Neotropical Rattlesnake (Crotalus simus) Venom Pharmacokinetics in Lymph and Blood Using an Ovine Model.

The most abundant protein families in viper venoms are Snake Venom Metalloproteases (SVMPs), Snake Venom Serine Proteases (SVSPs) and Phospholipases (PLA2s). These are primarily responsible for the pathophysiology caused by the bite of pit-vipers; however, there are few studies that analyze the pharmacokinetics (PK) of whole venom (WV) and its protein families. We studied the pathophysiology, PK profile and differential absorption of representative toxins from venom of Neotropical Rattlesnake (Crotalus simus) in a large animal model (ovine). Toxins studied included crotoxin (the main lethal component), which causes moderate to severe neurotoxicity; SVSPs, which deplete fibrinogen; and SVMPs, which cause local tissue damage and local and systemic hemorrhage. We found that Whole Venom (WV) was highly bioavailable (86%) 60 h following intramuscular (IM) injection, and extrapolation suggests that bioavailability may be as high as 92%. PK profiles of individual toxins were consistent with their physicochemical properties and expected clinical effects. Lymph cannulated animals absorbed 1.9% of WV through lymph during the first 12 h. Crotoxin was minimally detectable in serum after intravenous (IV) injection; however, following IM injection it was detected in lymph but not in blood. This suggests that crotoxin is quickly released from the blood toward its tissue targets.

Use of irradiated elapid and viperid venoms for antivenom production in small and large animals.

This work evaluated the feasibility of using toxoids obtained by gamma radiation in the production of antivenoms in small and large animals. Mixtures of African snake venoms from viperids or elapids were used. The viperid mixture contained the crude venom of five species of the genera Echis and Bitis, while the elapid mixture contained the crude venom of six species of the genera Naja and Dendroaspis. The viperid mixture had an LD50 of 1.25 mg/kg in mice, and the elapid mixture had an LD50 of 0.46 mg/kg. Both viper and elapid aqueous mixtures were subjected to Cobalt-60 gamma irradiation in three physical states: lyophilized, frozen and liquid. Radiation doses ranged from 0.5 to 100 kGy. The LD50s of the lyophilized and frozen mixtures of both viperid and elapid mixtures remained unaltered with radiation doses as high as 100 kGy; nevertheless, in the liquid state, doses of 3.5 and 5.5 kGy reduced the venom toxicity of both the viperid and elapid mixtures to 7.25 mg/kg and 1.74 mg/kg; less toxic by factors of 5.8 and 3.8, respectively. Groups of four rabbits and three horses were immunized with either irradiated or non-irradiated mixtures. In vitro and in vivo analysis of the rabbit and horse sera revealed that neutralizing antibodies were produced against both irradiated (toxoids) and native venom mixtures. None of the animals used in this study, either immunized with native venom or toxoids, developed severe local effects due to the application of venoms mixtures. Gamma-irradiated detoxified venoms mixtures, under well-controlled and studied conditions, could be a practical alternative for the production of polyvalent equine serum with high neutralization potency against snake venoms.

Biodistribution and Lymphatic Tracking of the Main Neurotoxin of Micrurus fulvius Venom by Molecular Imaging.

The venom of the Eastern coral snake Micrurus fulvius can cause respiratory paralysis in the bitten patient, which is attributable to ß-neurotoxins (ß-NTx). The aim of this work was to study the biodistribution and lymphatic tracking by molecular imaging of the main ß-NTx of M. fulvius venom. ß-NTx was bioconjugated with the chelator diethylenetriaminepenta-acetic acid (DTPA) and radiolabeled with the radionuclide Gallium-67. Radiolabeling efficiency was 60%-78%; radiochemical purity ≥92%; and stability at 48 h ≥ 85%. The median lethal dose (LD50) and PLA2 activity of bioconjugated ß-NTx decreased 3 and 2.5 times, respectively, in comparison with native ß-NTx. The immune recognition by polyclonal antibodies decreased 10 times. Biodistribution of ß-NTx-DTPA-(67)Ga in rats showed increased uptake in popliteal, lumbar nodes and kidneys that was not observed with (67)Ga-free. Accumulation in organs at 24 h was less than 1%, except for kidneys, where the average was 3.7%. The inoculation site works as a depot, since 10% of the initial dose of ß-NTx-DTPA-(67)Ga remains there for up to 48 h. This work clearly demonstrates the lymphatic system participation in the biodistribution of ß-NTx-DTPA-(67)Ga. Our approach could be applied to analyze the role of the lymphatic system in snakebite for a better understanding of envenoming.

Eastern coral snake Micrurus fulvius venom toxicity in mice is mainly determined by neurotoxic phospholipases A2.

Here we show for the first time that the venom from an elapid (Micrurus fulvius) contains three finger toxin (3FTxs) peptides with low toxicity but high content of lethal phospholipases A2 (PLA2). The intravenous venom LD50 in mice was 0.3µg/g. Fractionation on a C18 column yielded 22 fractions; in terms of abundance, 58.3% of them were components of 13-14kDa and 24.9% were molecules of 6-7kDa. Two fractions with PLA2 activity represented 33.4% of the whole venom and were the most lethal fractions. Fractions with low molecular mass (<7000Da) partially and reversibly blocked the nicotinic acetylcholine receptor (nAChR), with the exception of one that blocked it completely. The fraction that blocked 100% contained two protein species whose dose-response was determined; the IC50s were 13±1 and 9.5±0.3nM. Despite the apparent effect on nAChR none of the low molecular mass fractions were lethal in mice, at concentrations of 1µg/g. From 2D-PAGE and LC-MS/MS, we identified fourteen species of PLA2, four protein species of C-type lectin, three zinc metalloproteinases, one phosphodiesterase and one 3FTx. The N-terminal amino acid sequence of fractions with biological interest was obtained. BIOLOGICAL SIGNIFICANCE: In contrast with coral snake venoms from South America, M. fulvius has minor amounts of low molecular mass components, but high content of PLA2, which is responsible for the venom lethality of this species. The results reported here contribute to better understanding of envenomation development and to improve antivenom design and production. These findings break from the paradigm that neurotoxicity caused by Micrurus venoms is mainly attributable to 3FTx neurotoxins and encourage future studies on Micrurus evolution and venom specialization. This article is part of a Special Issue entitled Non-model organisms.

Biodegradation of organic pollutants by halophilic bacteria and archaea.

Hypersaline environments are important for both surface extension and ecological significance. As all other ecosystems, they are impacted by pollution. However, little information is available on the biodegradation of organic pollutants by halophilic microorganisms in such environments. In addition, it is estimated that 5% of industrial effluents are saline and hypersaline. Conventional nonextremophilic microorganisms are unable to efficiently perform the removal of organic pollutants at high salt concentrations. Halophilic microorganisms are metabolically different and are adapted to extreme salinity; these microorganisms are good candidates for the bioremediation of hypersaline environments and treatment of saline effluents. This literature survey indicates that both the moderately halophilic bacteria and the extremely halophilic archaea have a broader catabolic versatility and capability than previously thought. A diversity of contaminating compounds is susceptible to be degraded by halotolerant and halophile bacteria. Nevertheless, significant research efforts are still necessary in order to estimate the true potential of these microorganisms to be applied in environmental processes and in the remediation of contaminated hypersaline ecosystems. This effort should be also focused on basic research to understand the overall degradation mechanism, to identify the enzymes involved in the degradation process and the metabolism regulation.