent toxicity. T-2 toxin exhibits a broad spectrum of negative effects on poultry species, leading to substantial economic losses as well as concerns about animal welfare and food safety in modern agriculture. T-2 toxin exposure easily results in negative pathological consequences in the gastrointestinal tract, as well as in parenchymal tissues like the liver (as the key organ for its metabolism), kidneys, or reproductive organs. In addition, it also intensely damages immune system-related tissues such as the spleen, the bursa of Fabricius, or the thymus causing immunosuppression and increasing the susceptibility of the animals to infectious diseases, as well as making immunization programs less effective. The toxin also damages cellular processes on the transcriptional and translational levels and induces apoptosis through the activation of numerous cellular signaling cascades. Furthermore, according to recent studies, besides the direct effects on the abovementioned processes, T-2 toxin induces the production of reactive molecules and free radicals resulting in oxidative distress and concomitantly occurring cellular damage. In conclusion, this review article provides a complex and detailed overview of the metabolism, pathological consequences, mechanism of action as well as the immunomodulatory and oxidative stress-related effects of T-2 toxin. Understanding these effects in poultry is crucial for developing strategies to mitigate the impact of the T-2 toxin on avian health and food safety in the future.

Glycolysis and Reactive Oxygen Species Production Participate in T-2 Toxin-Stimulated Chicken Heterophil Extracellular Traps

T-2 toxin (T-2) is a kind of trichothecene toxin produced from Fusarium fungi, which is an environmental pollutant that endangers poultry and human health. Heterophil extracellular traps (HETs) are not only a form of chicken immune defense against pathogen infection but also involved in pathophysiological mechanisms of several diseases. However, the immunotoxicity of T-2 on HET formation in vitro has not yet been reported. In this study, heterophils were exposed to T-2 at doses of 20, 40, and 80 ng/mL for 90 min. Observation of the structure of HETs by immunofluorescence staining and the mechanism of HET formation was analyzed by inhibitors and PicoGreen. These results showed that T-2-triggered HET formation consisted of DNA, elastase, and citH3. Furthermore, T-2 increased reactive oxygen species (ROS) generation, and the formation of T-2-triggered HETs was also decreased by the inhibitors of glycolysis, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, p38 and extracellular signal-regulated kinase (ERK)_1/2 signaling pathways, suggesting that T-2-induced HETs are associated with glycolysis, ROS production, ERK_1/2 and p38 signaling pathways, and NADPH oxidase. Taken together, this study elucidates the mechanism of T-2-triggered HET formation, and it may provide new insight into understanding the immunotoxicity of T-2 to early innate immunity in chickens.

Virus-Induced Immunosuppression in Chickens

A healthy immune system is a cornerstone for poultry production. Any factor diminishing the immune responses will affect production parameters and increase cost. There are numerous factors, infectious and noninfectious, causing immunosuppression (IS) in chickens. This paper reviews the three viral diseases that most commonly induce IS or subclinical IS in chickens: Marek's disease virus (MDV), chicken infectious anemia virus (CIAV), and infectious bursal disease virus (IBDV), as well as the interactions among them. MDV-induced IS (MDV-IS) affects both humoral and cellular immune responses. It is very complex, poorly understood, and in many cases underdiagnosed. Vaccination protects against some but not all aspects of MDV-IS. CIAV induces apoptosis of the hemocytoblasts resulting in anemia, hemorrhages, and increased susceptibility to bacterial infections. It also causes apoptosis of thymocytes and dividing T lymphocytes, affecting T helper functions, which are essential for antibody production and cytotoxic T lymphocyte (CTL) functions. Control of CIAV is based on vaccination of breeders and maternal antibodies (MAbs). However, subclinical IS can occur after MAbs wane. IBDV infection affects the innate immune responses during virus replication and humoral immune responses as a consequence of the destruction of B-cell populations. Vaccines with various levels of attenuation are used to control IBDV. Interactions with MAbs and residual virulence of the vaccines need to be considered when designing vaccination plans. The interaction between IBDV, CIAV, and MDV is critical although underestimated in many cases. A proper control of IBDV is a must to have proper humoral immune responses needed to control CIAV. Equally, long-term control of MDV is not possible if chickens are coinfected with CIAV, as CIAV jeopardizes CTL functions critical for MDV control.

Delayed effects of autophagy on T-2 toxin-induced apoptosis in mouse primary Leydig cells

T-2 toxin is a type-A trichothecene produced by Fusarium found in several food commodities worldwide. T-2 toxin causes reproductive disorders, genotoxicity, and testicular toxicity in animals. Our previous research has reported that T-2 toxin can induce apoptosis via the Bax-dependent caspase-3 activation in mouse primary Leydig cells. However, little is known about the functions of autophagy and the cross talk between autophagy and apoptosis after exposure to T-2 toxin in Leydig cells. This study investigated these problems in mouse primary Leydig cells. Results showed that T-2 toxin treatment upregulated LC3-II and Beclin-1 expression, suggesting that T-2 toxin induced a high level of autophagy. Pretreatment with chloroquine (an autophagy inhibitor) and rapamycin (an autophagy inducer) increased and decreased the rate of apoptosis, respectively, in contrast to T-2 toxin-treated group. Autophagy delayed apoptosis in the T-2 toxin-treated Leydig cells. Therefore, autophagy may prevent cells from undergoing apoptosis by reducing T-2 toxin-induced cytotoxicity.

Elevation of IGFBP2 contributes to mycotoxin T-2-induced chondrocyte injury and metabolism

Kashin-Beck disease (KBD) is an endemic degenerative osteoarthropathy. The mycotoxin of T-2 toxin is extensively accepted as a major etiological contributor to KBD. However, its function and mechanism in KBD remains unclearly elucidated. Here, T-2 toxin treatment induced chondrocyte injury in a time- and dose-dependent manner by repressing cell viability and promoting cell necrosis and apoptosis. Importantly, T-2 suppressed the transcription of type II collagen and aggrecan, as well as the release of sulphated glycosaminoglycan (sGAG). Furthermore, exposure to T-2 enhanced the transcription of matrix metalloproteinases (MMPs), including MMP-1, -2, -3 and -9. In contrast to control groups, higher expression of insulin-like growth factor binding protein 2 (IGFBP2) was observed in chondrocytes from KBD patients. Interestingly, T-2 toxin caused a dramatical elevation of IGFBP2 expression in chondrocytes. Mechanism analysis corroborated that cessation of IGFBP2 expression alleviated T-2-induced damage to chondrocytes. Simultaneously, transfection with IGFBP2 siRNA also attenuated matrix synthesis and catabolism-related gene expressions of MMPs. Together, this study validated that T-2 toxin exposure might promote the progression of KBD by inducing chondrocyte injury, suppressing matrix synthesis and accelerating cellular catabolism through IGFBP2. Therefore, this research will elucidate a new insight about how T-2 toxin participate in the pathogenesis of KBD.