Long-term antibody response and protective effect induced by attenuated scorpion toxins: Involvement of memory plasma cells.

In Algeria, Androctonus australis hector scorpion envenomation remains a major problem of public health because of non-efficient therapy. The development of safe vaccine against scorpion venom could be one key strategy for the envenomation prevention. The irradiation of venom by γ-rays develops suitable immunogens which produced effective antivenom and safe vaccine. In this study, we investigated the ability of the irradiated toxic fraction (γ-FtoxG50) to induce long-term memory humoral response in immunized animals (mice and rabbits), by involving the long-lived plasma cells to prevent efficiently the lethality of scorpion envenomation. For this purpose, an appropriate immunization schedule was established in mice and rabbits using three (3) similar doses of γ-FtoxG50 associated with Alum adjuvant. Obtained results indicate that the long-term immunogenicity of γ-FtoxG50 is able to induce the long-term memory humoral response with a high level of specific antibodies. The long-term persistence of antibody levels could depend on bone marrow memory plasma cells. These cells produce continuously antibodies without antigen stimulus. Furthermore, an enhanced memory response was obtained post-repeated envenomation with toxic native venom that leads to improved protection of animals. Together, pre-existing protective antibodies and the activation of memory B-cells could induce a rapid neutralization of scorpion toxins and long-term protection against scorpion envenomation.

Bradykinin-Potentiating Activity of a Gamma-Irradiated Bioactive Fraction Isolated from Scorpion (Leiurus quinquestriatus) Venom in Rats with Doxorubicin-Induced Acute Cardiotoxicity: Favorable Modulation of Oxidative Stress and Inflammatory, Fibrogenic and Apoptotic Pathways.

Although doxorubicin (Dox) is a backbone of chemotherapy, the search for an effective and safe therapy to revoke Dox-induced acute cardiotoxicity remains a critical matter in cardiology and oncology. The current study was the first to explore the probable protective effects of native and gamma-irradiated fractions with bradykinin-potentiating activity (BPA) isolated from scorpion (Leiurus quinquestriatus) venom against Dox-induced acute cardiotoxicity in rats. Native or irradiated fractions (1 µg/g) were administered intraperitoneally (i.p.) twice per week for 3 weeks, and Dox (15 mg/kg, i.p.) was administered on day 21 at 1 h after the last native or irradiated fraction treatment. Electrocardiographic (ECG) aberrations were ameliorated in the Dox-treated rats pretreated with the native fraction, and the irradiated fraction provided greater amelioration of ECG changes than that of the native fraction. The group pretreated with native protein with BPA also exhibited significant improvements in the levels of oxidative stress-related, inflammatory, angiogenic, fibrogenic, and apoptotic markers compared with those of the Dox group. Notably, the irradiated fraction restored these biomarkers to their normal levels. Additionally, the irradiated fraction ameliorated Dox-induced histological changes and alleviated the severity of cardiac injury to a greater extent than that of the native fraction. In conclusion, the gamma-irradiated detoxified fraction of scorpion venom elicited a better cardioprotective effect than that of the native fraction against Dox-induced acute cardiotoxicity in rats.

Reactogenicity and safety assessment of an attenuated nanovaccine against scorpion envenomation: Preclinical study.

An attenuated nanovaccine (Nps - V∗) has been developed to protect humans from fatal scorpion envenomation in at-risk regions. This study was conducted to evaluate the toxicity and the local reactogenicity of the Nps - V∗ nanovaccine developed against Androctonus australis hector (Aah) venom. Assessment of the systemic inflammatory response and serum cytokine levels were evaluated in vaccinated mice with 100µg of irradiated Aah venom (V∗) encapsulated or not into polymeric calcium-alginate nanoparticles (Nps) and injected by subcutaneous (s.c) route. The local reactogenicity was evaluated by dermal Draize observations and skin tissue analysis at the injection site of vaccinated rabbits with 250 or 500µg of V∗-loaded into Nps. All animals gained weight and had normal food consumption during the study. Additionally, results showed that the nanoformulation Nps - V∗ did not cause clinical evidence of systemic toxicity in mice or rabbits, a transient edema/erythema at the injection site was only recorded as treatment-related reactogenicity. These results indicated a favorable safety profile for Nps - V∗ and supported its use in superior animal tests, then in a Phase 1 clinical trial.

Enhanced immune sera and vaccine: safe approach to treat scorpion envenoming.

Irradiation of Androctonus australis hector venom using a dose of 2 kGy has successfully abolished toxicity without reducing its antigenic or immunogenic properties. Toxicity of irradiated antigen was abolished until 20 times of LD(50) of native venom. Analysis of physiopathological effects induced by native and irradiated venoms was assessed by the analysis of tissue damage, immunohistochemistry and metabolical analysis in the organs (heart, lungs and liver). Immunological response of Aah venom using native or irradiated venom showed high titers of IgG1 in the plasma of immunized animals with native venom suggesting that Th2 cells were predominantly involved in the immune response. In the other hand, irradiated venom induced high titers of IgG2, indicating a predominantly Th1 type response. A protective effect of immunized mice with irradiated venom was evaluated. Immunized mice were protected from the toxic effects of native venom doses at one, three and six months after immunization. Mice were protected against a challenge of 4 LD(50) doses of native venom, one month after immunization. This protective effect was improved and effective at 3 and 6 months, all immunized mice were protected respectively against 6 and 10 LD(50) of native venom. At the one-month time point, the protective effect of mice was associated with high levels of antibodies in the plasma of immunized mice. However, despite the persistence of higher protection levels, the antibody titers decreased in a time-dependent manner. These results suggest that additional factors other than circulating antibodies provided the long-term protective activity produced by immunization with irradiated venom.

Effects of prenatal exposure to Tityus bahiensis scorpion venom on rat offspring development

Scorpion envenoming is a public health problem. In Brazil, the scorpion Tityus serrulatus is considered the most dangerous, but a large number of exposures also occur with Tityus bahiensis. There are quite a few studies in literature about the toxic effects of this venom but it is not known if the venom causes malformations or behavioral defects to the offspring of mothers exposed to the venom during pregnancy. The objective of this work was to determine, in rats, the possible toxic effects of T. bahiensis venom on offspring when injected into rats during different periods of fetal development. Rats were assigned to one of three groups: one control group and two experimental groups that were subcutaneously injected with venom (2.5 mg/kg) on the 10th (GD10) or on 16th day (GD16) of gestation. Pups were evaluated for changes in physical and behavioral development. GD10 treatment group offspring showed an increase in body weight gain, earlier ear unfolding, incisor tooth eruption and vaginal opening. A decrease in the time of palmar grasp and surface-righting reflexes was observed only for males. In GD16 treatment group, earlier ear unfolding, incisor tooth eruption, and delay in eye opening were observed in the offspring. In female pups a decrease in weight gain and in time for palmar grasp reflex, and an increase in time for negative geotaxis were observed. In male pups a delay in the testis descent, decrease in the time of palmar grasp, increase in the time of negative geotaxis reflex and in the general and locomotor activities could be noticed. Therefore, we concluded that a moderate dose of scorpion venom administered to pregnant rats was able to elicit alterations in physical and behavioral development in the offspring during the postnatal period.

Uso das soluções de cloreto de sódio a 0, 9 por cento e 7, 5 por cento e hidroxietilamido no tratamento do choque induzido por toxina escorpiônica em ratos / The use of 0, 9 per cent and 7, 5 per cent sodium chloride solution and hydroetyl starch in treatment of shock induced by scorpion toxin in rats

O veneno bruto do Tityus serralatus, ou sua toxina purificada, é capaaz de levar à instabilidade dos sistemas fisiológicos, podendo ser fatal em crianças e idosos. O efeito hipertensivo da toxina é intenso, secundário à estimulação autonômica e liberação de catecolaminas. Após este período hipertensivo, geralmente se segue a hipotensão prolongada podendo evoluir para choque refratário, explicado, pelo menos em parte, por uma resposta inflamatória sistêmica que pode lever a falência múltipla orgânica e morte. A toxina pode levar à arritmias respiratórias, apnéia e respiração tipo 'gasp'. A reposição volêmica é fundamental no tratamento do choque. Quanto melhor a resposta pressórica secundária a infusão volêmica, pior foram as complicações pulmonares de edema / The Tityus serrulatus venon or its purified toxin, can cause instability of physiological systems, what can be the cause of death in children and ederly people. The scorpion venon cause hipertension that is secundary to autonomatic stimulation and release of catecolamines. After hipertensive period, generaly a prolonged hypotension come and could evalue to a refratary shock. At least, a part of this process can be explained by a systemic inflammatory response, that can cause multiple organ failure and death. The scorpion venon can lead to arrythmias, apnea and "gasping". Volemic replace is essencial to treat the shock. The better is the secundary response to blood pressure to volemic infusion, the worse is the pulmonary complication of oedema...

Effect of gamma irradiation on toxicity and immunogenicity of Androctonus australis hector venom.

An investigation was made of the radiosensitivity of the toxic and immunological properties of Androctonus australis hector venom. This venom was irradiated with two doses of gamma rays (1 and 2 kGy) from a 60Co source. The results showed that venom toxicity was abolished for the two radiation doses (1 and 2 kGy) with, respectively, 10 and 25 times its initial LD50 value. However, irradiated venoms were immunogenic, and the antibodies elicited by them were able to recognize the native venom by enzyme-linked immunosorbent assay. Antisera raised against these toxoids (1 and 2 kGy) had a higher neutralizing capacity and immunoreactivity against all components of native venom than did the antiserum produced against the native venom. The antiserum of rabbits immunized with 2-kGy-irradiated venom was more efficient than 1-kGy-irradiated toxoid antiserum. Indeed, in vivo protection assays showed that the mice immunized with 2-kGy-irradiated venom resisted lethal doses (i.p.) of A. australis hector venom.