Trypanosoma cruzi infection and the rat central nervous system: Proliferation of parasites in astrocytes and the brain reaction to parasitism

Chagas' disease, caused by the protozoan Trypanosoma cruzi, is characterize d by an acute phase in which parasites circulate in the blood and prolifera te in several cell types, especially muscle cells. A life-long chronic phas e follows the acute phase. In young patients, the acute phase is more sever e, and meningoencephalitis frequently occurs in children before 2 years of age. parasites have been rarely observed in neurons but their presence insi de glial cells has been reported without characterization of the glial cell type. The cells involved in the brain reaction to the parasites and the ti me course of this reaction remain to be studied. Therefore, using suckling and juvenile rats and different T. cruzi populations, we aimed at determini ng the brain target for parasite proliferation and the cells involved in th e brain reaction. Around the middle of the acute phase, histological and ul trastructural findings indicated that T. cruzi proliferates in astrocytes, forming nests devoid of enclosing membrane as described for non-glial cells . The brain nodular reaction comprised astrocytes, microglia, macrophages a nd neutrophils. Resting microglia was devoid of parasites in contrast to ma crophages and neutrophils that probably participate in parasite removal. Su ckling animals were significantly more affected, the numbers of nests and n odules varying with inoculum size, Histoquantitative analysis showed higher number of nests at the parasitemic peak (day 13) and drastic fall at day 2 0 post-inoculation. The highest number of nodules occurred at day 20 with d rastic reduction at day 30, Recovery from histopathological alterations occ urred even in surviving younger animals. (C) 2000 Elsevier Science Inc.