A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription. We examined the mechanism of action and compared the anthelmintic efficacy of cysteine proteinases from papaya, pineapple, fig, kiwi fruit and Egyptian milkweed in vitro using the rodent gastrointestinal nematode Heligmosomoides polygyrus. Within a 2 h incubation period, all the cysteine proteinases, with the exception of the kiwi fruit extract, caused marked damage to the cuticle of H. polygyrus adult male and female worms, reflected in the loss of surface cuticular layers. Efficacy was comparable for both sexes of worms, was dependent on the presence of cysteine and was completely inhibited by the cysteine proteinase inhibitor, E-64. LD 50 values indicated that the purified proteinases were more efficacious than the proteinases in the crude latex, with purified ficin, papain, chymopapain, Egyptian milkweed latex extract and pineapple fruit extract, containing fruit bromelain, having the most potent effect. The mechanism of action of these plant enzymes (i.e. an attack on the protective cuticle of the worm) suggests that resistance would be slow to develop in the field. The efficacy and mode of action make plant cysteine proteinases potential candidates for a novel class of anthelmintics urgently required for the treatment of humans and domestic livestock.

The nematode cuticle is a protective collagenous extracellular matrix that is modified, cross-linked, and processed by a number of key enzymes. This Ecdysozoan-specific structure is synthesized repeatedly and allows growth and development in a linked degradative and biosynthetic process known as molting. A targeted RNA interference screen using a cuticle collagen marker has been employed to identify components of the cuticle biosynthetic pathway. We have characterized an essential peroxidase, MoLT-7 (MLT-7), that is responsible for proper cuticle molting and re-synthesis. MLT-7 is an active, inhibitable peroxidase that is expressed in the cuticle-synthesizing hypodermis coincident with each larval molt. mlt-7 mutants show a range of body morphology defects, most notably molt, dumpy, and early larval stage arrest phenotypes that can all be complemented with a wild type copy of mlt-7. The cuticles of these mutants lacks di-tyrosine cross-links, becomes permeable to dye and accessible to tyrosine iodination, and have aberrant collagen protein expression patterns. Overexpression of MLT-7 causes mutant phenotypes further supporting its proposed enzymatic role. In combination with BLI-3, an H 2 O 2 -generating NADPH dual oxidase, MLT-7 is essential for post-embryonic development. Disruption of mlt-7, and particularly bli-3, via RNA interference also causes dramatic changes to the in vivo cross-linking patterns of the cuticle collagens DPY-13 and COL-12. This points toward a functionally cooperative relationship for these two hypodermally expressed proteins that is essential for collagen cross-linking and proper extracellular matrix formation. Collagenous extracellular matrices (ECMs)3 serve numerous critical roles and are found throughout the animal kingdom. The cuticle is an ECM that makes up the most external surface of nematodes and its roles are diverse. This tough but flexible exoskeleton maintains body shape, provides a protective barrier to the environment, and permits motility via its attachments to muscles (1). There are two distinct sets of discernible cuticular structures on the surface of the nematode Caenorhabditis elegans, circumferential indentations termed annulae and longitudinal ridges termed alae. The latter are present only in the first and alternative third stage (dauer) larvae and in adult C. elegans (2). At the transition between consecutive larval stages, a new cuticle is synthesized from the underlying hypodermis. The term molting is used for the removal and re-synthesis of the cuticle. The cuticle is a complex and versatile tissue made up of multiple layers, each of which has distinct components and levels of structural integrity (3, 4). The principal components of the cuticle are the collagens. Over 180 cuticle collagens are encoded in the C. elegans genome, and their temporal expression is cyclical and corresponds to the larval molts (5). Each of these synthetic periods is further subdivided into distinct peaks as follows: 4 h prior to, 2 h prior to, and coincident with the molt. Collagens ...

(2006) In vitro and in vivo anthelmintic efficacy of plant cysteine proteinases against the rodent gastrointestinal nematode, Trichuris muris. Parasitology, 132 (5).

Graphical abstract

Parasitic infections are a major medical problem throughout the world, especially in developing countries where they cause more morbidity and mortality than other infectious diseases and are the primary cause of death. There are two main groups of parasites: (a) the protozoa, which are unicellular organisms and include the malaria parasite, Plasmodium; and (b) the helminths, which are metazoan organisms and include the cestodes, trematodes and nematodes. The protozoa are responsible for the majority of the mortality associated with parasitic infections, while the helminths generally produce long-term (or chronic), debilitating diseases: one of the reasons why there is more public awareness of parasitic protozoan infections than of infections with helminths. In this paper, we review the major human gastrointestinal nematodes, the problems associated with the control of these parasites and a potential new therapeutic approach. INTERNATIONAL JOURNAL OF EXPERIMENTAL PATHOLOGY SummaryGastrointestinal (GI) nematode infections affect 50% of the human population worldwide, and cause great morbidity as well as hundreds of thousands of deaths. Despite modern medical practices, the proportion of the population infected with GI nematodes is not falling. This is due to a number of factors, the most important being the lack of good healthcare, sanitation and health education in many developing countries. A relatively new problem is the development of resistance to the small number of drugs available to treat GI nematode infections. Here we review the most important parasitic GI nematodes and the methods available to control them. In addition, we discuss the current status of new anthelmintic treatments, particularly the plant cysteine proteinases from various sources of latex-bearing plants and fruits.