Biomedical subjects

M Goyffon

Publications and source records attributed to M Goyffon.

At least 19 recordsLinked to original sources

PubMed2006

[Venomous and poisonous animals--I. Overview].

Venomous animals that are able to innoculate or inject venom and poisonous animals that cannot inject venom but are toxic when ingested belong to all zoological groups. They can be encountered worldwide in any ecosystem on land and at sea but they are more common and more dangerous in tropical areas. This first article of a series to appear in the next issues of Medecine Tropicale presents an overview of species involved in envenomations and poisonings. In addition to a brief reviewing geographic risks and circumstances in which bites, stings or ingestion occur, some information is provided about antivenim therapy, the only etiological treatment.

Amphibians↗

PubMed2005

[Dangerous scorpions from Niger].

Two dangerous scorpion species are responsible for the severe human envenomations in Niger, Leiurus quinquestriatus (H. et E.), the most abundant, and Androctonus aeneas C.L. Koch, less frequent and described in a Sahel country for the first time. Up to now, A. aeneas was known in North Africa only. Its venom is highly toxic for humans, similar to those of the most dangerous species living in Africa, such as L. quinquestriatus and other species belonging to the genus Androctonus, A. australis (L.) and A. mauretanicus (Poc.), for the envenoming treatment of which specific antivenoms are prepared. Taking into account the absence of a specific antivenom for A. aeneas, the paraspecific neutralising effect of these antivenoms should be tested.

Animals↗

PubMed2005

Round table of November 20th, 2004: recommendations for improving the management of envenomations.

The round table underlines the necessity to follow the epidemiological and clinical surveys in order to precise the incidence and severity of snakebites and inform the health authorities that could thus arrange to take in charge envenomation accidents. Simple therapeutic protocols adapted to epidemiological and clinical data will be elaborated according to each level of health pyramid. They will be included in the health staff training and integrate traditional practitioners whose role must be clearly defined. An experimental and clinical validation must confirm its appropriateness with countries and victims needs. Some microeconomic surveys are necessary to identify adapted funding and thus improve their accessibility

Africa↗

PubMed2005

[Recombinant antibodies: a new application in scorpion envenomation?].

Serotherapy is the only specific treatment for envenomation. The antibodies are obtained after the purification of serum from hyperimmunised horses and are used after fragmentation in the form of polyclonal Fab or F(ab)'2. The anti-venom sera are heterogeneous, and their protective effect is often weak. The administration of these preparations induces risks of immediate or delayed side effects: hypersensitivity reactions, anaphylactic shock and serum sickness. This observation led us to develop new forms of antibodies produced by molecular engineering, capable of specifically neutralizing the neurotoxins responsible for the toxicity of the venom of Androctonus australis Hector. The recombinant antibody fragments are more homogeneous than conventional antivenoms and perfectly characterized in terms of specific activity. The method used to obtain them eliminates the risk of transmission by non-conventional transmissible agents. The earliest results confirm the importance of these new molecules (scFv recombinant Fab, diabody, triabody) and their ability to neutralize the action of scorpion neurotoxins. They could open the path to a new generation of more homogeneous antivenoms that are better tolerated and have well-characterized intrinsic properties.

Animals↗

PubMed2003

Design and evaluation of a diabody to improve protection against a potent scorpion neurotoxin.

Diabodies are recombinant, dimeric, antibody-based molecules composed of two non-covalently associated single-chain antibody fragments that bind to an antigen in a divalent manner. In an attempt to develop more effective therapeutic molecules against scorpion venoms, we designed a diabody derived from monoclonal antibody 9C2, which neutralizes the toxicity of scorpion neurotoxin AahI in mammals. The recombinant diabody produced in the periplasm of Escherichia coli was purified to homogeneity in a single step by protein L-agarose affinity chromatography. It was functional, and possessed a high binding affinity to AahI (8 x 10(-11) M). The bivalence of the diabody was confirmed by size-exclusion chromatography, isoelectrofocussing and electron microscopic observations. Finally, the diabody showed high thermal stability in serum and demonstrated protective activity when injected intraperitoneally in mice experimentally envenomed with toxin AahI. In conclusion, the diabody format gives the 9C2 molecule advantageous properties that are particularly important for potential clinical applications in the treatment of envenomations.

Animals↗

PubMed2002

[Action of venoms on blood coagulation: diagnosis of hemorrhagic syndromes].

Venoms from Viperidae, Crotalidae, some Australian Elapidae and few Colubridae are a mixture of enzymes which impact on blood coagulation in several ways. These proteins can be classified as haemorragins which induce disorders of the capillary permeability, disintegrins and related proteins which disturb the clotting time while acting on plate adhesion, and proteases which cleave peptides. Venoms contain molecules directed against several targets of the coagulation system. The same molecule may present different activities. Components of snake venoms are used in diagnostic coagulation tests, fundamental research and as drugs against infectious agents, cancer or haematological disorders. The structural differences between proteins from snake venoms and natural coagulation factors and the target diversity of the venom components explain why it remains illusory to treat bleedings when acting just at symptom level. Conversely, antivenom, whose components are directed against the venom proteins, is the only aetiological therapy effective against snake envenomations.

Animals↗

PubMed2002

[Clinical and biological surveillance of envenomed patients].

Faced with an envenomation, the problem is to take sufficiently rapidly the decision to administer the only effective treatment--immunotherapy--, to know which antivenom to choose and how long to administrate it. If the snake is not identified, symptoms and initial development give information on the type of venom. It is convenient to classify the symptoms according to four clinical types: i) the cobra syndrome with a potentially fatal evolution within two to ten hours and which resembles an Elapid bite, ii) the viper syndrome associating bleeding and inflammation, which can be due either to a viper, pit viper or, in Australia, to Elapids, iii) disturbance of blood circulating functions and iv) disturbance of other live functions. Between the third to the half of snakebite victims present no envenomation. Severe envenomations must be monitored in an intensive care unit, with experience in emergency management and monitoring of patients with major life-threatening conditions. Throughout the world, snakebites induce more than 100,000 deaths every year. Schematically, the emergency may be considered in terms of seconds for blood circulation disorders, minutes for respiratory paralysis, and hours for the coagulopathy.

Algorithms↗

PubMed2002

[Scorpion stings in sub-Saharan Africa].

Scorpionism in Sub-Saharan Africa is a poorly known problem but regarded as a public health preoccupation in several countries, especially Niger. The lack of knowledge of this question is due to non-existent information concerning mainly the composition of the scorpion fauna in Sub-Saharan areas, the distribution and density of dangerous species and the frequency and severity of scorpion stings in the Sub-Saharan areas. Until now, only the presence of Leiurus quinquestriatus and its involvement in fatal accidents have been attested to. In many areas, the presence of other classically dangerous species has not been confirmed, nor the dangerous potential of certain species belonging for example to the genera Androctonus. Buthus or Hottentota. The efficacy of prevention, treatment and scorpion control depend necessarily on further study of the fauna and medical investigations. Such studies are entirely feasible.

Africa South of the Sahara↗

PubMed2002

Round table and synthesis of the meeting.

Our knowledge of the epidemiology of scorpion stings and snakebites remains fragmentary but sufficient, nevertheless, to be able to confirm that envenomations constitute a real public health problem throughout Africa. In order for the health authorities to be able to improve management of this problem, data collection must be enhanced. The objective should be to determine what kinds of intervention are necessary (quantity of antivenom serum and drugs, in particular) and where they should be applied. Specialists must come to a rapid consensus for a simple therapeutic protocol to be used in peripheral health centres where means are often scarce. Training for health personnel is also insufficient. Appropriate courses must be organised for medical doctors and nurses within both their basic and on-going training. These courses must necessarily involve health personnel from rural zones must affected by envenomations. The availability of antivenom serum--the only specific, efficacious drug--must be improved as soon as possible. If quantitative and geographic needs can be determined by epidemiological studies, then distribution must be developed by original means (grouping orders at national level, direct orders) and diversified financial support (purchase on the open market, local authority grants, community participation). The symposium attendees agreed to meet again within two years' time to evaluate progress in the area.

Africa↗

PubMed2001

Construction and functional evaluation of a single-chain antibody fragment that neutralizes toxin AahI from the venom of the scorpion Androctonus australis hector.

9C2 is a murine monoclonal IgG that participates in the neutralization of Androctonus australis hector scorpion venom. It recognizes AahI and AahIII, two of the three main neurotoxins responsible for almost all the toxicity of the venom when injected into mammals. Using PCR we cloned the antibody variable region coding genes from 9C2 hybridoma cells and constructed a gene encoding a single-chain antibody variable fragment molecule (scFv). This scFv was produced in the periplasm of Escherichia coli in a soluble and functional form and purified in a single step using protein L-agarose beads yielding 1-2 mg.L(-1) of bacterial culture. scFv9C2 was predominantly monomeric but also tended to form dimeric and oligomeric structures, all capable of binding toxin AahI. The affinity of scFv and the parental mAb for toxin AahI and homologous toxin AahIII was of the same magnitude, in the nanomolar range. Similarly, purified forms of scFv9C2 completely inhibited the binding of toxin AahI to rat brain synaptosomes. Finally, scFv9C2 was efficient in protecting mice against the toxic effects of AahI after injection of the toxin and scFv to mice by the intracerebroventricular route in a molar ratio as low as 0.36 : 1. Thus, we produced a recombinant scFv that reproduces the recognition properties of the parent antibody and neutralizes the scorpion neurotoxin AahI, thereby opening new prospects for the treatment of envenomation.

Amino Acid Sequence↗

PubMed2001

A recombinant scFv/streptavidin-binding peptide fusion protein for the quantitative determination of the scorpion venom neurotoxin AahI.

We created a construct encoding a peptide known to mimic the binding properties of biotin fused to the carboxy-terminus of a scFv fragment that binds a scorpion toxin (AahI). This fusion protein was produced in the periplasm of bacteria and purified to homogeneity by single-step affinity chromatography on streptavidin-agarose with a yield close to 1 mg/l. DNA sequencing, dot blot and mass spectrometric analyses demonstrated the integrity of the soluble immunoconjugate. Fusion to the streptavidin-binding peptide did not affect the ability of the scFv to recognize its antigen with a high affinity (Kd = 2.3 x 10(-10) M). Similarly, the streptavidin-binding property was not impaired in the fusion protein. Thus, the immunoconjugate was bifunctional and had a low molecular mass of 28 kDa. This enabled us to develop rapid and sensitive immunoassays for the specific detection of the toxin AahI accurately to 0.6 ng/ml, opening up new perspectives for the diagnosis of envenomations.

Amino Acid Sequence↗

PubMed2000

Immunolabeling of CD3-positive lymphocytes with a recombinant single-chain antibody/alkaline phosphatase conjugate.

G3(3) is a novel murine monoclonal antibody directed against the CD3 antigen of human T lymphocytes which could be used to analyze lymphoid malignancies. We have produced and characterized a recombinant colorimetric immunoconjugate with the antigen-binding specificity of antibody G3(3). A gene encoding a single-chain antibody variable fragment (scFv) was assembled using the original hybridoma cells as a source of antibody variable heavy (VH) and variable light (VL) chain genes. The chimeric gene was introduced into a prokaryotic expression vector in order to produce a soluble scFv fused to bacterial alkaline phosphatase. DNA sequencing and Western blotting analyses demonstrated the integrity of the soluble immunoconjugate recovered from induced recombinant bacteria. The scFv/AP protein was bifunctional and similar in immunoreactivity to the parent G3(3) antibody. Flow cytometry and immunostaining experiments confirmed that the activity of the scFv/AP protein compares favourably with that of the parent antibody. The scFv/AP conjugate was bound to CD3 antigen at the surface of T cells and was directly detected by its enzymatic activity. Thus this novel fusion protein has potential applications as an immunodiagnostic reagent.

Alkaline Phosphatase↗

PubMed1999

A recombinant single-chain antibody fragment that neutralizes toxin II from the venom of the scorpion Androctonus australis hector.

Monoclonal antibody 4C1 specifically binds to and neutralizes the most potent neurotoxin (AahII) of the scorpion Androctonus australis. The cDNAs encoding the variable regions of this antibody were isolated by PCR-mediated cloning. A single-chain Fv gene was engineered and expressed in Escherichia coli. The recombinant protein had neutralizing activity similar to that of the intact antibody in vitro and in vivo. We have thus neutralized the pharmacological and biological properties of a scorpion neurotoxin with a single-chain Fv, which opens new perspectives for the treatment of envenomizations.

Amino Acid Sequence↗

PubMed1998

Production and characterization of a bivalent single chain Fv/alkaline phosphatase conjugate specific for the hemocyanin of the scorpion Androctonus australis.

A102 is a monoclonal antibody raised against the hemocyanin of the Tunisian scorpion Androctonus australis. It is directed against the subunit Aa6 and does not cross-react when tested against a variety of similar scorpion hemocyanins. Here, we report the construction of a plasmid encoding a recombinant enzyme-linked antigen-binding protein with the antigen-binding specificity of antibody A102. The DNA fragments encoding the variable domains of A102 were inserted into a prokaryotic expression vector so as to produce a single chain antibody variable fragment (scFv) fused to the bacterial alkaline phosphatase. The fusion protein preserved the IgG binding and alkaline phosphatase activities. Immunoelectron microscopic analysis showed that the recombinant protein bound antigen bivalently as is the case for natural antibodies. Crude preparations containing the conjugate were used in a rapid visual immunoassay for the specific detection of A. australis hemocyanin, using a droplet of hemolymph removed from live animals by puncture. The simplicity of the test made it suitable for the direct identification of animals belonging to this species. It could be useful in areas where A. australis, the most dangerous African scorpion, is found with other species from which it is not easy to distinguish using morphological criteria.

Alkaline Phosphatase↗

PubMed1998

Venoms, antivenoms and immunotherapy.

A century after the discovery of antivenom and despite real progress undertaken in its manufacture, its use remains largely empirical. Recent studies of pharmacokinetics of envenoming permitted improved understanding of immunotherapy. Improved purification of the antivenom by using immunoglobulin fragments has lead to increased tolerance and efficiency of antivenom. The respective advantages and disadvantages of F(ab')2 and F(ab) are discussed in relation to neutralising efficacy and clearance from the circulation. Although the time during which the action of antivenom remains beneficial after the bite is unknown, the superiority of intravenous administration has now been proved. Although immunisation procedures and purification and use of IgG fragments can be improved using modern technology, the future of immunotherapy seems promising. It is vital that therapeutic protocols should be rigidly adhered to in order to optimise immunotherapy. The use of vaccination has yet to be explored.

Animals↗

PubMed1998

[Scorpion toxins and defensins].

The scorpion venoms possess many neurotoxic peptides which constitute a group of molecular families with a common architecture and a high degree of polymorphism. This architecture is found also in circulating antimicrobial peptides belonging to the defensins family, which are especially structurally related to the blocking potassium channels neurotoxins. The diversification in functions with a unique architectural scheme is discussed taking in account the biophysiological characteristics of the scorpion order.

Animals↗

PubMed1997

Apamin improves learning in an object recognition task in rats.

Object recognition was investigated in rats in a two trial unrewarded task. In the first trial, two copies of the same object were presented. In the second trial, one of the familiar object and a new object were presented. Rats explored the new object longer than the familiar object when the intertrial time was 1 h, indicating that they remembered the familiar object, but not when the intertrial time was 24 h. Rats injected with apamin (a toxin which blocks specifically Ca(2+)-activated K(+)-channels) before the first trial spent more time in exploring the new object than the familiar object at the second trial, when it took place 24 h after the first trial. Injection of apamin just after the first trial or before the second trial did not modify the difference in exploration time between the new and the familiar object. These results suggest that the blockade of Ca(2+)-activated K(+)-channels could improve learning, but not consolidation nor restitution of the information, in an object recognition task.

Analysis of Variance↗

PubMed1997

[Snakes and scorpions: what are the risks for the traveler?].

The risk of being bitten by a snake or stung by a scorpion is low for the ordinary, non-thrill-seeking traveler. Travelers who plan hazardous outdoor activities should be advised to be careful and bring along adequate protective clothing (boots, long trousers, and gloves). If envenomation occurs, the victim should be immobilized and rushed to a treatment center. Administration of antivenin using massive doses in severe cases is the best therapy. For quickest and most efficient results, antivenins should be administered by the intravenous route. Packing antivenins is necessary only under special circumstances when high-risk activities are scheduled. In this case contingency planning may also be necessary taking into account health care facilities in the destination country and the availability of antivenins.

Animals↗