Comparison of Four Methods of RNA Extraction and cDNA Synthesis from The Venom of Peruvian Snakes of the Genus Bothrops of Clinical Importance

RNA purification and cDNA synthesis represents the starting point for molecular analyses of snake venom proteins-enzymes. Usually, the sacrifice of snakes is necessary for venom gland extraction to identify protein-coding transcripts; however, the venom can be used as a source of transcripts. Although there are methods for obtaining RNA from venom, no comparative analysis has been conducted in the Bothrops genus. In the present study, we compared four commercial methods for RNA purification and cDNA synthesis from venom (liquid, lyophilized, or long-term storage) of four clinically relevant species of Peruvian Bothrops. Our results show that the TRIzol method presents the highest yield of RNA purified from venom (59 ± 11 ng/100 µL or 10 mg). The SuperScript First-Strand Synthesis System kit produced high amounts of cDNA (3.2 ± 1.2 ng cDNA/ng RNA), and the highest value was from combination with the Dynabeads mRNA DIRECT kit (4.8 ± 2.0 ng cDNA/ng RNA). The utility of cDNA was demonstrated with the amplification of six relevant toxins: thrombin-like enzymes, P-I and P-III metalloproteinases, acid and basic phospholipases A2, and disintegrins. To our knowledge, this is the first comparative study of RNA purification and cDNA synthesis methodologies from Bothrops genus venom.

Pictolysin-III, a Hemorrhagic Type-III Metalloproteinase Isolated from Bothrops pictus (Serpentes: Viperidae) Venom, Reduces Mitochondrial Respiration and Induces Cytokine Secretion in Epithelial and Stromal Cell Lines

From the venom of the Bothrops pictus snake, an endemic species from Peru, we recently have described toxins that inhibited platelet aggregation and cancer cell migration. In this work, we characterize a novel P-III class snake venom metalloproteinase, called pictolysin-III (Pic-III). It is a 62 kDa proteinase that hydrolyzes dimethyl casein, azocasein, gelatin, fibrinogen, and fibrin. The cations Mg²⁺ and Ca²⁺ enhanced its enzymatic activity, whereas Zn²⁺ inhibited it. In addition, EDTA and marimastat were also effective inhibitors. The amino acid sequence deduced from cDNA shows a multidomain structure that includes a proprotein, metalloproteinase, disintegrin-like, and cysteine-rich domains. Additionally, Pic-III reduces the convulxin- and thrombin-stimulated platelet aggregation and in vivo, it has hemorrhagic activity (DHM = 0.3 µg). In epithelial cell lines (MDA-MB-231 and Caco-2) and RMF-621 fibroblast, it triggers morphological changes that are accompanied by a decrease in mitochondrial respiration, glycolysis, and ATP levels, and an increase in NAD(P)H, mitochondrial ROS, and cytokine secretion. Moreover, Pic-III sensitizes to the cytotoxic BH3 mimetic drug ABT-199 (Venetoclax) in MDA-MB-231 cells. To our knowledge, Pic-III is the first SVMP reported with action on mitochondrial bioenergetics and may offer novel opportunities for promising lead compounds that inhibit platelet aggregation or ECM-cancer-cell interactions.

Simultaneous identification of three clinically relevant peruvian pit vipers by multiplex loop-mediated isothermal amplification (mLAMP)

Previous knowledge about the taxonomic distribution of venomous snake species is very useful for epidemiological aspects of ophidism. Here, we sought to develop an assay for the differential identification of clinically relevant snakes in Peru: Bothrops atrox, Lachesis muta, and Crotalus durissus using a multiplex loop-mediated isothermal amplification (mLAMP) assay. For this, DNA was extracted from the shed snake skins and the mitochondrial genes Cytb, COI, and 12S rRNA were amplified and further sequenced, for the design of mLAMP reaction primers. For each snake species the forward and reverse primers, internal forward and reverse primers, and the loop primers were obtained, bearing the latter different fluorophores for product identification. Finally, the reaction was standardized in the presence of all primer sets, and an optimal amount of low molecular weight polyethyleneimine. The precipitated products were observed in a UV light transilluminator, finding a differential fluorescence according to the DNA used, with a detection limit to the naked eye in the range of 0.2-25 ng of DNA, within 30 min. This study is the first report on the use of mLAMP technology for the identification of venomous snakes.

Functional, immunological characterization, and anticancer activity of BaMtx: A new Lys49- PLA2 homologue isolated from the venom of Peruvian Bothrops atrox snake (Serpentes: Viperidae)

Bothorps atrox is responsible for most of the ophidism cases in Perú. As part of the envenoming, myotoxicity is one of the most recurrent and destructive effects. In this study, a myotoxin, named BaMtx, was purified from B. atrox venom to elucidate its biological, immunological, and molecular characteristics. BaMtx was purified using CM-Sephadex-C-25 ion-exchange resin and SDS-PAGE analysis showed a unique protein band of 13 kDa or 24 kDa under reducing or non-reducing conditions, respectively. cDNA sequence codified a 122-aa mature protein with high homology with other Lys49-PLA₂s; modeled structure showed a N-terminal helix, a β-wing region, and a C-terminal random coil. This protein has a poor phospholipase A2 enzymatic activity. BaMtx has myotoxic (DMM = 12.30 ± 0.95 μg) and edema-forming (DEM = 26.00 ± 1.15 μg) activities. Rabbit immunization with purified enzyme produced anti-BaMtx antibodies that reduced 50.28 ± 10.15% of myotoxic activity and showed significant cross-reactivity against B. brazili and B pictus venoms. On the other hand, BaMtx exhibits mild anti-proliferative and anti-migratory effects on breast cancer cells, affecting the ROS and NADH levels, which may reduce mitochondrial respiration. These results contribute to the understanding of B. atrox Lys49-PLA2 effects and establish the anticancer potential de BaMtx.

Fibrinogen-clotting enzyme, pictobin, from Bothrops pictus snake venom. Structural and functional characterization

A thrombin-like enzyme, pictobin, was purified from Bothrops pictus snake venom. It is a 41-kDa monomeric glycoprotein as showed by mass spectrometry and contains approx. 45% carbohydrate by mass which could be removed with N-glycosidase. Pictobin coagulates plasma and fibrinogen, releasing fibrinopeptide A and induces the formation of a friable/porous fibrin network as visualized by SEM. The enzyme promoted platelet aggregation in human PRP and defibrination in mouse model and showed catalytic activity on chromogenic substrates S-2266, S-2366, S-2160 and S-2238. Pictobin interacts with the plasma inhibitor α2-macroglobulin, which blocks its interaction with fibrinogen but not with the small substrate BApNA. Heparin does not affect its enzymatic activity. Pictobin cross reacted with polyvalent bothropic antivenom, and its deglycosylated form reduced its catalytic action and antivenom reaction. In breast and lung cancer cells, pictobin inhibits the fibronectin-stimulated migration. Moreover, it produces strong NADH oxidation, mitochondrial depolarization, ATP decrease and fragmentation of mitochondrial network. These results suggest by first time that a snake venom serinprotease produces mitochondrial dysfunction by affecting mitochondrial dynamics and bioenergetics. Structural model of pictobin reveals a conserved chymotrypsin fold β/β hydrolase. These data indicate that pictobin has therapeutic potential in the treatment of cardiovascular disorders and metastatic disease.

Biochemical and molecular characterization of the hyaluronidase from Bothrops atrox Peruvian snake venom

Snake venoms are a rich source of enzymes such as metalloproteinases, serine proteinases phospholipases A2 and myotoxins, that have been well characterized structurally and functionally. However, hyaluronidases (E.C.3.2.1.35) have not been studied extensively. In this study, we describe the biochemical and molecular features of a hyaluronidase (Hyal-Ba) isolated from the venom of the Peruvian snake Bothrops atrox. Hyal-Ba was purified by a combination of ion-exchange and gel filtration chromatography. Purified Hyal-Ba is a 69-kDa (SDS-PAGE) monomeric glycoprotein with an N-terminal amino acid sequence sharing high identity with homologous snake venom hyaluronidases. Detected associated carbohydrates were hexoses (16.38%), hexosamines (2.7%) and sialic acid (0.69%). Hyal-Ba selectively hydrolyzed only hyaluronic acid (HA; specific activity = 437.5 U/mg) but it did not hydrolyze chondroitin sulfate or heparin. The optimal pH and temperature for maximum activity were 6.0 and 40 °C, respectively, and its Km was 0.31 μM. Its activity was inhibited by EDTA, iodoacetate, 2-mercaptoethanol, TLCK and dexamethasone. Na⁺ and K⁺ (0.2 M) positively affect hyaluronidase activity; while Mg²⁺, Br²⁺, Ba²⁺, Cu²⁺, Zn²⁺, and Cd²⁺ reduced catalytic activity. Hyal-Ba potentiates the hemorrhagic and hemolytic activity of whole venom, but decreased subplantar edema caused by an l-amino acid oxidase (LAAO). The Hyal-Ba cDNA sequence (2020 bp) encodes 449 amino acid residues, including the catalytic site residues (Glu135, Asp133, Tyr206, Tyr253 and Trp328) and three functional motifs for N-linked glycosylation, which are conserved with other snake hyaluronidases. Spatial modeling of Hyal-Ba displayed a TIM-Barrel (α/β) fold and an EGF-like domain in the C-terminal portion. The phylogenetic analysis of Hyal-Ba with other homologous Hyals showed the monophyly of viperids. Further, Hyal-Ba studies may extend our knowledge of B. atrox toxinology and provides insight to improve the neutralizing strategies of therapeutic antivenoms.

[Characterization of thrombin like enzyme FROM Bothrops pictus venom]

OBJECTIVES

To perform a biochemical and molecular characterization of the coagulant principle from Bothrops pictus venom.

MATERIALS AND METHODS

We amplified the genetic sequence of this enzyme from cDNA and analyzed the homology of its nucleotide sequence and its deduced protein. This enzyme was also purified for N-terminal sequencing of first 20 amino acids and for coagulation assays using human plasma and human fibrinogen. Furthermore, cleavage pattern on fibrinogen was evaluated using SDS-PAGE and defibrinogenant activity on white mice (18-22 g). Finally, associated carbohydrate content, effect of protease inhibitors and chloride ions on its enzymatic activity were analyzed.

RESULTS

The Thrombin-like Enzyme from Bothrops pictus showed homology at primary level of structure with other previously reported TLEs from Viperidae family. Minimum Coagulant Dosis (MCD) on plasma and human fibrinogen were 18 and 6 µg, respectively, and its coagulant potency was 131.1 NHI Thrombin units. This TLE was stable under physiological conditions and chloride ions are not necessary for its activity. Detected associated carbohydrates were hexoses (25.76%), hexosamines (13.12%) and sialic acid (0.76%). Phenyl methyl sulphonyl fluoride (PMSF) and dithiothreitol (DTT) were the main inhibitors of its enzymatic activity, but heparin had no inhibitor effect.

CONCLUSIONS

The coagulant principle of Bothrops pictus venom is a Thrombin-like enzyme.

[Experimental efficacy of IgY antibodies produced in eggs against the venom of the Peruvian snake Bothrops atrox]

OBJECTIVES

To develop an immunization protocol in order to produce avian IgY immunoglobulins against Bothrops atrox Peruvian snake venom and to evaluate its neutralizing capacity.

MATERIALS AND METHODS

Six Hy Line Brown hens were immunized each two weeks using 500μg/doses of B. atrox venom in a period of two months. Each week, eggs were collected for IgY isolation from yolk using two consecutive steps with caprilic acid and ammonium sulfate. Detection of IgY anti-B. atrox were performed by double immunodiffusion, whereas title and cross-reactivity were analyzed using ELISA and Western Blot technics, respectively. Furthermore, letal dose (DL(50)) and Medium Effective Dose (DE(50)) were obtained by Probit analysis.

RESULTS

As a result of this protocol, chicken IgY's were obtained in a concentration of 8,5 ± 1,35 mg/yolk mL. DE50 from avian antivenom was 575 μL/venom mg. Cross-reactivity studies showed Bothrops atrox venom share more commom epitopes with Bothrops brazili (47%) than others Bothrops venoms showing Lachesis muta (19%) and Crotalus durissus (12%) venoms a low crossing reactivity, instead.

CONCLUSIONS

Using this procedure, we could purify chicken IgY with a neutralizant capacity of B. atrox venom which is comparable to the antivenom of equine origin and demonstrate its capacity as a immunoanalitical tool to evaluate the cross reactivity with others peruvian snakes.

[Variation of the enzymatic activity of Bothrops atrox "jergon" snake venom from three geographic regions, Peru]

OBJECTIVES

To study the variability in the composition and enzymatic activity of venom from adult Bothrops atrox specimens.

MATERIALS AND METHODS

We used venoms from adult snakes from Amazonas, Junín and Ucayali. Each of the venom samples underwent analysis for protein and number of bands by pagesds. Phospholipase A₂, hemolytic, amidolytic, coagulant, hemorrhagic activity were analyzed, also and proteolytic activity on casein and by zymogram. Additionally, immunodiffusion and neutralization assays in vitro were done with a polyvalent botropic serum from the national institute of health of Peru.

RESULTS

The amidolytic, coagulant, hemorrhagic, proteolytic by zymogram, phospholipase A₂, and indirect hemolytic activity were variable, demonstrating increased activity in the venoms from Amazonas, regarding proteolytic by zymogram, phospholipase A₂, and indirect hemolytic activity. While the amount of protein electrophoretic bands and proteolytic activity on casein did not demonstrated differences. Regarding neutralization tests, a 0.5 dose of antivenom was sufficient to effectively neutralize (>50%) the coagulant activity and phospholipase A₂ of all samples analyzed.

CONCLUSIONS

Some biological properties of the venom from adult Bothrops atrox of Peru are variable, without interference with the in vitro neutralization by the polyvalent botropic serum on coagulant and phospholipase A₂ properties of the venom.

Immunogenicity, safety and protective efficacy of one dose of the rhesus rotavirus vaccine and serotype 1 and 2 human-rhesus rotavirus reassortants in children from Lima, Peru

In a four cell trial, a single 10(4) plaque-forming unit dose of rhesus rotavirus (RRV) vaccine (serotype G3), a human rotavirus-rhesus rotavirus reassortant vaccine with serotype G1 specificity, a similar vaccine with serotype G2 specificity, or a placebo was administered with buffer orally at 2 months of age to 800 Peruvian infants. Only the RRV vaccine was associated with a febrile response (< 38 degrees C) that occurred in 9% of the infants on day 4 after vaccination. Diarrhea or other side-effects were not associated with administration of vaccine. Vaccine strains were shed by only 12-18% of the infants as determined by examination of a single stool specimen obtained on days 4 or 5 after vaccination. Fifty per cent of vaccines developed an IgA ELISA seroresponse; however, a serotype-specific seroresponse by plaque reduction neutralization was demonstrated in < 20% of the participants against each of the three candidate vaccine strains. Vaccine efficacy was evaluated by twice-weekly home surveillance for diarrheal diseases during 24 months post-immunization. Rotavirus diarrheal episodes were identified by ELISA. Only the RRV vaccine had a significant protective efficacy (29%, p = 0.03, chi-square test) against rotavirus diarrhea. Analysis of vaccine efficacy against rotavirus episodes of any severity in which no other enteropathogen was isolated showed a trend towards higher vaccine efficacy. In addition, a similar trend was observed in rotavirus-only episodes in which there was some degree of dehydration or when health services were utilized. Serotype G1 or G2 rotavirus strains were most prevalent during surveillance. Neither serotype G1 or serotype G2 vaccines were protective against serotype 1 or 2 rotavirus diarrhea, respectively. The serotype G2 vaccine was 84% protective against serotype 1 and 2 dehydrating rotavirus diarrhea in the small numbers of individuals evaluated. We conclude that one dose of 10(4) p.f.u. of the RRV, serotype G1, or serotype G2 rotavirus vaccine failed to induce either an adequate serotype-specific seroresponse or serotype-specific protection in children immunized at 2 months of age. Only the RRV vaccine induced a low level of protection against rotavirus diarrhea mainly of serotype G1 specificity. Future studies need to explore whether higher vaccine dose and/or more than one dose would increase the immunogenicity and efficacy of the rotavirus vaccine, especially in developing countries with a high level of baseline rotavirus antibodies.

Feeding during acute diarrhea as a risk factor for persistent diarrhea

Dietary intake during diarrhea in children less than three years of age was estimated from information recorded on illustrated dietary forms used by children's caretakers during the first week of illness in a prospective community-based study of diarrheal diseases in Lima, Peru. The frequency of consumption and the amount consumed of food groups and selected commonly consumed foods were analyzed by the final duration of the diarrheal episode. Cereals were less frequently consumed during the acute phase of diarrheal episodes that ultimately became persistent (> 14 days' duration), apparently shortening the duration of the episode by one day (median duration of four days in children not consuming vs three days in children consuming cereals during diarrhea, p < 0.02 Kaplan-Meier log-rank test). Only roots and tubers (mainly potatoes) were consumed in greater quantity during episodes that became persistent. There was no evidence that consumption of breast milk or non-maternal milk was associated with an alteration in diarrheal duration. This study provides further evidence of the beneficial effects of continuing feeding during diarrhea using foods available at the home level, especially cereals, which are commonly used in the diet of young children.

Transmission factors and socioeconomic status as determinants of diarrhoeal incidence in Lima, Peru

As part of a longitudinal, community-based study of diarrhoeal morbidity in a peri-urban community in Lima, Peru, a household survey was administered to ascertain possible risk factors, based on transmission routes, for diarrhoeal incidence. Socioeconomic information was also obtained in the survey and a composite socioeconomic status (SES) indicator was created based on four variables: income (wealth), ownership of 4 functioning electrical household appliances, community participation, and house construction. Both transmission factors and the SES indicator were analysed for their effects on diarrhoeal incidence using both bivariate and multivariate methods. The SES indicator, method of water storage, if the child was seen eating faeces or soil were all significantly associated with diarrhoeal incidence. In a final logistic model, water storage, location of defecation for children, child eating soil or faeces, and age, demonstrated significant results. Children in households with water stored in containers without a faucet were twice as likely to have a high incidence of diarrhoea (greater than 7 episodes/child/year). The SES indicator was not significant in the logistic model, but high SES was associated with whether or not the child was reported as having been seen eating faeces or soil and with non-use of latrines by adults. Also low SES households were more likely to have better water storage methods. Therefore, it would seem that (SES) does not independently determine diarrhoeal incidence, but rather may be functioning through these transmission factors to affect diarrhoeal incidence.

Epidemiologic, clinical, and laboratory characteristics of acute vs. persistent diarrhea in periurban Lima, Peru

Longitudinal studies of acute and persistent diarrhea in 677 children less than 3 years old were conducted for 27 months in an underprivileged, periurban community near Lima, Peru. Incidence rates and accurate durations of diarrhea were obtained by twice-weekly community-based surveillance and clinical and laboratory features of diarrheal episodes were documented. Study children had an overall incidence of diarrhea of 8.1 episodes per child-year and an incidence of persistent (greater than 14 days) diarrhea of 0.25 episodes per child-year. Episodes of longer duration were associated with young age (0-5 months) and more severe illness (greater than or equal to 6 diarrheal stools per day) in the first week. None of the laboratory tests performed in the first week of illness (fecal leukocytes, blood, reducing substances, pH, or fat) proved of value to identify episodes that would become persistent. Although steatorrhea was commonly present in the acute phase of the illness, it became less frequent by the third or subsequent week of illness in the persistent diarrheas. These results suggest that there are no clinical or laboratory features of acute diarrhea that are strongly predictive of the subset of diarrheas that persist. Thus, it is important that all diarrheal episodes should have appropriate fluid and dietary management and follow-up to detect the persistent diarrheas that may need special intervention.

Delayed cutaneous hypersensitivity: epidemiologic factors affecting and usefulness in predicting diarrheal incidence in young Peruvian children

Cell-mediated immunity, as assessed by delayed cutaneous hypersensitivity, can be diminished by malnutrition and viral infections. In turn, decreased immune functioning might lead to more frequent or more severe infectious diseases. Delayed cutaneous hypersensitivity was assessed in young Peruvian children by simultaneous application of seven standardized antigens and a negative control (Multitest CMI). Response to tuberculin was frequent and was higher in children vaccinated with Bacillus Calmette-Guérin, response to tetanus or diphtheria toxoids was also good, especially in children who had received at least two doses of diphtheria-tetanus toxoids-pertussis vaccine. Two summary assessments, the number of positive responses and the sum of indurations of all positive responses provided useful measures of delayed cutaneous hypersensitivity. Responsiveness, as assessed by these summary measures, was inversely related to the incidence of diarrhea, identified by household surveillance for the 6 months after the skin test. Undernutrition, as assessed by weight for age or length for age, was also a significant determinant of the incidence of diarrhea, but not the duration of episodes, in this group of study children. Depressed cell-mediated immunity and malnutrition may be important risk factors for diarrhea in developing country children.

Isolation and characterization of a fibrinogen-clotting enzyme from venom of the snake, Lachesis muta muta (Peruvian bushmaster)

A fibrinogen-clotting enzyme from the venom of the Peruvian bushmaster snake was purified to homogeneity by gel filtration on Sephadex G-100 followed by DEAE-cellulose ion-exchange chromatography using a linear ionic strength gradient with NaCl. The specific activity of the enzyme was 866 NIH U/mg, representing a 55-fold purification, with a recovery of 45%. The amino acid composition was Asx30, Thr14, Ser15, Glx33, Pro23, Gly22, Ala15, Val22, Cys18, Met3, Ile18, Leu23, Tyr2, Phe13, His8, Lys11, Arg11. The total carbohydrate content was 13.4%, comprised of 3.4% hexose, 8.7% hexosamine and 1.3% sialic acid. The enzyme was active against the synthetic amide substrate alpha-N-benzoyl-DL-arginine-p-nitroanilide (BAPNA) and against the ester substrates alpha-N-benzoyl-L-arginine ethyl ester (BAEE) and tosyl-L-arginine methyl ester (TAME). Kinetic parameters for TAME esterolysis were: Vmax, 135 mumoles/min/mg and Km, 2.5 x 10(-4) M. The pH optimum was 8.0. Vmax for BAPNA amidolysis was 0.363 mumoles/min/mg and Km, 7.5 x 10(-5) M. Enzyme activity was reduced by diethylpyrocarbonate and by photo-oxidation, suggesting that the enzyme is a serine protease with a histidine residue involved in the active site. The enzyme released fibrinopeptide A rapidly from purified human fibrinogen and fibrinopeptide B more slowly. Factor XIII was not activated and the clotting activity was not inhibited by heparin. A dose of 50 micrograms/kg brought about defibrinogenation in anaesthetized rats but rabbits were unaffected. A dose of 80 micrograms/kg defibrinogenated conscious rats after 5 hr. There were no hypotensive or haemorrhagic effects.