Immunoreactivity between venoms and commercial antiserums in four Chinese snakes and venom identification by species-specific antibody

Comparative analysis of Deinagkistrodon acutus venom from Taiwan and China utilizing chromatographic, electrophoretic, and bioinformatic approaches, along with ELISA employing a monospecific antivenom

Deinagkistrodon acutus is a medically important pitviper inhabiting mainly South China and Taiwan. The hemorrhagic effects of its envenoming are compatible to its venom, which is abundant in metalloproteases (svMPs) and C-type lectin-like proteins. In this study, we investigated geographic variations in the venom of D. acutus collected from Taiwan and four Mainland Chinese provinces: Fujian, Jiangxi, Anhui, and Hunan. The variations were assessed through high-performance liquid chromatography, non-metric multidimensional scaling analysis, gel electrophoresis, and enzyme-linked immunosorbent assay (ELISA) with a monospecific antivenom (DaMAV) generated against the Taiwanese D. acutus venom, and discussed based on venom-protein sequences in databases and literature related to D. acutus venom. Additionally, the cross-reactivity of DaMAV against Crotalus horridus and Calloselasma rhodostoma venoms was investigated. We noted differential abundances of D. acutus venom metalloproteases, C-type lectin-like proteins, and phospholipase A2, along with point mutations and selective expression of serine protease isoforms. The ELISA results revealed that the venom from Taiwan was more reactive toward Taiwanese DaMAV than the four Mainland Chinese venoms, consistent with chromatographic profile differences, whereas C. horridus venom presented moderate cross-reactivity with DaMAV. The observed immunoreactivities of these venom with DaMAV can be attributed to the high prevalence of their PIII-svMPs, which are the dominant antigens, and the conservation of PIII-svMP epitopes.

Forensic identification of a fatal snakebite from Bungarus multicinctus (Chinese krait) by pathological and toxicological findings: a case report

Bungarus multicinctus (B. multicinctus) is one of the top ten venomous snakes in China, ranking first in lethality at 26.9-33.3%. However, to our knowledge, no forensic autopsy-related cases of death from B. multicinctus bite poisoning have been reported. There are surprisingly few reported cases of death from poisoning by other species of neurotoxic snakes. Neurotoxic snake venom is often highly toxic, and death can quickly occur when bitten in the wild if victims are not taken to a doctor in time. We presented a case of an adult female in Fujian Province of China who was bitten by a poisonous snake while digging for bamboo shoots in the mountains and died from the bite of B. multicinctus confirmed by enzyme-linked immunosorbent assays (ELISA) results. The autopsy's results, histopathological findings, and ELISA results reported here can be helpful for future forensic practice in B. multicinctus venom poisoning; we also briefly review the pathological changes of neurotoxin poisoning, which may be useful in other types of neurotoxin snake venom poisoning.

Effect of Agkistrodon halys antivenom in patients bit by green pit viper and the prognostic role of the disease - a retrospective cohort study

BACKGROUND AND AIMS

In Mainland China and Hong Kong, health authorities utilize Agkistrodon halys antivenom in the treatment of patients who sustained bites from green pit vipers. However, the treatment benefit of Agkistrodon halys antivenom among such patients is still controversial. The purpose of this study is to evaluate the coagulation parameters normalization time of Agkistrodon halys antivenom in patients who sustained green pit viper bites and explore independent risk factors of patient prognosis.

METHODS

Data were extracted from the Donghua Hospital Information System. Comparison of the two groups of patients - who used antivenom (GPUA) and who did not use antivenom (GPNUA) were performed using stratified analysis, univariate and multivariate ordered logistic regression models to evaluate the coagulation parameters normalization time. Univariate and multivariate ordered logistic regression models were used to explore independent risk factors of patient prognosis.

RESULTS

Between the GPUA and GPNUA groups, there is no significant difference in the coagulation parameters normalization time with the treatment of Agkistrodon halys antivenom. GPNUA consumed more cryoprecipitate and platelets and had a lower cost. The patient's severity of the bite, first coagulation profile, and dosages of fresh frozen plasma, platelet, and red cell suspension was found to be risk factors for the normalization time of coagulation parameters.

CONCLUSIONS

The therapeutic effect of Agkistrodon halys antivenom in green pit vipers bite patients is not quite satisfying. In addition, more attention should be paid to the first coagulation profile, blood clotting factors indices, platelet count (PLT), and hemoglobin when treating such patients.

Unexpected death in a young man associated with a unilateral swollen leg: Pathological and toxicological findings in a fatal snakebite from Deinagkistrodon acutus (Chinese moccasin)

Deinagkistrodon acutus (D. acutus), also known as the Chinese moccasin, is a viper species found throughout the southeastern parts of China, northern Vietnam and Laos. D. acutus envenomation can result in coagulopathy and lead to death if not treated correctly. A 20-year-old man was discovered with a severely swollen left thigh with overlying dark purple, discolored skin. He was immediately transported to hospital. Laboratory examinations revealed dysfunctional coagulation and fluid-electrolyte imbalances. He died 2 h later despite resuscitation efforts. Surveillance footage revealed that he had walked through a grass field while returning home that night. Autopsy and pathological examination findings revealed a large area of muscle necrosis of the left thigh, renal tubular necrosis, and hepatocyte necrosis. Potential fang marks were found on the decedent's jeans. Due to our suspicions, we performed specific enzyme-linked immunosorbent assays (ELISA) and detected D. acutus venom in the kidneys, left thigh muscle, liver, lung, spleen, and heart tissues of the decedent. In conclusion, the clinical manifestations, autopsy, histopathological examination, ELISA, and investigation results confirmed D. acutus envenomation.

Immunoreactivity and neutralization study of Chinese Bungarus multicinctus antivenin and lab-prepared anti-bungarotoxin antisera towards purified bungarotoxins and snake venoms

Bungarus multicinctus is the most venomous snake distributed in China and neighboring countries of Myanmar, Laos, north Vietnam and Thailand. The high mortality rate of B. multicinctus envenomation is attributed to the lethal components of α-, β-, γ- and κ- bungarotoxins contained in the venom. Although anti-B. multicinctus sera were produced in Shanghai, Taiwan and Vietnam, the most widely clinic used product was term as B. multicinctus antivenin and manufactured by Shanghai Serum Bio-technology Co. Ltd. In the present investigation, high purity α-, β- and γ-bungarotoxins were separately isolated from B. multicinctus crude venom. Rabbit anti- α-, β- and γ-bungarotoxin antisera were prepared by common methods, respectively. LD50 values of α-, β- and γ-bungarotoxins were systematically determined via three administration pathways (intraperitoneal, intramuscular and intravenous injections) in Kunming mice. LD50 values of β-bungarotoxin were closely related with injection routines but those of both α- and γ-bungarotoxins were not dependent on the injection routines. Commercial B. multicinctus antivenin showed strong immunoreaction with high molecular weight fractions of the B. multicinctus but weakly recognized low molecular weight fractions like α- and γ-bungarotoxins. Although B. multicinctus antivenin showed immunoreaction with high molecular weight fractions of Bungarus fasciatus, Naja atra, Ophiophagus hannah venoms but the antivenin only demonstrated animal protection efficacy against O. hannah venom. These results indicated that the high molecular weight fractions of the O. hannah played an important role in venom lethality but those of B. fasciatus and N. atra did not have such a role.

Preparation and detection of sea snake antisera raised in rabbits

Antivenoms are currently the most effective medication used in the treatment of snakebites. However, there were relatively few studies on preparation of antivenoms targeting sea snakes, especially common sea snakes in China. In this study, we sought to prepare and detect mono- and bispecific antisera raised in rabbits against venoms of two sea snakes, Hydrophis cyanocinctus and H. curtus. The results of enzyme-linked immunosorbent assay showed that the rabbit antisera generally showed clearly detectable immunological cross-reactions after the third immunization and indicated that the strength of cross-reactions increased with an increase in the immunizing dose. Proteins within the H. cyanocinctus and H. curtus venoms showed similar profiles and were mainly concentrated in the low-molecular-weight region (8-25 kDa). Western blotting results revealed that the bands of these low-molecular weight proteins were dense and showed strong immunogenicity. Although we detected comparatively few bands of the high-molecular-weight proteins, these also showed strong immunogenicity. Our results indicate that both mono- and bispecific antisera both can neutralize H. cyanocinctus and H. curtus venoms, and in this regard, the monospecific H. curtus and bispecific antiserum were found to be superior to the H. cyanocinctus antiserum. Given the increasing frequency of snakebites worldwide, we believe that the findings of this study will have high practical applicability.

Snake venom characteristic peptides: novel fingerprints for species identification by sheathless capillary electrophoresis-electrospray ionization-mass spectrometry

Snake venom is a complex mixture mainly consisting of proteins and peptides which varies with different species. These variations lead to different toxic mechanisms and different anti-venom serums for treatment and the determination of their use as drugs. Hence, it is important to develop a sensitive and reliable method to identify the species of snakes from venoms. Herein, we present a novel strategy based on the sheathless capillary electrophoresis-electrospray ionization-mass spectrometry (CESI-MS) system to characterize snake venom proteins. Through the determination of peptides, we found the characteristic peptides of 8 different snakes with high sensitivity (1 μg mL^-1) and high selectivity, which provided a reliable method for the species identification and purity detection of snake venom samples.

Effectiveness of repeated antivenom therapy for snakebite-related systemic complications

Objective

This study aimed to determine the effect of repeated antivenom therapy compared with that of single antivenom therapy for treating snakebite-related systemic complications.

Methods

A retrospective medical record review from January 2008 to September 2016 was performed. Patients with snakebite injury who visited the Emergency Department in one tertiary center of Korea were included. The primary outcome was the survival rate. The secondary outcome was the effect of repeated antivenom therapy for treating snakebite-related systemic complications compared with that of single antivenom therapy on hospital length of stay.

Results

A total of 110 patients with snakebites were included. All patients survived to discharge. Twenty-nine (26.4%) patients had snakebite-related systemic complications. Of these, nine patients received repeated antivenom therapy and 20 patients received single antivenom therapy. The length of stay was significantly longer in those who received repeated antivenom therapy compared with those who received single antivenom therapy (10.0 [4.0–11.0] vs. 3.5 [0–7.0] days).

Conclusion

We were unable to demonstrate any superiority of repeated versus single antivenom therapy. However, repeated antivenom therapy is associated with a longer hospital stay. The reason for this finding is unknown.

Development of sandwich ELISA and lateral flow strip assays for diagnosing clinically significant snakebite in Taiwan

Taiwan is an island located in the south Pacific, a subtropical region that is home to 61 species of snakes. Of these snakes, four species—Trimeresurus stejnegeri, Protobothrops mucrosquamatus, Bungarus multicinctus and Naja atra—account for more than 90% of clinical envenomation cases. Currently, there are two types of bivalent antivenom: hemorrhagic antivenom against the venom of T. stejnegeri and P. mucrosquamatus, and neurotoxic antivenom for treatment of envenomation by B. multicinctus and N. atra. However, no suitable detection kits are available to precisely guide physicians in the use of antivenoms. Here, we sought to develop diagnostic assays for improving the clinical management of snakebite in Taiwan. A two-step affinity purification procedure was used to generate neurotoxic species-specific antibodies (NSS-Abs) and hemorrhagic species-specific antibodies (HSS-Abs) from antivenoms. These two SSAbs were then used to develop a sandwich ELISA (enzyme-linked immunosorbent assay) and a lateral flow assay comprising two test lines. The resulting ELISAs and lateral flow strip assays could successfully discriminate between neurotoxic and hemorrhagic venoms. The limits of quantification (LOQ) of the ELISA for neurotoxic venoms and hemorrhagic venoms were determined to be 0.39 and 0.78 ng/ml, respectively, and the lateral flow strips were capable of detecting neurotoxic and hemorrhagic venoms at concentrations lower than 5 and 50 ng/ml, respectively, in 10–15 min. Tests of lateral flow strips in 21 clinical snakebite cases showed 100% specificity and 100% sensitivity for neurotoxic envenomation, whereas the sensitivity for detecting hemorrhagic envenomation samples was 36.4%. We herein presented a feasible strategy for developing a sensitive sandwich ELISA and lateral flow strip assay for detecting and differentiating venom proteins from hemorrhagic and neurotoxic snakes. A useful snakebite diagnostic guideline according to the lateral flow strip results and clinical symptoms was proposed to help physicians to use antivenoms appropriately. The two-test-line lateral flow strip assay could potentially be applied in an emergency room setting to help physicians diagnose and manage snakebite victims.

Snakebite is a public health issue that causes life-threatening medical emergencies. Rapid diagnosis of snakebite in the clinic is a critical necessity in many tropical and subtropical countries, where various venomous snakes are common. Venoms from different snake species contain distinct protein components that require treatment with different antivenoms. However, given the similarity in clinical symptoms among some snake envenomations, it is often challenging for physicians to precisely define the snake species responsible for envenomation. Thus, a reliable method or assay for rapidly diagnosing envenoming species is urgently needed. Here, we present a two-step affinity purification procedure for generating species-specific antibodies (SSAbs) from antivenom, followed by the development of a sandwich ELISA (enzyme-linked immunosorbent assay) and lateral flow strip assay using these SSAbs. This feasible and cost-effective strategy allowed us to develop workable assays for distinguishing between venom proteins from hemorrhagic and neurotoxic snakes in Taiwan. The usefulness of this strategy was demonstrated in the clinic, where both diagnostic assays were shown capable of detecting venoms in blood samples from snakebite patients. Together with the observation of clinical symptoms, the two-test-line lateral flow strip assay is potentially applicable in an emergency room setting to improve snakebite diagnosis and management.

Development of dot-ELISA for the detection of venoms of major Indian venomous snakes

India remained an epicenter for the snakebite-related mortality and morbidities due to widespread agricultural activities across the country and a considerable number of snakebites offended by Indian cobra (Naja naja), common krait (Bungarus caeruleus), Russell's viper (Daboia russelii), and saw-scaled viper (Echis carinatus). Presently, there is no selective test available for the detection of snake envenomation in India before the administration of snake antivenin. Therefore, the present study aimed to develop rapid, sensitive assay for the management of snakebite, which can detect venom, responsible snake species and serve as a tool for the reasonable administration of snake antivenin, which have scarcity across the world. The selective envenomation detection assay needs venom specific antibodies (VSAbs) for that monovalent antisera was prepared by hyperimmunization of rabbits with specific venom. However, obtained antibodies exhibit maximum activity towards homologous venom as well as quantifiable degree of cross-reactivity with heterologous venoms. Use of these antibodies for development of selective envenomation detection assay may create ambiguity in results, therefore needs to isolate VSAbs from monovalent antisera. The cross-reacting antibodies were specifically removed by immunoaffinity chromatography to obtain VSAbs. For the development of venom detection ELISA test (VDET), two different species of antibodies were used that offers enhanced sensitivity along with selective identification of the venoms of the responsible snakes. In conclusion, the developed VDET is rapid, specific, yet sensitive to detect venoms of offending snake species, and its venom concentration down to 1.0 ng/ml. However, the device observed with lowest venom concentration detection ability in the range <1.0 ng/ml from experimentally envenomated samples. The implementation of VDET will help in avoiding unnecessary usage and adverse reactions of snake antivenin. The test has all the merits to become a choice of method in envenomation diagnosis from medically important snakes of India.

Rapid and selective detection of experimental snake envenomation - Use of gold nanoparticle based lateral flow assay

In this study, we have developed a gold nanoparticle based simple, rapid lateral flow assay (LFA) for detection of Indian Cobra venom (CV) and Russell's viper venom (RV). Presently, there is no rapid, reliable, and field diagnostic test available in India, where snake bite cases are rampant. Therefore, this test has an immense potential from the public health point of view. The test is based on the principle of the paper immunochromatography assay for detection of two snake venom species using polyvalent antisnake venom antibodies (ASVA) raised in equines and species-specific antibodies (SSAbs) against venoms raised in rabbits for conjugation and impregnation respectively. The developed, snake envenomation detection immunoassay (SEDIA) was rapid, selective, and sensitive to detect venom concentrations up to 0.1 ng/ml. The functionality of SEDIA strips was confirmed by experimental envenomation in mice and the results obtained were specific for the corresponding venom. The SEDIA has a potential to be a field diagnostic test to detect snake envenomation and assist in saving lives of snakebite victims.

Proteomic characterization and comparison of venoms from two elapid snakes (Bungarus multicinctus and Naja atra) from China

Bungarus multicinctus (many-banded krait) and Naja atra (Chinese cobra) are widely distributed and medically important venomous snakes in China; however, their venom proteomic profiles have not been fully compared. Here, we fractionated crude venoms and analyzed them using a combination of proteomic techniques. Three-finger toxins (3-FTx) and phospholipase A2 (PLA2) were most abundant in both species, respectively accounting for 32.6% and 66.4% of total B. multicinctus venom, and 84.3% and 12.2% of total N. atra venom. Venoms from these two species contained one common protein family and six less abundant species-specific protein families. The proteomic profiles of B. multicinctus and N. atra venoms and analysis of toxicological activity in mice suggested that 3-FTx and PLA2 are the major contributors to clinical symptoms caused by envenomation. The venoms differed in enzymatic activity, likely the result of inter-specific variation in the amount of related venom components. Antivenomics assessment revealed that a small number of venom components (3-FTxs and PLA2s in B. multicinctus, and 3-FTxs in N. atra) could not be immunocaptured completely, suggesting that we should pay attention to enhancing the immune response of these components in designing commercial antivenoms for B. multicinctus and N. atra.

BIOLOGICAL SIGNIFICANCE

The proteomic profiles of venoms from two medically important snake species - B. multicinctus and N. atra - have been explored. Quantitative and qualitative differences are evident in both venoms when proteomic profiles and transcriptomic results are compared; this is a reminder that combined approaches are needed to explore the precise composition of snake venom. Two protein families (3-FTx and PLA2) of high abundance in these snake venoms are major players in the biochemical and pharmacological effects of envenomation. Elucidation of the proteomic profiles of these snake venoms is helpful in understanding composition-function relationships and will facilitate the clinical application of antivenoms.

Recognition of Bungarus multicinctus venom by a DNA aptamer against β-bungarotoxin

Antibody-based technology is the main method for diagnosis and treatment of snake bite envenoming currently. However, the development of an antibody, polyclonal or monoclonal, is a complicated and costly procedure. Aptamers are single stranded oligonucleotides that recognize specific targets such as proteins and have shown great potential over the years as diagnostic and therapeutic agents. In contrast to antibodies, aptamers can be selected in vitro without immunization of animals, and synthesized chemically with extreme accuracy, low cost and high degree of purity. In this study we firstly report on the identification of DNA aptamers that bind to β-bungarotoxin (β-BuTx), a neurotoxin from the venom of Bungarus multicinctus. A plate-SELEX method was used for the selection of β-BuTx specific aptamers. After 10 rounds of selection, four aptamer candidates were obtained, with the dissociation constant ranged from 65.9 nM to 995 nM measured by fluorescence spectroscopy. Competitive binding assays using both the fluorescently labeled and unlabeled aptamers revealed that the four aptamers bound to the same binding site of β-BuTx. The best binder, βB-1, bound specifically to β-BuTx, but not to BSA, casein or α-Bungarotoxin. Moreover, electrophoretic mobility shift assay and enzyme-linked aptamer assay demonstrated that βB-1 could discriminate B. multicinctus venom from other snake venoms tested. The results suggest that aptamer βB-1 can serve as a useful tool for the design and development of drugs and diagnostic tests for β-BuTx poisoning and B. multicinctus bites.