Variation in the antigenic characteristics of venom from the Mojave rattlesnake (Crotalus scutulatus scutulatus)

Genetic Basis for Variation of Metalloproteinase-Associated Biochemical Activity in Venom of the Mojave Rattlesnake (Crotalus scutulatus scutulatus)

The metalloproteinase composition and biochemical profiles of rattlesnake venom can be highly variable among rattlesnakes of the same species. We have previously shown that the neurotoxic properties of the Mojave rattlesnake (Crotalus scutulatus scutulatus) are associated with the presence of the Mojave toxin A subunit suggesting the existence of a genetic basis for rattlesnake venom composition. In this report, we hypothesized the existence of a genetic basis for intraspecies variation in metalloproteinase-associated biochemical properties of rattlesnake venom of the Mojave rattlesnake. To address this question, we PCR-amplified and compared the genomic DNA nucleotide sequences that code for the mature metalloproteinase domain of fourteen Mojave rattlesnakes captured from different geographical locations across the southwest region of the United States. In addition, the venoms from the same rattlesnakes were tested for their ability to hydrolyze fibrinogen, fibrin, casein, and hide powder azure and for induction of hemorrhage in mice. Overall, based on genomic sequencing and biochemical data, we classified Mojave rattlesnake venom into four distinct groups of metalloproteinases. These findings indicate that differences in nucleotide sequences encoding the mature proteinase domain and noncoding regions contribute to differences in venom metalloproteinase activities among rattlesnakes of the same species.

Complement inactivating proteins and intraspecies venom variation in Crotalus oreganus helleri

Complement inactivating properties were detected in venom from the southern California distribution of Crotalus oreganus helleri (Southern Pacific Rattlesnake). This activity showed strong geographic bias to the San Bernardino Mountain range, and venom from this area reacted strongly with Fraction 5 antiserum (AF5). However, venoms from the San Jacinto Mountain range, which have been previously shown to contain Mojave toxin, did not inhibit complement and did not react with AF5. AF5 has been previously shown to recognize a protease in C. scutulatus venom that inactivates complement, but the identity of this protein has remained unknown. Using a functional venomic approach, utilizing two-dimensional gel electrophoresis coupled with liquid chromatography and tandem mass spectrometry (LC/MS/MS), we have identified catrocollastatin and hemorrhagic toxin II (HT-2) as the primary proteins recognized by AF5. The information we present within this manuscript further illustrates the now well-known reality of intraspecies venom variation and the challenges faced in providing comprehensive polyvalent antivenoms.

The efficacy of two antivenoms against the venom of North American snakes

Mortality due to snake envenomation is not a major problem in the United States with approximately 8-12 deaths per year, but envenomation is a serious problem that can result in functional disability, loss of extremities, and a costly recovery. Physicians encounter different clinical situations with each new snakebite victim because of the geographical variations in snake venoms. The best and most acceptable form of treatment is the use of antivenom; however, it must be administered as soon as possible since it is not so effective at reducing local signs of envenomation such as necrosis. The antivenom in the United States is in short supply, expensive and may not even be the most effective for neutralizing all North American snake venoms. In this study, we tested two antivenoms. The first was a Crotalidae Polyvalent Fab fragment with Ovine origin (FabO) manufactured in London, and the second was Antivipmyn, a Mexican manufactured antivenom that is F(ab')(2) fragment produced in horse (Fab(2)H). The efficacy of the two antivenoms was tested with 15 different snake venoms found in North America. Three different assays were used to test the efficacy of the antivenoms, the in vivo serum protection test (ED(50)), antihemorrhagic and anticoagulant. The Fab(2)H antivenom was most effective in neutralizing the hemorrhagic activity of 78% of the hemorrhagic venoms used in this study. In the ED(50) assay, the Fab(2)H antivenom was effective in neutralizing all venoms used in this study, while FabO neutralized all but C. m. molossus venom. However, in most cases, FabO required less antivenom than Fab(2)H antivenom to neutralize three LD(50).

An internet database of crotaline venom found in the United States

Many snake venoms have been shown to be complex mixtures of pharmacologically important molecules, some of which have potential therapeutic value in the treatment of clot-induced ischemia, cancer and other human disorders. The literature contains many references on how venom and/or venom components are being used in medicine. Within the United States, there are 44 subspecies of poisonous snakes. Despite this rather vast diversity, 90% of the venom-related biomedical research conducted on native snakes found in the United States has been done on a limited number of the more common species. Since the venoms from most of the native species are not available or characterized, their composition and potential usefulness in medicine and applied biomedical research has not been explored. The Natural Toxins Research Center (NTRC) at Texas A&M University-Kingsville has developed a serpentarium that presently houses a population of over 250 snakes composed of 11 species and 20 subspecies. These snakes are cataloged on the Internet database along with their geographical location data, proteolytic activities, high performance liquid chromatography (HPLC) and electrophoretic titration (ET) profiles. Many of these snake venoms have never been characterized and few locale-specific differences within a species have been examined. These venoms can be queried through an on-line search routine. The database will be a useful starting point for anyone interested in isolating fibrinolytic enzymes, specific toxins, hemorrhagins, or other pharmacologically active proteins from snake venoms.

Envenomations

Envenomations are uncommon, challenging causes of critical care admissions. This article describes the diagnosis and treatment of envenomations that cause the most critical care admissions in the United States. Most are caused by the following animals: rattlesnakes, copperheads, cottonmouths, coral snakes, brown recluse spiders, and bark scorpions.

Mojave rattlesnake envenomation in southern California: a review of suspected cases

To clarify whether Mojave rattlesnake (Crotalus scutulatus scutulatus) envenomations occurring in California cause typical crotalid tissue effects, pain, edema, and ecchymosis, we reviewed charts of snakebite victims at a tertiary care teaching hospital and a moderate-size community hospital. Forty-two patients were bitten within the range of Mojave rattlesnakes. Eight snakes were identified as Mojave rattlesnakes (group 1); of these, four were confirmed by experts in snake identification (group 1a). Fifteen patients were reported bitten by other rattlesnake species (group 2), and in 19 envenomations the species was unknown (group 3). Seventy-five percent of patients in group 1 were reported to have local edema at the envenomation site compared with all of the patients in group 2. Ecchymosis was found in 25% of group 1 patients and 73% of group 2 patients. Pain was documented in only 12% of group 1 and 67% of group 2 victims. Neurotropic events, many severe, were found in 75% of group 1 patients compared with 7% of those in group 2. Although this study does not have the power to justify statistical evaluation, C. scutulatus envenomations do appear inclined to less tissue reaction. A disturbing trend toward severe neurotropic manifestations was also suggested in presumed Mojave rattlesnake envenomations.

Detection of alkaline phosphatase in venom by blotting methods

Venom alkaline phosphatase was detected using a blotting method following electrophoresis. The enzyme gave strong reactions in some venoms, but was absent in other venoms, some within the same species. The mol. wt of the enzyme is close to 100,000 and its pI is between 3.6 and 4.8. The enzyme was inactivated by EDTA and 2-mercaptoethanol, and lost activity by freezing and thawing. Endogenous venom alkaline phosphatase can interfere with alkaline phosphatase-based detection methods. Pre-screening for endogenous venom alkaline phosphatase is recommended prior to using alkaline phosphatase-based detection methods when studying snake venom.

Hemorrhagic and Mojave toxins in the venoms of the offspring of two Mojave rattlesnakes (Crotalus scutulatus scutulatus)

1. The venoms of two Mojave rattlesnakes and those of their offsprings were analyzed for Mojave toxin and hemorrhagic toxin. 2. The venom of one female, collected in Pima County, Arizona, and the venoms of her six offspring contained hemorrhagic toxin but not Mojave toxin (venom B). 3. The venom of the second female, captured in El Paso County, Texas, contained both toxins (A+B venom). Of her 10 offspring, five contained venom with both toxins, two had hemorrhagic toxin only, and three contained neither toxin. 4. Venoms that caused hemorrhage also inactivated complement. A pool of the venoms of the venom B offspring was less toxic than adult pooled venom A.

Cross-reactivities of monoclonal antibodies to a myotoxin from the venom of the broad-banded copperhead (Agkistrodon contortrix laticinctus)

A panel of murine monoclonal antibodies (MAbs) specific for a 14,500 mol. wt myotoxin of Agkistrodon contortrix laticinctus (broad-banded copperhead) venom was produced by cell fusion using the purified toxin as immunogen. The MAbs were used in immunoblotting and ELISA experiments to determine their immunological cross-reactivities. The three MAbs used in this study showed different immunoblotting and ELISA patterns when they were tested against 43 related and unrelated venom samples, indicating that they are specific for three different epitopes. MAb-42a specifically reacted with 50% of Agkistrodon venoms tested without cross-reacting with venoms of closely related species. This MAb reacted with venoms collected from Agkistrodon specimens from Florida, Kansas and Texas, but did not react with those from Louisiana, South Carolina, Ohio, New York or Mexico. MAb-6a showed similar reactivity but did react with venoms of snakes from Mexico. These results clearly indicate a geographical variation of the epitopes present in the myotoxin. Another antibody, MAb-18a, recognized an epitope present in the 14,500 mol. wt protein of all Agkistrodon venoms tested, but also reacted weakly with non-14,500 proteins from some Crotalus and Bothrops venoms tested. Both MAb-6a and MAb-18a neutralized the toxin-induced myonecrosis, but MAb-42a did not. Based on these results, the 14,500 mol. wt protein could serve as a general marker for venoms from snakes in the genus Agkistrodon found in North America.