Influence of ionizing radiation on crotoxin: biochemical and immunological aspects

Scavenger receptors mediate increased uptake of irradiated T.gondii extracts by J774 macrophages

PURPOSE

Protein extracts developed increased immunogenicity without the aid of adjuvants after gamma irradiation. Gamma irradiation of snake venom increased antivenin production by detoxification and enhanced immunity, probably due preferential uptake of irradiated venoms by macrophage scavenger receptors. We studied this uptake of irradiated soluble Toxoplasma gondii extract (STag) by the J774 macrophage cell line similar to antigen presenting cells.

MATERIAL AND METHODS

We labeled STag by biosynthesis in living tachyzoites with radioactive amino acids before purification and irradiation or by adding labels as biotin or fluorescein in stored STag, for quantitative studies or subcellular distribution visualization.

RESULTS

There was enhanced binding and uptake of irradiated STag into the cells compared to non-irradiated STag. Using fluorescein labeled antigens and morphological assays, we confirmed that cells avidly ingested both native and irradiated proteins but native STag were digested after ingestion while irradiated proteins remained in the cell, suggesting diverse intracytoplasmic pathways. Native or irradiated STag present the same in vitro sensitivity to three types of peptidases. Inhibitors of scavenger receptors (SRs) such as Dextran sulfate (SR-A1 blocker) or Probucol (SR-B blocker) affect the specific uptake of irradiated antigens, suggesting its association with enhanced immunity.

CONCLUSIONS

Our data suggests that cell SRs recognize irradiated proteins, mainly SRs for oxidized proteins, leading to antigen uptake by an intracytoplasmic pathway with fewer peptidases that prolongs presentation to nascent major histocompatibility complex I or II and enhances immunity by better antigen presentation.

Toxoplasma gondii in CD36 -/- mice shows lethal infection and poor immunization with probable macrophage immune defects

Experimental toxoplasmosis is an excellent model for adaptive immune response. Gamma-irradiated tachyzoites or soluble tachyzoite antigen extracts (STag) induce protection against experimental toxoplasmosis in mice. Scavenger receptors recognize irradiated proteins, promote their entry into cells, and lead to antigen presentation. CD36 is a specific scavenger receptor involved in intracellular transport of free fatty acid (FFA), cellular recycling, and intracellular trafficking in lipid rafts outside the lysosomal pathways. CD36 is also associated with an altered immune response, as CD36^-/- mice presented some immune defects in the cyst-forming Toxoplasma gondii. We studied T. gondii infection in CD36^-/- mice, naïve or immunized, with irradiated T. gondii STags by investigating protection, antibody production, and primed macrophage transplantation. CD36^-/- mice presented no resistance against the viable RH tachyzoites, even after immunization with gamma-irradiated STags that protected wild-type mice. The animals presented poor humoral responses to both immunogens despite adequate levels of serum immunoglobulins. CD36^-/- mice failed to induce protection against virulent T. gondii infection with inadequate antibody production or an innate response. Irradiated antigens failed to induce antibodies in CD36^-/- mice and only produced adequate levels of immunoglobulin G when transplanted with irradiated STag-primed wild-type macrophages. The CD36 pathway is necessary for humoral response against the irradiated antigen; however, several other pathways are also involved in mounting a humoral response against any antigen. CD36 is a multipurpose molecule for FFA and lipid transport, as well as for the immune response, and gamma radiation mimics the innate response by targeting irradiated antigens of this pathway.

Lyophilized Progenitor Tenocyte Extracts: Sterilizable Cytotherapeutic Derivatives with Antioxidant Properties and Hyaluronan Hydrogel Functionalization Effects

Cultured primary progenitor tenocytes in lyophilized form were previously shown to possess intrinsic antioxidant properties and hyaluronan-based hydrogel viscosity-modulating effects in vitro. The aim of this study was to prepare and functionally characterize several stabilized (lyophilized) cell-free progenitor tenocyte extracts for inclusion in cytotherapy-inspired complex injectable preparations. Fractionation and sterilization methods were included in specific biotechnological manufacturing workflows of such extracts. Comparative and functional-oriented characterizations of the various extracts were performed using several orthogonal descriptive, colorimetric, rheological, mechanical, and proteomic readouts. Specifically, an optimal sugar-based (saccharose/dextran) excipient formula was retained to produce sterilizable cytotherapeutic derivatives with appropriate functions. It was shown that extracts containing soluble cell-derived fractions possessed conserved and significant antioxidant properties (TEAC) compared to the freshly harvested cellular starting materials. Progenitor tenocyte extracts submitted to sub-micron filtration (0.22 µm) and 60Co gamma irradiation terminal sterilization (5−50 kGy) were shown to retain significant antioxidant properties and hyaluronan-based hydrogel viscosity modulating effects. Hydrogel combination products displayed important efficacy-related characteristics (friction modulation, tendon bioadhesivity) with significant (p < 0.05) protective effects of the cellular extracts in oxidative environments. Overall, the present study sets forth robust control methodologies (antioxidant assays, H2O2-challenged rheological setups) for stabilized cell-free progenitor tenocyte extracts. Importantly, it was shown that highly sensitive phases of cytotherapeutic derivative manufacturing process development (purification, terminal sterilization) allowed for the conservation of critical biological extract attributes.

Long-term antibody response and protective effect induced by attenuated scorpion toxins: Involvement of memory plasma cells

In Algeria, Androctonus australis hector scorpion envenomation remains a major problem of public health because of non-efficient therapy. The development of safe vaccine against scorpion venom could be one key strategy for the envenomation prevention. The irradiation of venom by γ-rays develops suitable immunogens which produced effective antivenom and safe vaccine. In this study, we investigated the ability of the irradiated toxic fraction (γ-FtoxG50) to induce long-term memory humoral response in immunized animals (mice and rabbits), by involving the long-lived plasma cells to prevent efficiently the lethality of scorpion envenomation. For this purpose, an appropriate immunization schedule was established in mice and rabbits using three (3) similar doses of γ-FtoxG50 associated with Alum adjuvant. Obtained results indicate that the long-term immunogenicity of γ-FtoxG50 is able to induce the long-term memory humoral response with a high level of specific antibodies. The long-term persistence of antibody levels could depend on bone marrow memory plasma cells. These cells produce continuously antibodies without antigen stimulus. Furthermore, an enhanced memory response was obtained post-repeated envenomation with toxic native venom that leads to improved protection of animals. Together, pre-existing protective antibodies and the activation of memory B-cells could induce a rapid neutralization of scorpion toxins and long-term protection against scorpion envenomation.

Characterization and evaluation of the enzymatic activity of tetanus toxin submitted to cobalt-60 gamma radiation

BACKGROUND

Tetanus toxin blocks the release of the inhibitory neurotransmitters in the central nervous system and causes tetanus and its main form of prevention is through vaccination. The vaccine is produced by inactivation of tetanus toxin with formaldehyde, which may cause side effects. An alternative way is the use of ionizing radiation for inactivation of the toxin and also to improve the potential immunogenic response and to reduce the post-vaccination side effects. Therefore, the aim of this study was to characterize the tetanus toxin structure after different doses of ionizing radiation of 60Co.

METHODS

Irradiated and native tetanus toxin was characterized by SDS PAGE in reducing and non-reducing conditions and MALD-TOF. Enzymatic activity was measured by FRET substrate. Also, antigenic properties were assessed by ELISA and Western Blot data.

RESULTS

Characterization analysis revealed gradual modification on the tetanus toxin structure according to doses increase. Also, fragmentation and possible aggregations of the protein fragments were observed in higher doses. In the analysis of peptide preservation by enzymatic digestion and mass spectrometry, there was a slight modification in the identification up to the dose of 4 kGy. At subsequent doses, peptide identification was minimal. The analysis of the enzymatic activity by fluorescence showed 35 % attenuation in the activity even at higher doses. In the antigenic evaluation, anti-tetanus toxin antibodies were detected against the irradiated toxins at the different doses, with a gradual decrease as the dose increased, but remaining at satisfactory levels.

CONCLUSION

Ionizing radiation promoted structural changes in the tetanus toxin such as fragmentation and/or aggregation and attenuation of enzymatic activity as the dose increased, but antigenic recognition of the toxin remained at good levels indicating its possible use as an immunogen. However, studies of enzymatic activity of tetanus toxin irradiated with doses above 8 kGy should be further analyzed.

Bradykinin-Potentiating Activity of a Gamma-Irradiated Bioactive Fraction Isolated from Scorpion (Leiurus quinquestriatus) Venom in Rats with Doxorubicin-Induced Acute Cardiotoxicity: Favorable Modulation of Oxidative Stress and Inflammatory, Fibrogenic and Apoptotic Pathways

Although doxorubicin (Dox) is a backbone of chemotherapy, the search for an effective and safe therapy to revoke Dox-induced acute cardiotoxicity remains a critical matter in cardiology and oncology. The current study was the first to explore the probable protective effects of native and gamma-irradiated fractions with bradykinin-potentiating activity (BPA) isolated from scorpion (Leiurus quinquestriatus) venom against Dox-induced acute cardiotoxicity in rats. Native or irradiated fractions (1 μg/g) were administered intraperitoneally (i.p.) twice per week for 3 weeks, and Dox (15 mg/kg, i.p.) was administered on day 21 at 1 h after the last native or irradiated fraction treatment. Electrocardiographic (ECG) aberrations were ameliorated in the Dox-treated rats pretreated with the native fraction, and the irradiated fraction provided greater amelioration of ECG changes than that of the native fraction. The group pretreated with native protein with BPA also exhibited significant improvements in the levels of oxidative stress-related, inflammatory, angiogenic, fibrogenic, and apoptotic markers compared with those of the Dox group. Notably, the irradiated fraction restored these biomarkers to their normal levels. Additionally, the irradiated fraction ameliorated Dox-induced histological changes and alleviated the severity of cardiac injury to a greater extent than that of the native fraction. In conclusion, the gamma-irradiated detoxified fraction of scorpion venom elicited a better cardioprotective effect than that of the native fraction against Dox-induced acute cardiotoxicity in rats.

Gamma irradiated protease from Echis pyramidum venom: A promising immunogen to improve viper bites treatment

Echis pyramidum (Epy) is a venomous snake belongs to Viperidae family; it causes fetal coagulopathy systemic effects and death. Searching for more effective and safe antivenom is mandatory for viper bites treatment. Proteases are the most lethal components in viper venom inducing hemorrhage, edema and coagulation problems. Thus, the study aims to evaluate the potency of the prepared antisera and their neutralizing properties against the biological activities induced by whole Epy venom individually. Echis pyramidum metalloprotease enzyme (60 kDa) was purified using size-exclusion followed by DEAE-ion exchange chromatography. The purified Epy metalloprotease enzyme (SVMP) was detoxified with 1.5 kGy gamma rays from cobalt⁶⁰ gamma cell and used for immunization. 1.5 kGy irradiated Epy metalloprotease (SVMPi) showed less lethal activity (LD₅₀) compared to the corresponding native immunogen. The prepared antisera boosted against whole Epy venom (WV), 1.5 kGy irradiated whole Epy venom (WVi), SVMP and SVMPi were tested for neutralization of lethality and biological activities induced by Epy venom. The antibodies elicited against WVi and SVMPi were 30,000 and 20,000 EU, respectively. The anti-SVMPi serum showed the highest neutralization of lethality (ED₅₀) compared to the other prepared antisera. In addition, it prolonged the clotting time from 49.0 ± 2.5 to 176.2 ± 1.4 s. Furthermore, it demonstrated a highly neutralizing activity against edema induction and hemorrhage of Epy venom by 66.8% and 94.3%, respectively compared with the other prepared antisera. These findings would encourage further studies for using gamma irradiated purified fraction(s) from different snake venoms as safe antigen(s) to produce more effective antivenoms.

Radiation effects on Toxoplasma antigens: different immune responses of irradiated intact tachyzoites or soluble antigens in experimental mice models

Purpose: Purpose: Protein irradiation causes aggregation, chain breakage, and oxidation, enhancing its uptake by antigen-presenting cells. To evaluate if irradiated proteins participate on the protection, we studied the immune response induced in mice immunized with irradiated soluble extracts of T. gondii tachyzoites (STag) or irradiated intact T. gondii RH tachyzoites (RH^0.25 kGy).Material and Methods: Soluble extracts of Toxoplasma gondii tachyzoites (STag) were irradiated at different dose by Cobalt-60 source. By polyacrylamide gel electrophoresis (SDS-Page) we evaluated the effects on primary structures of protein STags induced by irradiation. By Enzyme-linked Immunosorbent Assay (ELISA) we evaluated the difference between humoral immune response induced by irradiated STag or RH tachyzoites in immunized mice from the detection of specific immunoglobulin G (IgG) antibodies in the serum of immunized mice. From challenge with viable RH strain of T. gondii we evaluated the protection induced in the immunized animals. By cytometry we performed the phenotyping of T and B lymphocytes in the peripheral blood of the immunized animals.Results: Irradiation dose of 1.5 kGy induced minimal changes in most proteins, without affecting their antigenicity or immunogenicity. Immunization showed saturation at the dose of 10 µg/mice, with worst response at higher doses. STag irradiated at 1.5  kGy (STag^1.5 kGy) induced higher survival and protection similar to T. gondii RH strain irradiated at 0.25 kGy (RH^0.25 kGy), with higher serum levels of high affinity IgG compared to STag native. Blood immune memory cells of mice immunized with STag^1.5 kGy had higher proportions of CD19⁺ (cluster of differentiation 19) and CD4⁺ (cluster of differentiation 14) cells, whereas mice RH^0.25 kGy had high proportion of memory CD8⁺ (cluster of differentiation 8) cells.Conclusions: Our data suggest that major histocompatibility complex type I (MHCI) pathway, appears seem to be used by RH^0.25 kGy to generate cytotoxic cells while STag1.5 kGy uses a major histocompatibility complex type II (MHCII) pathway for B-cell memory, but both induce sufficient immune response for protection in mice without any adjuvant. Irradiation of soluble protein extracts enhances their immune response, allowing similar protection against T. gondii in mice as compared to irradiated intact parasites.

Gamma irradiation of Toxoplasma gondii protein extract improve immune response and protection in mice models

Gamma radiation induces protein changes that enhance immunogenicity for venoms, used in antivenin production. Coccidian parasites exposed to gamma radiation elicit immune response with protection in mice and man, but without studies on the effect of gamma radiation in soluble acellular extracts or isolated proteins. Toxoplasmosis is a highly prevalent coccidian disease with only one vaccine for veterinary use but with remaining tissue cysts. Total parasite extracts or recombinant proteins used as immunogen induce usually low protection. Here, we study gamma radiation effect on T. gondii extracts proteins (STAG) and its induced immunity in experimental mice models. By SDS-PAGE, protein degradation is seen at high radiation doses, but at ideal dose (1500 Gy), there are preservation of the antigenicity and immunogenicity, detected by specific antibody recognition or production after mice immunization. Immunization with STAG irradiated at 1500 Gy induced significant protection in mice immunized and challenged with distinct T. gondii strains. In their blood, higher levels of specific CD19⁺, CD3⁺CD4⁺ and CD3⁺CD8⁺ activated cells were found when compared to mice immunized with STAG. Irradiated T. gondii tachyzoites extracts induce immune response and protection in mice in addition, could be a feasible alternative for Toxoplasma vaccine.

New insights into the structural characteristics of irradiated crotamine

Background

Since ionizing radiation has the potential to alter the molecular structure and affect the biological properties of biomolecules, it has been successfully employed to attenuate animal toxins. The present study aimed to characterize the structural modifications on irradiated crotamine, a toxin from Crotalus durissus terrificus venom, using circular dichroism (CD), fluorescence, Fourier transformed infrared spectroscopy (FTIR), atomic force microscopy (AFM) and differential scanning calorimetry (DSC).

Methods

A combination of size exclusion and ion-exchange chromatography was used to purify the peptide using crude venom. The pure toxin was then submitted to 2 kGy gamma irradiation doses from a cobalt-60 source. Native and irradiated crotamine were analyzed using a fluorescence spectrophotometer. Wavelength was fixed at 295 nm and fluorescence emission scans were collected from 300 to 400 nm. CD and FTIR techniques were used to identify the secondary structure of both samples. DSC analyses were performed at a starting temperature of 20 °C up to a final temperature of 90 °C. AFM provided a 3D profile of the surfaces of both crotamine forms adsorbed on mica.

Results

Fluorescence spectroscopy showed that the quantum yield of the irradiated form decreased. CD spectra of native and irradiated crotamine solutions showed differences between the samples in wavelength, indicating that irradiation induced a transition of a small portion of the random coil regions towards an α-helical conformation. FTIR and CD showed that the native and irradiated crotamine spectra were different with regard to secondary structure. The thermodynamic analysis showed that irradiation caused changes in the calorimetric profile and CD showed that temperature-induced changes also occur in the secondary structure. Finally, AFM showed the possible formation of insoluble aggregates.

Conclusions

Our results indicate that irradiation leads to progressive changes in the structure of the toxin, which could explain a decrease in myotoxic activity.

Development and evaluation of gamma irradiated toxoid vaccine of Salmonella enterica var Typhimurium

Development of a single effective vaccine against non-typhoidal salmonellosis is very challenging due to the presence of hundreds of serovars of Salmonella which are antigenically different from each other. The Salmonella enterotoxin (Stn), a common virulence factor occurring amongst a wide range of serovars, used as a formalized toxoid vaccine has been found to be effective against homologous and heterologous serovars. However, the process of formalization has its own drawbacks. Gamma radiation (γ) on the other hand is widely used as a safe and convenient method of sterilization worldwide. In this experiment we used gamma rays to inactivate the partially purified Stn of Salmonella enterica serovar Typhimurium (DT 193). The toxoid obtained was tested for its immunogenicity and loss of toxicity and then used to formulate a gamma irradiated toxoid vaccine (ITST). The efficacy of the developed ITST was tested in Kuroiler, a Broiler breed, against homologous and heterologous challenges (S. Typhimurium and S. Gallinarum) administered intra-peritoneally and orally. Birds in groups challenged with S. Typhimurium by both routes recorded protective indices (PI) of 100% while birds in groups challenged intra-peritoneally with S. Gallinarum recorded PI of 83.33% and those challenged orally scored 100%. The overall protective index (PI) being 95.83%. The antibody titres calculated as geometric mean with standard error at 1:10(-4) dilutions showed a steep rise after the first dose and peaked at week 6 post primary vaccinations. Thus the ITST was found very effective in protecting poultry against both the challenge organisms tested.

New nanostructured silica adjuvant (SBA-15) employed to produce antivenom in young sheep using Crotalus durissus terrificus and Apis mellifera venoms detoxified by cobalt-60

Equine antivenom is considered the only treatment for animal-generated envenomations, but it is costly. The study aimed to produce Apis mellifera (Africanized honeybee) and Crotalus durissus terrificus (C.d.t.) antivenoms using nanostructured silica (SBA-15) as adjuvant and cobalt-60 ((60)Co)-detoxified venoms utilizing young sheep. Natural and (60)Co-irradiated venoms were employed in four different hyperimmunization protocols. Thus, 8 groups of 60- to 90-d-old sheep were hyperimmunized, enzyme-linked immunosorbent assay (ELISA) serum titers collected every 14 d were assessed clinically daily, and individual weight were measured, until d 84. Incomplete Freund's (IFA) and nanostructured silica (SBA15) adjuvants were compared. The lethal dose (LD(50)) for both venoms was determined following intraperitoneal (ip) administration to mice. High-performance liquid chromatography on reversed phase (HPLC-RP) was used also to measure the (60)Co irradiation effects on Apis venom. At the end of the study, sheep were killed in a slaughterhouse. Kidneys were histologically analyzed. LD(50) was 5.97 mg/kg Apis and 0.07 mg/kg C.d.t. for native compared to 13.44 mg/kg Apis and 0.35 mg/kg C.d.t. for irradiated venoms. HPLC revealed significant differences in chromatographic profiles between native and irradiated Apis venoms. Native venom plus IFA compared with SBA-15 showed significantly higher antibody titers for both venoms. Apis-irradiated venom plus IFA or SBA-15 displayed similar antibody titers but were significantly lower when compared with native venom plus IFA. Weight gain did not differ significantly among all groups. (60)Co irradiation decreased toxicity and maintained venom immunogenic capacity, while IFA produced higher antibody titers. SBA-15 was able to act as an adjuvant without producing adverse effects. Hyperimmunization did not affect sheep weight gain, which would considerably reduce the cost of antiserum production, as these sheep were still approved for human consumption even after being subjected to hyperimmunization.

Ovalbumin modified by gamma irradiation alters its immunological functions and allergic responses

It is well known that gamma (gamma)-ray irradiation results in the alteration of biological function of bioactive materials such as proteins, saccharides and lipids. In this study the effect of gamma-irradiation on the chemical and immunological property of an allergen, ovalbumin (OVA), was investigated. Irradiation of more than 10 kGy resulted in the alteration of the structure of OVA. However, OVA treated with 10 kGy irradiation (10 kGy-OVA), but not 100 kGy-OVA, fully maintained immunological reactivity to a monoclonal antibody specific to the intact allergen (clone 14). Mice immunized with 10 kGy- as well as 100 kGy-OVA showed significantly lower antibody response to the allergen than those with intact OVA in a gamma-ray dosage-dependent manner. Especially immunization of both 10 kGy- and 100 kGy-OVA induced a significant decrease of OVA-specific IgE. Splenocytes of mice immunized with irradiated OVA showed a significant reduction in OVA-specific T cell proliferation and the secretion of Th1-type (IFN-gamma and IL-2) and Th2-type cytokines (IL-4 and IL-6). The expression of T cell activation markers such as CD25 and CD44 was also down-regulated in T cells of mice immunized with irradiated OVAs. These results suggest that gamma-ray irradiation of OVA suppress humoral and cellular immune responses specific to the allergen OVA, and the modification method with gamma-irradiation may be available for the control of allergy.

Distribution of 125I-labeled crotamine in mice tissues

Crotamine is a strong basic polypeptide from Crotalus durissus terrificus (Cdt) venom composed of 42 amino acid residues tightly bound by three disulfide bonds. It causes skeletal muscle spasms leading to spastic paralysis of hind limbs in mice. The objective of this paper was to study the distribution of crotamine injected intraperitoneally (ip) in mice. Crotamine was purified from Cdt venom by gel filtration followed by ion exchange chromatography, using a fast-performance liquid chromatography (FPLC) system. Purified crotamine was irradiated at 2 kGy in order to detoxify. Both native and irradiated proteins were labeled with (125)I using chloramine T method, and separated by gel filtration. Male Swiss mice were injected ip with 0.1 mL (2 x 10(6)cpm/mouse) of (125)I native or irradiated crotamine. At various time intervals, the animals were killed by ether inhalation and blood, spleen, liver, kidneys, brain, lungs, heart, and skeletal muscle were collected in order to determine the radioactivity content. The highest levels of radioactivity were found in the kidneys and the liver, and the lowest in the brain.

Evaluation of the effect of gamma rays on the venom of Vipera lebetina by biochemical study

Snake bites represent a serious public health problem in many areas of the world. In Algeria, two widespread snakes are Vipera lebetina and Cerastes cerastes. Vipera lebetina venom causes local hemorrhage and necrosis, and it may lead to permanent limb loss. The principal causes of mortality after snakebites are acute renal failure and hemorrhage, which occur not only locally, at the site of the bite, but also systemically, contributing to the cardiovascular shock characteristic of severe envenomation. Gamma radiation has been shown to be effective for attenuating venom toxicity. Vipera lebetina venom was irradiated with two doses of gamma rays (1 and 2 kGy) from a 60Co source, and the venom's toxic, enzymatic, and structural properties were analyzed. Intraperitoneal injection of the irradiated venoms (100–500 µg/20 g mouse body mass) revealed a significant decrease of the toxicity. Irradiated venoms with 1 and 2 kGy doses were four and nine times less toxic, respectively, than the native venom. A biochemical characterization of in vitro enzymatic activities was performed. Vipera lebetina displayed in vitro caseinolytic, amidolytic, esterasic, coagulant, and phospholipase A2 activities. Caseinolytic, amidolytic, esterasic, and coagulative activities were reduced for the irradiated venoms; only phospholipase A2 activity was abolished in the irradiated venom with a dose of 2 kGy. The native and irradiated venoms were separated by gel filtration and electrophoresis. Chromatographic and electrophoretic profiles were drastically changed as compared with the native venom. Vipera lebetina venom detoxified by gamma rays was used for active immunization, and the presence of antibody in the immune sera was detected by ELISA. The immunogenic properties were preserved and the antisera obtained with the irradiated venoms could cross-react. Antisera were able to neutralize the toxic effect of V. lebetina native venom. These results indicate that irradiation of V. lebetina venom with a dose of 2 kGy can promote a significant detoxification, keeping the immunological properties intact.Key words: Vipera lebetina venom, gamma radiation, enzymes, detoxification, immune sera, immunoreactivity.

60Co gamma irradiation prevents Bothrops jararacussu venom neurotoxicity and myotoxicity in isolated mouse neuromuscular junction

The ability of gamma radiation from 60Co (2000 Gy) to attenuate the toxic effects of Bothrops jararacussu venom was investigated on mouse neuromuscular preparations in vitro. A comparative study between the effects of native and irradiated venoms was performed on both phrenic--diaphragm (PD) and extensor digitorum longus (EDL) preparations by means of myographic, biochemical and morphological techniques. Native venom (10 and 20 micro g/ml) induced a concentration--dependent paralysis of both directly and indirectly evoked contractions on PD preparations. At 20 micro g /ml, it also caused a pronounced myotoxic effect on the EDL muscle preparation that was characterized by an increase of creatine kinase release and by several morphological changes of this preparation. By contrast, irradiated venom, even at concentrations as high as 40 micro g/ml, induced neither paralyzing nor myotoxic effects. It was concluded that 60Co gamma radiation is able to abolish both the paralyzing and the myotoxic effects of B. jararacussu venom on the mouse neuromuscular junction. These findings support the hypothesis that gamma radiation could be an important tool to improve antisera production by reducing toxicity while preserving immunogenicity.

Effects of (60)Co gamma radiation on crotamine

Ionizing radiation can change the molecular structure and affect the biological properties of biomolecules. This has been employed to attenuate animal toxins. Crotamine is a strongly basic polypeptide (pI 10.3) from Crotalus durissus terrificus venom composed of 42 amino acid residues. It induces skeletal muscle spasms leading to a spastic paralysis of hind limbs in mice. The objective of the present study was to carry out a biochemical study and a toxic activity assay on native and irradiated crotamine. Crotamine was purified from C.d. terrificus venom by Sephadex G-100 gel filtration followed by ion-exchange chromatography, and irradiated at 2 mg/ml in 0.15 M NaCl with 2.0 kGy gamma radiation emitted by a 60Co source. The native and irradiated toxins were evaluated in terms of structure and toxic activity (LD50). Irradiation did not change the protein concentration, the electrophoretic profile or the primary structure of the protein although differences were shown by spectroscopic techniques. Gamma radiation reduced crotamine toxicity by 48.3%, but did not eliminate it.

Effect of heating on the toxic, immunogenic and immunosuppressive activities of Crotalus durissus terrificus venom

The venom of South American rattlesnake Crotalus durissus terrificus is very toxic but poorly immunogenic and it has an immunosuppressive ability. The heating of venom at 56, 70 or 100 degrees C for 30 min caused a diminution in the lethal, phospholipase A(2) and myotoxic activities. SDS-PAGE analysis of the heated venom showed that the proteins of higher molecular weights were the most affected by heating whereas proteins with lower molecular weights (20,000-14, 000) were the most resistant to heating. The immunosuppressive effect was studied in mice immunized with human serum albumin (HSA) 1 h after receiving either heated venom or heated crotoxin. The heating of venom at 70 or 100 degrees C reduced its immunosuppressive effect whereas crotoxin had its suppressive effect reduced only when heated at 100 degrees C. The heating of venom at 56, 70 or 100 degrees C did not change its immunogenicity. These results suggest that heat treatment may be a useful technique to help in the production of antiserum to crotalid venom.

Influence of temperature upon effects of crotoxin and gamma-irradiated crotoxin at rat neuromuscular transmission

The influence of temperature upon the effects of crotoxin (CTX), from Crotalus durissus terrificus venom, and gamma-irradiated (60Co, 2000 Gy) crotoxin (iCTX) was studied in rat neuromuscular transmission 'in vitro'. Indirect twitches were evoked in the phrenic-diaphragm preparation by supramaximal strength pulses with a duration of 0.5 ms and frequency of 0.5 Hz. The phospholipase A(2) (PLA(2)) enzymatic activity of CTX and iCTX was assayed against phosphadityl choline in Triton X-100. At 27 degrees C, CTX (14 microg/ml) did not affect the amplitude of indirectly evoked twitches. However, at 37 degrees C, CTX induced a time-dependent blockade of the neuromuscular transmission that started at 90 min and was completed within 240 min. iCTX (14 microg/ml) was inneffective on the neuromuscular transmission either at 27 or 37 degrees C. The PLA(2) enzymatic activity of CTX at 37 degrees C was 84 and that at 27 degrees C was 27 micromol fatty acid released/min/mg protein, and that of the iCTX at 37 degrees C was 39 micromol fatty acid released/min/mg protein. Thus, it was concluded that the mechanism of detoxification of CTX by gamma radiation at the neuromuscular level relies on the loss of its PLA(2) enzymatic activity.

Gabaergic-benzodiazepine system is involved in the crotoxin-induced anxiogenic effect

The behavioral effects of crotoxin (CTX), the major component of Crotalus durissus terrificus venom, were studied in rats submitted to the open field, holeboard, and social interaction tests. CTX (100, 250, and 500 microg/kg, i.p.) was administered 2 h before the tests. In the open field, CTX reduced ambulation (250 microg/kg) and rearing (250 and 500 microg/kg) and increased grooming (100 and 250 microg/kg) and freezing (250 microg/kg). In the holeboard and social interaction, all the CTX doses evaluated decreased, respectively, head dip and head dipping, and social interaction time. The CTX-induced behavioral alterations could be attributed to its neuromuscular transmission blockade, but this possibility was ruled out because CTX (250 and 500 microg/kg, i.p., 2 h before the rotarod test) was unable to modify the rotarod performance of rats. The involvement of the benzodiazepine receptor in the CTX-induced behavioral alterations was investigated through the pretreatment (30 min before the tests, i.p.) of the animals with diazepam (1.2 mg/kg), or flumazenil (4 and 10 mg/kg). Both diazepam and flumazenil antagonized the CTX-induced behavioral alterations in the open field, holeboard, and social interaction tests. This study demonstrated that: (1) CTX is an anxiogenic compound; and (2) the gabaergic-benzodiazepine system may play a role in the CTX-induced anxiogenic effect.

Toxicity and immunogenicity of Crotalus durissus terrificus venom treated with different doses of gamma rays

Crotalus durissus terrificus venom (CDT venom) was irradiated with four different doses of gamma rays (2, 3, 5 and 10 kGy) from a 60Co source and their structural, toxic and immunogenic properties were analysed. Venom irradiated with 2 and 3 kGy were, respectively, 2.7 and 13.5 times less toxic than the native one, whereas the 5 or 10 kGy irradiated venom were at least 100 times less toxic than nonirradiated venom. Irradiated venom with all doses were immunogenic and the antibodies elicited by them were able to recognise the native venom in ELISA. However the toxoid produced with 2 kGy irradiation dose had its immunogenicity improved. Antisera raised against this toxoid had a higher neutralising capacity than those produced against the native venom. Irradiation of venom with 2 kGy dose was the most effective to inactivate the CDT venom toxicity and improve its immunogenicity.

Tests for detection of snake venoms, toxins and venom antibodies: review on recent trends (1987-1997)

Various methods developed for the detection of snake venoms, toxins and venom antibodies, during the last decade is reviewed. Radioimmunoassay, agglutination assay, enzyme-linked immunosorbent assay (ELISA), fluorescence immunoassay etc. have been used for detection of venoms and toxins. Important contributions have been made to improve the specificity, sensitivity, rapidity and simplicity of the ELISA method. Monoclonal antibodies and affinity-purified venom-specific antibodies were used to achieve species specificity of ELISA and the latter seems to be the ideal for venom detection. Incorporation of avidin-biotin system as well as the fluorogenic substrate in the enzyme immunoassay sufficiently increased the sensitivity of the assay to detect venom concentrations to picogram levels. The ability to use undiluted blood and other whole biological fluids reduce the assay time considerably. Although there have been several reports were on venom detection, so far only a few field kits have been developed. This implies that the experiments and design were only at the laboratory levels and still more work has to be carried out before it could be used in the field. Concerning the venom antibody detection, ELISA has been used extensively and the humoral response of patients envenomed by snake has been investigated in detail. Non-specific reactivity along with cross-reactivity still limits the use of ELISA for species identification in epidemiological studies. Overall, ELISA remains the suitable method for the detection of snake venoms, toxins and venom antibodies in body fluids. The possible use of a biosensor approach to solve some of the problems associated with the ELISA method are also discussed.

Reduction of crotoxin-induced neuromuscular blockade by gamma radiation

A comparative study between crotoxin and gamma irradiated crotoxin was performed on the indirectly evoked twitches and tetani of sciatic nerve-extensor digitorum longus muscle of rats. Crotoxin (3 to 14 microg/ml) decreased the amplitude of twitches and induced a slight tetanic fade, and irradiated crotoxin did not significantly affect either twitch amplitude or tetanic tension. Since gamma radiation reduced the neurotoxicity of crotoxin it may be useful for the production of anticrotalic serum.

Effect of gamma irradiation on the behavioral properties of crotoxin

Crotoxin has been detoxified with gamma radiation in order to improve crotalic antiserum production. Nevertheless, present knowledge of the biological characteristics of irradiated crotoxin is insufficient to propose it as an immunizing agent. Crotoxin is known to increase the emotional state of rats and to decrease their exploratory behavior (Moreira EG, Nascimento N, Rosa GJM, Rogero JR and Vassilieff VS (1996) Brazilian Journal of Medical and Biological Research, 29: 629-632). Therefore, we decided 1) to evaluate the effects of crotoxin in the social interaction test, which has been widely used for the evaluation of anxiogenic drugs, and 2) to determine if irradiated crotoxin induces behavioral alterations similar to those of crotoxin in the social interaction, open-field and hole-board tests. Male Wistar rats (180-220 g) were used. Crotoxin (100, 250, and 500 micrograms/kg) was injected intraperitoneally 2 h before the social interaction test. Similarly, irradiated crotoxin (2000 Gy gamma radiation from a 60Co source) was administered at the doses of 100, 250, and 500 micrograms/kg for the hole-board test, and at the doses of 1000 and 2500 micrograms/kg for the open-field and social interaction tests. ANOVA complemented with the Dunnett test was used for statistical analysis (P < 0.05). Crotoxin decreased the social interaction time(s) at the doses of 100, 250 and 500 micrograms/kg (means +/- SEM) from 51.6 +/- 4.4 to 32.6 +/- 3.7, 28.0 +/- 3.6 and 31.6 +/- 4.4, respectively. Irradiated crotoxin did not induce behavioral alterations. These results indicate that 1) crotoxin may be an anxiogenic compound, and 2) in contrast to crotoxin, irradiated crotoxin was unable to induce behavioral alterations, which makes it a promising compound for the production of crotalic antiserum.