Impairment of the in ̄ ammatory reaction on implanted Taenia solium metacestodes in mice by a T . solium RNA-peptide : a scanning electron microscopy study

Content Provider	Semantic Scholar
Copyright Year	1998
Abstract	Inhibition of in ̄ammation by a Taenia solium RNA-peptide (metacestode factor, MF) was studied by scanning electron microscopy (SEM). Viable (96%) T. solium metacestodes obtained from a naturally infected pig were dissected and implanted in treated and control mice, removed at 6 and 12 days postimplantation (p.i.), and studied by SEM. At day 6, metacestodes in control mice showed vigorous in ̄ammation, whereas in mice treated with MF they were apparently intact with exiguous in ̄ammation. Mice immunized with T. solium metacestode antigens showed a moderate in̄ammation; those treated with both MF and T. solium antigens presented scanty in ̄ammation. At day 12, metacestodes presented copious in ̄ammation and severe damage to the sucker tissues in mice immunized with T. solium; in mice treated with either MF or MF and T. solium antigens there was only discrete in ̄ammation. These observations illustrate the central role of MF in the inhibition of the early events leading to the parasite's destruction by means of an in ̄ammatory response. Introduction Taenia solium human neurocysticercosis follows a prolonged asymptomatic period (typically 4±5 years) before the onset of symptoms (Dixon and Lipscomb 1961). Rabiela et al. (1982), Ridaura (1987), and White et al. (1995) have reported that parasites without in ̄ammation are more frequent in asymptomatic and immunode®cient patients. Another sign of immune depression in human neurocysticercosis is the negative antibody response that is often observed in asymptomatic patients and in those without in ̄ammatory cells in their cerebrospinal ̄uid (Ridaura 1987; del Brutto and Sotelo 1988). In porcine cysticercosis, metacestodes without in ̄ammatory reaction have also been reported (de Aluja and Vargas 1988). A close relationship between high metacestode viability (94±96%), a discrete in ̄ammatory reaction around metacestodes, and an immunosuppressed state in naturally cysticercotic pigs has been reported (Molinari et al. 1993). Therefore, it appears that the clinical manifestations of human neurocysticercosis are closely related to the degree of the in ̄ammatory reaction surrounding T. solium metacestodes. In the early stage of illness, in ̄ammation and humoral response seem to be two immunological functions inhibited by T. solium metacestodes. Research on molecules obtained from T. solium that inhibit the immune response has yielded some insight into this problem. A small RNA-peptide molecule (1,450 Da; metacestode factor, MF) obtained from cultures of viable T. solium metacestodes depresses the phytohemagglutininor concanavalin-A-stimulated incorporation of [H]-thymidine into human or murine lymphocytes (Molinari et al. 1990; Tato et al. 1995). In mice, MF inhibits the immune response to Salmonella typhimurium antigens (Molinari et al. 1989). In other studies we have observed that in mice, MF prevents the in ̄ammatory reaction around implanted T. solium metacestodes and depresses humoral and cellular responses to homologous antigens; in addition, we have found that in comparison with the Parasitol Res (1998) 84: 173±180 Ó Springer-Verlag 1998 J.L. Molinari (&) á J. Sepu lveda Departamento de Gene tica Molecular, Instituto de Fisiologõ a Celular, UNAM, AP:70-242, Me xico, D.F., 04510 Me xico Tel.: 525 6-22-56-53, Fax: 525 6-22-56-3; e-mail: jmolinar@ifcsun1.i®siol.unam.mx P. Tato á S. Solano Departamento de Microbiologõ a y Parasitologõ a, Facultad de Medicina, UNAM, Me xico, D.F., Me xico D. Rodrõ guez Colegio Superior Agropecuario del Estado de Guerrero, Cocula, Guerrero, Me xico M. Rubio Departamento de Inmunologõ a, Instituto de Investigaciones Biome dicas, UNAM, Me xico, D.F., Me xico natural host, naive and primarily immunized mice produce a faster and more vigorous in ̄ammatory response against the implanted metacestodes (Tato et al. 1996). Since in human and pig cysticercosis the in ̄ammatory reaction around the parasite is a slow, insidious, and progressive process that may last several months or years (Ma rquez 1971; Herna ndez-Ja uregui et al. 1973; Willms et al. 1980; Rabiela et al. 1982; Escobar 1983; Villagran and Olvera 1988; de Aluja and Vargas 1988), the characteristics of the in ̄ammatory reaction induced by implanted cysticerci in the murine model could be used to study immune and in ̄ammatory reactions in a short period. Therefore, we conducted the present study to determine by scanning electron microscopy some of the early events of the inhibition of the in ̄ammatory reaction induced by the T. solium MF on implanted T. solium metacestodes in naive and immunized mice. Materials and methods
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