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Protective immune response of Isospora felis-infected mice against Babesia microti infection
M Takahashi1, Y Omata, H Oikawa
1Department of Veterinary Physiology, Obihiro University of Agriculture and Veterinary Medicine, Japan.
Abstract:
Protective response against Babesia microti was studied in Isospora felis-infected mice. Isospora felis-infected mice which were exposed to B. microti on the 28th day post-infection showed absolute resistance against Babesia microti. Interestingly, these mice showed no anti-B. microti antibodies. Mice that received spleen cells from I. felis-infected donors that were subsequently exposed to B. microti showed lower peak parasitemia (10.3% +/- 2.6) compared to those mice that received normal spleen cells (60.9% +/- 15.0), and no spleen cells at all (47.3% +/- 8.5). Treatment of I. felis-infected mice with monoclonal antibodies against L3T4+ cells resulted to a depression of their resistance to B. microti, as clearly manifested by high levels of parasitemia. Findings of the present study demonstrate the role of cell mediated immunity, specifically by L3T4+ T-cells induced by I. felis infection, in providing mice protection against B. microti.
Insights
Isospora felis infection induces resistance to Babesia microti in mice through cell-mediated immunity, specifically involving L3T4+ T-cells, without antibody production.
Area of Science:
- Immunology
- Parasitology
- Cellular Immunology
Background:
- Babesia microti is an intraerythrocytic parasite causing babesiosis.
- Isospora felis is a coccidian parasite that infects the intestinal tract.
- The immune mechanisms conferring protection against parasitic infections are complex and varied.
Purpose of the Study:
- To investigate the protective immune response against Babesia microti in mice infected with Isospora felis.
- To elucidate the role of cell-mediated immunity in protection against Babesia microti.
Main Methods:
- Mice were infected with Isospora felis and subsequently exposed to Babesia microti.
- Spleen cells from infected donors were transferred to naive recipients.
- Monoclonal antibodies targeting L3T4+ cells were used to assess T-cell involvement.
- Parasitemia levels were monitored to evaluate protection.
Main Results:
- Isospora felis-infected mice exhibited absolute resistance to Babesia microti challenge.
- No anti-Babesia microti antibodies were detected in the resistant mice.
- Spleen cell transfer from infected donors significantly reduced Babesia microti parasitemia.
- Depletion of L3T4+ T-cells abrogated the protective effect, leading to high parasitemia.
Conclusions:
- Isospora felis infection induces a potent cell-mediated immune response conferring protection against Babesia microti.
- L3T4+ T-cells play a critical role in this protective immunity.
- The protective mechanism is independent of antibody production.