Helminth anti-oxidant enzymes: a protective mechanism against host oxidants?

Sativa seeds against Schistosoma mansoni different stages

“…Adult S. mansoni in the mesentric vein are resistant to the host immune response which at the same time is capable of overcoming further infection by cercariae (Smithers & Terry 1969, James 1992. The major component of the immune response is cell mediated and as part of that response, the parasite is exposed to reactive oxygen species (ROS) generated by the host effector cells as macrophages, eosinophils, neutrophils , and platelets (Callahan et al 1988, Maizels et al 1993, James 1994. To defend themselves against oxygen-mediated killing mechanisms of host, parasites have developed antioxidant enzyme systems.…”

“…In S. mansoni superoxide dismutase, SOD, glutathione peroxidase, GPX, glutathione reductase, GR, and glutathione-s-transferase, GST, are major antioxidant enzymes that are involved in detoxification processes (Callahan et al 1988, Mkoji et al 1988a,b, Nare et al 1990, O'Leary & Tracy 1991, O'Leary et al 1992, James 1994, Mei & LoVerde 1995. These schistosome oxidant-detoxicating systems play a role in protecting the parasite from damage as a result of ROS (Callahan et al 1988a,b, Brophy & Pritchard 1992, James 1994. Therefore, the antioxidant defence mechanisms of adult worms may represent potentially good target for chemotherapy.…”

Vaccination with antioxidant enzymes confers protective immunity against challenge infection with Schistosoma mansoni

“…Indeed, immunolocalization studies demonstrated that SmCT-SOD, SmSP-SOD, and SmGPX localized to the tegument (host-parasite interface) of adult but not in larval parasites supporting the notion that antioxidant enzymes are important in immune evasion by adult schistosome parasites (Mei & LoVerde 1997). Thus, antioxidant enzymes are hypothesized to play a role in protecting the parasite from damage caused by reactive oxygen species such as superoxide radical anion and hydroxyl radicals (Callahan et al 1988, Brophy 1992, LoVerde 1998, Maizels et al 1993, James 1994. As catalase activity has never been demonstrated in schistosomes (Mkoji et al 1988a,b), we further hypothesize that the first line of enzymatic cellular defense against tegument attack (lipid peroxidation) in adult worms that results from the release of reactive oxygen species by host cells, involves parasite SOD and GPX ( Fig.…”

“…We postulate that in order to survive in the portal circulation of the liver, the adult worm stage has evolved a defense against the immune attack that involves the expression of antioxidant enzymes (Fig. 2), among other mechanisms (Callahan et al 1988, Brophy & Pritchard 1992, Maizels et al 1993, Mei and LoVerde 1997, LoVerde 1998 (James 1994, LoVerde 1998. One of our strategies has been to identify mechanisms that the schistosome adult parasite employs to evade the immune responses and use this information to identify and evaluate candidate vaccines.…”

A novel NADPH/NADH‐dependent aldehyde reduction enzyme isolated from the tapeworm Moniezia expansa

“…There are 3 candidate routes: via reduction by alcohol dehydrogenase/aldehyde reductase, via oxidation by aldehyde dehydrogenase and via glutathione conjugation by glutathione transferases [2][3][4][5][6]. Cytotoxic aldehydes in parasitic worms may arise from lipid peroxidation produced by the release of free-radicals from host-immune effector cells [7,8]. Glutathione transferase has previously been implicated as an aldehyde defence enzyme in parasites including Moniezia expansa [6].…”