Viral hyperinfection of the central nervous system and high mortality after hematopoietic stem cell transplantation for treatment of Theiler's murineencephalomyelitis virus-induced demyelinating disease

Theiler's murine encephalomyelitis virus (TMEV) establishes a persistent in fection in the central nervous system (CNS) leading to an inflammatory demy elinating disease of the CNS in which the histology and clinical course is similar to multiple sclerosis (MS). Disease pathogenesis is primarily due t o T-cell-mediated destruction of myelin, which has been attributed to cytop athic effects of the virus, but immune-mediated destruction of myelin media ted via both virus-specific and myelin-specific T cells appear to play the major role, To determine if bone marrow transplantation would be an effecti ve therapy for a virus-initiated autoimmune disease and to better separate viral cytopathic effects from immune-mediated demyelination, we ablated the immune system of TMEV-infected animals with 1,100 cGy total body irradiati on, and then the animal's immunity was reconstituted by transplantation of disease-susceptible SJL/J mice with syngeneic marrow or disease-susceptible DBA/2J with marrow from disease-resistant (C57BI/6 x DBA/2)F1 (B6D2) donor s. Hematopoietic transplant performed after onset of disease resulted in 42 % mortality in SJL/J syngeneic transplants, 47% mortality in diseased DBA2 recipients restored with marrow from naive B6D2 donors, and 12% in diseased DBA2 recipients receiving marrow from B6D2 donors previously infected with TMEV. Delayed type hypersensitivity (DTH) to both virion and myelin protei ns was decreased in surviving mice that underwent transplantation; however, CNS viral titers were significantly elevated compared with nontransplanted controls, We conclude that a functional immune system with appropriate T-c ell responses are important in prevention of lethal cytopathic CNS effects from TMEV. Relevant to the clinical use of bone marrow transplantation, att empts to ablate the immune system in viral-mediated immune diseases or viru s-initiated autoimmune disease may have acute and lethal consequences. Our results raise concern about the attempted use of autologous hematopoietic t ransplantation in patients with MS, an autoimmune disease with a suspected virus etiology, particularly if the graft is aggressively depleted of lymph ocytes. (C) 1999 by The American Society of Hematology.