Cross-reactivity of some Micrurus venoms against experimental and therapeutic anti-Micrurus antivenoms.

We developed experimental equine polyvalent and monovalent antivenoms against the venoms of Micrurus (M.) fulvius, M. nigrocinctus and M. surinamensis and studied their immunochemical reactivity on the venoms used as immunogens and on M. pyrrhocryptus, M altirostris and M. balyocoriphus venoms. Assessment of the neutralizing capacity of the polyvalent experimental antivenom was based on inhibition of lethality (preincubation and rescue assay experiments in mice) and indirect hemolytic and phospholipase activities. The immunochemical reactivity and neutralizing capacity were compared with those of two therapeutic antivenoms used for the treatment of coral snake envenomation in North America and in Argentina. In general, the experimental antivenom conferred a comparable level of neutralization against the venoms used as immunogens when compared to the therapeutic antivenoms and a certain level of cross-neutralization against the other venoms. The results suggest the need for additional venoms in the immunogenic mixture used, in order to obtain a broad spectrum anti-Micrurus antivenom with a good neutralizing potency. Paraspecific neutralization of South American coral snake venoms, although present at a higher level than the neutralization conferred by available nonspecific Micrurus therapeutic antivenoms, was rather low in relation to the specific neutralizing capacity.

Toxicological study of bee venom (Apis mellifera mellifera) from different regions of the province of Buenos Aires, Argentina.

Samples of Apis mellifera mellifera venom from different hives in two regions of the Buenos Aires province and its pool were analyzed for their lethal potency, myotoxic, defibrinogenating, hemolytic and inflammatory-edematizing activity and for the histological alterations they produce in the heart, lungs, kidneys, skeletal muscle and liver of mice. In vitro studies focused on the venom's hemolytic activity in different systems and species (horse, man, sheep and rabbit), the cytotoxicity in cellular lines, and on the proteolytic and coagulant activity in plasma and fibrinogen. Hemolytic activity, either observed in vitro or in vivo, showed similar toxicity levels for all samples. Erythrocytes of different species varied in their sensitivity to the venom pool, equines being the most sensitive and sheep the most resistant to direct hemolytic action. Local and systemic myotoxicity was evidenced by either the elevation of serum creatine kinase and/or histopathological lesions, observed in different muscles. All samples caused significant pathological alterations; pulmonary, cardiac, renal and skeletal muscle lesions were substantive and can be related to the pathophysiological mechanisms of envenomation. The venoms from different apiaries and regions of the Buenos Aires province showed very similar toxicological characteristics. These results suggest that severity of envenomation in case of a swarming could therefore be more related to the number of bees than to the differential toxicity of the venom from different regions of the province. This is the first study on the toxicity and toxicological characteristics of Apis mellifera venom in Argentina.

Study on the obtaining of Tityus trivittatus venom in Argentina.

Envenomation by scorpions of the genus Tityus is an important public health problem in Argentina, involving near 8000 stings and 2 deaths each year. Treatment for envenomation is the use of specific antivenom and intensive hospital care. Antivenom is produced by the Ministry of Health and freely distributed throughout the country. For antivenom production it is necessary to collect scorpion venom, which is a difficult task because although scorpions can be found in Argentina, they are less abundant than in warmer latitudes. For this reason venom collection constitutes a bottleneck for antivenom production. Although in Argentina several species of Tityus can be found, most of the accidents are caused by Tityus trivittatus, and the venom of this scorpion has historically been the venom used for antivenom production. We analyzed retrospectively 26 pools of telson homogenates (6964 telsons) and 37 pools of milked venom obtained by electrical stimulation (equivalent to 6841 milkings). Lethal potencies of samples from different provinces were very similar, although venom from scorpions of Buenos Aires city showed the lowest potency. The venom obtained by milking (median LD50 12.3 µg), provided batches containing LD50s more potent when compared with the venom obtained from telson homogenates (p < 0.0001). Many batches of telson homogenates (30%) showed lower potencies than acceptable for antivenom production and control. In addition to the study of the venom yield, the records of immunization of horses, the potency of the batches and the protein content of each batch of anti-scorpion antivenom produced were analyzed, comparing those produced using milked venom with those using telson homogenates as immunogens. Batches produced using milked venom required a shorter period of immunization (p < 0.0001), rendered higher neutralizing titers (p 0.0350) and possessed lower protein content (p 0.0092). Results clearly showed that the milking of scorpions is a more efficient tool to obtain venom for antivenom production in comparison to the use of telson homogenates.

Antivenom against Crotalus durissus terrificus venom: Immunochemical reactivity and experimental neutralizing capacity.

The venom of Crotalus durissus terrificus produces a neurotoxic and myotoxic syndrome that can lead to the death. Specific antivenom is the only treatment to neutralize the toxicity of the venom and the precocity in applying the antivenom is crucial for the efficiency of the treatment. We studied the variation of the immunochemical reactivity and neutralizing capacity of the specific antivenom on this venom in pre-incubation and rescue experiments, at different times. ELISA titers increased with longer venom-antivenom incubation times (p < 0.05) nevertheless incubation times had no effect on the neutralizing capacity of the antivenom. The antivenom dose necessary to rescue mice injected with 1.5 MMD (minimal mortal dose) 30 min after venom inoculation was over ten folds the dose of antivenom theoretically required to neutralize the same dose of venom according values obtained from pre-incubation experiments. Results showed that the in vitro immunochemical reactivity is not directly related to the neutralizing capacity. These observations underline the need for a rapid antivenom administration. Although preincubation experiments in mice are a powerful tool for the validation of the potency of the antivenoms in the productive process, it is clear that the nominal neutralization of the antivenoms must not be considered as a "stoichiometric" value regarding the venom to be neutralized in case of natural envenomation and emphasize the need of realization of clinical trials in order to evaluate the adequate doses of antivenom to be therapeutically used.

Multiparity upregulates placental plasminogen and urokinase-type plasminogen activator.

PROBLEM: Multiparity increased the number of trophoblast cells in decidua of both low and high fetal loss mouse models. However, they differ in fetal survival rate and maternal thymocyte subpopulations, suggesting that trophoblast invasiveness is not equivalent. Our aim was to explore the involved mechanism. METHOD OF STUDY: We studied placentae from primiparous and multiparous females of low and high fetal loss models. We investigated invasiveness in vitro, expression of plasminogen, and its activators: tissue type (tPA)-urokinase type (uPA), and activity and expression of matrix metalloproteinases (MMP)-2 and MMP-9. RESULTS: Placental invasiveness is upregulated by multiparity, but lesser in the high fetal loss model. Multiparous animals showed elevated expression of plasminogen and uPA. However, the high fetal loss combination showed higher expression of a short and less active fragment of uPA (LMW-uPA). MMP-2, MMP-9, and tPA were unaffected. CONCLUSION: uPA would participate in the increased multiparity-associated placental invasiveness.

Optimización en la recuperación de inmunoglobulinas, como molécula entera y fragmento F(ab´)2, en la producción de antivenenos / Optimization in the immunoglobulins recovery, as whole molecule and F(ab´)2 fragment, in the antivenim production

En la actualidad se utilizan, principalmente, dos métodos de purificación de anticuerpos a partir de plasmas equinos hiperinmunes para la producción de antivenenos a nivel industrial, obteniéndose preparaciones enriquecidas en moléculas de inmunoglobulinas G ó fragmentos F(ab´)2. Con ambos métodos, luego de la precipitación, se observa una importante pérdida de capacidad neutralizante en comparación con la capacidad neutralizante de los plasmas de partida. En este trabajo, se realizó el fraccionamiento de plasmas equinos hiperinmunes utilizando ácido caprílico con y sin digestión enzimática con pepsina. El objetivo del trabajo fue dar a conocer la proporción de recuperación de la capacidad neutralizante luego del fraccionamiento; resultando ésta menor cuando el plasma se trató enzimáticamente. Adicionalmente, se propuso establecer cuál sería la etapa responsable de la diferencia en la recuperación de anticuerpos entre una metodología y otra. Cuando se purificaron las inmunoglobulinas enteras, se recuperó aproximadamente un 53% de la capacidad neutralizante mientras que cuando la muestra se purificó luego de ser tratada enzimáticamente, se obtuvo alrededor del 30% de esa actividad. Una relación de similar magnitud se verifica en la recuperación de la masa de proteínas solubles luego de remover los contaminantes, entre una metodología y otra. La insolubilización del fragmento Fc generado durante la digestión sería el responsable de esa pérdida adicional de proteína y capacidad neutralizante.

Today two methods are mainly used for the purification of antibodies from hyperimmune equine plasma at industrial level obtaining enriched preparations of immunoglobulin G (IgG) molecules or F(ab´)2 fragments. In both methods, after the precipitation, an important loss in the neutralizing capability was observed compared to the one of the original plasma. In this work, we performed the fractionation of hyperimmune equine plasma using caprylic acid, with and without enzymatic digestion with pepsin. The aim was to explain the percentage of recovery of the neutralizing capability after the fractionation; which resulted minor when the plasma was enzymatically treated. Additionally, we intended to establish which stage, in the purification process, was the responsible for the difference in the antibody recovery between one methodology and the other. When entire immunoglobulins were purified, approximately 53% of the neutralizing capacity was recovered, but when the sample was purified after the enzymatic treatment, around the 30% of the activity was obtained. A ratio of similar magnitude is verified on the recovery of the soluble protein mass after the removal of contaminants, between the two methods. The insolubilization of the fragment Fc generated during digestion would be responsible for the additional loss of protein and neutralizing capacity.

Optimización en la recuperación de inmunoglobulinas, como molécula entera y fragmento F(ab´)2, en la producción de antivenenos / Optimization in the immunoglobulins recovery, as whole molecule and F(ab´)2 fragment, in the antivenim production

En la actualidad se utilizan, principalmente, dos métodos de purificación de anticuerpos a partir de plasmas equinos hiperinmunes para la producción de antivenenos a nivel industrial, obteniéndose preparaciones enriquecidas en moléculas de inmunoglobulinas G ó fragmentos F(ab´)2. Con ambos métodos, luego de la precipitación, se observa una importante pérdida de capacidad neutralizante en comparación con la capacidad neutralizante de los plasmas de partida. En este trabajo, se realizó el fraccionamiento de plasmas equinos hiperinmunes utilizando ácido caprílico con y sin digestión enzimática con pepsina. El objetivo del trabajo fue dar a conocer la proporción de recuperación de la capacidad neutralizante luego del fraccionamiento; resultando ésta menor cuando el plasma se trató enzimáticamente. Adicionalmente, se propuso establecer cuál sería la etapa responsable de la diferencia en la recuperación de anticuerpos entre una metodología y otra. Cuando se purificaron las inmunoglobulinas enteras, se recuperó aproximadamente un 53% de la capacidad neutralizante mientras que cuando la muestra se purificó luego de ser tratada enzimáticamente, se obtuvo alrededor del 30% de esa actividad. Una relación de similar magnitud se verifica en la recuperación de la masa de proteínas solubles luego de remover los contaminantes, entre una metodología y otra. La insolubilización del fragmento Fc generado durante la digestión sería el responsable de esa pérdida adicional de proteína y capacidad neutralizante.(AU)

Today two methods are mainly used for the purification of antibodies from hyperimmune equine plasma at industrial level obtaining enriched preparations of immunoglobulin G (IgG) molecules or F(ab´)2 fragments. In both methods, after the precipitation, an important loss in the neutralizing capability was observed compared to the one of the original plasma. In this work, we performed the fractionation of hyperimmune equine plasma using caprylic acid, with and without enzymatic digestion with pepsin. The aim was to explain the percentage of recovery of the neutralizing capability after the fractionation; which resulted minor when the plasma was enzymatically treated. Additionally, we intended to establish which stage, in the purification process, was the responsible for the difference in the antibody recovery between one methodology and the other. When entire immunoglobulins were purified, approximately 53% of the neutralizing capacity was recovered, but when the sample was purified after the enzymatic treatment, around the 30% of the activity was obtained. A ratio of similar magnitude is verified on the recovery of the soluble protein mass after the removal of contaminants, between the two methods. The insolubilization of the fragment Fc generated during digestion would be responsible for the additional loss of protein and neutralizing capacity.(AU)

Impact of mouse pregnancy on thymic T lymphocyte subsets.

It has been reported that fetal lymphoid progenitor cells are acquired during gestation and are able to develop in the maternal mouse thymus into functional T cells. Moreover, previous pregnancies increase the number of fetal cells in the mother. In the present study, we investigated whether mouse pregnancy induces changes in T lymphocyte subsets in the maternal thymus. We determined the T lymphocyte subsets in two allogeneic cross-breedings, namely CBA/J×BALB/c (normal) and CBA/J×DBA/2 (abortion prone), and investigated the effects of the age and parity of the female, as well as pregnancy outcome, on thymocyte populations. In addition, hormonal effects were evaluated in a syngeneic combination (CBA/J×CBA/J). We found that during pregnancy both hormonal and allogeneic stimuli induced a reduction in the CD4(+)CD8(+) subset with an increase in the CD4(+)CD8(-) population. Only young females of the normal combination exhibited an increase in the CD4(-)CD8(+) population. All young mice showed an increase in CD4(+)CD25(+)FoxP3(+) T cells. Interestingly, the γδT thymus pool was increased in all females of the normal allogeneic pregnancy only, suggesting the participation of this pool in the observed beneficial effect of multiparity in this cross-breeding. Our results demonstrate that allogeneic pregnancies induce important variations in maternal thymocyte subpopulations depending on the age of the female and the male component of the cross-breeding.

Comparación entre dos métodos de producción para la elaboración de antivenenos ofídicos / Snake antivenin: Comparison between two production methods

Las mordeduras producidas por serpientes venenosas son un serio problema médico en varias regiones del mundo y sobre las cuales los sistemas de salud actúan en diferentes grados en lo referente a tratamiento y prevención. Sin embargo, el tratamiento de las mordeduras de serpientes venenosas en animales domésticos puede resultar difícil por diversos motivos, siendo uno de estos la baja oferta o ausencia de antivenenos para uso veterinario. Las presiones comerciales en la industria farmacéutica han llevado a una reducción en la producción de antivenenos en varias partes del mundo, su disponibilidad es, a veces, bastante limitada y en algunos casos, son imposibles de conseguir. En este trabajo, inmunizamos caballos con veneno de serpientes Sudamericanas para obtener el plasma hiperinmune que fue procesado para obtener IgG entera o fragmentos F(ab´)2 usando dos métodos convencionales (fraccionamiento por ácido caprílico o doble precipitación salina y digestión con pepsina). Los antivenenos así obtenidos fueron probados en sus características bioquímicas e inmunoquímicas, así como en su potencia neutralizante. El SDS-PAGE de los antivenenos mostró bandas en el orden de los 150 y 100 kDa en los antivenenos conteniendo IgG entera o fragmentos F(ab´)2, respectivamente. La presencia de albúmina o contaminantes de alto o bajo peso molecular no fue detectada en ninguna de las preparaciones. No se observaron diferencias importantes en la potencia neutralizante de los antivenenos, aunque el costo de producción fue mucho más bajo en la obtención de IgG completa. A partir de esto, se sugiere que los bajos costos de producción en la obtención de antivenenos de IgG entera para uso veterinario, hacen a esta tecnología adecuada y rentable cuando la producción de F(ab´)2 no es posible.

Bites by venomous snakes are a serious medical problem in several regions of the world, on which the different health systems act with different modalities. Nevertheless, the treatment of venomous snakebites in domestic animals can turn difficult due several problems among which, the conspicuous, is the low availability or lack of antivenoms for veterinary use. As commercial pressures on the pharmaceutical industry have led to a reduction in the production of antivenins in several parts of the world, their availability is sometimes rather limited and sometimes these products are impossible to obtain. In this work, we immunized horses with venom of South American vipers to obtain hyperimmune plasma. The plasma was processed to separate whole IgG of F(ab´)2 fragments using two conventional methods (caprylic acid fractionation or double saline precipitation and pepsin digestion). The obtained antivenins were tested for their biochemical and immunochemical characteristics and neutralizing potency. The SDS-PAGE of the antivenins showed, in the processed antivenin, bands in the order of 150 and 100 kDa in the whole IgG or F(ab´)2 fragments, respectively. The presence of albumin or contaminants of high or low molecular weight was not detected in any of the preparations. No important differences were observed in the neutralizing potency of the antivenins, although production cost was very low with the method used to obtain pure IgG. The low production cost makes the production of antivenins for veterinary use profitable when the production of F(ab´)2 fragments is not possible.

Multiparity increases trophoblast invasion and vascular endothelial growth factor expression at the maternal-fetal interface in mice.

To analyze immunomodulating effects related to parity status, we studied trophoblast invasion grade, placental expression and systemic concentration of VEGF and its receptor Flt-1 in normal fertile (CBA/JxBALB/c) mice and abortion-prone (CBA/JxDBA/2) H-2(d)xH-2(k) mice. BALB/c or DBA/2 mated CBA/J females were, respectively, divided into the following groups: primiparous young (3.0+/-0.5 months old); primiparous old (8.5+/-0.5 months old) and multiparous old (8.5+/-0.5 months old, with 4 pregnancies). Immunohistochemical analysis of term placentae from both multiparous groups revealed various layers of invasive trophoblast tissue, identified as cytokeratin+/vimentin- cells, in contrast to the single layer detected in the placentae of primiparous animals, indicating that multiparity increases trophoblast invasion regardless of the success of the pregnancy outcome. Invasive trophoblast tissue from primiparous CBA/JxDBA/2 placentae showed diminished VEGF expression in comparison with the normal fertile group, while both multiparous groups demonstrated high expression of VEGF in the invasive trophoblast tissue. Placental expression of Flt-1 was similar in all groups. However, the primiparous CBA/JxBALB/c group showed the highest plasma concentration of sFlt-1 at term, while both multiparous groups demonstrated low circulating levels. No differences in circulating VEGF levels were observed among the groups. These results demonstrate an increase in trophoblast invasion tissue and expression of VEGF in the maternal-fetal interface in multiparous mice compared to primiparous mice. Moreover, the placenta appears to be able to regulate the circulating levels of VEGF by releasing sFlt-1.

Toxicity of two North American Loxosceles (brown recluse spiders) venoms and their neutralization by antivenoms.

The toxic, biochemical, and immunological characteristics of L. boneti and L. reclusa venoms and its neutralization by anti-L. boneti and anti-L. reclusa antivenoms were studied. The electrophoretic profile showed very similar patterns and the toxic activities were very close. Immunological studies showed cross-reactivity among L. boneti and L. reclusa venoms, with L. boneti and L. reclusa experimental antivenoms, and anti-L. gaucho and anti-L. laeta antivenoms. The venom of L. laeta showed low immunological reactivity with the North American Loxosceles antivenoms. Experimental anti-North American Loxosceles antivenoms protected mice of the systemic toxicity and were able to prevent necrosis in rabbit skin after the injection of the venom. Both antivenoms displayed cross neutralization. The results showed that both Loxosceles venoms have very close toxic, biochemical, and immunological characteristics, and that either monospecific antivenoms or an antivenom raised with L. boneti and L. reclusa venoms as immunogens could be useful for treating bites by North American Loxosceles spiders.

Comparative immunohistochemical study of M-CSF and G-CSF in feto-maternal interface in a multiparity mouse model.

PROBLEM: Multiparity status has been found to bring beneficial effects both to the maintenance of pregnancy and to the offspring; however, these effects have not been fully explained. We have previously reported that placentae obtained from multiparous females belonging to a syngeneic mouse crossbreeding showed an important increase in the number of placental macrophages, suggesting that they might constitute a protective subpopulation. Taking into account that macrophage-colony stimulating factor (M-CSF) and granulocyte-colony stimulating factor (G-CSF) have proved to modulate macrophage activity and that both factors and/or their receptors have been found at feto-maternal interface, in this paper we analyzed the presence of M-CSF and G-CSF in placental tissue employing the same multiparity mouse model in order to investigate the influence of parity status on local immunoregulation factors of macrophage activity. METHOD OF STUDY: Three groups of mice (CBA/J x CBA/J) were analyzed: Primiparous Young, 3.0 +/- 0.5 months old (PY); Primiparous Old, 8.5 +/- 0.5 months old (PO) and Multiparous Old, 8.5 +/- 0.5 months old, with three to four previous pregnancies (MO). The presence of M-CSF and G-CSF in placental tissue was analyzed by immunohistochemistry. Cytokeratin (CK) and vimentin (VIM) expression and PAS staining were also studied. RESULTS: The three groups showed a similar immunostaining pattern for M-CSF in the whole placental trophoblast, while the expression of G-CSF was significantly higher only in the spongy zone in the MO group. Furthermore, all the MO placentae showed 5-11 layers of cells adjacent to the decidua, where G-CSF and M-CSF were highly detected. Conversely, they constituted a thin layer in PY and PO placentae. These cells were proved to be CK(+) and VIM(-) thus demonstrating their trophoblast origin. In addition, the layers closer to the decidua were also PAS+ suggesting that they could be interstitial cells, a type of invading trophoblast. CONCLUSIONS: In our mouse model, we observed an increase in the expression of G-CSF in placental spongiotrophoblast cells in multiparous females, which have been previously proposed as progenitors of the interstitial cells. Furthermore, this is the first report that indicates that parity status increases trophoblast invasion inducing a proliferative effect of the invading cells on the maternal tissue. We suggest that M-CSF and G-CSF secreted by these invading cells could favor the recruitment of macrophages to the trophoblast and might modulate their activity inducing a switch to a protective, non-inflammatory population.

[Toxicity of venoms from snakes of medical importance in México]. / Toxicidad de venenos de serpientes de importancia médica en México.

The characterization of the toxic activities of snake venoms is necessary to understand the physiopathology of the envenomation and to test the potency of the antivenoms used to treat this pathology. Because of the lack of data on the toxic activities of venoms from Mexican snakes of medical importance, we studied the venoms from Bothrops asper, Athropoides nummifrr, Agkistrodon billineatus, Crotalus durissus durissus, Crotalus basiliscus, Crotalus scutulatus, Crotalus atrox and Micrurus nigrocinctus. The studies performed were: SDS-PAOE, determination of lethal potency, hemorrhagic, necrotizing, coagulation on plasma and fibrinogen, phospholipasic and fibri(noge)nolytic activities. In addition we studied the neutralizing capacity of the toxic activities of an antivenom currently used for the treatment of snakebites in Mexico. The venom from viperids showed important hemorrhagic, necrotizing, coagulative on plasma, prothrombinic, fibrinogenolytic and phospholipase activities. The venoms with the highest lethal potency were those of Micrurus nigrocinctus and Crotalus scutulatus; however, the viperine venom that globally displayed the most potent toxic activities was from Bothrops asper. All the venoms showed toxic activities of similar range to those described for other American venomous snakes. The activity on plasma or fibrinogen varied widely among the different venoms but all displayed capacity to act on the coagulation system. The antivenom tested not only neutralized the lethality B. asper venom but also its other toxic activities.

Toxicidad de venenos de serpientes de importancia médica en México / Toxicity of venoms from snakes of medical importance in Mexico

La caracterización de las actividades tóxicas de los venenos de serpientes es necesaria para el cabal entendimiento de los procesos fisiopatológicos que se producen ante su mordedura, como también para evaluar la potencia neutralizante de los antivenenos utilizados para tratar estos envenenamientos. A causa de los pocos datos disponibles sobre la toxicidad del veneno de serpientes con importancia sanitaria en México, estudiamos las actividades tóxicas de los venenos de Bothrops asper, Athropoides nummifer, Agkistrodon billineatus> Crotalus durissus durissus, Crotalus basiliscus, Crotalus scutulatus, Crotalus atrox y Micrurus nigrocinctus. A los venenos se les realizaron los siguientes estudios: SDS-PAUE, determinación de la potencia letal, y de las actividades hemorrágica, necrotizante, coagulante en plasma y fibrinógeno, fosfolipásica y fibrinogenolítica. Se estudió además la capacidad neutralizante de un antiveneno de uso corriente para la terapéutica de las mordeduras de serpientes venenosas en México, sobre varias de estas actividades. Los venenos de vipéridos mostraron actividades hemorrágicas, necrotizante, coagulante sobre plasma, protrombínica, fibrinogenolítica y fosfolipásica importantes. Los venenos de mayor potencia letal fueron los de Micrurus nigrocinctus y Crotalus scutulatus, sin embargo el veneno que presentó en general potencias tóxicas mayores fue el de Bothrops asper. Las diferentes potencias tóxicas halladas se encontraron dentro de los márgenes descritos para especies de vipéridos y elápidos de Sudamérica. La actividad sobre el plasma y el fibrinógeno fue muy diferente en los diferentes venenos viperinos, sin embargo todos mostraron ser capaces de afectar componentes del sistema de la coagulación. El antiveneno probado no sólo neutralizó la letalidad del veneno sino también sus actividades tóxicas.

The characterization of the toxic activities of snake venoms is necessary to understand the physiopathology of the envenomation and to test the potency of the antivenoms used to treat this pathology. Because of the lack of data on the toxic activities of venoms from Mexican snakes of medical importance, we studied the venoms from Bothrops asper, Athropoides nummifer, Agkistrodon billineatus, Crotalus durissus durissus, Crotalus basiliscus, Crotalus scutulatus, Crotalus atrox and Micrurus nigrocinctus. The studies performed were : SDS-PAOE, determination of lethal potency, hemorrhagic, necrotizing, coagulation on plasma and fibrinogen, phospholipasic and fibrinogenolytic activities. In addition we studied the neutralizing capacity of the toxic activities of an antivenom currently used for the treatment of snakebites in Mexico. The venom from viperids showed important hemorrhagic, necrotizing, coagulative on plasma, prothrombinic, fibrinogenolytic and phospholipase activities. The venoms with the highest lethal potency were those of Micrurus nigrocinctus and Crotalus scutulatus; however, the viperine venom that globally displayed the most potent toxic activities was from Bothrops asper. All the venoms showed toxic activities of similar range to those described for other American venomous snakes. The activity on plasma or fibrinogen varied widely among the different venoms but all displayed capacity to act on the coagulation system. The antivenom tested not only neutralized the lethalityB. asper venom but also its other toxic activities.

Recombinant GRA4 or ROP2 protein combined with alum or the gra4 gene provides partial protection in chronic murine models of toxoplasmosis.

The efficacy of vaccination with Toxoplasma gondii recombinant GRA4 (rGRA4) and ROP2 (rRPO2) proteins and a mix of both combined with alum were evaluated in C57BL/6 and C3H mice. In C57BL/6 mice, rGRA4 and rGRA4-rROP2 immunizations generated similar levels of immunoglobulin G1 (IgG1) and IgG2a isotypes against GRA4, whereas immunizations with rROP2 and the mix induced a predominant IgG1 production against ROP2. All groups of C3H vaccinated mice exhibited higher levels of IgG1 than IgG2a. rGRA4-stimulated splenocytes from vaccinated mice produced primarily gamma interferon while those stimulated with rROP2 produced interleukin-4. Challenge of rGRA4- or rGRA4-rROP2-vaccinated mice from both strains with ME49 cysts resulted in fewer brain cysts than the controls, whereas vaccination with rROP2 alone only conferred protection to C3H mice. Immunization with a plasmid carrying the entire open reading frame of GRA4 showed a protective level similar to that of rGRA4 combined with alum. These results suggest that GRA4 can be a good candidate for a multiantigen anti-T. gondii vaccine based on the use of alum as an adjuvant.

Effectiveness of two common antivenoms for North, Central, and South American Micrurus envenomations.

Micrurus snakes (coral snakes) may produce severe envenomation that can lead to death by peripheral respiratory paralysis. Only few laboratories produce specific antivenoms, and despite the cross-reactivity found in some Micrurus species venoms, the treatment is not always effective. To test two therapeutic antivenoms against the venom of four species of Micrurus from Southern America, North of South America, Central America, and North America, the determination of the lethal potency of the venoms, the study of some biochemical and immunochemical characteristics, and the determination of the neutralizing activity of both antivenoms were studied. North American and South American antivenoms neutralized well venoms from Micrurus species of the corresponding hemisphere but displayed lower effectiveness against venoms of species from different hemispheres. It was concluded that the neutralization of Micrurus venoms by regional antivenoms could be useful to treat the envenomation by some Micrurus snakes but is necessary to evaluate carefully the antivenoms to be used with the venoms from the snakes of the region. Also, considering the difficulties for coral snake antivenom production, the development of a polyvalent antivenom is useful to treat the envenomation by coral snakes from different regions is necessary.

Hydrolysis of DNA by 17 snake venoms.

DNA hydrolysis caused by venoms of 17 species of snakes was studied by different methodologies. Endonucleolytic activity was tested by incubation of the venoms with the plasmid pBluescript and subsequent visualization of the electrophoretic patterns in 1% agarose gels stained with ethidium bromide. DNA was sequentially degraded, from supercoiled to opened circle, to linear form, in a concentration dependent manner. The highest hydrolytic activity was observed in Bothrops (B.) neuwiedii and Naja (N.) siamensis venoms. Exonucleolytic activity was analyzed on pBluescript digested with SmaI or EcoRI. All venoms caused complete hydrolysis after 2 h of incubation. SDS-PAGE analysis in gels containing calf thymus DNA showed that the hydrolytic bands were located at approximately 30 kDa. DNA degradation was studied by radial hydrolysis in 1% agarose gels containing calf thymus DNA plus ethidium bromide and visualized by UV light. Venom of B. neuwiedii showed the highest activity whereas those of B. ammodytoides and Ovophis okinavensis (P<0.05) showed the lowest activity. Antibodies against venom of B. neuwiedii or N. siamensis neutralized the DNAse activity of both venoms. In conclusion, venom from different snakes showed endo- and exonucleolytic activity on DNA. The inhibition of DNA hydrolysis by EDTA and heterologous antibodies suggests similarities in the structure of the venom components involved.

Hemorrhagic activity of Bothrops venoms determined by two different methods and relationship with proteolytic activity on gelatin and lethality.

The changes in hemorrhagic activity, proteolytic activity on gelatin and the lethal potency of four Bothrops venoms treated at different pH values or with EDTA were studied. Venoms from B. alternatus, B. jararaca, B. moojeni and B. neuwiedii of Argentina were preincubated at pH 5.8, 5.1 or 3.8 or with EDTA and the hemorrhagic activity expressed as size of the hemorrhagic lesion or as the amount of hemoglobin extracted, the proteolytic activity on gelatin and the lethal potency were determined. Although the MHDs recorded in rats were 19-56 fold higher than those recorded in mice, the A(550) extracted per gram of hemorrhagic haloes was very similar in rats or mice independent of the venom dose. Inhibition of proteolytic activity after preincubation at pH 5.1 or 3.8, agrees with the decreased amount of hemoglobin extracted from the hemorrhagic haloes, and with the increase in mean survival time after the i.p. injection to mice. Preincubation with EDTA resulted in 80% inhibition of hemorrhagic activity of B. jararaca venom and complete inhibition with the other Bothrops venoms tested. Measurement of the amount of hemoglobin extracted gives significant information in comparative studies, not available by measurement of the size of hemorrhagic haloes.

A reduced immunization scheme to obtain an experimental anti-Loxosceles laeta ("violinist spider") venom.

Bites by Loxosceles (L.) laeta spiders can produce severe envenomation in humans. The only specific treatment is the early administration of antivenom. The production of anti-Loxosceles antivenom is hampered by the extremely low venom yield by these spiders and by the difficulties in maintaining a large breeder of Loxosceles. We developed an experimental equinum L. laeta antivenom, using as immunogen venom glands homogenates from spiders captured in Argentina. Horses immunized with venom gland homogenate (1.0 mg total protein per horse) by the subcutaneous route were bled after completion of the immunization scheme. Plasma was fractionated by ammonium sulfate precipitation and treated with pepsin to obtain F(ab')2 fragments. The protein composition of the experimental antivenom was assessed by SDS-PAGE, and its immunochemical reactivity was compared with those of other anti-Loxosceles antivenoms available for therapeutic use in Argentina by ELISA and Western blot. The experimental, homologous anti-L. laeta antivenom appeared to be more efficient in neutralizing the lethal potency in mice and the necrotizing activity in rabbits than of the heterologous antivenom.

Neutralizacion cruzada de veneno de bothrops jararacussu por sueros antiofidicos heterologo / Cross neutralization of bothrops jararacussu venom by heterologous antivenoms

En la Argentina se utilizan tres tipos de sueros antiofídicos frete a la mordedura de crotálidos, el Anticrotálico Monovalente, contra el veneno de Crotalus durissus terrifucus ("víbora de cascabel"), el Botrópico Bivalente y el Botrópico Tetravalente ("Misiones") contra los venenos de las diferentes especies de Bothrops que se encuentran en la Argentina (las diferentes "y"rará")" Además, existe un suero Botrópico-Crotálico (Trivalente) el cual cubriria el mismo espectro que el Bivalente más el Anticrotálico. En este trabajo estudiamos la reactividad inmunoquímica de los sueros antibotrópicos Bivalente y Tetravalente, del Botrópico Crotálico (Trivalente) y del Anticrotálico Monovalente con el veneno de Bothrops jararacussu ("yararacuzú", "tapete dourado"). Además, se estudió la capacidad neutralizante de estos antivenenos sobre la potencia letal, y las actividades hemorrágica, necrotizante, procoagulante y hemolítica indirecta del veneno de B. jararacussu. La potencia neutralizante sobre las actividades biológicas y tóxicas de este veneno por todos los antivenenos utilizados es similar a la obtenida con el suero antibotrópico tetravalente (homólogo). Estos resultados sugieren la posibilidad de emplear sueros antibotrópicos heterólogos en el tratamiento de los accidentes por B. jararacussu.