Studies on the development and role of some cell-mediated immune responses in experimental toxocarosis in mice
The studies were undertaken to investigate the development of some cell-mediated immune responses in experimental toxocarosis in mice and to assess the influence of these responses on the course of infection. Mice were infected orally with 350 eggs of Toxocara canis and reinfected with the same dose of parasites after 8 weeks. Groups of infected animals were killed each week of the experiments to obtain spleens, livers and brains for further studies. Lymphocytes from removed spleens were analysed by flow-cytometry for CD4 and CD8 expression and cultured in vitro to measure their responses to Concanavalin A and excretory-secretory (ES) antigen of T. canis in a lymphocyte transformation test. Pieces of livers were used to prepare paraffin sections to be stained later with haematoxylin and eosin, whereas whole brains of the infected animals were examined for the presence of parasite larvae. The results of the studies showed depression of T-cell responses to ConA in early stages of infection and significant increase in the blastogenic responses to the ES antigen from week 4 following infection. The depression of T-cell responses was accompanied by lowered CD4+/CD8+ ratio resulting from increased percentages of CD8+ T cells. Histopathological examination of liver sections revealed trapping of larvae in T. canis reinfected mice. The intensity of infection as measured by larval recoveries from the brains of mice increased gradually up to the 8th week of infection, but did not show significant changes after reinfection, testifying to the development of long-lasting protective immunity during primary infection.
- Abo-Shehada M.N., Al.-Zubaidy B.A., Herbert I.V. 1991. Acquired immunity to Toxocara canis infection in mice. Veterinary Parasitology, 38, 289–298.
- Aldawek A.M., Levkut M., Revajova V., Dvoroznakova E. 2002. Larval toxocarosis in mice: immunoreactivity after multiple high dose infections. Acta Parasitologica, 47, 249–254.
- De Savigny D. 1975. In vitro maintenance of Toxocara canis larvae and a simple method for the production of Toxocara ES antigen for use in serodiagnostic tests for visceral larva migrans. Journal of Parasitology, 61, 781–782.
- Despommier D. 2003. Toxocariasis: clinical aspects, epidemiology, medical ecology, and molecular aspects. Clinical Microbiology Reviews, 16, 265–272. DOI: 10.1128/CMR.16.2.265-272.2003.
- Kayes S.G. 1984. Spleen cell responses in experimental murine toxocariasis. Journal of Parasitology, 70, 522–529.
- Kayes S.G., Jones R.E., Omholt P.E. 1987. Use of bronchoalveolar lavage to compare local pulmonary immunity with the systemic immune response of Toxocara canis-infected mice. Infection and Immunity, 55, 2132–2136.
- Kayes S.G., Oaks J.A. 1978. Development of the granulomatous response in murine toxocariasis. American Journal of Pathology, 93, 277–294.
- Kayes S.G., Omholt P.E., Grieve R.B. 1985. Immune responses of CBA/J mice to graded infections with Toxocara canis. Infection and Immunity, 48, 697–703.
- Metwali A., Setiawan T., Blum A.M., Urban J., Elliot D.E., Hang L., Weinstock J.V. 2006. Induction of CD8+ regulatory T cells in the intestine by Heligmosomoides polygyrus infection. American Journal of Physiology. Gastrointestinal and Liver Physiology, 291, 253–259. DOI: 10.1152/ajpgi.00409.2005.
- Noble A., Giorgini A., Leggat J.A. 2006. Cytokine-induced IL-10-secreting CD8 T cells represent a phenotypically distinct suppressor T cell lineage. Blood, 107, 4475–4483. DOI: 10.1182/blood-2005-10-3994.
- Sugane K., Oshima T. 1983. Trapping of large numbers of larvae in the livers of Toxocara canis-reinfected mice. Journal of Helminthology, 57, 95–97.
- Yamashita U., Jiang H., Inoue H., Mutoh Y., Furukawa T. 1993. Japanese Journal of Parasitology, 42, 211–219.