Ermila Rojas

An alternative in vitro method for testing the potency of the polyvalent antivenom produced in Costa Rica

The ability of several batches of polyvalent antivenom to neutralize indirect hemolytic activity of Bothrops asper venom was studied using a sensitive plate test. All samples of antivenom tested effectively neutralized this activity. A highly significant correlation was observed between neutralization of indirect hemolysis and neutralization of lethal activity. This simple and sensitive in vitro test could be used to monitor antibody levels in horses immunized to produce polyvalent antivenom.

Neutralizacion de los efectos locales del veneno de Bothrops asper por un antiveneno polivalente

Abstract Neutralization of lethality, myonecrosis, hemorrhage and edema induced by Bothrops asper venom in mice was studied using the polyvalent antivenom produced in the Instituto Clodomiro Picado. The neutralizing effect ( ed 50 ) on each of these toxic activities varied; the neutralization of lethal and hemorrhagic effects being more effective than the neutralization of myonecrosis and edema. With independent inoculation of venom and antivenom, antivenom was not effective in neutralizing edema-forming activity. The myonecrotic effect was only partially neutralized when serum was given i.v. immediately after envenomation; however, antivenin effectively neutralized the hemorrhagic activity. The ineffectiveness of antivenom in neutralizing edema and myonecrosis could be partially explained by the rapid development of these effects. Hence, the time interval between envenomation and antivenom administration and the route of serum administration both play an important role in the neutralization of local effects.

Local effects induced by coral snake venoms: Evidence of myonecrosis after experimental inoculations of venoms from five species

The local effects induced by intramuscular inoculations of venoms from six species of coral snakes were studied in mice. Venoms of Micrurus nigrocinctus nigrocinctus, M. n. mosquitensis, M. alleni, M. frontalis, M. carinicauda and M. surinamensis induced prominent myonecrosis which was observed histologically. From a morphological point of view all these venoms induced a similar pattern of myonecrosis, characterized by a conspicuous alteration of the intracellular structure. This myotoxic activity was corroborated by an increase in plasma creatine kinase levels 3 hr after i.m. injection of M. n. nigrocinctus, M. n. mosquitensis, M. frontalis and M. carinicauda venoms. M. mipartitus venom did not induce myonecrosis. None of the venoms induced edema or hemorrhage at the site of injection.

The venom of Bothrops asper from Guatemala: toxic activities and neutralization by antivenoms

Bothrops asper is responsible for approximately half of the snakebite envenomations in Central America. Despite its medical relevance, only the venom of Costa Rican populations of this species has been studied to some detail, and there is very little information on intraspecies variability in venom composition and toxicity. Venom of B. asper from Guatemala was analyzed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and two-dimensional gel electrophoresis, and its basic pharmacological activities were investigated with standard laboratory assays. Venom has lethal, hemorrhagic, myotoxic, edema-forming, coagulant, defibrinating and phospholipase A(2) activities, showing a similar toxicological profile to the one previously described for B. asper from Costa Rica. In addition, polyvalent antivenoms produced in Mexico and Costa Rica, and currently used in Guatemala, were tested for their ability to neutralize venoms toxic activities. Both antivenoms were effective against all effects studied, although the Costa Rican product showed higher potency against most activities tested and higher antibody titer against venom components, as determined by enzyme immunoassay. It is suggested that different dosage regimes should be considered when using these antivenoms in B. asper envenomations in Guatemala.

Efectos locales inducidos por el veneno de la serpiente coral Micrurus nigrocinctus en ratón blanco

Abstract The venom of the coral snake, Micrurus nigrocintus , from Costa Rica produces a myonecrotic effect in the white mouse. Experimental inoculation induces histological necrosis of the skeletal muscles, which becomes evident a few min after inoculation. This activity was confirmed by high levels of the enzyme creatinephosphokinase (CPK) which reach maximum levels 3 hr after inoculation, descending to near normal values at 24 hr. An infiltrate rich in polymorphonuclear neutrophils was present, reaching a maximum at 24–48 hr. One or two weeks after inoculation, the histological picture was of necrotic and regenerative tissue, fibroblasts and exudative cells of a mononuclear type. There were no vascular alterations nor hemorrhagic effects and the Kondo skin test in mice was negative. Furthermore, the venom produced little edema at the inoculation site and a weak proteolytic effect on casein.

Venom of the crotaline snake Atropoides nummifer (jumping viper) from Guatemala and Honduras: comparative toxicological characterization, isolation of a myotoxic phospholipase A2 homologue and neutralization by two antivenoms

A comparative study was performed on the venoms of the crotaline snake Atropoides nummifer from Guatemala and Honduras. SDS-polyacrylamide gel electrophoresis, under reducing conditions, revealed a highly similar pattern of these venoms, and between them and the venom of the same species from Costa Rica. Similar patterns were also observed in ion-exchange chromatography on CM-Shephadex C-25, in which a highly basic myotoxic fraction was present. This fraction was devoid of phospholipase A(2) activity and strongly reacted, by enzyme-immunoassay, with an antiserum against Bothrops asper myotoxin II, a Lys-49 phospholipase A(2) homologue. A basic myotoxin of 16 kDa was isolated to homogeneity from the venom of A. nummifer from Honduras, showing amino acid composition and N-terminal sequence similar to those of Lys-49 phospholipase A(2) variants previously isolated from other crotaline snake venoms. Guatemalan and Honduran A. nummifer venoms have a qualitatively similar toxicological profile, characterized by: lethal; hemorrhagic; myotoxic; edema-forming; coagulant; and defibrinating activities, although there were significant quantitative variations in some of these activities between the two venoms. Neutralization of toxic activities by two commercially-available antivenoms in the region was studied. Polyvalent antivenom produced by Instituto Clodomiro Picado was effective in the neutralization of: lethal; hemorrhagic; myotoxic; coagulant; defibrinating; and phospholipase A(2) activities, but ineffective against edema-forming activity. On the other hand, MYN polyvalent antivenom neutralized: hemorrhagic; myotoxic; coagulant; defibrinating; and phospholipase A(2) activities, albeit with a lower potency than Instituto Clodomiro Picado antivenom. MYN antivenom failed to neutralize lethal and edema-forming activities of A. nummifer venoms.