Immunodepression induced by Trypanosoma cruzi and mouse hepatitis virus type 3 is associated with thymus apoptosis.
Trypanosoma cruzi-infected mice show disturbance in the peripheral immune system such as polyclonal lymphocyte activation, autoantibody production, and immunosuppression of T lymphocytes. Previous observations in our laboratory showed that some stocks of T. cruzi can be contaminated with mouse hepatitis virus type 3 (MHV-3). Literature has shown that MHV-3 infection induces immunologic disorders characterized by thymic involution with marked cell depletion. However, the effects of interactions between MHV-3 and the parasite on the immune system are not well understood. In the present study specific-pathogen-free CBA mice were inoculated with MHV-3, alone or associated with different stocks of T. cruzi. Concurrent murine virus infection resulted in increased pathogenicity of T. cruzi infection shown by profound thymic atrophy; loss of cortical thymocytes; depletion of Thy1.2+, CD4+, and CD8+ cells; enhancement of in situ labeling of nuclear DNA fragmentation; and eventually, death of the animals. Such lines of evidence show that the mechanism underlying this thymic atrophy is associated with apoptosis. These results also suggest that MHV-3 can account for the increased immunosuppression observed during experimental infection with the parasite.
Verinaud
L
L
Department of Microbiology and Immunology, UNICAMP, Campinas, São Paulo, Brazil.
Da Cruz-Höfling
M A
MA
Sakurada
J K
JK
Rangel
H A
HA
Vassallo
J
J
Wakelin
D
D
Sewell
H F
HF
Camargo
I J
IJ
D000818:Animals; D017209:Apoptosis / Q000276:immunology*; D001323:Autoantibodies / Q000276:immunology; D014355:Chagas Disease / Q000276:immunology*; D006524:Hepatitis, Viral, Animal / Q000276:immunology*; D007165:Immunosuppression Therapy; D051379:Mice; D008808:Mice, Inbred CBA; D006517:Murine hepatitis virus / Q000276:immunology*; D013950:Thymus Gland / Q000276:immunology* / Q000473:pathology; D014349:Trypanosoma cruzi / Q000276:immunology*
D001323:Autoantibodies