Safety of snake antivenom immunoglobulins: Efficacy of viral inactivation in a complete downstream process

Viral safety remains a challenge when processing a plasma‐derived product. A variety of pathogens might be present in the starting material, which requires a downstream process capable of broad viral reduction. In this article, we used a wide panel of viruses to assess viral removal/inactivation of our downstream process for Snake Antivenom Immunoglobulin (SAI). First, we screened and excluded equine plasma that cross‐reacted with any model virus, a procedure not published before for antivenoms. In addition, we evaluated for the first time the virucidal capacity of phenol applied to SAI products. Among the steps analyzed in the process, phenol addition was the most effective one, followed by heat, caprylic acid, and pepsin. All viruses were fully inactivated only by phenol treatment; heat, the second most effective step, did not inactivate the rotavirus and the adenovirus used. We therefore present a SAI downstream method that is cost‐effective and eliminates viruses to the extent required by WHO for a safe product. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:972–979, 2013     

中华眼镜蛇伤致局部组织损伤治疗的实验研究

目的 探讨中华眼镜蛇伤致局部组织损伤的最佳治疗方法。方法 用中华眼镜蛇毒作家兔局部组织损伤模型,分别采用抗蛇素血清局部注射、糜蛋白酶局部注射、蛇伤药酒外敷、坏死组织早期切除、局部烧灼法、局部组织切开冲洗,共6种处理方法进行局部治疗,观察其疗效。结果 6种治疗方法从优到劣依次是：抗蛇毒血清局部注射、糜蛋白酶局部注射、蛇伤药酒外敷、坏死组织早期切除、局部烧灼法、局部组织切开冲洗。结论 中华眼镜蛇伤致局部组织损伤的治疗方法应首选抗蛇毒血清局部注射和糜蛋白酶局部注射,其次选用蛇伤药酒外敷。     

精制抗蛇毒血清救治孕妇毒蛇咬伤的临床研究

目的 观察蛇毒毒素（神经毒、血循毒、混合毒）、抗蛇毒血清制品对孕妇和胎儿有影响。方法 对6种不同毒蛇咬伤的12例孕妇,采用精制抗蛇毒血清治疗,配合抗生素、中医中药等。结果 12例患者中治愈10例,占83．3％;好转2例,占16．7％,总有效率达100％。出生后新生儿全部存活,无畸形,发育正常。结论 抗蛇毒血清治疗孕妇毒蛇咬伤有显著疗效,使用过程中无明显的过敏反应,也无流产、早产及胎儿致畸现象。研究表明,胎盘的屏障作用完全可以抵御蛇毒素、抗蛇毒血清制品对胎儿的损害,关键是要尽早使用足量的抗蛇毒血清。     

Purification of equine IgG using membrane based enhanced hybrid bioseparation technique: a potential method for manufacturing hyperimmune antibody

Hyperimmune equine IgG is widely used as antivenom and anti-rabies agents. This article discusses a membrane based enhanced hybrid bioseparation technique for efficient and scalable purification of equine immunoglobulin G (IgG) from horse serum. This technique is an improved version of a standard hybrid bioseparation technique developed within our group earlier for fractionation of human plasma proteins (Ghosh. 2004. J Membr Sci 237: 109-117). In the presence of a high antichaotropic salt concentration, equine IgG is selectively and reversibly captured within a stirred cell membrane module from horse serum, partly due to precipitation and microfiltration, and partly due to hydrophobic interaction based membrane adsorption, while the impurities are washed out from the device. The reversibly sequestered IgG is then released by lowering the salt concentration which favor both dissolution of the precipitated IgG and desorption of the membrane bound IgG. The enhanced hybrid bioseparation technique improves the IgG recovery from the membrane module by switching from a stirring to non-stirring mode during the IgG release phase. It also reduces membrane fouling by an appropriate pH switch. The effects of operating conditions on equine IgG capture were first systematically studied. The enhanced hybrid bioseparation technique was followed by an ultrafiltration step to remove ammonium sulfate and low molecular weight impurities. The equine IgG purity obtained under optimized conditions was 88% and its recovery was over 90%, both being significantly higher than corresponding values obtained using currently used purification techniques.     

Binding of a Naja naja venom acidic phospholipase A2 cognate complex to membrane-bound vimentin of rat L6 cells: Implications in cobra venom-induced cytotoxicity

An acidic phospholipase A₂ enzyme (NnPLA₂-I) interacts with three finger toxins (cytotoxin and neurotoxin) from Naja naja venom to form cognate complexes to enhance its cytotoxicity towards rat L6 myogenic cells. The cytotoxicity was further enhanced in presence of trace quantity of venom nerve growth factor. The purified rat myoblast cell membrane protein showing interaction with NnPLA₂-I was identified as vimentin by LC-MS/MS analysis. The ELISA, immunoblot and spectrofluorometric analyses showed greater binding of NnPLA₂-I cognate complex to vimentin as compared to the binding of individual NnPLA₂-I. The immunofluorescence and confocal microscopy studies evidenced the internalization of NnPLA₂-I to partially differentiated myoblasts post binding with vimentin in a time-dependent manner. Pre-incubation of polyvalent antivenom with NnPLA₂-I cognate complex demonstrated better neutralization of cytotoxicity towards L6 cells as compared to exogenous addition of polyvalent antivenom 60–240 min post treatment of L6 cells with cognate complex suggesting clinical advantage of early antivenom treatment to prevent cobra venom-induced cytotoxicity. The in silico analysis showed that 19–22 residues, inclusive of Asp48 residue, of NnPLA₂-I preferentially binds with the rod domain (99–189 and 261–335 regions) of vimentin with a predicted free binding energy (ΔG) and dissociation constant (K_D) values of ?12.86 kcal/mol and 3.67 × 10^?10 M, respectively; however, NnPLA₂-I cognate complex showed greater binding with the same regions of vimentin indicating the pathophysiological significance of cognate complex in cobra venom-induced cytotoxicity.     

Quantitative proteomic analysis of venom from Southern India common krait (Bungarus caeruleus) and identification of poorly immunogenic toxins by immune-profiling against commercial antivenom

Objectives: To study the venom proteome composition of Southern India (SI) Common Krait (Bungarus caeruleus) and immunological cross-reactivity between venom against commercial antivenom.

Methods: Proteomic analysis was done by nano LC-MS/MS and toxins were quantitated by label-free analysis. The immunological cross-reactivity of venom towards polyvalent antivenom (PAV) was assessed by ELISA, Immunoblotting, and immuno-chromatographic methods.

Results: A total of 57 enzymatic and non-enzymatic proteins belonging to 12 snake venom protein families were identified. The three finger toxins (3FTx) (48.3%) and phospholipase A₂ (PLA₂) (37.6%) represented the most abundant non-enzymatic and enzymatic proteins, respectively. β-bungarotoxin (12.9%), a presynaptic neurotoxin, was also identified. The venom proteome composition is well correlated with its enzymatic activities, reported pharmacological properties, and clinical manifestations of krait envenomation. Immuno-cross-reactivity studies demonstrated better recognition of high molecular weight proteins (>45 kDa) of this venom by PAVs compared to low molecular weight (<15 kDa) toxins such as PLA₂ and 3FTxs.

Conclusion: The poor recognition of <15 kDa mass SI B. caeruleus venom proteins is of grave concern for the successful treatment of krait envenomation. Therefore, emphasis should be given to improve the immunization protocols and/or supplement of antibodies raised specifically against the <15 kDa toxins of this venom.     

Purification and characterization of a potent hemolytic toxin with phospholipase A2 activity from the venom of Indian Russell's viper

A potent toxin with phospholipase A₂ (PLA₂) and hemolytic activity in vitro was purified from the Russell's viper venom of eastern India (RVV-EI). The purified protein (RVV-PFIIc) of 15.3 kDa molecular weight, and a lethal toxicity dose (LD₅₀ i.p.) of 0.1 mg/kg body weight, was the most toxic PLA₂ so far reported from the Indian subcontinent. The material also possessed anticoagulant activity as it enhanced the prothrombin induced plasma clotting time in vitro. The PLA₂ toxin (RVV-PFIIc) was shown to be different from other PLA₂s of RVV in respect to one or more of these parameters e.g. molecular weight, isoelectric pH, in vivo toxicity, specific activity of the enzyme and certain other biological activities. The first 19 amino terminal sequence (NLFQFAEMIVKMTGKEAVH) of RVV-PFIIc showed variable degree of homology (42.1–94.7%) with those of other RVV-PLA₂s described in the literature. Antisera raised against RVV-EI or RVV-PFIIc, though completely neutralized the in vivo lethal toxicity of RVV-EI or RVV-PFIIc, failed to inhibit their PLA₂ activity in vitro thereby suggesting that in vivo toxicity and in vitro activity of the enzyme may not be directly related. Apart from RVV-PFIIc, at least two other PLA₂ isozymes were found to be present in RVV-EI that were distinct from RVV-PFIIc in respect to their molecular, biological as well as serological properties. The significance of these and related data in antivenom therapy is discussed.     

Opossum peptide that can neutralize rattlesnake venom is expressed in Escherichia coli

An eleven amino acid ribosomal peptide was shown to completely neutralize Western Diamondback Rattlesnake (Crotalus atrox) venom in mice when a lethal dose of the venom was pre‐incubated with the peptide prior to intravenous injection. We have expressed the peptide as a concatenated chain of peptides and cleaved them apart from an immobilized metal affinity column using a protease. After ultrafiltration steps, the mixture was shown to partially neutralize rattlesnake venom in mice. Preliminary experiments are described here that suggest a potential life‐saving therapy could be developed. To date, no recombinant therapies targeting cytotoxic envenomation have been reported. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 33:81–86, 2017     

Plant DNases are potent therapeutic agents against Echis carinatus venom-induced tissue necrosis in mice

Echis carinatus envenomation leads to severe tissue necrosis at the bitten site by releasing DNA from immune cells that blocks the blood flow. An earlier report has shown that exogenous DNase 1 offers protection against such severe local tissue necrosis. Tricosanthus tricuspidata is a medicinal plant and the paste prepared from its leaves has been used extensively for the treatment of snakebite-induced tissue necrosis. Most studies including reports from our laboratory focused on plant secondary metabolite as therapeutic molecules against snakebite envenomation. However, the involvement of hydrolytic enzymes including DNase in treating snake venom-induced tissue necrosis has not been addressed. Several folk medicinal plants used against snakebite treatment showed the presence of DNase activity and found to be rich in T. tricuspidata. Further, purified T. tricuspidata DNase showed a single sharp peak in reversed-phase high-performance liquid chromatography (RP-HPLC) with an apparent molecular mass of 17 kDa. T. tricuspidata DNase exhibited potent DNA degrading activity performed using agarose gel electrophoresis, spectrophotometric assay, and DNA zymography. In addition, purified DNase from T. tricuspidata was able to neutralize E. carinatus venom-induced mouse tail tissue necrosis and normalized elevated serum creatine kinase (CK) and lactate dehydrogenase (LDH) levels 30 minutes post venom injection. T. tricuspidata DNase was also able to reverse E. carinatus venom-induced histopathological changes and collagen depletion in mice tail tissue. All these observed pharmacological actions of T. tricuspidata DNase were inhibited by sodium fluoride (NaF). This study provides scientific validation of the traditional use of T. tricuspidata leaf paste in the healing of snakebite-induced tissue necrosis and might be exploited to treat snake venom-induced local toxicity.     

Venom proteomic analysis of medically important Nigerian viper Echis ocellatus and Bitis arietans snake species

Snakebite envenoming remains a neglected tropical disease which poses severe health hazard, especially for the rural inhabitants in Africa. In Nigeria, vipers are responsible for the highest number of deaths. Hydrophilic interaction liquid chromatography coupled with LC-MS/MS was used to analyze the crude venoms of Echis ocellatus (Carpet viper) and Bitis arietans (Puff adder) in order to understand their venom proteomic identities. Results obtained revealed that gel-free proteomic analysis of the crude venoms led to the identification of 85 and 79 proteins, respectively. Seventy-eight (78) proteins were common between the two snake species with a 91.8% similarity score. The identified proteins belong to 18 protein families in E. ocellatus and 14 protein families in B. arietans. Serine proteases (22.31%) and metalloproteinases (21.06%) were the dominant proteins in the venom of B. arietans; while metalloproteinases (34.84%), phospholipase A₂s (21.19%) and serine proteases (15.50%) represent the major toxins in the E. ocellatus venom. Other protein families such as three-finger toxins and cysteine-rich venom proteins were detected in low proportions. This study provides an insight into the venom proteomic analysis of the two Nigerian viper species, which could be useful in identifying the toxin families to be neutralized in case of envenomation.