Virulent P. berghei malaria: prolonged survival and decreased cerebral pathology in cell-dependent nude mice.

The course of lethal Plasmodium berghei infection was examined in nu/+ and T cell-deficient nu/nu BALB/c mice. A rapidly fatal neurologic syndrome, including ataxia, hemiparesis, and seizures, was seen in the nu/+ mice early in the infection, whereas this syndrome was absent in the nu/nu mice. The nu/nu mice also developed anemia more slowly, had lower levels of immune complexes and total IgG, and had smaller decreases in serum C3 compared with the nu/+ mice. Histopathologic examination of the brains revealed cerebral malaria lesions, including vascular plugging and micro-hemorrhages, in the nu/+ mice but not in the nu/nu mice. Cerebral lesions similar in frequency and severity to those in nu/+ mice developed in nu/nu mice given spleen cells from normal nu/+ mice. The results suggest that an intact immune system is necessary for the expression of cerebral malaria.