Fasciola hepatica in vitro: increased susceptibility to fasciolicides in a defined serum-free medium

Abstract

The cidal properties of some phenolic, halogenated diphenyl, salicylanilide, benzimidazole and diaminophenoxyalkane anthelmintics, against 6-week-old worms of Fasciola hepatica were assessed in vitro. In a conventional fluke culture medium containing RPMI 1640, supplemented with serum with or without rabbit erythrocytes or pink-ghosts, only the halogenated diphenyl and salicylanilide compounds showed activity at concentrations equal to or less than 100 microM. However, when basal, serum and cell-free RPMI 1640 was used, all compounds other than diamphenethide were highly active, their minimum lethal concentrations being some 25-125 times lower under these conditions. The inclusion of rabbit liver microsomes in the basal culture medium resulted in diamphenethide exhibiting cidal activity equivalent to that seen when its free-amine active metabolite was assayed. The possibility that the activity of many of these compounds was masked in vitro because of their serum binding properties is discussed. Recommendations are made that in vitro screens for new fasciolicides should be carried out in serum-free medium and that additional replicates containing mammalian liver microsomes and liver cytosolic extracts be included as means for the metabolic activation of certain otherwise undetectable prodrugs.

The In Vitro Secretion of Acetylcholinesterase by Adult Stages of Heligmosomoides polygyrus: the Effects of Broad‐Spectrum Anthelmintics

“…In the present study, in vitro secretion was found to be increased in the presence of FCS or BSA. However, it should be noted that chemical and physical characteristics of the culture medium can influence the in vitro drug activity (Jenkins et al, 1980;Rosenfeld and Laubach, 1986;Jenkins et al, 1987); in the present case, some drugs could bind to serum proteins becoming less available to the worms. Given this possibility, the worms were always exposed to the drugs in supplement-free medium, and medium with BSA was only used to study the secretion post-drug-treatment.…”

The synthetic peroxide OZ78 is effective against Echinostoma caproni and Fasciola hepatica

“…A similar observation was made in a previous study, which evaluated the fasciocidal properties of phenolic, halogenated diphenyl, salicylanilide, benzimidazole and diaminophenoxyalkane anthelmintics in serum-free and serum-supplemented media. 17 The increased potency of the fasciolicides in the absence of serum has been explained by drug serum protein binding, which renders the drugs less accessible to the flukes. 17 In conclusion, we have presented the first evidence of the potent fasciocidal properties of a 1,2,4-trioxolane and this is supported by in vivo and in vitro studies and underscored by SEM observations.…”

“…17 The increased potency of the fasciolicides in the absence of serum has been explained by drug serum protein binding, which renders the drugs less accessible to the flukes. 17 In conclusion, we have presented the first evidence of the potent fasciocidal properties of a 1,2,4-trioxolane and this is supported by in vivo and in vitro studies and underscored by SEM observations. Our results call for additional studies in larger mammals, e.g.…”

Drug activity against Onchocerca gutturosa males in vitro: a model for chemotherapeutic research on onchocerciasis

“…New compounds are now tested in our laboratory under both sets of conditions which in some instances provides useful additional information about their properties. The use of metabolizing agents such as the inclusion of rabbit liver microsomes to the culture system (JENKINS et al, 1987) may further improve the evaluation of some types of compound.…”