Immunotoxic effects of T-2 mycotoxin on cell-mediated resistance to Listeria monocytogenes infection

The effect of T-2 toxin on cell-mediated resistance to bacterial infection was evaluated in mice exposed to Listeria monocytogenes. Mice were inoculated with 4.0 X 10(5) (LD50) or 4.0 X 10(4) (nonlethal) L. monocytogenes on day 0 and treated orally on days 0, 1, 2, and 3 with 2.0, 1.0, or 0 mg/kg T-2 toxin. Toxin induced suppression of resistance was indicated by the rapid growth of Listeria in the spleen and by significant (P less than 0.005) increases in mortality due to listeriosis. Necrosis and depletion of lymphoid tissue, lymphopenia, and a marked decrease in the influx of lymphocytes and macrophages into Listeria elicited peritoneal exudates and at sites of infection in the liver and spleen occurred in the toxin treated mice. The immunotoxic effect of T-2 toxin on cell-mediated resistance to listeriosis was dosage dependent and attributed to toxin induced lymphoid depletion and the failure of surviving lymphocytes and mononuclear cells to clear the host of infection.     

Differential effect of T-2 toxin on murine host resistance to three facultative intracellular bacterial pathogens: Listeria monocytogenes, Salmonella typhimurium, and Mycobacterium bovis

The effect of T-2 toxin, a radiomimetic immunosuppressive agent, on resistance to the facultative intracellular bacterial pathogens Listeria monocytogenes (strain EGD), Mycobacterium bovis (BCG Copenhagen 1331), and Salmonella typhimurium was determined. Female Swiss ICR mice were given a single dose of T-2 toxin (4 mg/kg of body weight) by gastric gavage. On the seventh day after toxin administration, the mice were infected by intraperitoneal inoculation with L monocytogenes, S typhimurium, or M bovis. Mice given the toxin also were exposed to respirable droplet nuclei containing L monocytogenes or M bovis. The effect of the toxin on the course of infection was monitored by observing mortality or by enumeration of bacteria in the spleen or lungs of infected mice. The toxin increased resistance to infection with L monocytogenes initiated by intraperitoneal inoculation, but reduced resistance to M bovis infection initiated by intraperitoneal inoculation. The toxin had no appreciable effect on the course of salmonellosis or on resistance to infection initiated by inhalation of L monocytogenes or M bovis aerosols. Therefore, it was concluded that T-2 toxin does not necessarily reduce resistance to infection in mice. The toxin's effect on the course of in vivo bacterial infections depends on the nature of the infective agent and the route of inoculation.     

T-2 toxin-enhanced resistance against listeriosis in mice: importance of gastrointestinal lesions

The role of T-2 toxin-induced gastrointestinal lesions in T-2 toxin-enhanced resistance to listeriosis in mice was evaluated. The T-2 toxin-induced lesions did not cause a starvation effect sufficient to enhance resistance to listeriosis. Administration of polymyxin E markedly reduced the gram-negative intestinal microflora and did not eliminate the toxin-induced resistance to listeriosis. The T-2 toxin did not cause an increased expression of Ia surface antigens on peritoneal macrophages. Thus, toxin-induced anorexia and starvation or absorption of gram-negative intestinal bacteria and endotoxins through toxin-induced gastrointestinal lesions did not account for the enhancing effect of T-2 toxin on resistance to Listeria monocytogenes infection in mice.     

Effects of T-2 mycotoxin on tumor susceptibility in mice

The effect of Fusarium-produced T-2 toxin on tumor growth was evaluated in ICR, CFW, and C57B6/6 mice inoculated with murine sarcoma, Ehrlich ascites carcinoma, or B16F1 melanoma tumor cell lines. Mice were given T-2 toxin intragastrically either at the rate of 2 mg of toxin/kg of body weight daily for 5 days or a single dosage of 4 mg of toxin/kg and were inoculated SC with tumor cells 1 or 2 days after administration of toxin. Tumor growth was assessed 15 to 41 days after tumor challenge by determining the frequency of tumor development and tumor weights. Significant increases in the frequency of development of murine sarcoma (P less than 0.005), Ehrlich ascites carcinoma (P less than 0.01), and B16F1 melanoma tumors (P less than 0.05) were detected in toxin-treated mice, compared with control mice. Murine sarcoma and B16F1 melanoma tumor weights also were significantly (P less than 0.01) higher in toxin-treated mice. The effect of T-2 toxin on tumor growth was more marked after 5 daily treatments than after a single dose.     

Comparison of effects of dietary T-2 toxin on growth, immunogenic organs, antibody formation, and pathologic changes in turkeys and chickens.

The effect of T-2 toxin (trichothecene mycotoxin) consumption on Broad-Breasted White turkey poults and White Leghorn chicks was studied. Groups of ten 8-day-old poults were fed rations containing T-2 at 10 ppm, 2ppm, or 0 ppm (controls) for a period of 4 weeks; a 4th group (inanition control) was fed control rations equal to the amount consumed by the group fed rations containing T-2 at 10 ppm during the previous 24 hours. A similar experimental design was used to study the effect of the toxin on 1-day-old chicks. The thymus glands of the poults given the feed containing 10 ppm were markedly decreased in size compared with thymus glands from poults in the control group, 0.182 vs 0.331 (percentage of body weight). There was no significant (P less than or equal to 0.05) decrease in thymus gland size in poults given 2 ppm or in the inanition controls. Dietary treatment did not appear to affect the size of the bursa or spleen of the poults. Histopathologic examination of thymus glands from poults given 10 ppm of T-2 revealed a depletion of cortical lymphocytes. Chicks appeared less sensitive to T-2 toxin than did the poults. There was no effect by any dietary treatment on the size of the thymus gland, bursa, or spleen of chicks. Reductions were noticed in feed efficiency and weight gain. There was no effect of T-2 toxin on agglutinating antibody formation to Pasteurella multocida bacterin.     

Regulation of murine macrophage phagocytosis of sheep erythrocytes by T-2 toxin

The effect of a single oral dose of 4 mg of T-2 toxin/kg of body weight on in vivo phagocytosis of sheep RBC by peritoneal macrophages was evaluated in nonsensitized mice and in mice sensitized with sheep RBC. T-2 toxin treatment had no effect on the viability or phagocytic activity of resident peritoneal macrophages in nonsensitized mice. However, a significant (P less than 0.005) increase in phagocytic activity occurred in cells from mice treated with toxin and subsequently sensitized with sheep RBC. In contrast, phagocytosis of sheep RBC was significantly (P less than 0.05) suppressed in cells from mice treated with toxin after sensitization. Toxin treatment induced necrosis of lymphocytes and significant decreases in thymus and spleen weights. Seemingly, T-2 toxin, administered at a dose that caused marked lymphoid depletion, suppressed or enhanced in vivo macrophage phagocytic activity in antigenically sensitized mice, and enhancement or suppression of phagocytosis was a function of the time of toxin treatment in relation to antigenic stimulation.     

Determination of the acute 50% lethal dose T-2 toxin in adult bobwhite quail: additional studies on the effect of T-2 mycotoxin on blood chemistry and the morphology of internal organs

Three experiments were conducted to assess mortality rate, blood chemistry, and histologic changes associated with acute exposure to T-2 mycotoxin in adult bobwhite quail. In Experiment 1, adult quail were orally dosed with T-2 toxin to determine the lethal dose that resulted in 50% mortality of the affected population (LD50), and that dose was determined to be 14.7 mg of T-2 toxin per kilogram of body weight (BW). A second experiment was performed to study the effects of 12-18 mg/kg BW T-2 toxin on blood chemistry and liver enzyme profiles. Posttreatment uric acid, aspartate aminotransferase, lactic dehydrogenase, and gamma glutamyltransferase increased as compared with pretreatment values. In contrast, posttreatment plasma total protein, cholesterol, and triglyceride levels numerically decreased as compared with pretreatment values. Changes in blood chemistry values were consistent with liver and kidney damage after T-2 toxin exposure. In Experiment 3, histologic analyses of bone marrow, spleen, liver, small intestine, kidney, and heart were conducted on birds dosed in Experiment 2. Marked lymphocyte necrosis and depletion throughout the spleen, thymus, bursa, and gut-associated lymphoid tissue in the small intestine were observed in birds dosed with 15 and 18 mg/kg BW T-2 toxin. Necrosis of liver and lipid accumulation as a result of malfunctioning hepatocytes were also observed. Little or no morphologic change was observed in bone marrow and heart tissue. The LD50 for adult bobwhite quail as found in this study is two to three times higher than that reported for other species of commercial poultry. Results from these data confirm previous reports of immunosuppressive and/or cytotoxic effects of T-2 toxin in other mammalian and avian species. T-2 toxin may have a negative impact on the viability of wild quail populations.     

The effects of dietary T-2 toxin on acute herpes simplex virus type 1 infection in mice

Young male white Swiss mice were fed control diet or diet supplemented with 20 or 10 parts per million (ppm) of T-2 toxin for two or three weeks. These mice then were inoculated with herpes simplex virus type 1 (HSV-1) (9.6 x 10(6) plaque forming units) intraperitoneally. To compare the effects of T-2 toxin against a known immunosuppressive drug, cyclophosphamide was injected intraperitoneally at 150 mg/kg, 24 hours after treatment with HSV-1, into mice fed the control diet. Mice were necropsied and tissues were collected for microscopic and virologic examination. White Swiss mice which consumed a daily diet containing 20 ppm of T-2 toxin for two or three weeks were highly susceptible to HSV-1 infection and 27 of 36 (75%) died as a result of extensive hepatic and adrenal necrosis. Although HSV-1 was isolated from livers and brains of mice fed 20 ppm of T-2 toxin for two or three weeks, there was little or no inflammatory response found in the adrenals, livers, spinal cords, brains, or ganglia. The necrotizing encephalomyelitis observed in control mice was absent. High levels of dietary T-2 toxin appeared to be more immunosuppressive than cyclophosphamide because only one mouse died after treatment with HSV-1 and cyclophosphamide. Mice treated with cyclophosphamide had changes in brain, spinal cord, spleens, thymus, and bone marrow which were similar to those fed 20 ppm of T-2 toxin and infected with HSV-1, however, liver lesions were much less severe. HSV-1-infected mice on a diet with 10 ppm T-2 toxin had lesions of intermediate severity when compared with HSV-1-infected mice fed a diet with 20 ppm T-2 toxin and HSV-1-infected mice on control diets. Necrosis was less extensive in the livers and adrenals. The infrequent isolation of virus from liver and brain was consistent with the lack of intranuclear inclusion bodies and a more marked inflammatory response. Ten ppm of dietary T-2 toxin only depressed bone marrow and splenic red pulp to a mild or moderate degree. This may have enhanced the necrotizing encephalomyelitis observed in mice killed on days 6 and 8 after HSV-1 infection. Liver lesions were mild and those of the adrenals were moderate in mice fed control diet. The rare isolation of HSV-1 from the liver and brain and the findings of a moderate to severe necrotizing encephalomyelitis in these mice was consistent with an essentially functional immune system.     

Immunopathological effects of experimental T-2 mycotoxocosis in broiler chicken co-infected with infectious bronchitis virus (IBV)

A total of 128 1-week-old chicks were classified into four groups; T-2 toxin fed (T-2), IBV infected (IBV), T-2 toxin fed and co-infected with IBV (T-2+IBV), and untreated (control) for a period of 6 weeks. Within their respective groups, the birds belonged to T-2 and T-2+IBV were exposed to 2 ppm of T-2 toxin contaminated feed for 6 weeks, and 0.2 ml of 10 EID(50) (10(5.69)/0.2 ml) inoculums of IBV isolate (India/LKW/56/IVRI/08) was used to challenge the chicks belonged to IBV alone and T-2+IBV groups after 3 weeks of the experiment. To study immunopathological effects, parameters such as lymphocyte stimulation indices (SI), haemagglutination inhibition, enzyme linked immunosorbant assay (ELISA), peripheral lymphocytes CD(4)(+) and CD(8)(+) analysis, and histopathological examination of lymphoid organs were done. Accordingly, SI values were significantly (P<0.05) lower in all the treatment groups as compared to control, however, the SI values of IBV infected group were significantly higher than the values in toxin fed groups. The mean HI titres to ND vaccine was significantly (P<0.05) lower in the toxin groups at all the intervals, and the antibody titres in IBV infected group were significantly (P<0.05) higher than that of T-2 toxin fed and co-infected with IBV group but were significantly (P<0.05) lower than the control at 21 (3) and 28 (10) days of toxin feeding (DTF) (days post infection (DPI)). Similarly, the mean IBV ELISA antibody titres in the toxin fed groups were significantly (P<0.01) reduced as compared with the IBV ELISA antibody titres of IBV infected but not toxin fed group, at all intervals. Peripheral CD(4)(+):CD(8)(+) ratios in T-2+IBV group and number of CD(4)(+) and CD(8)(+) peripheral lymphocytes in all treatment groups were significantly reduced as compared to the values in control birds. However, CD(4)(+):CD(8)(+) ratios of IBV infected group at 42 (21) DTF (DPI) were found significantly (P<0.05) higher than the values in control birds. Histopathologically, lymphoid organs (bursa of Fabricius, spleen, thymus, caecal tonsils and Harderian glands) showed moderate to severe necrosis (lymphocytolysis) and extensive lymphocyte depletion in all the toxin groups (T-2 and T-2+IBV groups) where the severity and extent of the lesions were more in T-2+IBV group. The findings of the present experiment revealed immunosuppressive effects of T-2 toxin and aggravated the pathology and pathogenesis of IBV infection.     

Effects of testosterone on the prevention of T-2 toxin-induced adrenocortical necrosis in mice

To evaluate the effect of exogenous testosterone on the development of T-2 toxin-induced necrosis of adrenal glands, mice were allotted to 3 treatment groups. Each treatment group contained castrated male, and castrated and sexually intact female mice. Each mouse in group 1 was given 0.16 mg testosterone propionate at 48-hour intervals for a total of 12 injections, group-2 mice were given similar injections of only the vehicle, and group-3 mice were given no treatment. Twenty-four hours after the last injection, the mice in all 3 groups were exposed for 10 minutes to an aerosol of T-2 toxin. All mice alive at 24 hours after exposure were euthanatized and the adrenal glands and thymuses were examined histologically. Necrosis of the adrenal cortex was not found in any of the mice given preexposure treatment with exogenous testosterone, whereas all mice given vehicle only or no treatment had T-2 toxin-induced necrosis of the inner portion of the adrenal cortex. Lymphocytolysis in the cortex of the thymus confirmed that each mouse of all 3 treatment groups had experienced systemic mycotoxicosis. The uniform severity of the lesion in all mice suggests that the thymus was not protected by exogenous testosterone administration or by the castration status of the mice. We propose that T-2 toxin-induced adrenal necrosis in mice is prevented by the presence of testosterone.     

单增李斯特菌srtA基因缺失株的构建及srtA基因对其毒力的影响研究

为了研究srtA 基因对单增李斯特菌LM90SB2毒力的影响,本研究利用同源重组技术构建了LM90SB2 srtA 基因缺失株LM90SB2-ΔsrtA,比较分析了亲本株LM90SB2与缺失株LM90SB2-ΔsrtA对MBMEC、HBMEC、RAW264.7、SIEC 4种细胞系的粘附、侵袭、胞内增值能力及LM90SB2和LM90SB2-ΔsrtA 感染小鼠后,小鼠的LD50及肝脏、脾脏、脑载菌量变化差异。结果显示,本研究成功构建了srtA 基因缺失株;与亲本株LM90SB2比较,缺失株LM90SB2-ΔsrtA 对RAW264.7和SIEC的粘附率、侵袭率及胞内细菌数量均下降,且差异具有显著统计学意义(p <0.05);小鼠 LD50降低了21.38倍,肝脏、脾脏载菌量降低,差异具有显著统计学意义(p <0.05)。本研究结果表明,srtA 基因对单增李斯特菌LM90SB2的毒力具有关键作用,参与粘附、侵袭BMEC,该研究结果为进一步阐明单增李斯特菌毒力因子的致病机制提供理论依据。     

单核细胞增生李斯特菌prfA基因重组菌的构建及其生物学特性研究

为制备单核细胞增生李斯特菌(LM)减毒的prfA基因重组菌,本研究通过构建重组质粒pKSV7-ΔprfA-gfp,电转化至LM TA感受态细胞中,将绿色荧光蛋白基因gfp插入LM的prfA基因第25 bp～93 bp之间,在42℃和10μg/mL氯霉素的双重选择压力下,筛选LM重组菌(rLM-ΔprfA-gfp),并对其生物学特性进行鉴定。试验结果表明,重组菌与亲本菌相比具有相似的体外生长特性,溶血素基因(hly)mRNA的转录水平降低;对小鼠的毒力显著减弱,其LD50由105.53升高到109.79,对肝、脾、肾的损伤不明显;免疫保护力试验显示重组菌与LM TA灭活疫苗的保护率分别为90%和35%,表明rLM-ΔprfA-gfp比传统疫苗具有更高的保护力。本研究构建的rLM-ΔprfA-gfp具有良好的遗传稳定性,并且具有较好的免疫原性,为LM活疫苗载体和分子标记疫苗的研制奠定了基础。     

Mycotoxicosis caused by aerosolized T-2 toxin administered to female mice

Thymus, spleen, adrenal glands, and small intestine of female mice exposed to aerosolized T-2 mycotoxin were examined at postexposure hours (PEH) 0.25, 1, 2, 4, 6, 9, 12, and 24. Lymphocyte necrosis was observed at PEH 1 in the thymus, spleen, and lamina propria and Peyer patches of the small intestine. Necrosis of small intestinal crypt epithelial cells was observed at PEH 2, and necrosis of parenchymal cells and increased number of neutrophils were seen in sinusoids of the adrenal cortex at PEH 4. These results indicated that the earliest microscopic evidence of T-2 mycotoxicosis after aerosol exposure was necrosis of lymphocytes in the thymus, spleen, and lamina propria and Peyer patches of the small intestine.     

Subacute toxicity of Dietary T-2 toxin in mice: influence of protein nutrition.

The subacute toxic effects of dietary T-2 toxin (20 ppm) incorporated in semipurified diets of 8%, 12% or 16% protein, were examined in young Swiss mice after one, two, three and four weeks. Dietary T-2 toxin caused substantial reductions in growth and food consumptaion, the degrees of which were greatest in mice fed the diets of reduced protein content. T-2 toxin consistently caused similar degrees of nonregenerative anemia, lymphopenia, thymic atrophy and gastric hyperkeratosis irrespective of the dietary protein level. However, erythroid hypoplasia was temporary in mice fed T-2 toxin in the 16%-protein diet such that erythroid precursors regenerated in splenic and bone marrow and were hyperplastic after four weeks. Liver to body weight ratios of mice fed T-2 toxin in the 16%-and 12%-protein diets increased during the four week trial in comparison to control mice fed at a similar rate. These observations indicated that suppression of erythropoiesis in mice by dietary T-2 toxin was temporarty and that the interval before regeneration was prolonged by diets of reduced protein content.     

Subacute toxicity of dietary T-2 toxin in mice: morphological and hematological effects.

Changes in hematopoietic and lymphoid tissues of young Swiss mice fed a balanced semipurified diet containing T-2 toxin (20 ppm) were examined after one, two, three, four or six weeks. During the first three weeks of exposure of T-2 toxin, lymphoid tissues, bone marrow and splenic red pulp became hypoplastic, resulting in anemia, lymphopenia and eosinopenia. Subsequently, during continued exposure to T-2 toxin, hematopoietic cells regenerated in bone marrow and splenic red pulp and became hyperplastic by six weeks. Granulopoiesis and thrombopoiesis resumed in advance of erythropoiesis. All lymphoid tissues remained atrophic throughout the six week trial. Mice exposed to T-2 toxin also developed perioral dermatitis and hyperkeratosis with ulceration of the mucosa of the esophageal region of the stomach. These results indicated that young mice were susceptible to both the irritant and the hematopoietic-suppressive toxic effects of dietary T-2 toxin. However, supression of hematopoiesis was transient and did not lead to hematopoietic failure.     

In vitro study of Listeria monocytogenes infection to murine primary and human transformed B cells

Immunity to Listeria monocytogenes is largely mediated by T lymphocytes. Recently, B lymphocytes or their secreted products are implicated to provide immunity against L. monocytogenes infection. To understand whether L. monocytogenes can infect and kill B cells as a possible strategy to initiate an infection, we examined the effects of L. monocytogenes on a human B lymphoma (Ramos RA-1) and mouse primary B cells in vitro. L. monocytogenes infection resulted in significantly (p相似文献   

Interaction of T-2 fusariotoxin and monensin in broiler chickens infected with Coccidia

Field observations suggest that coccidiosis is a common cause of death in broiler chicken flocks fed diets containing sufficient amounts of ionophore antibiotics (monensin, narasin, etc.) and contaminated with mycotoxins, particularly with T-2 fusariotoxin. To study this phenomenon, broiler chickens fed diets containing different amounts of T-2 toxin and free from monensin, or containing a preventive dose (100 mg/kg of feed) of monensin, were infected experimentally with coccidian oocysts. In all groups fed a diet containing monensin plus T-2 toxin severe clinical symptoms of coccidiosis (blood-stained faeces etc). occurred. Deaths and retarded growth depended on the toxin dose and were considerable. The body mass gain of chicks fed a diet containing monensin and T-2 toxin but not infected with coccidia was inferior to that of groups fed diets which contained either monensin or T-2 toxin (experiment 2). On the basis of these findings a negative interaction of the two compounds is assumed. This seems to be supported by the results of experiment 3, i. e. the finding that the lethal dose of narasin, a compound closely related to monensin both in chemical structure and mechanism of action, proved to be much lower (LD50 = 102 mg/kg body mass) for chickens fed a diet supplemented with T-2 toxin than for the control chickens (LD50 = 176 mg/kg body mass). The present results suggest that the feeding of diets severely contaminated with T-2 toxin may alter the anticoccidial efficacy of monensin.     

Embryotoxic effects of prenatal T-2 toxin exposure in mice.

Pregnant CD-1 mice were administered T-2 toxin by gastric intubation on day 11 of gestation at dosages of 0, 0.75 and 1.5 mg/kg. The T-lymphocyte dependent antibody response against sheep red blood cells which was evaluated in the offspring at six weeks of age was not affected by T-2 toxin exposure. Individual birth and weaning weights were not influenced by T-2 toxin, but the litter size was reduced in the high dose group, without affecting the number of implantation sites per dam. The number of female offspring produced by dams exposed to 1.5 mg/kg T-2 toxin was less compared to other treatment groups, suggesting that the female fetus was more susceptible to embryolethal effects of prenatal T-2 toxin exposure. These results suggest that prenatal T-2 toxin exposure is unlikely to be a significant health problem with respect to primary humoral immunity. At the dosages given, T-2 toxin produced substantial embryotoxicity without alteration in antibody production. The embryolethal effects are a primary limiting factor which may preclude the expression of any immunoteratological manifestations associated with humoral immunity under natural field conditions.     

Comparison of the effect of T-2 toxin with that of dexamethasone or cyclophosphamide on resistance to Babesia microti infection in mice

The effect of T-2 toxin on host resistance to acute and latent Babesia microti infections was evaluated in mice and was compared with the effects of the immunosuppressive drugs dexamethasone and cyclophosphamide. Mice with acute or latent B microti infection were treated with 2 mg of T-2 toxin/kg of body weight, 0.2 mg of dexamethasone/kg, or 30 mg of cyclophosphamide/kg daily for 5 days. Treatment with dexamethasone or cyclophosphamide caused significant (P less than 0.05) increases in Babesia parasitemia during acute infection and significantly (P less than 0.05) prolonged the duration of parasitemia during acute babesiosis. Treatment with T-2 toxin caused a transient significant (P less than 0.05) increase in Babesia parasitemia on day 10 after acute infection and numerical, though statistically nonsignificant, increases in the maximal level and duration of parasitemia during acute babesiosis. Significant (P less than 0.005) recrudescence of parasitemia was observed in the dexamethasone- and cyclophosphamide-treated mice with latent Babesia infection. Treatment with T-2 toxin did not cause recrudescence of parasitemia in mice with latent Babesia infection.     

Fatal placental hemorrhage in pregnant CD-1 mice following one oral dose of T-2 toxin.

Forty-eight hours after oral administration of a single dose (3.0 mg/kg BW) of T-2 toxin to mice on days 7, 8, 10, 11 and 12 of pregnancy, 17% maternal mortality following vaginal hemorrhage was encountered. Necropsy examination of the dead females revealed that massive hemorrhages originating from the placental regions had occurred into the reproductive tract. This observation supports the studies in which hemorrhagic disease has been described as characteristic for intoxications with T-2 toxin. The results suggest that fatal hemorrhage during pregnancy can occur in hemochorial and hemoendotheliochorial placental mammals as a result of T-2 toxin administration.