Immunomodulatory effects of crotoxin isolated from Crotalus durissus terrificus venom in mice immunised with human serum albumin

Crotalus durissus terrificus venom and its main component, crotoxin (CTX), have the ability to down-modulate the immune system. Certain mechanisms mediated by cells and solublefactors of the immune system are responsible for the elimination of pathogenic molecules to ensure the specific protection against subsequent antigen contact. Accordingly, weevaluated the immunomodulatory effects of CTX on the immune response of mice that had been previously primed by immunisation with human serum albumin (HSA). CTX inoculationafter HSA immunisation, along with complete Freund’s adjuvant (CFA) or Aluminium hydroxide (Alum) immunisation, was able to suppress anti-HSA IgG1 and IgG2a antibodyproduction. We showed that the inhibitory effects of this toxin are not mediated by necrosis or apoptosis of any lymphoid cell population. Lower proliferation of T lymphocytesfrom mice immunised with HSA/CFA or HSA/Alum that received the toxin wasobserved in comparison to the mice that were only immunised. In conclusion, CTX is able to exert potent inhibitory effects on humoural and cellular responses induced by HSAimmunisation, even when injected after an innate immune response has been initiated.

Immunomodulatory effects of crotoxin isolated from Crotalus durissus terrificus venom in mice immunised with human serum albumin.

Crotalus durissus terrificus venom and its main component, crotoxin (CTX), have the ability to down-modulate the immune system. Certain mechanisms mediated by cells and soluble factors of the immune system are responsible for the elimination of pathogenic molecules to ensure the specific protection against subsequent antigen contact. Accordingly, we evaluated the immunomodulatory effects of CTX on the immune response of mice that had been previously primed by immunisation with human serum albumin (HSA). CTX inoculation after HSA immunisation, along with complete Freund's adjuvant (CFA) or Aluminium hydroxide (Alum) immunisation, was able to suppress anti-HSA IgG1 and IgG2a antibody production. We showed that the inhibitory effects of this toxin are not mediated by necrosis or apoptosis of any lymphoid cell population. Lower proliferation of T lymphocytes from mice immunised with HSA/CFA or HSA/Alum that received the toxin was observed in comparison to the mice that were only immunised. In conclusion, CTX is able to exert potent inhibitory effects on humoral and cellular responses induced by HSA immunisation, even when injected after an innate immune response has been initiated.

Immunochemical and biological characterization of monoclonal antibodies against BaP1, a metalloproteinase from Bothrops asper snake venom.

BaP1 is a P-I class of Snake Venom Metalloproteinase (SVMP) relevant in the local tissue damage associated with envenomations by Bothrops asper, a medically-important species in Central America and parts of South America. Six monoclonal antibodies (MoAb) against BaP1 (MABaP1) were produced and characterized regarding their isotype, dissociation constant (K(d)), specificity and ability to neutralize BaP1-induced hemorrhagic and proteolytic activity. Two MABaP1 are IgM, three are IgG1 and one is IgG2b. The K(d)s of IgG MoAbs were in the nM range. All IgG MoAbs recognized conformational epitopes of BaP1 and B. asper venom components but failed to recognize venoms from 27 species of Viperidae, Colubridae and Elapidae families. Clone 7 cross-reacted with three P-I SVMPs tested (moojeni protease, insularinase and neuwiedase). BaP1-induced hemorrhage was totally neutralized by clones 3, 6 and 8 but not by clone 7. Inhibition of BaP1 enzymatic activity on a synthetic substrate by MABaP1 was totally achieved by clones 3 and 6, and partially by clone 8, but not by clone 7. In conclusion, these neutralizing MoAbs against BaP1 may become important tools to understand structure-function relationships of BaP1 and the role of P-I class SVMP in snakebite envenomation.

Immunochemical and biological characterization of monoclonalantibodies against BaP1, a metalloproteinase from Bothrops aspersnake venom

BaP1 is a P-I class of Snake Venom Metalloproteinase (SVMP) relevant in the local tissue damage associated with envenomations by Bothrops asper, a medically-important species in Central America and parts of South America. Six monoclonal antibodies (MoAb) against BaP1 (MABaP1) were produced and characterized regarding their isotype, dissociation constant (Kd), specificity and ability to neutralize BaP1-induced hemorrhagic and proteolytic activity. Two MABaP1 are IgM, three are IgG1 and one is IgG2b. The Kds of IgG MoAbs were in the nM range. All IgG MoAbs recognized conformational epitopes of BaP1 and B. asper venom components but failed to recognize venoms from 27 species of Viperidae, Colubridae and Elapidae families. Clone 7 cross-reacted with three P-I SVMPs tested (moojeni protease, insularinase and neuwiedase). BaP1-induced hemorrhage was totally neutralized by clones 3, 6 and 8 but not by clone 7. Inhibition of BaP1 enzymatic activity on a synthetic substrate by MABaP1 was totally achieved by clones 3 and 6, and partially by clone 8, but not by clone 7. In conclusion, these neutralizing MoAbs against BaP1 may become important tools to understand structure–function relationships of BaP1 and the role of P-I class SVMP in snakebite envenomation.

Tolerance to the antinociceptive effect of Crotalus durissus terrificus snake venom in mice is mediated by pharmacodynamic mechanisms.

Crotalus durissus terrificus venom exerts central and peripheral antinociceptive effect mediated by opioid receptors. The present work investigated the tolerance to the antinociceptive effect of the venom and characterised the mechanisms involved in this phenomenon. The hot plate test, applied in mice, was used for pain threshold determination. The venom (200 microg/kg) was administered by oral route, daily, for 14 days, and the nociceptive test was applied before and on days 1, 7 and 14 of the treatment. Prolonged treatment with venom lead to the development of tolerance to the antinociceptive effect. Tolerant animals exhibited increased sodium pentobarbital-induced sleeping time, although total hepatic microsomal cytochrome P450 was not altered. The antinociceptive effect of a single dose of venom (200 microg/kg) is mediated by kappa opioid receptors. Mice long-term-treated with venom showed cross-tolerance to U-TRANS, an agonist of kappa-opioid receptor, but not to morphine or DAMGO, two mu-opioid receptor agonists. Prolonged administration of venom did not cause symptoms of abstinence syndrome. These data indicate that prolonged treatment with C. durissus terrificus venom induces tolerance to the antinociceptive effect and that pharmacodynamic mechanisms are involved in the genesis of this phenomenon.

Efficacy of bothropic antivenom and its IgG(T) fraction in restoring fibrinogen levels of Bothrops jararaca envenomed mice.

Bothropic antivenom and its IgG(T) fraction, administered 4 h after experimental envenoming by Bothrops jararaca in Swiss mice, were compared for their abilities to restore fibrinogen 24 or 48 h after treatment. IgG(T) was able to normalise fibrinogen levels as efficiently as conventional antivenom. As IgG(T) also neutralises most anti-toxic activities of Bothrops venom, our results suggest that IgG(T) could be a better alternative treatment for envenoming due to the reduced amount of extraneous proteins, which may facilitate the induction of early adverse reactions.

Neutralization of Thalassophryne nattereri (niquim) fish venom by an experimental antivenom.

T. nattereri (niquim) is a venomous fish involved in many human accidents in Brazil. The clinical picture includes mild local erythema, severe edema, intense pain and rapid progression to necrosis. The present therapy with anti-inflammatory and analgesic drugs is ineffective and, therefore, we decided to assess serum therapy as an alternative treatment using an experimental antivenom. The antivenom used was raised in rabbits showing an ELISA antibody titer of 1:8,192,000 and its ability to neutralize lethality, necrosis, nociception and edema was evaluated both by pre-incubating the venom with antivenom before injection into mice or by independent injections of venom and antivenom. Lethality was completely neutralized by pre-incubation (ED(50)=141.5 microl/mg) while necrosis and nociception were neutralized by pre-incubation or the independent injection of antivenom. Edema was only partially prevented even when large amounts of antivenom were used. These data suggest that antivenom may be a promising treatment for patients stung by T. nattereri and suggest the viability of producing a horse antivenom for use in clinical trials.

Horse IgG isotypes and cross-neutralization of two snake antivenoms produced in Brazil and Costa Rica.

Horse IgG isotypes and cross-neutralization of two snake antivenoms produced in Brazil and Costa Rica. Toxicon 000-000. This work compared the specificity, ELISA titers and IgG subclass content of the polyvalent antivenom (anti-Bothrops asper, Crotalus durissus durissus and Lachesis muta stenophrys) of Instituto Clodomiro Picado (Costa Rica) and the bothropic antivenom (anti-Bothrops jararaca, B. jararacussu, B. moojeni, B. neuwiedi and B. alternatus) of Instituto Butantan (Brazil). The role of IgG(T) and IgGa subclasses in neutralization of some venom toxic activities and the cross neutralization of the antivenoms against B. jararaca and B. asper venoms were also evaluated. Both antivenoms were able to recognize B. asper and B. jararaca venoms by immunoblotting and presented similar antibody titers when assayed by ELISA. IgG(T) was highest, followed by IgGa, IgGb and IgGc. IgGa and IgG(T) isotypes isolated from both antivenoms by affinity chromatography were tested for neutralization of lethal, hemorrhagic, coagulant and phospholipase A2 activities of the homologous venoms. In both antivenoms, IgG(T) was the major isotype responsible for neutralization of all the tested activities, followed by IgGa. These results suggest that Instituto Butantan and Instituto Clodomiro Picado antivenoms have the same IgG profile and their neutralizing ability is due mostly to the IgG(T) isotype. Also, they neutralize lethality in mice induced by homologous and heterologous venoms, the bothropic antivenom of Instituto Butantan being more effective.

Neutralization of bothropic and crotalic venom toxic activities by IgG(T) and IgGa subclasses isolated from immune horse serum.

IgG(T) and IgGa isotypes were isolated from horse hyperimmune anti-bothropic and anti-crotalic sera using a combination of two affinity chromatographic processes. IgG(T) and IgGa isotypes were isolated from these sera by chromatography on protein A-Sepharose followed by separation of the two isotypes by chromatography on a column of anti-IgG(T)-Sepharose. LO-HoGT-1, a rat anti-horse IgG(T) monoclonal antibody, was used. A comparative study of the efficiency of these isotypes in neutralizing the main toxic activities of the homologous venoms was carried out. It was found that IgG(T) was about three-fold and seven-fold more protective than IgGa for neutralization of the lethal activity of B. jararaca and C. d. terrificus venoms, respectively. IgG(T) was also more effective than IgGa for the neutralization of the haemorrhagic activity induced by B. jararaca venom, while both isotypes neutralized equally well the blood incoagulability induced by this venom. The results suggest that IgG(T) is the most protective isotype present in both anti-bothropic and anti-crotalic sera, followed by IgGa. Owing to their very low concentration in the serum, other IgG isotypes are not likely to be important in neutralizing the venoms' toxic activities.

Antigenic cross-reactivity among components of Brazilian Elapidae snake venoms.

Snake venoms from M. corallinus (LD50 = 7.1 +/- 0.83 micrograms), M. frontalis (LD50 = 19.3 +/- 3.13 micrograms), M. ibiboboca (LD50 = 19.8 +/- 2.07 micrograms) and M. spiixi (LD50 = 6.7 +/- 1.25 micrograms) (family Elapidae, genus Micrurus) injected into horses alone or in combination (M. corallinus with M. frontalis) elicit antibody production, as indicated in vivo by neutralization of venom lethality and in vitro by enzyme-linked immunosorbent assay (ELISA), immunoelectrophoresis (IE) and Western blotting (WB). Venom lethality was efficiently neutralized by the antisera, with the monovalent antivenoms being more efficient than the bivalent antivenom. Antibodies against venom components were detected by all antisera at different titers by ELISA. Upon IE, antisera against M. spiixi and M. frontalis venoms cross-reacted with the four types of venoms studied and recognized several molecular components, the precipitin lines obtained had distinct intensities and electrophoretic motilities, whereas the antivenom against M. corallinus only recognized components of its venom but not of the others. All antivenoms cross-reacted with all the elapid venoms in WB revealing several bands with distinct MWs in M. corallinus and M. spiixi venoms, two very sharp and separate bands in M. corallinus venom and a very sharp band of high MW together with several other smaller and faint bands in M. frontalis venom. The data indicate that snake venoms of the genus Micrurus are good immunogens that contain many cross-reactive molecules, and that their toxic components are neutralized more effectively by monovalent rather than by bivalent antivenom.

Antigenic cross-reactivity among components of Brazilian Elapidae snake venoms

Snake venoms from M. corallinus (LD5=7.1 + or - 0.83 µg), M.frontalis (LD50=19.3 + or - 3.13 µg), M. ibiboboca (LD50=19.8 + or - 2.07 µg) and M. spiixi (LD50=6.7 + or - 1.25 µg) (family Elapidae, genus Micrurus) injected into horses alone or in combination (M. corallinus with M. frontalis) elicit antibody production, as indicated in vivo by neutralization of venom lethality and in vitro by enzyme-linked immunosorbent assay (ELISA), immunoelectrophoresis (IE) and Western blotting (WB). Venom lethality was efficiently neutralized by the antisera, with the monovalent antivenoms being more efficient than the bivalent antivenom. Antibodies against venom components were detected by all artisera at different titers by ELISA. Upon IE, antisera against M. spiixi and M. frontalis venoms cross-reacted with the four types of venoms studied and recognized several molecular components, the precipitin lines obtained had distinct intensities and electrophoretic motilities, whereas the antivenom against M. corallinus only recognized components of its venom but not of the others. All antivenoms cross-reacted with all the elapid venoms in WB revealing several blands with distinct MWs in M. corallinus and M. spiixi venoms, two very sharp and separate bands in M. corallinus venom and a very sharp band of high MW together with several other smaller and faint bands in M. frontalis venom. The data indicate that snake venoms of the genus Micrurus are good immunogens that contain many cross-reactive molecules, and that their toxic components are neutralized more effectively by monovalent rather than by bivalent antivenom

A rapid and efficient purification method for horse IgG(T) using a rat monoclonal antibody.

1. Louvain rats (IgK-1a) were immunized with horse IgG(T). To generate mAb to IgG(T), popliteal lymph node cells taken from the immunized animals were fused to a non-secreting LOU/C immunocytoma (IR983F). The hybridomas were cultured in HAT-containing medium and cloned under limiting dilution conditions. Supernatants from the growing hybrids were screened by ELISA using plates coated with horse IgG(T) or IgGa+b+c. 2. The anti-IgG(T) mAb obtained was named LO-HoGT-1 (LOU anti-horse IgG(T)). It is an IgG2a rat antibody whose light chain allotype is IgK-1a, and with an affinity constant of 2.9 x 10(10) M-1. 3. Ascites was induced in LOU (IgK-1b) rats by injecting the hybridoma cells and incomplete Freund's adjuvant ip. To obtain purified mAb, ascitic fluid was applied to a Sepharose anti-rat LOU IgK-1a chain column. 4. The purified mAb was then coupled to Sepharose. Immunoelectrophoretically pure IgG(T) was obtained by passage of horse serum through this column. The entire procedure took less than 30 min and resulted in a highly purified IgG(T).

Detection and neutralization of B. jararaca venom in mice.

1. Bothrops jararaca venom was detected by ELISA at different times in the skin, muscle, blood, liver, lung, heart, kidney and spleen of mice injected with venom i.m. or i.d. 2. The results showed that even 10 min after i.m. injection the venom is detected mostly in skin rather than in the muscle of the venom injection site. A small amount of venom was detected in the kidney up to 12 h after im venom injection, and none was detected in tissues of lung, heart, liver or spleen. 3. However, in mice injected i.d., the venom could be detected in the skin up to 24 h after injection. Local necrosis and haemorrhage could be neutralized by antivenom injected by the i.d. or i.v. routes only if the antivenom was given a short time after venom injection, even when antivenom is administered in high concentration. 4. In contrast, experiments performed in mice receiving venom i.d. and treated by i.d. or i.v. routes with antivenom injected at different times after envenoming showed that the effect of venom on blood coagulation could be counteracted by antivenom administered by either route up to 2 h after venom injection. 5. We suggest that a feasible amount of antivenom administered i.d. could be given as a first aid measure after a snake bite accident. However, further experimental studies using the i.d. route for antivenom administration are essential to confirm this possibility.

A rapid and efficient purification method for horse IgG(T) usin a rat monoclonal antibody

1. Louvain rats (IgK-1a) were immunized with horse IgG(T). To generate mAb to IgG(T), popliteal lymph node cells taken from the immunized animals were fused to a non-secreting LOU/C immunocytoma (IR983F). The hybridomas were cultured in HAT -containing medium and cloned under limiting dilution conditions. Supernatants from the growing hybrids were screened by ELISE using plates coated with horse IgG(T) or IgGa+b+c. 2. The anti-IgG(T) mAb obtained was named LO-HoGT-1 (LOU anti-horse IgG(T)). It is an IgG2a rat antibody whose light chain allotype is IgK-1a, and with an affinity constant of 2.9 x 1010 M-1. 3. Ascites was isnduced in LOU (IgK-1b) rats by injecting the hybridoma cells and incomplete Freund's adjuvant ip. To obtain purified mAb, ascitic fluid was applied to a Sepharose anti-rat LOU IgK-1 a chain column. 4. The purified mAb was then coupled to Sepharose. Immunoelectrophoretically pure IgG(T) was obtained by passage of horse serum through this column. The entire procedure took less than 30 min and resulted in a highly purified IgG(T)

Detection and neutralization of B. jararaca venom in mice

1. Bothrops jararaca venom was detected by ELISA at different times in the skin, muscle, blood, liver, lung, heart, kidney and spleen of mice injected with venom im or id. 2. The results showed that even 10 min after im injection the venom is detected mostly in skin rather than in the muscle of the venom injection site. A small amount of venom was detected in the kidney up to 12 h after im venom injection, and none was detected in tissues of lung, heart, liver or spleen. 3. However, in mice injected id, the venom could be detected in the skin up to 24 h after injection. Local necrosis and haemorrhage could be neutralized by antivenom injected by the id or iv routes only if the antivenom was given a short time after venom injection, even when antivenom is adminsitered in high concentration. 4. In contrast, experiments performed in mice receiving venom id and treated by id or iv routes with antivenom injected at different times after envenoming showed that the effect of venom on blood coagulation could be counteracted by antivenom administered by either route up to 2 h after venom injection 5. We suggest that a feasible amount of antivenom administered id could be given as a first aid measure after a snake bite accident. However, further experimental studies using the id route for antivenom administration are essential to confirm this possibility

Isolation of IgGT from hyperimmune horse anti-snake venom serum: its protective ability.

Hyperimmune horse anti-bothropic serum, used in serum therapy, was analyzed for its IgGT content and protective ability. IgGT was isolated through a combination of salt-mediated hydrophobic chromatography and protein A affinity chromatography. The chromatographic fractions obtained were analyzed with regard to their isotype content and protective ability. The results suggest that the protective ability of hyperimmune anti-venom serum is located mainly in the IgGT subclass.

The possible mechanism of action of IgG antibodies and platelets protecting against Trypanosoma cruzi infection.

1. The role of IgG antibody and platelets in the mechanism of defense against Trypanosoma cruzi infection is reviewed. 2. Experimental data showing the participation of the different IgG subclasses in the immune lysis and immune clearance of the parasites are discussed. 3. The involvement of the platelets in the removal of the parasites from the circulation is considered. 4. It is suggested that IgG anti-T. cruzi antibodies interact with circulating parasites leading to formation of microaggregates, activation of C3 and deposition of C3b on the immune aggregates followed by adherence of platelets through C3b receptors. The immune aggregates would then be taken up by cells of the mononuclear phagocytic system.

Isolation of horse IgG with protein A.

Horse immunoglobulins were obtained from normal serum defatted with dextran sulfate and precipitated with ammonium sulfate. Eight mg of this preparation was submitted to affinity chromatography with protein A-Sepharose CL-4B. Low temperature (4 degrees C) and a starting buffer at pH 8.0 were conditions required for all IgG subclasses to bind to protein A, even those with low affinity. The IgGs bound to protein A were eluted with glycine buffer at pH 2.8. The yield was about 90%. It is suggested that isolated IgG, instead of whole Igs, be used in serum therapy, reducing the amount of Igs and diminishing serum-related reactions.

Isolation of horse IgG with protein A

Horse immunoglobulins were obtained from normal defatted with dextran sulfate and precipitated with ammonium sulfate. Eight mg of this preparation was submitted to affinity chromatography with protein A-Sepharose CL-4B. Low temperature (4-C) and a starting buffer at pH 8.0 were conditions required for all IgG subclasses to bind to protein A, even those with low affinity. The IgGs bound to protein A were eluted with glycine buffer at pH 2.8. The yield was about 90%. Its suggested that isolated IgG, instead of whole Igs, be used in serum therapy, reducing the amount of Igs and diminishing serum-related reactions

The possible mechanism of action of IgG antibodies and platelets protecting against Trypanosoma cruzi infection

1. The role of IgG antibody and platelets in the mechanism of defense against Trypanosoma cruzi infection is reviewed. 2. Experimental data showing the participation of the different IgG subclasses in the immune lysis and immune clearance of the parasites are discussed. 3. The involvement of the platelets in the removal of the parasites from the circulation is considered. 4. It is suggested that IgG anti-T. cruzi antibodies interact with circulating parasites leading to formation of microaggregates, activation of C3 and deposition of C3 and deposition of C3b on the immune aggregates followed by adherence of platelets through C3b receptors. The immune aggregates would then be taken up by cells of the mononuclear phagocytic system