Action of cyclosporin A on the tapeworm Hymenolepis diminuta in mice

SUMMARYCyclosporin A (CsA), administered in 5 daily subcutaneous doses of 50 mg/kg to MF1 mice immediately following infection withHymenolepis diminutaenhanced parasite growth relative to controls. Drug administered at 24 h intervals for 10 days, and thereafter every 48 h to MF1 and CBA/Ca mice infected withH. diminuta, increased worm survival and growth, delayed host-mediated expulsion of the parasite and enabled some worms to develop to patency. Worm survival and weight both increased in a dose-dependent manner following daily CsA treatment of infected CBA/Ca and BALB/c mice (0–150 mg/kg CsA/day). Delay in parasite elimination was accompanied by increased frequency of worm-attachment in the anterior small intestine (MF1 mice given 5 daily doses of CsA [0–150 mg/kg] following infection); posteriad migration of worms was restricted in a dose-dependent manner. The data presented contrast markedly with the action of the same drug onH. microstomain mice. Thus CsA treatment acts in opposing ways on two closely related parasites in the same host; this possibly reflects the mechanistic antagonism between immunosuppression and anthelmintic activity. This paper reports the first use of a specific T cell-suppressive drug onH. diminutain the mouse, implicating the role of T cells in protective immunity to this parasite.