Physicochemical characterization of commercial freeze-dried snake antivenoms

Intraspecific variability of the Central American rattlesnake (Crotalus simus) venom and its usefulness to obtain a representative standard venom

Snake venoms are mixtures of proteins whose physicochemical features confer them toxicity and immunogenicity. Animals (e.g., horses or sheep) immunized with snake venoms produce antibodies towards the venom proteins. Since these antibodies can neutralize the venom toxicity, they have been used to formulate snake antivenoms. The efficacy of the antivenoms is widely accepted, and standard venoms are expected to be representative of the snake's population that inhabit in the region where the antivenom is intended to be used. The representativeness of a single venom collected from a Crotalus simus snake, and its usefulness as standard venom to produce an antivenom is evaluated. The use of an "average venom" might be as representative of the population intended to be used, as the standard venom composed by many venom samples. Variations in the relative abundance concentration of crotoxin in the C. simus leads to different clinical manifestations, as well as differences in the neutralization efficacy of the antivenoms. A monovalent anti-Cs antivenom was produced from a single venom C. simus specimen, and its efficacy in neutralizing the lethal activity of 30 C. simus snakes was tested. Despite the variations in the relative abundance content of crotoxin found in the proteomes, the monovalent anti-Cs antivenom was successful in neutralize the toxicity caused by the variations on the venom composition of three different snake population used. Interestingly, it seems that the sex is not a key factor in the lethality of the venoms tested. The concept of representative venom mixtures for immunization should be revised for the case of C. simus on the populations found in Costa Rica, since it might use as less as one representative individual whose venom covers the mainly toxic enzymes.

Assessment of quality and pre-clinical efficacy of a newly developed polyvalent antivenom against the medically important snakes of Sri Lanka

Snake envenomation is a severe problem in Sri Lanka (SL) and Indian polyvalent antivenom (PAV) is mostly used for treating snakebite albeit due to geographical variation in venom composition, Indian PAV shows poor efficacy in neutralizing the lethality and toxicity of venom from the same species of snakes in SL. Therefore, the quality and in vivo venom neutralization potency of a country-specific PAV produced against the venom of the five most medically important snakes of SL (Daboia russelii, Echis carinatus, Hypnale hypnale, Naja naja, Bungarus caeruleus) was assessed. LC-MS/MS analysis of two batches of PAV showed the presence of 88.7-97.2% IgG and traces of other plasma proteins. The tested PAVs contained minor amounts of undigested IgG and F(ab')2 aggregates, showed complement activation, were devoid of IgE, endotoxin, and content of preservative was below the threshold level. Immunological cross-reactivity and in vitro neutralization of enzymatic activities, pharmacological properties demonstrated superior efficacy of SL PAV compared to Indian PAV against SL snake venoms. The in vivo neutralization study showed that the tested PAVs are potent to neutralize the lethality and venom-induced toxicity of SL snake venoms. Therefore, our study suggests that introduction of SL-specific PAV will improve snakebite management in SL.

Use of freeze-dried trivalent antivenom to neutralize the toxic activities of Bothrops atrox snake venoms from the Amazon

In Brazil, antivenom for snakebite is currently formulated in liquid form and requires storage at 4 °C. Here, a new freeze-dried trivalent antivenom, which would enable cold-chain free storage, was determined to have efficacy in neutralizing the biological activities of Bothrops atrox venoms from Manaus (Brazil) and Leticia (Colombia), exhibiting an efficacy similar to those of currently available liquid Bothrops antivenoms. These results indicate that freeze-dried trivalent antivenom may be beneficial for applications in the Brazilian and Colombian Amazon regions.

The application of laboratory-based analytical tools and techniques for the quality assessment and improvement of commercial antivenoms used in the treatment of snakebite envenomation

Snakebite envenomation is a public health problem of high impact, particularly for the developing world. Antivenom, which contains whole or protease-digested immunoglobulin G, purified from the plasma of hyper-immunized animals (mainly horses), is the mainstay for the treatment of snakebite envenomation. The success of antivenom therapy depends upon its ability to abrogate or reduce the local and systemic toxicity of envenomation. In addition, antivenom administration must be safe for the patients. Therefore, antivenom manufacturers must ensure that these products are effective and safe in the treatment of envenomations. Antivenom efficacy and safety are determined by the physicochemical characteristics of formulations, purity of the immunoglobulin fragments and antibodies, presence of protein aggregates, endotoxin burden, preservative load, and batch to batch variation, as well as on the ability to neutralize the most important toxins of the venoms against which the antivenom is designed. In this context, recent studies have shown that laboratory-based simple analytical techniques, for example, size exclusion chromatography, sodium dodecyl sulphate polyacrylamide gel electrophoresis, mass spectrometry, immunological profiling including immuno-turbidimetry and enzyme-linked immunosorbent assays, Western blotting, immune-chromatographic technique coupled to mass spectrometry analysis, reverse-phase high performance liquid chromatography, spectrofluorometric analysis, in vitro neutralization of venom enzymatic activities, and other methodologies, can be applied for the assessment of antivenom quality, safety, stability, and efficacy. This article reviews the usefulness of different analytical techniques for the quality assessment of commercial antivenoms. It is suggested that these tests should be applied for screening the quality of commercial antivenoms before their preclinical and clinical assessment.

Assessment of snakebite burdens, clinical features of envenomation, and strategies to improve snakebite management in Vietnam

The sheer paucity of scientific documentation of herpetofauna in Vietnam and the rudimentary healthcare response to snakebite have stimulated this review. Over six decades of data culled from public data bases and search engines, have been used to assess snakebite burdens, clinical features of envenomation, and strategies for snakebite management in Vietnam. In addition, biochemical and proteomic analyses to decipher venom composition, rapid analytical techniques to be used for clinical diagnosis of snakebite in Vietnam have been discussed in detail. The assessment of efficacy, safety, and quality of commercial antivenom produced in Vietnam and improvement of antivenom production to meet the national requirement has been critically examined. It is apparent that snake bite incidence in Vietnam is exacerbated by mismatch in demand and supply of antivenom therapy, insufficient medical facilities, preference for traditional healers and poor management of clinical records. The impediments arising from geographical and species-specific variation in venom composition can be overcome by the 'Omics approach', and scientific documentation of pathophysiological manifestations post envenomation. The development of next generation of therapeutics, encouraging clinical research, novel approaches and social awareness against snakebite and its treatments have been suggested to significantly reduce the snakebite mortality and morbidity in this region.

History and perspectives on how to ensure antivenom accessibility in the most remote areas in Brazil

A plan to achieve self-sufficiency in manufacturing biologicals for public health has been structured for the last 40 years in Brazil, in the context of a reform in the health system. Industrial plants of the national public laboratories have been modernized, and a program for reducing morbidity and mortality of venomous snakebite has been created, as part of the National Epidemiological Surveillance System. The epidemiological data are essential to plan for the antivenom production of 400,000 vials of snake antivenoms per year, and the acquisition by the Ministry of Health, which is the exclusive purchaser in the country. Distribution is decentralized to reach hospitals in almost 3000 municipalities, and to provide free of charge antivenom treatment. The National Sanitary Surveillance Agency organized the regulatory environment to implement rules and supervise compliance of GMP procedures, elevating the quality of the biologicals that are produced, as well as reducing the costs in production. Despite all the advances in the health system, antivenom availability and accessibility is not uniform in regards to the most vulnerable parts of the populations, which inhabit remote areas in the Brazilian Amazon region. Better logistics and transportation of liquid form antivenoms is an issue to be addressed and realistic and comprehensive health programs for indigenous groups should be effectively structured, in order to reduce the high morbidity and mortality rates associated with snakebite envenoming.

The corneal epitheliotrophic abilities of lyophilized powder form human platelet lysates

Purpose

To evaluate whether lyophilized human platelet lysate (HPL) powder can preserve the growth factor concentrations and epitheliotrophic properties of liquid HPL, and potentially be used as a clinically-friendly treatment option.

Methods

Two commercialized liquid HPLs, UltraGRO TM (Helios, Atlanta, GA) and PLTMax (Mill Creek, Rochester, MI), were obtained and converted to lyophilized powder. After redissolution, lyophilized powder HPLs were compared with liquid HPLs, as well as human peripheral serum (HPS) and fetal bovine serum (FBS) in liquid or redissolved lyophilized powder forms. Concentrations of epidermal growth factor (EGF), transforming growth factor-β1 (TGF-β1), platelet-derived growth factor-AB (PDGF-AB) and platelet-derived growth factor-BB (PDGF-BB) were evaluated by enzyme-linked immunosorbent assay (ELISA). Human corneal epithelial cell line was incubated with the blood derivatives and evaluated for cell migration with scratch-induced directional wounding and proliferation with MTS assays. Cell differentiation was examined by transepithelial electrical resistance (TEER). Fluorescein staining and in vivo confocal microscopy were used to evaluate in vivo corneal epithelial wound healing in Sprague-Dawley rats that underwent corneal debridement and topical application of liquid and redissolved powder HPLs.

Results

Liquid form and redissolved lyophilized powder form HPLs had similar concentrations of EGF, TGF-β1, PDGF-AB and PDGF-BB. In vitro experiments on cell migration, proliferation and differentiation and rat models on wound healing demonstrated no significant difference between the liquid and redissolved lyophilized powder forms for HPLs, HPS and FBS. In vivo confocal microscopy revealed similar wound healing process at different layers of cornea after corneal epithelial debridement between liquid form and redissolved lyophilized power form of HPLs.

Conclusions

The redissolved lyophilized powder form of both commercialized HPLs showed similar growth factor concentrations and corneal epitheliotrophic abilities compared to the liquid form. Results suggest that the properties of liquid HPLs can be retained despite lyophilization and that lyophilized HPLs can be a treatment option for corneal epithelial disorders.

Safety and efficacy of a freeze-dried trivalent antivenom for snakebites in the Brazilian Amazon: An open randomized controlled phase IIb clinical trial

BACKGROUND

In tropical areas, a major concern regarding snakebites treatment effectiveness relates to the failure in liquid antivenom (AV) distribution due to the lack of an adequate cold chain in remote areas. To minimize this problem, freeze-drying has been suggested to improve AV stability.

METHODS AND FINDINGS

This study compares the safety and efficacy of a freeze-dried trivalent antivenom (FDTAV) and the standard liquid AV provided by the Brazilian Ministry of Health (SLAV) to treat Bothrops, Lachesis and Crotalus snakebites. This was a prospective, randomized, open, phase IIb trial, carried out from June 2005 to May 2008 in the Brazilian Amazon. Primary efficacy endpoints were the suppression of clinical manifestations and return of hemostasis and renal function markers to normal ranges within the first 24 hours of follow-up. Primary safety endpoint was the presence of early adverse reactions (EAR) in the first 24 hours after treatment. FDTAV thermal stability was determined by estimating AV potency over one year at 56°C. Of the patients recruited, 65 and 51 were assigned to FDTAV and SLAV groups, respectively. Only mild EARs were reported, and they were not different between groups. There were no differences in fibrinogen (p = 0.911) and clotting time (p = 0.982) recovery between FDTAV and SLAV treated groups for Bothrops snakebites. For Lachesis and Crotalus snakebites, coagulation parameters and creatine phosphokinase presented normal values 24 hours after AV therapy for both antivenoms.

CONCLUSIONS/SIGNIFICANCE

Since promising results were observed for efficacy, safety and thermal stability, our results indicate that FDTAV is suitable for a larger phase III trial.

TRIAL REGISTRATION

ISRCTNregistry: ISRCTN12845255; DOI: 10.1186/ISRCTN12845255 (http://www.isrctn.com/ISRCTN12845255).

Freeze-dried EchiTAb+ICP antivenom formulated with sucrose is more resistant to thermal stress than the liquid formulation stabilized with sorbitol

EchiTAb + ICP is a pan-African antivenom used for the treatment of snakebite envenomation in rural sub-Saharan African communities, where the cold chain can be difficult to maintain. To develop a formulation of EchiTAb + ICP that can be distributed and stored without refrigeration, we submitted three different formulations of EchiTAb + ICP: control (i.e. liquid antivenom formulated without stabilizer), liquid antivenom stabilized with sorbitol, and freeze-dried antivenom formulated with sucrose, to an accelerated stability study (i.e. 38 ± 2 °C and 75% relative humidity for 6 months). We analyzed changes in color, residual humidity, reconstitution time (for freeze-dried preparation), pH, osmolality, total protein concentration, antibody monomers content, turbidity, bacterial endotoxins, and pre-clinical neutralizing efficacy of the lethal effect of Echis ocellatus venom at 0, 3 and 6 months. In the control formulation, instability was evidenced by the development of a yellow coloration and an increment in aggregation and turbidity, without change in its neutralizing activity. The sorbitol-stabilized formulation did not develop marked aggregation or turbidity, but instability was evidenced by the development of yellow coloration and a drop in the neutralizing potency. The freeze-dried formulation maintained its neutralizing potency and did not show marked signs of instability, thus indicating that freeze-drying could confer EchiTAb + ICP with improved thermal stability required for distribution and storage at room temperature in sub-Saharan Africa.