Increased exposure of parasite antigens at the surface of adult male Schistosoma mansoni exposed to praziquantel in vitro

Abstract

SUMMARYPraziquantel is a broad-spectrum anthelmintic active against schistosome species which are major parasites of man. Two major effects on Schistosoma mansoni have been demonstrated; (i) spastic paralysis of the parasite musculature, possibly arising as a consequence of an influx of Ca2+ into the worm (Pax, Bennett & Fetterer, 1978; Coles, 1979) and (ii) vacuolation and degeneration of the worm tegument (Becker, Mehlhorn, Andrews, Thomas & Eckert, 1980). These events may contribute to the elimination of schistosomes in vivo, but this elimination may partly be dependent on the host immune response as infected T-cell-deprived mice are less able than immunologically intact animals to reduce their worm burdens following drug treatment (Doenhoff, Harrison, Sabah, Murare, Dunne & Hassounah, 1982). This latter observation raises the possibility that praziquantel may lower the ability of the parasite to evade host immunity by increasing the exposure of parasite antigens capable of acting as targets for host antibody, or antibody-armed cells at the worm surface. Consistent with this idea is the observation that adult schistosomes in praziquantel-treated mice are invaded a few hours after treatment by host granulocytes (Mehlhorn, Becker, Andrews, Thomas & Frenkel, 1981).

Schistosoma mansoni: a method for inducing resistance to praziquantel using infected Biomphalaria glabrata snails

“…Recent results confirm that this isolate remains less susceptible to PZQ (unpublished data). The complete mechanism of action of PZQ has not been clearly defined (Doenhoff et al 2008), but it is well known that PZQ causes a severe muscular contraction due to intense calcium influx (Pax et al 1978), immediate tegumental lesions (Harnett & Kusel 1986), reduction of glutathione levels (Ribeiro et al 1998) and interruption of the excretory activity of adult worms . After eight days of culture the adult worms of the LE strain showed typical alterations in morphology of susceptible parasites in contact with the drug including intense contraction, reduced oviposition and tegumental changes.…”

Chemotherapy for Schistosomiasis in Ugandan Fishermen: Treatment Can Cause a Rapid Increase in Interleukin-5 Levels in Plasma but Decreased Levels of Eosinophilia and Worm-Specific Immunoglobulin E

“…Studies in vitro have shown that PZQ initially affects the outer tegument of worms, causing rupture of the membranes with release or exposure of internal antigens (24,37). Studies of mice have shown that by 17 h after PZQ treatment cells of the host immune system have adhered to and penetrated the worms (3,8,35).…”

Comparative parasitological and electron microscopic studies on the effects of Nitazoxanide and Praziquantel in Schistosoma mansoni-infected mice

“…(Hassan M et al 2003) As it was thought that focal tegumental changes induced by an these drugs might be repaired in a period of 7-14 days after cessation of treatment while in case of severe damage, the host immune response might impact this repair process effectively. (Popiel I et al, 1985) These morphological damages are associated with an increased exposure of the worm antigens (epitopes) at its surface (Harnett W & Kusel JR 1986), leading to the disappearance of the immunological ''disguise'' and inability to engulf food by oral and ventral suckers. This is believed to cause death of the worms.…”