1
|
Chan YW, Tan CH, Heh CH, Tan KY. An immunoinformatic approach to assessing the immunogenic capacity of alpha-neurotoxins in elapid snake venoms. Front Pharmacol 2023; 14:1143437. [PMID: 37153801 PMCID: PMC10155835 DOI: 10.3389/fphar.2023.1143437] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 03/27/2023] [Indexed: 05/10/2023] Open
Abstract
Introduction: Most elapid snakes produce venoms that contain alpha-neurotoxins (α-NTXs), which are proteins that cause post-synaptic blockade and paralysis in snakebite envenoming. However, existing elapid antivenoms are known for their low potency in neutralizing the neurotoxic activity of α-NTXs, while the immunological basis has not been elucidated. Methods: In this study, a structure-based major histocompatibility complex II (MHCII) epitope predictor of horse (Equus caballus), complemented with DM-editing determinant screening algorithm was adopted to assess the immunogenicity of α-NTXs in the venoms of major Asiatic elapids (Naja kaouthia, Ophiophagus hannah, Laticauda colubrina, Hydrophis schistosus, Hydrophis curtus). Results: The scoring metric M2R, representing the relative immunogenic performance of respective α-NTXs, showed all α-NTXs have an overall low M2R of <0.3, and most of the predicted binders feature non-optimal P1 anchor residues. The M2R scores correlate strongly (R2 = 0.82) with the potency scores (p-score) generated based on the relative abundances of α-NTXs and the neutralization potency of commercial antivenoms. Discussion: The immunoinformatic analysis indicates that the inferior antigenicity of α-NTXs is not only due to their small molecular size but also the subpar immunogenicity affected by their amino acid composition. Structural modification with conjugation and synthetic epitope as immunogen may potentially enhance the immunogenicity for improved antivenom potency against α-NTXs of elapid snakes.
Collapse
Affiliation(s)
- Yi Wei Chan
- Protein and Interactomics Laboratory, Department of Molecular Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Choo Hock Tan
- Venom Research and Toxicology Laboratory, Department of Pharmacology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Choon Han Heh
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Malaya, Kuala Lumpur, Malaysia
| | - Kae Yi Tan
- Protein and Interactomics Laboratory, Department of Molecular Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
- *Correspondence: Kae Yi Tan,
| |
Collapse
|
2
|
Gómez A, Sánchez A, Durán G, Cordero D, Segura Á, Vargas M, Solano D, Herrera M, Chaves-Araya S, Villalta M, Sánchez M, Arguedas M, Díaz C, Gutiérrez JM, León G. Intrageneric cross-reactivity of monospecific rabbit antisera against venoms of the medically most important Bitis spp. and Echis spp. African snakes. PLoS Negl Trop Dis 2022; 16:e0010643. [PMID: 35960772 PMCID: PMC9374258 DOI: 10.1371/journal.pntd.0010643] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Accepted: 07/08/2022] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Snakebite envenomation exerts a heavy toll in sub-Saharan Africa. The design and production of effective polyspecific antivenoms for this region demand a better understanding of the immunological characteristics of the different venoms from the most medically important snakes, to select the most appropriate venom combinations for generating antivenoms of wide neutralizing scope. Bitis spp. and Echis spp. represent the most important viperid snake genera in Africa. METHODOLOGY/PRINCIPAL FINDINGS Eight rabbit-derived monospecific antisera were raised against the venoms of four species of Bitis spp. and four species of Echis spp. The effects of immunization in the rabbits were assessed, as well as the development of antibody titers, as judged by immunochemical assays and neutralization of lethal, hemorrhagic, and in vitro coagulant effects. At the end of immunizations, local and pulmonary hemorrhage, together with slight increments in the plasma activity of creatine kinase (CK), were observed owing to the action of hemorrhagic and myotoxic venom components. Immunologic analyses revealed a considerable extent of cross-reactivity of monospecific antisera against heterologous venoms within each genus, although some antisera provided a more extensive cross-reactivity than others. The venoms that generated antisera with the broadest coverage were those of Bitis gabonica and B. rhinoceros within Bitis spp. and Echis leucogaster within Echis spp. CONCLUSIONS/SIGNIFICANCE The methodology followed in this study provides a rational basis for the selection of the best combination of venoms for generating antivenoms of high cross-reactivity against viperid venoms in sub-Saharan Africa. Results suggest that the venoms of B. gabonica, B. rhinoceros, and E. leucogaster generate antisera with the broadest cross-reactivity within their genera. These experimental results in rabbits need to be translated to large animals used in antivenom production to assess whether these predictions are reproduced in horses or sheep.
Collapse
Affiliation(s)
- Aarón Gómez
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Andrés Sánchez
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Gina Durán
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Daniel Cordero
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Álvaro Segura
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Mariángela Vargas
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Daniela Solano
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - María Herrera
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Stephanie Chaves-Araya
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Mauren Villalta
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Melvin Sánchez
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Mauricio Arguedas
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Cecilia Díaz
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - José María Gutiérrez
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Guillermo León
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| |
Collapse
|
3
|
Affiliation(s)
- Ravikar Ralph
- Department of Internal Medicine, Christian Medical College, Vellore, Tamil Nadu, 632004, India
| | | | - Sanjib Kumar Sharma
- Department of Internal Medicine, B.P. Koirala Institute of Health Sciences, Dharan, 76500, Nepal
| | - Isabela Ribeiro
- Dynamic Portfolio, Drugs for Neglected Diseases initiative (DNDi), 15 Chemin Louis-Dunant, 1202, Geneva, Switzerland
| | - François Chappuis
- Division of Tropical and Humanitarian Medicine, Geneva University Hospitals, Rue Gabrielle-Perret-Gentil 6, Geneva, CH 1211, Switzerland
| |
Collapse
|
4
|
Potet J, Beran D, Ray N, Alcoba G, Habib AG, Iliyasu G, Waldmann B, Ralph R, Faiz MA, Monteiro WM, de Almeida Gonçalves Sachett J, di Fabio JL, Cortés MDLÁ, Brown NI, Williams DJ. Access to antivenoms in the developing world: A multidisciplinary analysis. Toxicon X 2021; 12:100086. [PMID: 34786555 PMCID: PMC8578041 DOI: 10.1016/j.toxcx.2021.100086] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 10/01/2021] [Accepted: 10/04/2021] [Indexed: 11/21/2022] Open
Abstract
Access to safe, effective, quality-assured antivenom products that are tailored to endemic venomous snake species is a crucial component of recent coordinated efforts to reduce the global burden of snakebite envenoming. Multiple access barriers may affect the journey of antivenoms from manufacturers to the bedsides of patients. Our review describes the antivenom ecosystem at different levels and identifies solutions to overcome these challenges. At the global level, there is insufficient manufacturing output to meet clinical needs, notably for antivenoms intended for use in regions with a scarcity of producers. At national level, variable funding and deficient regulation of certain antivenom markets can lead to the procurement of substandard antivenom. This is particularly true when producers fail to seek registration of their products in the countries where they should be used, or where weak assessment frameworks allow registration without local clinical evaluation. Out-of-pocket expenses by snakebite victims are often the main source of financing antivenoms, which results in the underuse or under-dosing of antivenoms, and a preference for low-cost products regardless of efficacy. In resource-constrained rural areas, where the majority of victims are bitten, supply of antivenom in peripheral health facilities is often unreliable. Misconceptions about treatment of snakebite envenoming are common, further reducing demand for antivenom and exacerbating delays in reaching facilities equipped for antivenom use. Multifaceted interventions are needed to improve antivenom access in resource-limited settings. Particular attention should be paid to the comprehensive list of actions proposed within the WHO Strategy for Prevention and Control of Snakebite Envenoming.
Collapse
Affiliation(s)
- Julien Potet
- Médecins Sans Frontières Access Campaign, Geneva, Switzerland
| | - David Beran
- Division of Tropical and Humanitarian Medicine, Geneva University Hospitals, Geneva, Switzerland
- Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Nicolas Ray
- GeoHealth Group, Institute of Global Health, Faculty of Medicine, University of Geneva, Geneva, Switzerland
- Institute for Environmental Sciences, University of Geneva, Geneva, Switzerland
| | - Gabriel Alcoba
- Division of Tropical and Humanitarian Medicine, Geneva University Hospitals, Geneva, Switzerland
- Médecins Sans Frontières, Medical Department, Operational Center Geneva, Geneva, Switzerland
| | - Abdulrazaq Garba Habib
- Infectious Disease and Tropical Medicine Unit, Department of Medicine, College of Health Science, Bayero University Kano, Nigeria
| | - Garba Iliyasu
- Infectious Disease and Tropical Medicine Unit, Department of Medicine, College of Health Science, Bayero University Kano, Nigeria
| | | | - Ravikar Ralph
- Department of Internal Medicine & Poisons Information Center, Christian Medical College, Vellore, 632004, Tamil Nadu, India
| | | | - Wuelton Marcelo Monteiro
- Department of Research, Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Brazil
- School of Health Sciences, Universidade Do Estado Do Amazonas, Manaus, Brazil
| | | | | | | | - Nicholas I. Brown
- Global Snakebite Initiative, 19 Haig Street, Ashgrove, Qld, 4060, Australia
- University of Queensland, Australia
| | - David J. Williams
- Global Snakebite Initiative, 19 Haig Street, Ashgrove, Qld, 4060, Australia
| |
Collapse
|
5
|
Okumu MO, Mbaria JM, Gikunju JK, Mbuthia PG, Madadi VO, Ochola FO, Jepkorir MS. Artemia salina as an animal model for the preliminary evaluation of snake venom-induced toxicity. Toxicon X 2021; 12:100082. [PMID: 34471870 PMCID: PMC8390515 DOI: 10.1016/j.toxcx.2021.100082] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 08/12/2021] [Accepted: 08/16/2021] [Indexed: 12/02/2022] Open
Abstract
Lethality and cytotoxicity assays of snake venoms and their neutralization by antivenom require many mice for the experiments. Recent developments have prompted researchers to seek alternative strategies that minimize the use of mice in line with Russel and Burch's 3Rs philosophy (Replacement, Reduction, and Refinement). Artemia salina is an animal model widely used for toxicity screening. However, its use in snake venom toxinology is limited by a lack of data. The present study compared the toxicity of venoms from Bitis arietans, Naja ashei, and Naja subfulva using mice and Artemia salina. In the Artemia salina test at 24 h and the dermonecrotic test in mice, the toxicity of the venoms was in the order Naja ashei ~ Naja subfulva > Bitis arietans. In the lethality test in mice, the toxicity of the venoms was in the order Naja subfulva > Naja ashei > Bitis arietans. These findings suggest that the toxicity of the venoms in Artemia salina and the dermonecrotic bioassay in mice have a similar trend but differ from the lethality test in mice. Therefore, it may be relevant to further explore the Artemia salina bioassay as a potential surrogate test of dermonecrosis in mice. Studies with more venoms may be needed to establish the correlation between the Artemia salina bioassay and the dermonecrotic assay in mice. Bitis arietans, Naja ashei, and Naja subfulva snake venom-induced toxicities were compared in Artemia salina and in mice. Venom-induced toxicity in Artemia salina has a similar trend to necrosis in mice but not lethality. The Artemia salina bioassay may be further explored along the 3Rs (Reduction, Replacement, and Refinement) concept.
Collapse
Affiliation(s)
- Mitchel Otieno Okumu
- Department of Public Health, Pharmacology, and Toxicology, University of Nairobi, Kenya
| | - James Mucunu Mbaria
- Department of Public Health, Pharmacology, and Toxicology, University of Nairobi, Kenya
| | - Joseph Kangangi Gikunju
- Department of Medical Laboratory Science, Jomo Kenyatta University of Agriculture and Technology, Kenya
| | - Paul Gichohi Mbuthia
- Department of Veterinary Pathology, Microbiology, and Parasitology, University of Nairobi, Kenya
| | | | | | - Mercy Seroney Jepkorir
- Centre for Traditional Medicine and Drug Research, Kenya Medical Research Institute, Kenya
| |
Collapse
|
6
|
Gutiérrez JM, Vargas M, Segura Á, Herrera M, Villalta M, Solano G, Sánchez A, Herrera C, León G. In Vitro Tests for Assessing the Neutralizing Ability of Snake Antivenoms: Toward the 3Rs Principles. Front Immunol 2021; 11:617429. [PMID: 33505403 PMCID: PMC7829219 DOI: 10.3389/fimmu.2020.617429] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Accepted: 11/23/2020] [Indexed: 12/24/2022] Open
Abstract
There is an urgent need to strengthen the implementation of the 3Rs principle (Replacement, Reduction and Refinement) in the use of experimental animals in toxinological research and in the assessment of the neutralizing efficacy of snake antivenoms. This is a challenging task owing to the inherent complexity of snake venoms. The state of the art on this topic is hereby reviewed, with emphasis on the studies in which a correlation has been observed between in vivo toxicity tests and in vitro surrogate assays, particularly in the study of lethal activity of venoms and its neutralization. Correlations have been described with some venoms-antivenoms when using: (a) enzyme immunoassays, (b) hemagglutination, (c) enzyme assays (proteinase, phospholipase A2), (d) in vitro coagulant effect on plasma, (e) cell culture assays for cytotoxicity, (f) functional assays for assessing neurotoxicity in vitro, (g) use of hens’ eggs, and (h) antivenomics. Additionally, the routine introduction of analgesia in these assays and the design of more ‘humane’ protocols for the lethality test are being pursued. It is expected that the next years will witness a growing awareness of the relevance of the 3Rs principles in antivenom testing, and that new in vitro alternatives and more ‘humane’ experimental designs will emerge in this field.
Collapse
Affiliation(s)
| | - Mariángela Vargas
- Instituto Clodomiro Picado, Facultad de Microbiología, San José, Costa Rica
| | - Álvaro Segura
- Instituto Clodomiro Picado, Facultad de Microbiología, San José, Costa Rica
| | - María Herrera
- Instituto Clodomiro Picado, Facultad de Microbiología, San José, Costa Rica
| | - Mauren Villalta
- Instituto Clodomiro Picado, Facultad de Microbiología, San José, Costa Rica
| | - Gabriela Solano
- Instituto Clodomiro Picado, Facultad de Microbiología, San José, Costa Rica
| | - Andrés Sánchez
- Instituto Clodomiro Picado, Facultad de Microbiología, San José, Costa Rica
| | - Cristina Herrera
- Facultad de Farmacia, Universidad de Costa Rica, San José, Costa Rica
| | - Guillermo León
- Instituto Clodomiro Picado, Facultad de Microbiología, San José, Costa Rica
| |
Collapse
|
7
|
Abd El-Aziz TM, Soares AG, Stockand JD. Advances in venomics: Modern separation techniques and mass spectrometry. J Chromatogr B Analyt Technol Biomed Life Sci 2020; 1160:122352. [PMID: 32971366 PMCID: PMC8174749 DOI: 10.1016/j.jchromb.2020.122352] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 08/25/2020] [Accepted: 08/26/2020] [Indexed: 12/31/2022]
Abstract
Snake venoms are complex chemical mixtures of biologically active proteins and non-protein components. Toxins have a wide range of targets and effects to include ion channels and membrane receptors, and platelet aggregation and platelet plug formation. Toxins target these effectors and effects at high affinity and selectivity. From a pharmacological perspective, snake venom compounds are a valuable resource for drug discovery and development. However, a major challenge to drug discovery using snake venoms is isolating and analyzing the bioactive proteins and peptides in these complex mixtures. Getting molecular information from complex mixtures such as snake venoms requires proteomic analyses, generally combined with transcriptomic analyses of venom glands. The present review summarizes current knowledge and highlights important recent advances in venomics with special emphasis on contemporary separation techniques and bioinformatics that have begun to elaborate the complexity of snake venoms. Several analytical techniques such as two-dimensional gel electrophoresis, RP-HPLC, size exclusion chromatography, ion exchange chromatography, MALDI-TOF-MS, and LC-ESI-QTOF-MS have been employed in this regard. The improvement of separation approaches such as multidimensional-HPLC, 2D-electrophoresis coupled to soft-ionization (MALDI and ESI) mass spectrometry has been critical to obtain an accurate picture of the startling complexity of venoms. In the case of bioinformatics, a variety of software tools such as PEAKS also has been used successfully. Such information gleaned from venomics is important to both predicting and resolving the biological activity of the active components of venoms, which in turn is key for the development of new drugs based on these venom components.
Collapse
Affiliation(s)
- Tarek Mohamed Abd El-Aziz
- Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229-3900, USA; Zoology Department, Faculty of Science, Minia University, El-Minia 61519, Egypt.
| | - Antonio G Soares
- Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229-3900, USA
| | - James D Stockand
- Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229-3900, USA
| |
Collapse
|
8
|
Quintana-Castillo JC, Estrada-Gómez S, Cardona-Arias JA. Economic Evaluations of Interventions for Snakebites: A Systematic Review. CLINICOECONOMICS AND OUTCOMES RESEARCH 2020; 12:547-554. [PMID: 32982344 PMCID: PMC7509330 DOI: 10.2147/ceor.s259426] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 08/12/2020] [Indexed: 02/01/2023] Open
Abstract
Background Snakebite is an often-neglected event with a high rate of mortality and is concentrated in poor areas. We aimed to assess the economic impact and health effects of the implementation of interventions for snakebites through a systematic review of the scientific literature. Methods Thirty search strategies were conducted in seven databases, applying PRISMA’s identification, screening, selection, and inclusion phases. The reproducibility of the selection of studies and the extraction of information were guaranteed. The methodological quality was evaluated using the Consolidated Health Economic Evaluation Reporting Standards. Qualitative synthesis and meta-analysis were performed for determining the average cost-effectiveness (ACE) for each death and disability-adjusted life years (DALY) avoided. Results Six cost-effectiveness studies were included for the supply of antivenom (AV), taken as outcomes on days of hospitalization or in ICU, death and DALYs avoided. All studies only included institutional costs, and majority of them did not specify the analytical model or economic evaluation parameters and did not perform uncertainty analyses. The management protocol standardization with interdisciplinary attention improves ACE of AV. Cost-effectiveness ratio (CER) of treatment with AV was USD 1253 (constant value for the year 2017, adjusted by purchasing power parity) for each death avoided and USD 51 per DALY avoided. Conclusion High cost-effectiveness of the AV treatment for snakebites was evidenced, which shows that the allocation of resources for this event should be a healthcare priority in addition to implementation of strategies that improve the access to, opportunity, and quality of hospital and pre-hospital care and reduce the cost of AV.
Collapse
|
9
|
Ainsworth S, Menzies SK, Casewell NR, Harrison RA. An analysis of preclinical efficacy testing of antivenoms for sub-Saharan Africa: Inadequate independent scrutiny and poor-quality reporting are barriers to improving snakebite treatment and management. PLoS Negl Trop Dis 2020; 14:e0008579. [PMID: 32817682 PMCID: PMC7462309 DOI: 10.1371/journal.pntd.0008579] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Revised: 09/01/2020] [Accepted: 07/08/2020] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The World Health Organization's strategy to halve snakebite mortality and morbidity by 2030 includes an emphasis on a risk-benefit process assessing the preclinical efficacy of antivenoms manufactured for sub-Saharan Africa. To assist this process, we systematically collected, standardised and analysed all publicly available data on the preclinical efficacy of antivenoms designed for sub-Saharan Africa. METHODOLOGY/PRINCIPAL FINDINGS Using a systematic search of publication databases, we focused on publicly available preclinical reports of the efficacy of 16 antivenom products available in sub Saharan Africa. Publications since 1999 reporting the industry standard intravenous pre-incubation method of murine in vivo neutralisation of venom lethality (median effective dose [ED50]) were included. Eighteen publications met the criteria. To permit comparison of the several different reported ED50 values, it was necessary to standardise these to microlitre of antivenom resulting in 50% survival of mice challenged per milligram of venom (μl/mg). We were unable to identify publicly available preclinical data on four antivenoms, whilst data for six polyspecific antivenoms were restricted to a small number of venoms. Only four antivenoms were tested against a wide range of venoms. Examination of these studies for the reporting of key metrics required for interpreting antivenom ED50s were highly variable, as evidenced by eight different units being used for the described ED50 values. CONCLUSIONS/SIGNIFICANCE There is a disturbing lack of (i) preclinical efficacy testing of antivenom for sub Saharan Africa, (ii) publicly available reports and (iii) independent scrutiny of this medically important data. Where reports do exist, the methods and metrics used are highly variable. This prevents comprehensive meta-analysis of antivenom preclinical efficacy, and severely reduces the utility of antivenom ED50 results in the decision making of physicians treating patients and of national and international health agencies. Here, we propose the use of a standardised result reporting checklist to resolve this issue. Implementation of these straightforward steps will deliver uniform evaluation of products across laboratories, facilitate meta-analyses, and contribute vital information for designing the clinical trials needed to achieve the WHO target of halving snakebite morbidity and mortality by 2030.
Collapse
Affiliation(s)
- Stuart Ainsworth
- Centre for Snakebite Research and Interventions, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - Stefanie K. Menzies
- Centre for Snakebite Research and Interventions, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - Nicholas R. Casewell
- Centre for Snakebite Research and Interventions, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - Robert A. Harrison
- Centre for Snakebite Research and Interventions, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| |
Collapse
|
10
|
Krause KE, Jenkins TP, Skaarup C, Engmark M, Casewell NR, Ainsworth S, Lomonte B, Fernández J, Gutiérrez JM, Lund O, Laustsen AH. An interactive database for the investigation of high-density peptide microarray guided interaction patterns and antivenom cross-reactivity. PLoS Negl Trop Dis 2020; 14:e0008366. [PMID: 32579606 PMCID: PMC7313730 DOI: 10.1371/journal.pntd.0008366] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 05/06/2020] [Indexed: 12/19/2022] Open
Abstract
Snakebite envenoming is a major neglected tropical disease that affects millions of people every year. The only effective treatment against snakebite envenoming consists of unspecified cocktails of polyclonal antibodies purified from the plasma of immunized production animals. Currently, little data exists on the molecular interactions between venom-toxin epitopes and antivenom-antibody paratopes. To address this issue, high-density peptide microarray (hdpm) technology has recently been adapted to the field of toxinology. However, analysis of such valuable datasets requires expert understanding and, thus, complicates its broad application within the field. In the present study, we developed a user-friendly, and high-throughput web application named "Snake Toxin and Antivenom Binding Profiles" (STAB Profiles), to allow straight-forward analysis of hdpm datasets. To test our tool and evaluate its performance with a large dataset, we conducted hdpm assays using all African snake toxin protein sequences available in the UniProt database at the time of study design, together with eight commercial antivenoms in clinical use in Africa, thus representing the largest venom-antivenom dataset to date. Furthermore, we introduced a novel method for evaluating raw signals from a peptide microarray experiment and a data normalization protocol enabling intra-microarray and even inter-microarray chip comparisons. Finally, these data, alongside all the data from previous similar studies by Engmark et al., were preprocessed according to our newly developed protocol and made publicly available for download through the STAB Profiles web application (http://tropicalpharmacology.com/tools/stab-profiles/). With these data and our tool, we were able to gain key insights into toxin-antivenom interactions and were able to differentiate the ability of different antivenoms to interact with certain toxins of interest. The data, as well as the web application, we present in this article should be of significant value to the venom-antivenom research community. Knowledge gained from our current and future analyses of this dataset carry the potential to guide the improvement and optimization of current antivenoms for maximum patient benefit, as well as aid the development of next-generation antivenoms.
Collapse
Affiliation(s)
- Kamille E. Krause
- Department of Bio and Health Informatics, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Timothy P. Jenkins
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Carina Skaarup
- Department of Bio and Health Informatics, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Mikael Engmark
- Department of Bio and Health Informatics, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Nicholas R. Casewell
- Centre for Snakebite Research & Interventions, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - Stuart Ainsworth
- Centre for Snakebite Research & Interventions, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - Bruno Lomonte
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Julián Fernández
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - José M. Gutiérrez
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Ole Lund
- Department of Bio and Health Informatics, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Andreas H. Laustsen
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby, Denmark
| |
Collapse
|
11
|
Factor XII-Deficient Chicken Plasma as a Useful Target for Screening of Pro- and Anticoagulant Animal Venom Toxins. Toxins (Basel) 2020; 12:toxins12020079. [PMID: 31979411 PMCID: PMC7076771 DOI: 10.3390/toxins12020079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 01/14/2020] [Accepted: 01/20/2020] [Indexed: 11/24/2022] Open
Abstract
The sensitivity of vertebrate citrated plasma to pro- and anticoagulant venom or toxins occurs on a microscale level (micrograms). Although it improves responses to agonists, recalcification triggers a relatively fast thrombin formation process in mammalian plasma. As it has a natural factor XII deficiency, the recalcification time (RT) of chicken plasma (CP) is comparatively long [≥ 1800 seconds (s)]. Our objective was to compare the ability of bee venom phospholipase A2 (bvPLA2) to neutralize clot formation induced by an activator of coagulation (the aPTT clot) in recalcified human and chicken plasmas, through rotational thromboelastometry. The strategy used in this study was to find doses of bvPLA2 that were sufficient enough to prolong the clotting time (CT) of these activated plasmas to values within their normal RT range. The CT of CP was prolonged in a dose-dependent manner by bvPLA2, with 17 ± 2.8 ng (n = 6) being sufficient to displace the CT values of the activated samples to ≥ 1800 s. Only amounts up to 380 ± 41 ng (n = 6) of bvPLA2 induced the same effect in activated human plasma samples. In conclusion, the high sensitivity of CP to agonists and rotational thromboelastometry could be useful. For example, during screening procedures for assaying the effects of toxins in several stages of the coagulation pathway, such as clot initiation, formation, stability, strength, or dissolution.
Collapse
|
12
|
Beyond the 'big four': Venom profiling of the medically important yet neglected Indian snakes reveals disturbing antivenom deficiencies. PLoS Negl Trop Dis 2019; 13:e0007899. [PMID: 31805055 PMCID: PMC6894822 DOI: 10.1371/journal.pntd.0007899] [Citation(s) in RCA: 79] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Accepted: 11/01/2019] [Indexed: 11/19/2022] Open
Abstract
Background Snakebite in India causes the highest annual rates of death (46,000) and disability (140,000) than any other country. Antivenom is the mainstay treatment of snakebite, whose manufacturing protocols, in essence, have remained unchanged for over a century. In India, a polyvalent antivenom is produced for the treatment of envenomations from the so called ‘big four’ snakes: the spectacled cobra (Naja naja), common krait (Bungarus caeruleus), Russell’s viper (Daboia russelii), and saw-scaled viper (Echis carinatus). In addition to the ‘big four’, India is abode to many other species of venomous snakes that have the potential to inflict severe clinical or, even, lethal envenomations in their human bite victims. Unfortunately, specific antivenoms are not produced against these species and, instead, the ‘big four’ antivenom is routinely used for the treatment. Methods We characterized the venom compositions, biochemical and pharmacological activities and toxicity profiles (mouse model) of the major neglected yet medically important Indian snakes (E. c. sochureki, B. sindanus, B. fasciatus, and two populations of N. kaouthia) and their closest ‘big four’ congeners. By performing WHO recommended in vitro and in vivo preclinical assays, we evaluated the efficiencies of the commercially marketed Indian antivenoms in recognizing venoms and neutralizing envenomations by these neglected species. Findings As a consequence of dissimilar ecologies and diet, the medically important snakes investigated exhibited dramatic inter- and intraspecific differences in their venom profiles. Currently marketed antivenoms were found to exhibit poor dose efficacy and venom recognition potential against the ‘neglected many’. Premium Serums antivenom failed to neutralise bites from many of the neglected species and one of the ‘big four’ snakes (North Indian population of B. caeruleus). Conclusions This study unravels disturbing deficiencies in dose efficacy and neutralisation capabilities of the currently marketed Indian antivenoms, and emphasises the pressing need to develop region-specific snakebite therapy for the ‘neglected many’. Snakebite is a ‘neglected tropical disease’ that majorly affects the rural populations in developing countries. India bears the brunt of snakebites with over 46,000 deaths and 140,000 disabilities, annually. A significant number of these bites are attributed to the widely distributed ‘big four’ snakes, namely spectacled cobra (Naja naja), common krait (Bungarus caeruleus), Russell’s viper (Daboia russelii), and saw-scaled viper (Echis carinatus). The commercial antivenoms marketed in India are only manufactured against these four species, while neglecting many other medically relevant snakes with restricted geographic distribution. Snakebite pathology is dependent on the venom composition of the population/species, which can, in turn, vary intra- and inter-specifically. Though this variation severely limits the cross-population/species antivenom efficacy, envenomations by the neglected snakes in India are treated with the ‘big four’ antivenom. Therefore, to unravel the underlying venom variability, we investigated venom proteomic, biochemical/pharmacological and toxicity profiles of the major neglected Indian snakes and their ‘big four’ relatives. To assess the effectiveness of the ‘big four’ antivenom in treating bites from these neglected snakes, we performed preclinical experiments, which revealed alarming inadequacies of the commercial antivenoms. Our findings accentuate the compelling necessity for the innovation of highly efficacious next-generation snakebite therapy in India.
Collapse
|
13
|
Comparative analysis of Naja kaouthia venom from North-East India and Bangladesh and its cross reactivity with Indian polyvalent antivenoms. Toxicon 2019; 164:31-43. [DOI: 10.1016/j.toxicon.2019.03.025] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 03/26/2019] [Accepted: 03/31/2019] [Indexed: 01/01/2023]
|
14
|
Esiéné A, Etoundi PO, Tochie JN, Metogo AJM, Minkande JZ. Severe Viperidae envenomation complicated by a state of shock, acute kidney injury, and gangrene presenting late at the emergency department: a case report. BMC Emerg Med 2019; 19:26. [PMID: 30871512 PMCID: PMC6419359 DOI: 10.1186/s12873-019-0239-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Accepted: 03/01/2019] [Indexed: 12/02/2022] Open
Abstract
Background Snake envenomation is an underestimated pathology in sub-Saharan Africa associated with severe emergencies, and even death in case of late presentation. We herein present a case of severe envenomation managed at the surgical emergency department of the Yaoundé Central Hospital. Case presentation We report a case of a 47-year-old female farmer with no relevant past history who sustained a snakebite by an Echis occellatus viper during an agricultural activity. Her initial management consisted in visiting a traditional healer who administered her some herbal remedies orally and applied a white balm on the affected limb. Due to progressive deterioration of her condition, she was rushed to our surgical department where she arrived 20 h after the snakebite incident. On admission she presented in a state of shock (suggestive of an anaphylactic shock), coagulopathy, renal impairment, and gangrene of the entire right upper limb. Emergency management consisted of fluid resuscitation, repeated boluses of adrenaline, a total of three vials of polyvalent anti-venom sera, promethazine, analgesics, corticosteroids, and administration of fresh frozen plasma. Within four hours of emergency department hospitalisation she developped signs of sepsis and persistent hypotension refractory to fluid resuscitation, suggestive of an associated septic shock. Management pursued with antiobiotherapy and administration of noradrenaline through an electric pump syringe to achieve a mean arterial blood pressure above 65 mmHg. The patient deceased at the 10th hour of hospitalisation in a state of circulatory collapse unresponsive to vasopressors, coagulopathy, renal failure, sepsis and gangrene of the right forearm. Conclusion The authors highlight this unusual presentation but equally pinpoint how late presentation to the emergency department, harmful tradition practices, poverty and cultural beliefs can adversely affect the prognosis of snakebite in our setting.
Collapse
Affiliation(s)
- Agnès Esiéné
- Department of Emergency medicine, Anesthesiology and critical care, Faculty of Medicine and Biomedical Sciences, University of Yaoundé I, Yaoundé, Cameroon.,Department of Emergency medicine, Anesthesiology and critical care, Yaounde Central Hospital, Yaoundé, Cameroon
| | - Paul Owono Etoundi
- Department of Emergency medicine, Anesthesiology and critical care, Faculty of Medicine and Biomedical Sciences, University of Yaoundé I, Yaoundé, Cameroon.,Department of Emergency medicine, Anesthesiology and critical care, Yaounde Central Hospital, Yaoundé, Cameroon
| | - Joel Noutakdie Tochie
- Department of Emergency medicine, Anesthesiology and critical care, Faculty of Medicine and Biomedical Sciences, University of Yaoundé I, Yaoundé, Cameroon.
| | - Arlette Junette Mbengono Metogo
- Department of Emergency medicine, Anesthesiology and critical care, Faculty of Medicine and Biomedical Sciences, University of Yaoundé I, Yaoundé, Cameroon
| | - Jacqueline Ze Minkande
- Department of Emergency medicine, Anesthesiology and critical care, Faculty of Medicine and Biomedical Sciences, University of Yaoundé I, Yaoundé, Cameroon.,Department of Emergency medicine, Anesthesiology and critical care, Yaoundé Gynaeco-Obstetrics and Paediatric Hospital, Yaoundé, Cameroon
| |
Collapse
|
15
|
Guiding recombinant antivenom development by omics technologies. N Biotechnol 2018; 45:19-27. [DOI: 10.1016/j.nbt.2017.05.005] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 05/16/2017] [Indexed: 11/23/2022]
|
16
|
Antibody Cross-Reactivity in Antivenom Research. Toxins (Basel) 2018; 10:toxins10100393. [PMID: 30261694 PMCID: PMC6215175 DOI: 10.3390/toxins10100393] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Revised: 09/21/2018] [Accepted: 09/25/2018] [Indexed: 12/04/2022] Open
Abstract
Antivenom cross-reactivity has been investigated for decades to determine which antivenoms can be used to treat snakebite envenomings from different snake species. Traditionally, the methods used for analyzing cross-reactivity have been immunodiffusion, immunoblotting, enzyme-linked immunosorbent assay (ELISA), enzymatic assays, and in vivo neutralization studies. In recent years, new methods for determination of cross-reactivity have emerged, including surface plasmon resonance, antivenomics, and high-density peptide microarray technology. Antivenomics involves a top-down assessment of the toxin-binding capacities of antivenoms, whereas high-density peptide microarray technology may be harnessed to provide in-depth knowledge on which toxin epitopes are recognized by antivenoms. This review provides an overview of both the classical and new methods used to investigate antivenom cross-reactivity, the advantages and disadvantages of each method, and examples of studies using the methods. A special focus is given to antivenomics and high-density peptide microarray technology as these high-throughput methods have recently been introduced in this field and may enable more detailed assessments of antivenom cross-reactivity.
Collapse
|
17
|
A functional and thromboelastometric-based micromethod for assessing crotoxin anticoagulant activity and antiserum relative potency against Crotalus durissus terrificus venom. Toxicon 2018; 148:26-32. [PMID: 29654870 DOI: 10.1016/j.toxicon.2018.04.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Revised: 04/05/2018] [Accepted: 04/10/2018] [Indexed: 11/20/2022]
Abstract
The assessment of the capacity of antivenoms to neutralize the lethal activity of snake venoms still relies on traditional rodent in vivo lethality assay. ED50 and LD50 assays require large quantities of venoms and antivenoms, and besides leading to animal suffering. Therefore, in vitro tests should be introduced for assessing antivenom neutralizing capacity in intermediary steps of antivenom production. This task is facilitated when one key lethal toxin is identified. A good example is crotoxin, a β-neurotoxin phospholipase A2-like toxin that presents anticoagulant activity in vitro and is responsible for the lethality of venoms of Crotalus durissus snakes. By using rotational thromboelastometry, we reported recently one sensitive coagulation assay for assessing relative potency of the anti-bothropic serum in neutralizing procoagulant activity of Bothrops jararaca venom upon recalcified factor-XII-deficient chicken plasma samples (CPS). In this study, we stablished conditions for determining relative potency of four batches of the anti-crotalic serum (ACS) (antagonist) in inactivating crotoxin anticoagulant activity in CPS (target) simultaneously treated with one classical activator of coagulation (agonists). The correlation coefficient (r) between values related the ACS potency in inactivating both in vitro crotoxin anticoagulant activity and the in vivo lethality of whole venom (ED50) was 0.94 (p value < 0.05). In conclusion, slowness in spontaneous thrombin/fibrin generation even after recalcification elicit time lapse sufficient for elaboration of one dose-response curve to pro- or anti-coagulant agonists in CPS. We propose this methodology as an alternative and sensitive assay for assessing antivenom neutralizing ability in plasma of immunized horses as well as for in-process quality control.
Collapse
|
18
|
Calvete JJ, Rodríguez Y, Quesada-Bernat S, Pla D. Toxin-resolved antivenomics-guided assessment of the immunorecognition landscape of antivenoms. Toxicon 2018; 148:107-122. [PMID: 29704534 DOI: 10.1016/j.toxicon.2018.04.015] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 03/26/2018] [Accepted: 04/22/2018] [Indexed: 01/23/2023]
Abstract
Snakebite envenoming represents a major issue in rural areas of tropical and subtropical regions across sub-Saharan Africa, South to Southeast Asia, Latin America and Oceania. Antivenoms constitute the only scientifically validated therapy for snakebite envenomings, provided they are safe, effective, affordable, accessible and administered appropriately. However, the lack of financial incentives in a technology that has remained relatively unchanged for more than a century, has contributed to some manufacturers leaving the market and others downscaling production or increasing the prices, leading to a decline in the availability and accessibility for these life-saving antidotes to millions of rural poor most at risk from snakebites in low income countries. The shortage of antivenoms can be significantly alleviated by optimizing the use of current antivenoms (through the assessment of their specific and paraspecific efficacy against the different medically relevant homologous and heterologous snake venoms) and by generating novel polyspecific antivenoms exhibiting broad clinical spectrum and wide geographic distribution range. Research on venoms has been continuously enhanced by advances in technology. Particularly, the last decade has witnessed the development of omics strategies for unravelling the toxin composition of venoms ("venomics") and to assess the immunorecognition profile of antivenoms ("antivenomics"). Here, we review recent developments and reflect on near future innovations that promise to revolutionize the mutually enlightening relationship between evolutionary and translational venomics.
Collapse
Affiliation(s)
- Juan J Calvete
- Evolutionary and Translational Venomics Laboratory, Consejo Superior de Investigaciones Científicas (CSIC), Valencia, Spain.
| | - Yania Rodríguez
- Evolutionary and Translational Venomics Laboratory, Consejo Superior de Investigaciones Científicas (CSIC), Valencia, Spain
| | - Sarai Quesada-Bernat
- Evolutionary and Translational Venomics Laboratory, Consejo Superior de Investigaciones Científicas (CSIC), Valencia, Spain
| | - Davinia Pla
- Evolutionary and Translational Venomics Laboratory, Consejo Superior de Investigaciones Científicas (CSIC), Valencia, Spain.
| |
Collapse
|
19
|
Knudsen C, Laustsen AH. Recent Advances in Next Generation Snakebite Antivenoms. Trop Med Infect Dis 2018; 3:tropicalmed3020042. [PMID: 30274438 PMCID: PMC6073149 DOI: 10.3390/tropicalmed3020042] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Revised: 04/05/2018] [Accepted: 04/09/2018] [Indexed: 12/26/2022] Open
Abstract
With the inclusion of snakebite envenoming on the World Health Organization’s list of Neglected Tropical Diseases, an incentive has been established to promote research and development effort in novel snakebite antivenom therapies. Various technological approaches are being pursued by different research groups, including the use of small molecule inhibitors against enzymatic toxins as well as peptide- and oligonucleotide-based aptamers and antibody-based biotherapeutics against both enzymatic and non-enzymatic toxins. In this article, the most recent advances in these fields are presented, and the advantages, disadvantages, and feasibility of using different toxin-neutralizing molecules are reviewed. Particular focus within small molecules is directed towards the inhibitors varespladib, batimastat, and marimastat, while in the field of antibody-based therapies, novel recombinant polyclonal plantivenom technology is discussed.
Collapse
Affiliation(s)
- Cecilie Knudsen
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby, DK-2800, Denmark.
| | - Andreas H Laustsen
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby, DK-2800, Denmark.
| |
Collapse
|
20
|
Wang Y, Zhang J, Zhang D, Xiao H, Xiong S, Huang C. Exploration of the Inhibitory Potential of Varespladib for Snakebite Envenomation. Molecules 2018; 23:molecules23020391. [PMID: 29439513 PMCID: PMC6017252 DOI: 10.3390/molecules23020391] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Revised: 02/08/2018] [Accepted: 02/09/2018] [Indexed: 11/22/2022] Open
Abstract
Phospholipase A2s (PLA2) is a major component of snake venom with diverse pathologic toxicities and, therefore, a potential target for antivenom therapy. Varespladib was initially designed as an inhibitor of mammal PLA2s, and was recently repurposed to a broad-spectrum inhibitor of PLA2 in snake venom. To evaluate the protective abilities of varespladib to hemorrhage, myonecrosis, and systemic toxicities that are inflicted by different crude snake venoms, subcutaneous ecchymosis, muscle damage, and biochemical variation in serum enzymes derived from the envenomed mice were determined, respectively. Varespladib treatment showed a significant inhibitory effect to snake venom PLA2, which was estimated by IC50 in vitro and ED50 in vivo. In animal models, the severely hemorrhagic toxicity of D. acutus and A. halys venom was almost fully inhibited after administration of varespladib. Moreover, signs of edema in gastrocnemius muscle were remarkably attenuated by administration of varespladib, with a reduced loss of myonecrosis and desmin. Serum levels of creatine kinase, lactate dehydrogenase isoenzyme 1, aspartate transaminase, and alanine transaminase were down-regulated after treatment with varespladib, which indicated the protection to viscera injury. In conclusion, varespladib may be a potential first-line drug candidate in snakebite envenomation first aid or clinical therapy.
Collapse
Affiliation(s)
- Yiding Wang
- School of Basic Medical Sciences, Nanchang University, Nanchang 330006, China.
| | - Jing Zhang
- School of Basic Medical Sciences, Nanchang University, Nanchang 330006, China.
| | - Denghong Zhang
- School of Basic Medical Sciences, Nanchang University, Nanchang 330006, China.
| | - Huixiang Xiao
- School of Basic Medical Sciences, Nanchang University, Nanchang 330006, China.
| | - Shengwei Xiong
- School of Basic Medical Sciences, Nanchang University, Nanchang 330006, China.
| | - Chunhong Huang
- School of Basic Medical Sciences, Nanchang University, Nanchang 330006, China.
| |
Collapse
|
21
|
Rogalski A, Soerensen C, Op den Brouw B, Lister C, Dashevsky D, Arbuckle K, Gloria A, Zdenek CN, Casewell NR, Gutiérrez JM, Wüster W, Ali SA, Masci P, Rowley P, Frank N, Fry BG. Differential procoagulant effects of saw-scaled viper (Serpentes: Viperidae: Echis) snake venoms on human plasma and the narrow taxonomic ranges of antivenom efficacies. Toxicol Lett 2017; 280:159-170. [PMID: 28847519 DOI: 10.1016/j.toxlet.2017.08.020] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 08/21/2017] [Accepted: 08/21/2017] [Indexed: 10/19/2022]
Abstract
Saw-scaled vipers (genus Echis) are one of the leading causes of snakebite morbidity and mortality in parts of Sub-Saharan Africa, the Middle East, and vast regions of Asia, constituting a public health burden exceeding that of almost any other snake genus globally. Venom-induced consumption coagulopathy, owing to the action of potent procoagulant toxins, is one of the most relevant clinical manifestations of envenomings by Echis spp. Clinical experience and prior studies examining a limited range of venoms and restricted antivenoms have demonstrated for some antivenoms an extreme lack of antivenom cross-reactivity between different species of this genus, sometimes resulting in catastrophic treatment failure. This study undertook the most comprehensive testing of Echis venom effects upon the coagulation of human plasma, and also the broadest examination of antivenom potency and cross-reactivity, to-date. 10 Echis species/populations and four antivenoms (two African, two Asian) were studied. The results indicate that the venoms are, in general, potently procoagulant but that the relative dependence on calcium or phospholipid cofactors is highly variable. Additionally, three out of the four antivenoms tested demonstrated only a very narrow taxonomic range of effectiveness in preventing coagulopathy, with only the SAIMR antivenom displaying significant levels of cross-reactivity. These results were in conflict with previous studies using prolonged preincubation of antivenom with venom to suggest effective cross-reactivity levels for the ICP Echi-Tab antivenom. These findings both inform upon potential clinical effects of envenomation in humans and highlight the extreme limitations of available treatment. It is hoped that this will spur efforts into the development of antivenoms with more comprehensive coverage for bites not only from wild snakes but also from specimens widely kept in zoological collections.
Collapse
Affiliation(s)
- Aymeric Rogalski
- Venom Evolution Lab, School of Biological Sciences, University of Queensland, St Lucia QLD 4072 Australia
| | - Christoffer Soerensen
- Venom Evolution Lab, School of Biological Sciences, University of Queensland, St Lucia QLD 4072 Australia
| | - Bianca Op den Brouw
- Venom Evolution Lab, School of Biological Sciences, University of Queensland, St Lucia QLD 4072 Australia
| | - Callum Lister
- Venom Evolution Lab, School of Biological Sciences, University of Queensland, St Lucia QLD 4072 Australia
| | - Daniel Dashevsky
- Venom Evolution Lab, School of Biological Sciences, University of Queensland, St Lucia QLD 4072 Australia
| | - Kevin Arbuckle
- Department of Biosciences, College of Science, Swansea University, Swansea SA2 8PP, UK
| | - Alexandra Gloria
- Venom Evolution Lab, School of Biological Sciences, University of Queensland, St Lucia QLD 4072 Australia
| | - Christina N Zdenek
- Venom Evolution Lab, School of Biological Sciences, University of Queensland, St Lucia QLD 4072 Australia
| | - Nicholas R Casewell
- Alistair Reid Venom Research Unit, Parasitology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - José María Gutiérrez
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Wolfgang Wüster
- Molecular Ecology and Fisheries Genetics Laboratory (MEFGL), School of Biological Sciences, Bangor University, Bangor LL57 2UW, UK
| | - Syed A Ali
- Venom Evolution Lab, School of Biological Sciences, University of Queensland, St Lucia QLD 4072 Australia; HEJ Research Institute of Chemistry, International Centre for Chemical and Biological Sciences (ICCBS), University of Karachi, Karachi 75270, Pakistan
| | - Paul Masci
- Princess Alexandra Hospital, Translational Research Institute, University of Queensland, St Lucia, QLD 4072, Australia
| | - Paul Rowley
- Alistair Reid Venom Research Unit, Parasitology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | | | - Bryan G Fry
- Venom Evolution Lab, School of Biological Sciences, University of Queensland, St Lucia QLD 4072 Australia.
| |
Collapse
|
22
|
Tochie JN, Temgoua MN, Njim T, Celestin D, Tankeu R, Nkemngu NJ. The neglected burden of snakebites in Cameroon: a review of the epidemiology, management and public health challenges. BMC Res Notes 2017; 10:405. [PMID: 28807018 PMCID: PMC5557567 DOI: 10.1186/s13104-017-2718-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Accepted: 07/29/2017] [Indexed: 12/01/2022] Open
Abstract
Objectives Snakebite is an underestimated medical and surgical emergency in developing countries responsible for a high disease burden. Optimal management of snake envenomation in these resource-limited settings is precluded by several public health challenges. In this review, we discuss the disease burden of snakebites in Cameroon and the public health challenges of its management in view of making recommendations essential for policy-making. MEDLINE, African Journals Online and Google Scholar were searched from January 1990 to February 2017 for studies addressing snakebite in Cameroon. Our search extended to include grey literature from book chapters, conference proceedings, theses and documents from organizations. Results Our results suggest that snakebites pose a significant health and economic burden in Cameroon. A composite of factors contributes to the challenge of managing snakebites in Cameroon and include: inadequate disease surveillance; poor health-seeking behaviours of patients; under-production and scarcity of anti-venom serum and the relatively high cost of anti-venom serum. There is an urgent need to revamp the current health policies through health education, promotion and building of sustainable health systems. Disease surveillance and management can be improved by providing refresher courses for healthcare providers and subsidization of the prices of anti-venom serum in pharmacies in the country.
Collapse
Affiliation(s)
- Joel Noutakdie Tochie
- Department of Surgery and Sub-Specialties, Faculty of Medicine and Biomedical Sciences, University of Yaoundé I, Yaoundé, Cameroon. .,Health and Human Development (2HD) Research Group, Douala, Littoral Region, Cameroon.
| | - Mazou N Temgoua
- Department of Medicine and Specialties, Faculty of Medicine and Biomedical Sciences, University of Yaoundé I, Yaoundé, Cameroon
| | - Tsi Njim
- Health and Human Development (2HD) Research Group, Douala, Littoral Region, Cameroon.,Centre for Global Health and Tropical Medicine, Nuffield Department of Medicine, University of Oxford, Oxfordshire, UK
| | - Danwang Celestin
- Department of Surgery and Sub-Specialties, Faculty of Medicine and Biomedical Sciences, University of Yaoundé I, Yaoundé, Cameroon
| | - Ronni Tankeu
- Department of Medicine and Specialties, Faculty of Medicine and Biomedical Sciences, University of Yaoundé I, Yaoundé, Cameroon
| | | |
Collapse
|
23
|
Cross-reactivity, antivenomics, and neutralization of toxic activities of Lachesis venoms by polyspecific and monospecific antivenoms. PLoS Negl Trop Dis 2017; 11:e0005793. [PMID: 28787445 PMCID: PMC5560760 DOI: 10.1371/journal.pntd.0005793] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Revised: 08/17/2017] [Accepted: 07/11/2017] [Indexed: 11/19/2022] Open
Abstract
Background Bothrops, Crotalus and Lachesis represent the most medically relevant genera of pitvipers in Central and South America. Similarity in venom phenotype and physiopathological profile of envenomings caused by the four nominal Lachesis species led us to hypothesize that an antivenom prepared against venom from any of them may exhibit paraspecificity against all the other congeneric taxa. Methods To assess this hypothesis, in this work we have applied antivenomics and immunochemical methods to investigate the immunoreactivity of three monovalent antivenoms and two polyvalent antivenoms towards the venoms from different geographic populations of three different Lachesis species. The ability of the antivenoms to neutralize the proteolytic, hemorrhagic, coagulant, and lethal activities of the seven Lachesis venoms was also investigated. Results A conspicuous pattern of immunorecognition and cross-neutralization for all effects was evident by the polyspecific antivenoms, indicating large immunoreactive epitope conservation across the genus during more than 10 million years since the Central and South American bushmasters diverged. Conclusions Despite the broad geographic distribution of Lachesis, antivenoms against venoms of different species are effective in the neutralization of congeneric venoms not used in the immunization mixture, indicating that they can be used equivalently for the clinical treatment of any lachesic envenoming. General significance This study demonstrates that antivenoms raised against venom of different Lachesis species are indistinctly effective in the neutralization of congeneric venoms not used in the immunization mixture, indicating that antivenoms against conspecific venoms may be used equivalently for the clinical treatment of envenomings caused by any bushmaster species. Snakebite envenoming is a neglected public health problem in many developing countries and antivenom administration constitutes the mainstay in the treatment of such envenomings. Therapeutic antivenoms contain animal-derived antibodies against venom toxins and are produced by immunizing animals with the venom from one or several snake species from a defined geographical area. Defining the geographic boundaries of the efficiency of an antivenom therefore has implications for its rational and efficient use. In Central and South America most accidents are caused by pitvipers of the genus Bothrops, Crotalus and Lachesis. There are four Lachesis species distributed in a variety of habitats ranging from the Caribbean coast of Central America to the Atlantic rainforest of Brazil. Lachesis species cause severe envenomings in humans due to the toxicity of their venoms and also to the large amount of venom they inject into their victims. In this work we investigate the capability of several antivenoms to neutralize the toxic activities of a panel of Lachesis venoms. The results demonstrate that antivenoms raised by immunizing horses with the venoms of different Lachesis species are effective at neutralizing congeneric venoms not used in the immunization, indicating that they could be used equivalently for the clinical treatment of any lachesic envenoming.
Collapse
|
24
|
Gutiérrez JM, Solano G, Pla D, Herrera M, Segura Á, Vargas M, Villalta M, Sánchez A, Sanz L, Lomonte B, León G, Calvete JJ. Preclinical Evaluation of the Efficacy of Antivenoms for Snakebite Envenoming: State-of-the-Art and Challenges Ahead. Toxins (Basel) 2017; 9:toxins9050163. [PMID: 28505100 PMCID: PMC5450711 DOI: 10.3390/toxins9050163] [Citation(s) in RCA: 104] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Revised: 04/17/2017] [Accepted: 05/10/2017] [Indexed: 01/09/2023] Open
Abstract
Animal-derived antivenoms constitute the mainstay in the therapy of snakebite envenoming. The efficacy of antivenoms to neutralize toxicity of medically-relevant snake venoms has to be demonstrated through meticulous preclinical testing before their introduction into the clinical setting. The gold standard in the preclinical assessment and quality control of antivenoms is the neutralization of venom-induced lethality. In addition, depending on the pathophysiological profile of snake venoms, the neutralization of other toxic activities has to be evaluated, such as hemorrhagic, myotoxic, edema-forming, dermonecrotic, in vitro coagulant, and defibrinogenating effects. There is a need to develop laboratory assays to evaluate neutralization of other relevant venom activities. The concept of the 3Rs (Replacement, Reduction, and Refinement) in Toxinology is of utmost importance, and some advances have been performed in their implementation. A significant leap forward in the study of the immunological reactivity of antivenoms against venoms has been the development of “antivenomics”, which brings the analytical power of mass spectrometry to the evaluation of antivenoms. International partnerships are required to assess the preclinical efficacy of antivenoms against snake venoms in different regions of the world in order to have a detailed knowledge on the neutralizing profile of these immunotherapeutics.
Collapse
Affiliation(s)
- José María Gutiérrez
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José 11501-2060, Costa Rica.
| | - Gabriela Solano
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José 11501-2060, Costa Rica.
| | - Davinia Pla
- Instituto de Biomedicina de Valencia, CSIC, Valencia 46010, Spain.
| | - María Herrera
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José 11501-2060, Costa Rica.
- Sección de Química Analítica, Escuela de Química, Universidad de Costa Rica, San José 11501-2060, Costa Rica.
| | - Álvaro Segura
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José 11501-2060, Costa Rica.
| | - Mariángela Vargas
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José 11501-2060, Costa Rica.
| | - Mauren Villalta
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José 11501-2060, Costa Rica.
| | - Andrés Sánchez
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José 11501-2060, Costa Rica.
| | - Libia Sanz
- Instituto de Biomedicina de Valencia, CSIC, Valencia 46010, Spain.
| | - Bruno Lomonte
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José 11501-2060, Costa Rica.
| | - Guillermo León
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José 11501-2060, Costa Rica.
| | - Juan J Calvete
- Instituto de Biomedicina de Valencia, CSIC, Valencia 46010, Spain.
| |
Collapse
|
25
|
Pla D, Rodríguez Y, Calvete JJ. Third Generation Antivenomics: Pushing the Limits of the In Vitro Preclinical Assessment of Antivenoms. Toxins (Basel) 2017; 9:toxins9050158. [PMID: 28489039 PMCID: PMC5450706 DOI: 10.3390/toxins9050158] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Revised: 05/05/2017] [Accepted: 05/05/2017] [Indexed: 12/18/2022] Open
Abstract
Second generation antivenomics is a translational venomics approach designed to complement in vivo preclinical neutralization assays. It provides qualitative and quantitative information on the set of homologous and heterologous venom proteins presenting antivenom-recognized epitopes and those exhibiting impaired immunoreactivity. In a situation of worrying antivenom shortage in many tropical and sub-tropical regions with high snakebite mortality and morbidity rates, such knowledge has the potential to facilitate the optimal deployment of currently existing antivenoms and to aid in the rational design of novel broad specificity antidotes. The aim of the present work was to expand the analytical capability of the immunoaffinity second-generation antivenomics platform, endowing it with the ability to determine the maximal binding capacity of an antivenom toward the different toxins present in a venom, and to quantify the fraction of venom-specific antibodies present in a given antivenom. The application of this new platform, termed third generation (3G) antivenomics, in the preclinical evaluation of antivenoms is illustrated in this paper for the case of antivenom EchiTAb-Plus-ICP® reactivity towards the toxins of homologous (B. arietans) and heterologous (N. melanoleuca) venoms.
Collapse
Affiliation(s)
- Davinia Pla
- Laboratorio de Venómica Estructural y Funcional, Instituto de Biomedicina de Valencia, CSIC, Jaime Roig 11, 46010 Valencia, Spain.
| | - Yania Rodríguez
- Laboratorio de Venómica Estructural y Funcional, Instituto de Biomedicina de Valencia, CSIC, Jaime Roig 11, 46010 Valencia, Spain.
| | - Juan J Calvete
- Laboratorio de Venómica Estructural y Funcional, Instituto de Biomedicina de Valencia, CSIC, Jaime Roig 11, 46010 Valencia, Spain.
| |
Collapse
|
26
|
Lomonte B, Calvete JJ. Strategies in 'snake venomics' aiming at an integrative view of compositional, functional, and immunological characteristics of venoms. J Venom Anim Toxins Incl Trop Dis 2017; 23:26. [PMID: 28465677 PMCID: PMC5408369 DOI: 10.1186/s40409-017-0117-8] [Citation(s) in RCA: 104] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Accepted: 04/19/2017] [Indexed: 12/21/2022] Open
Abstract
This work offers a general overview on the evolving strategies for the proteomic analysis of snake venoms, and discusses how these may be combined through diverse experimental approaches with the goal of achieving a more comprehensive knowledge on the compositional, toxic, and immunological characteristics of venoms. Some recent developments in this field are summarized, highlighting how strategies have evolved from the mere cataloguing of venom components (proteomics/venomics), to a broader exploration of their immunological (antivenomics) and functional (toxicovenomics) characteristics. Altogether, the combination of these complementary strategies is helping to build a wider, more integrative view of the life-threatening protein cocktails produced by venomous snakes, responsible for thousands of deaths every year.
Collapse
Affiliation(s)
- Bruno Lomonte
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, 11501 Costa Rica
| | - Juan J Calvete
- Structural and Functional Venomics Laboratory, Instituto de Biomedicina de Valencia, CSIC, Valencia, Spain
| |
Collapse
|
27
|
Harrison RA, Gutiérrez JM. Priority Actions and Progress to Substantially and Sustainably Reduce the Mortality, Morbidity and Socioeconomic Burden of Tropical Snakebite. Toxins (Basel) 2016; 8:toxins8120351. [PMID: 27886134 PMCID: PMC5198546 DOI: 10.3390/toxins8120351] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 11/09/2016] [Accepted: 11/18/2016] [Indexed: 11/16/2022] Open
Abstract
The deliberations and conclusions of a Hinxton Retreat convened in September 2015, entitled “Mechanisms to reverse the public health neglect of snakebite victims” are reported. The participants recommended that the following priority actions be included in strategies to reduce the global impact of snake envenoming: (a) collection of accurate global snakebite incidence, mortality and morbidity data to underpin advocacy efforts and help design public health campaigns; (b) promotion of (i) public education prevention campaigns; (ii) transport systems to improve access to hospitals and (iii) establishment of regional antivenom-efficacy testing facilities to ensure antivenoms’ effectiveness and safety; (c) exploration of funding models for investment in the production of antivenoms to address deficiencies in some regions; (d) establishment of (i) programs for training in effective first aid, hospital management and post-treatment care of victims; (ii) a clinical network to generate treatment guidelines and (iii) a clinical trials system to improve the clinical management of snakebite; (e) development of (i) novel treatments of the systemic and local tissue-destructive effects of envenoming and (ii) affordable, simple, point-of-care snakebite diagnostic kits to improve the accuracy and rapidity of treatment; (f) devising and implementation of interventions to help the people and communities affected by physical and psychological sequelae of snakebite.
Collapse
Affiliation(s)
- Robert A Harrison
- Alistair Reid Venom Research Unit, Liverpool School of Tropical, Liverpool L35QA, UK.
| | - José María Gutiérrez
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José 11501-2060, Costa Rica.
| |
Collapse
|
28
|
Lewin M, Samuel S, Merkel J, Bickler P. Varespladib (LY315920) Appears to Be a Potent, Broad-Spectrum, Inhibitor of Snake Venom Phospholipase A2 and a Possible Pre-Referral Treatment for Envenomation. Toxins (Basel) 2016; 8:toxins8090248. [PMID: 27571102 PMCID: PMC5037474 DOI: 10.3390/toxins8090248] [Citation(s) in RCA: 139] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Revised: 08/11/2016] [Accepted: 08/15/2016] [Indexed: 01/07/2023] Open
Abstract
Snakebite remains a neglected medical problem of the developing world with up to 125,000 deaths each year despite more than a century of calls to improve snakebite prevention and care. An estimated 75% of fatalities from snakebite occur outside the hospital setting. Because phospholipase A2 (PLA2) activity is an important component of venom toxicity, we sought candidate PLA2 inhibitors by directly testing drugs. Surprisingly, varespladib and its orally bioavailable prodrug, methyl-varespladib showed high-level secretory PLA2 (sPLA2) inhibition at nanomolar and picomolar concentrations against 28 medically important snake venoms from six continents. In vivo proof-of-concept studies with varespladib had striking survival benefit against lethal doses of Micrurus fulvius and Vipera berus venom, and suppressed venom-induced sPLA2 activity in rats challenged with 100% lethal doses of M. fulvius venom. Rapid development and deployment of a broad-spectrum PLA2 inhibitor alone or in combination with other small molecule inhibitors of snake toxins (e.g., metalloproteases) could fill the critical therapeutic gap spanning pre-referral and hospital setting. Lower barriers for clinical testing of safety tested, repurposed small molecule therapeutics are a potentially economical and effective path forward to fill the pre-referral gap in the setting of snakebite.
Collapse
Affiliation(s)
- Matthew Lewin
- Research and Development, Ophirex, Inc., Corte Madera, CA 94925, USA.
- Center for Exploration and Travel Health, California Academy of Sciences, San Francisco, CA 94118, USA.
| | - Stephen Samuel
- General Medicine, Queen Elizabeth Hospital, King's Lynn, Norfolk PE30 4ET, UK.
| | - Janie Merkel
- Yale Center for Molecular Discovery, Yale University, West Haven, CT 06516, USA.
| | - Philip Bickler
- Anesthesia and Perioperative Care, University of California, San Francisco, CA 94143, USA.
| |
Collapse
|