RESUMO
Bitis arietans is a medically important snake found in Sub-Saharan Africa. The envenomation is characterized by local and systemic effects, and the lack of antivenoms aggravates the treatment. This study aimed to identify venom toxins and develop antitoxins. The F2 fraction obtained from Bitis arietans venom (BaV) demonstrated the presence of several proteins in its composition, including metalloproteases. Titration assays carried out together with the immunization of mice demonstrated the development of anti-F2 fraction antibodies by the animals. The determination of the affinity of antibodies against different Bitis venoms was evaluated, revealing that only BaV had peptides recognized by anti-F2 fraction antibodies. In vivo analyses demonstrated the hemorrhagic capacity of the venom and the effectiveness of the antibodies in inhibiting up to 80% of the hemorrhage and 0% of the lethality caused by BaV. Together, the data indicate: (1) the prevalence of proteins that influence hemostasis and envenomation; (2) the effectiveness of antibodies in inhibiting specific activities of BaV; and (3) isolation and characterization of toxins can become crucial steps in the development of new alternative treatments. Thus, the results obtained help in understanding the envenoming mechanism and may be useful for the study of new complementary therapies.
Assuntos
Mordeduras de Serpentes , Viperidae , Camundongos , Animais , Viperidae/metabolismo , Venenos de Serpentes/metabolismo , Antivenenos , Metaloproteases/metabolismo , Hemorragia , Imunoglobulina G/metabolismoRESUMO
Accidents with snakes are responsible for about 32,000 deaths annually in sub-Saharan Africa, caused mostly by snakes from the genus Bitis, in particular Bitis arietans. B. arietans venom is composed of a complex mixture of toxins, mainly metalloproteases, serine proteases, phospholipases, lectins, and disintegrins. In this work, we compared two approaches to anti-B. arietans antivenom production: immunization with crude snake venom (“traditional approach”) and immunization with selected key toxins isolated from the snake venom (“toxin oriented” approach). Fractions from B. arietans venom were isolated by size exclusion chromatography. Crude venom and samples containing serine proteases or metalloproteases were selected for the immunization of BALB/c mice. Anti-B. arietans and anti-serine proteases plasmas showed a similar recognition profile and higher titers and affinity than the anti-metalloproteases plasma. Cross-recognition of other Bitis venoms was observed, but with low intensity. Although the plasma of all experimental groups inhibited the enzymatic activity of B. arietans venom in vitro, in vivo protection was not achieved. Our results have shown limitations in both approaches considered. Based on this, we proposed a model of polyclonal, species-specific, monovalent antivenoms that could be used as a base to produce customizable polyvalent sera for use in sub-Saharan Africa.
RESUMO
Bitis arietans is a medically important snake found in Sub-Saharan Africa. The envenomation is characterized by local and systemic effects, and the lack of antivenoms aggravates the treatment. This study aimed to identify venom toxins and develop antitoxins. The F2 fraction obtained from Bitis arietans venom (BaV) demonstrated the presence of several proteins in its composition, including metalloproteases. Titration assays carried out together with the immunization of mice demonstrated the development of anti-F2 fraction antibodies by the animals. The determination of the affinity of antibodies against different Bitis venoms was evaluated, revealing that only BaV had peptides recognized by anti-F2 fraction antibodies. In vivo analyses demonstrated the hemorrhagic capacity of the venom and the effectiveness of the antibodies in inhibiting up to 80% of the hemorrhage and 0% of the lethality caused by BaV. Together, the data indicate: (1) the prevalence of proteins that influence hemostasis and envenomation; (2) the effectiveness of antibodies in inhibiting specific activities of BaV; and (3) isolation and characterization of toxins can become crucial steps in the development of new alternative treatments. Thus, the results obtained help in understanding the envenoming mechanism and may be useful for the study of new complementary therapies.
RESUMO
Bitis arietans is a medical importance snake found predominantly in sub-Saharan Africa. The envenomation is characterized by local and systemic reactions, which can lead the victims to death or permanent disabilities. However, the lack of antivenoms makes the treatment worse. Therefore, the present work aimed to identify venom toxins, learn about their properties and develop antitoxins. The F2 fraction obtained from affinity chromatography fractionation of B. arietans venom showed the major proteolytic activity of SVMPs from enzymatic tests. Based on mass spectrometry analysis, 57 different peptides were identified in the F2 fraction. Among the most prevalent peptides are SVMPs. ELISA titration assays performed together with the mouse immunization step (BALB/c) demonstrated the development of anti-F2 fraction antibodies by the animals. The determination of the affinity of antibodies against different Bitis venoms was evaluated, revealing that only the B. arietans venom has peptides recognized by anti-F2 fraction antibodies. In vivo analyzes demonstrated the hemorrhagic capacity of the venom, the effectiveness of the antibodies to inhibit up to 80% of hemorrhage and 0% of the lethality caused by the venom. Taken together, the data indicate: 1) the prevalence of peptides that influence hemostasis and the dissemination of local and systemic effects caused by poisoning; 2) the effectiveness of monospecific antibodies in inhibiting specific activities of the venom; and 3) the isolation of toxins, production and characterization of antibodies is a crucial step in the development of new antivenoms. Therefore, the obtained results help in understanding the mechanism involved in the envenomation and can be useful for the study of new complementary therapies to antivenom in the treatment of accidents by Bitis arietans.
Bitis arietans é uma serpente de importância médica encontrada predominantemente na África Subsaariana. O envenenamento é caracterizado por efeitos locais e sistêmicos, que podem levar a morte ou incapacidades permanentes. No entanto, a carência de antivenenos agravam o tratamento. Portanto, este trabalho teve como objetivo identificar toxinas do veneno, conhecer suas propriedades e desenvolver antitoxinas. A fração F2 obtida do fracionamento por cromatografia de afinidade do veneno de B. arietans, demonstrou a atividade proteolítica majoritária de SVMPs a partir de testes enzimáticos. Com base na análise por espectrometria de massas, foram identificados 57 peptídeos diferentes na fração F2. Entre os peptídeos de maior prevalência estão as SVMPs. Ensaios de titulação por ELISA realizados em conjunto à etapa de imunização de camundongos (BALB/c), demonstraram o desenvolvimento de anticorpos anti-fração F2 pelos animais. A determinação da afinidade dos anticorpos contra diferentes venenos de Bitis foi avaliada, revelando que somente o veneno de B. arietans possui peptídeos reconhecidos pelos anticorpos anti-fração F2. Análises in vivo demonstraram a capacidade hemorrágica do veneno, a eficácia dos anticorpos de inibir em até 80% a hemorragia e em 0% da letalidade causadas pelo veneno. Em conjunto, os dados indicam: 1) a prevalência de peptídeos que atuam influenciando na hemostasia e na disseminação de efeitos locais e sistêmicos causados pelo envenenamento; 2) a eficácia de anticorpos monoespecíficos em inibir atividades específicas do veneno; e 3) o isolamento de toxinas, produção e caracterização de anticorpos é uma etapa crucial no desenvolvimento de novos antivenenos. Desta forma, os resultados obtidos auxiliam na compreensão no mecanismo de envenenamento e podem ser úteis para o estudo de novas terapias complementares ao antiveneno no tratamento dos acidentes por Bitis arietans.
RESUMO
Snakebite envenomation is considered a neglected tropical disease, affecting tens of thousands of people each year. The recommended treatment is the use of antivenom, which is composed of immunoglobulins or immunoglobulin fragments obtained from the plasma of animals hyperimmunized with one (monospecific) or several (polyspecific) venoms. In this review, the efforts made in the improvement of the already available antivenoms and the development of new antivenoms, focusing on snakes of medical importance from sub-Saharan Africa and Latin America, are described. Some antivenoms currently used are composed of whole IgGs, whereas others use F(ab’)2 fragments. The classic methods of attaining snake antivenoms are presented, in addition to new strategies to improve their effectiveness. Punctual changes in immunization protocols, in addition to the use of cross-reactivity between venoms from different snakes for the manufacture of more potent and widely used antivenoms, are presented. It is known that venoms are a complex mixture of components; however, advances in the field of antivenoms have shown that there are key toxins that, if effectively blocked, are capable of reversing the condition of in vivo envenomation. These studies provide an opportunity for the use of monoclonal antibodies in the development of new-generation antivenoms. Thus, monoclonal antibodies and their fragments are described as a possible alternative for the production of antivenoms, regardless of the venom. This review also highlights the challenges associated with their development.
O envenenamento por picada de cobra é considerado uma doença tropical negligenciada, afetando dezenas de milhares de pessoas a cada ano. O tratamento recomendado é o uso de antiveneno, que é composto por imunoglobulinas ou fragmentos de imunoglobulinas obtidos do plasma de animais hiperimunizados com um (monoespecífico) ou vários (poliespecíficos) venenos. Nesta revisão, são descritos os esforços realizados no aprimoramento dos antivenenos já disponíveis e no desenvolvimento de novos antivenenos, com foco em serpentes de importância médica da África Subsaariana e América Latina. Alguns antivenenos atualmente utilizados são compostos por IgGs inteiros, enquanto outros usam fragmentos F(ab’)2. São apresentados os métodos clássicos de obtenção de soros de serpentes, além de novas estratégias para melhorar sua eficácia. São apresentadas mudanças pontuais nos protocolos de imunização, além do uso de reatividade cruzada entre venenos de diferentes serpentes para a fabricação de antivenenos mais potentes e amplamente utilizados. Sabe-se que os venenos são uma mistura complexa de componentes; no entanto, avanços na área de antivenenos mostraram que existem toxinas-chave que, se efetivamente bloqueadas, são capazes de reverter a condição de envenenamento in vivo. Esses estudos oferecem uma oportunidade para o uso de anticorpos monoclonais no desenvolvimento de antivenenos de nova geração. Assim, anticorpos monoclonais e seus fragmentos são descritos como uma possível alternativa para a produção de antivenenos, independente do veneno. Esta revisão também destaca os desafios associados ao seu desenvolvimento.
RESUMO
Bitis arietans is a snake of medical importance found throughout sub-Saharan Africa and in savannas and pastures of Morocco and western Arabia. The effects of its venom are characterized by local and systemic alterations, such as inflammation and cardiovascular and hemostatic disturbances, which can lead to victims’ death or permanent disability. To better characterize the inflammatory process induced by this snake’s venom, the participation of eicosanoids and PAF (platelet- activating factor) in this response were demonstrated in a previous study. In addition, edema and early increased vascular permeability followed by an accumulation of polymorphonuclear (PMN) cells in the peritoneal cavity were accompanied by the production of the eicosanoids LTB4, LTC4, TXB2, and PGE2, and local and systemic production of IL-6 and MCP-1. In this context, the present study focused on the identification of inflammatory mediators produced by human macrophages derived from THP-1 cells in response to Bitis arietans venom (BaV), and Kn-Ba, a serine protease purified from this venom. Here, we show that Kn-Ba, and even the less intensive BaV, induced the production of the cytokine TNF and the chemokines RANTES and IL-8. Only Kn-Ba was able to induce the production of IL-6, MCP-1, and IP-10, whereas PGE2 was produced only in response to BaV. Finally, the release of IL-1β in culture supernatants suggests the activation of the inflammasomes by the venom of Bitis arietans and by Kn-Ba, which will be investigated in more detail in future studies.