Recombinant human IFN-alpha inhibits cerebral malaria and reduces parasite burden in mice.

Most C57BL/6 mice infected i.p. with Plasmodium berghei ANKA (PbA) die between 7 and 14 days with neurologic signs, and the remainder die later (>15 days) with severe anemia. Daily i.p. injections of a recombinant human IFN-alpha (active on mouse cells) prevented death by cerebral malaria (87% deaths in the control mice vs 6% in IFN-alpha-treated mice). The mechanisms of this IFN-alpha protective effect were multiple. IFN-alpha-treated, PbA-infected mice showed 1) a marked decrease in the number of PbA parasites in the blood mediated by IFN-gamma, 2) less sequestered parasites in cerebral vessels, 3) reduced up-regulation of ICAM-1 expression in brain endothelial cells, 4) milder rise of blood levels of TNF, 5) increased levels of IFN-gamma in the blood resulting from an increased production by splenic CD8+ T cells, and 6) fewer leukocytes (especially CD8+ T cells) sequestered in cerebral vessels. On the other hand, IFN-alpha treatment did not affect the marked anemia observed in PbA-infected mice. Survival time in IFN-alpha-treated mice was further increased by performing three blood transfusions over consecutive days.