Monoclonal antibodies to T-2 toxin. In vitro neutralization of protein synthesis inhibition and protection of rats against lethal toxemia

Subchronic dermal exposure to T-2 toxin produces cardiac toxicity in experimental Wistar rats

Our study aimed to determine the cardiac toxicities of T-2 toxin, a representative mycotoxin that frequently contaminates maize, cereals, and other agricultural products, harvested and stored under damp and cold conditions. Dermal exposure to T-2 toxin caused severe cardiotoxicity in experimental Wistar rats. Electrocardiography studies showed the conduction abnormalities including prolongation of the QT and corrected QT interval, shortening of the PR interval, and tachycardia. Biochemical studies also reported the toxicity of T-2 toxin. T-2 toxin induced acute cardiotoxicity in rats and characterized by significant ( p < 0.05) elevation of serum troponin I, creatine kinase (CK) isoenzyme MB, CK isoenzyme NAC, and lactate dehydrogenase as compared to control rats. It is concluded that cardiotoxicity effects of T-2 toxin are thought to be due to direct action on electrocardiac potentials and biochemical changes.

Chicken nucleated blood cells as a cellular model for genotoxicity testing using the comet assay

Mycotoxins can frequently occur in animal feed and human food. T-2 toxin, as the most toxic trichothecene, has been implicated as the causative agent in a variety of animal diseases and is associated with some human diseases. The comet assay was performed as a test for detection of DNA damage caused by T-2 toxin in peripheral blood cells of chicken. The suitability of the comet assay as a biomarker for genotoxic analysis has been applied in studies using human white blood cells. It can be applied to any tissue from which a single cell suspension can be obtained. The method has already been applied to chicken as a foodstuff for detection of irradiation of food containing DNA. However, application of the method on chicken blood cells has not been set up yet. The aim of this research was to develop a protocol for detection of DNA damage induced by T-2 toxin in chicken blood cells. Chickens were administered orally with T-2 toxin and the samples of whole blood were collected at 24 h post treatment. The DNA damage was determined by an increase in the comet parameters in tested animals. Our results show that T-2 toxin had induced significant DNA damage in treated chicken as compared with control animals, indicating that the assay can be used for the assessment of primary DNA damage caused by mycotoxins.

Antibody-based resistance to plant pathogens

Plant diseases are a major threat to the world food supply, as up to 15% of production is lost to pathogens. In the past, disease control and the generation of resistant plant lines protected against viral, bacterial or fungal pathogens, was achieved using conventional breeding based on crossings, mutant screenings and backcrossing. Many approaches in this field have failed or the resistance obtained has been rapidly broken by the pathogens. Recent advances in molecular biotechnology have made it possible to obtain and to modify genes that are useful for generating disease resistant crops. Several strategies, including expression of pathogen-derived sequences or anti-pathogenic agents, have been developed to engineer improved pathogen resistance in transgenic plants. Antibody-based resistance is a novel strategy for generating transgenic plants resistant to pathogens. Decades ago it was shown that polyclonal and monoclonal antibodies can neutralize viruses, bacteria and selected fungi. This approach has been improved recently by the development of recombinant antibodies (rAbs). Crop resistance can be engineered by the expression of pathogen-specific antibodies, antibody fragments or antibody fusion proteins. The advantages of this approach are that rAbs can be engineered against almost any target molecule, and it has been demonstrated that expression of functional pathogen-specific rAbs in plants confers effective pathogen protection. The efficacy of antibody-based resistance was first shown for plant viruses and its application to other plant pathogens is becoming more established. However, successful use of antibodies to generate plant pathogen resistance relies on appropriate target selection, careful antibody design, efficient antibody expression, stability and targeting to appropriate cellular compartments.

Molecular farming of recombinant antibodies in plants

'Molecular farming' is the production of recombinant proteins in plants. It is intended to harness the power of agriculture to cultivate and harvest transgenic plants producing recombinant therapeutics. Molecular farming has the potential to provide virtually unlimited quantities of recombinant antibodies for use as diagnostic and therapeutic tools in both health care and the life sciences. Importantly, recombinant antibody expression can be used to modify the inherent properties of plants, for example by using expressed antipathogen antibodies to increase disease resistance. Plant transformation is technically straightforward for model plant species and some cereals, and the functional expression of recombinant proteins can be rapidly analyzed using transient expression systems in intact or virally infected plants. Protein production can then be increased using plant suspension cell production in fermenters, or by the propagation of stably transformed plant lines in the field. Transgenic plants can be exploited to produce organs rich in a recombinant protein for its long-term storage. This demonstrates the promise of using transgenic plants as bioreactors for the 'molecular farming' of recombinant therapeutics, blood substitutes and diagnostics, such as recombinant antibodies.

Economic losses and decontamination

Mycotoxin contamination of crops may cause economic losses at all levels of food and feed production including crop and animal production, and crop distribution and processing. The national economy would be affected adversely by losses incurred by crop and livestock producers and the multiplier effect this has on other industries as a result of the reduced spending power of producers. Costs of chemical analyses, quality control and regulatory programs, research and development, extension services, law suits, and the cost of human illnesses must all be borne by the national economy. The value of the losses encountered depends on grain, animal, and animal product prices, interest rates, degree of contamination, and other economic variables. Even during favourable seasons it is likely that millions of dollars are lost as a result of the contamination of crops with mycotoxins. Many compounds and treatments have been tested in order to reduce mycotoxin concentrations in food and feed or to alleviate their adverse effects on animals. Some of these treatments show promising prospects for commercial application, while others have had commercial applications already. However, until reliable, cost-effective, commercially applicable methods are more widely available, problems associated with mycotoxin contamination and the economic losses resulting, will continue to be seen in food and agriculture industries.

Influence of glucocorticoids and activated charcoal on the lethality of rats after acute poisoning with T-2 toxin, diacetoxyscirpenol, or roridin A

Lethal doses of the trichothecene mycotoxins T-2 toxin (1.5 mg/kg), diacetoxyscirpenol (DAS; 2.3 mg/kg) or roridin A (1.3 mg/kg) were intravenously administered to rats. When rats were treated with either activated charcoal (Superchar liquid, Norit A; 1 g/kg, po) or dexamethasone (8 mg/kg, iv) 30 min after poisoning with one of the trichothecenes, lethality was only marginally reduced. However, when the combination of activated charcoal (Superchar liquid or Norit A) and dexamethasone was administered, the survival rate of animals after 30 days was significantly enhanced by up to 50%. Comparison between 2 preparations of activated charcoal, Norit AR with a surface area of 1,000 m2/g and Superchar liquidR with a surface area of 3,000 m2/g, each in combination with dexamethasone, revealed no difference in their therapeutic efficacy. Prednisolone (60 mg/kg) was as effective as dexamethasone (8 mg/kg), each administered with activated charcoal, in preventing death in acute T-2 toxicosis.

In vitro neutralization of T-2 toxin toxicity by a monoclonal antibody

A T-2 toxin specific monoclonal antibody, IgG1 K, with a low level of ELISA cross-reactivity to Acetyl T-2, HT-2, and iso T-2 toxins has been produced. The ability of this monoclonal antibody to neutralize the cytotoxicity of T-2 toxin in PHA stimulated cultures of human lymphocytes was determined by the MTT method. The complete neutralization of the toxic effect of 0.02 microM T-2 toxin was obtained with 0.03 microM of MoAb, whereas the 50% neutralizing dose (ND50) was observed at 0.009 microM of MoAb. Partial neutralization was observed with Acetyl T-2 toxin (ND50 = 0.038 microM) and HT-2 (ND50 = 0.94 microM). These results could represent a rational for clinical use of T-2 toxin specific monoclonal antibody in prophylaxis and therapy of T-2 toxemia.

Immunologic protection against VX intoxication in experimental animals

Rabbits immunized with an artificial VX-antigen could survive 1 x LD95 of VX challenge on the 7th day and the 31st day after the last immunization. One hundred microliters of rabbit anti-VX antiserum given intravenously immediately before 1 x LD95 of VX or 200 microliters of antiserum intraperitoneally 1-10 days before 1 x LD95 VX protected all the tested mice from death. The antiserum could prevent the in vitro inhibition of Torpedo AChE activity by VX and reduced its effect on brain AChE activity in vivo. No protective effect of the antiserum was observed on the Torpedo AChE activity inhibited by sarin and soman.

Management of toxicoses

This article provides information on the detoxification of and supportive care for poisoned animals. Involved are measures to control life-threatening manifestations of toxicoses, to remove agents from the digestive tract, skin, or eyes, and to promote removal of systemically absorbed toxicants. The use of these methods is often of paramount importance in an effort to limit organ damage and to enable a poisoned animal to survive.

Monoclonal antibodies against the presynaptic calcium channel antagonist omega-conotoxin GVI A from cone snail poison

Monoclonal antibodies have been prepared against omega-conotoxin GVI A, a peptide isolated from marine snails of the genus Conus (Conus geographus and Conus magus). This toxin is a blocker of select presynaptic Ca2+ channels in the central nervous system. Antigenic omega-conotoxin GVI A was synthesized as a covalent conjugate with bovine serum albumin and injected s.c. An ELISA assay combined with a competitive inhibition assay was used to select and characterize monoclonal antibodies able to recognize and bind the free toxin. Several of the antibodies were found to block omega-conotoxin GVI A inhibition of 45Ca transport into rat brain synaptosomes and to block omega-conotoxin GVI A binding to membranes from the same preparation. The antibodies recognize native, synthetic toxin, and are useful for analysis of toxin in biological fluids.

Reduction of anguidine toxicity in rats by atropine and methylatropine

Lethality of anguidine (diacetoxyscirpenol) in rats and mice appears to be the result of primary or secondary cardiovascular collapse and to be related to severe tissue destruction in the gut and elsewhere. Experiments were performed in rats to examine the effect on anguidine lethality of treatment with several agents that alter gut function or toxic effects of other chemicals in the gut. Administration of atropine sulfate or methylatropine nitrate by sc injection to rats immediately following administration of an LD50 of anguidine and again 4 hr later gave modest but significant protection against anguidine lethality. The drugs were effective over a range of doses between 2.5 and 20 mg/kg, without a clear dose response, and probably were effective at doses lower than 2.5 mg/kg. S-Adenosylmethionine, 25 mg/kg, given to rats at the time of administration of an LD50 of anguidine and again 4 hr later gave some evidence of protection also. Semiquantitative evaluation of pathologic changes in the small intestine, a target of anguidine, indicated partial protection by atropine sulfate against anguidine toxicity at that site. Atropine-treated rats showed less severe damage, earlier resolution of damage, or both.

Therapeutic effect of dexamethasone in T-2 toxicosis

T-2 Toxin is a mycotoxin that induces toxemia characterized by numerous hematological and biochemical changes. We have previously shown that prostaglandin (PG) production in brain tissue is increased following T-2 toxin. The present study was designed in order to test the effect of dexamethasone on brain prostaglandins and survival of rats subjected to T-2 toxin. Furthermore, the effect of BW 755c, a dual inhibitor of the cyclooxygenase and lipoxygenase pathways of arachidonate metabolism, on the survival of rats exposed to T-2 toxin was also examined. The present study demonstrated that dexamethasone increases the survival of rats exposed to a highly lethal T-2 toxicosis. This effect was demonstrated at low as well as high doses and at different times after T-2 administration. Dexamethasone depressed PGE2 levels in the brain cortex 6 hr after T-2 toxin but abolished the reduction of PGE2 in brain cortex seen 24 hr after T-2. BW 755c had no consistent effect on the survival of rats in T-2 toxicosis. It is suggested that dexamethasone might be a useful therapeutic agent in T-2 toxicosis in animals and humans, but its mechanism of action remains obscure.

Protective effect of a PAF-acether antagonist, BN 52021, in trichothecene toxicosis

Trichothecenes are mycotoxins which produce lethal toxicosis in humans and animals, yet no adequate therapeutic regimen has been developed. This study provides evidence that the selective platelet activating factor (PAF) antagonist, BN 52021 (5-15 mg/kg i.v.) can prolong the survival of conscious rats exposed to a highly lethal T-2 toxicosis. These data also suggest that PAF is an important mediator of this unique toxicosis.