Potentiation of Experimental Arbovirus Encephalitis by Immunosuppressive Doses of Cyclophosphamide

THE role of the immune response in recovery from primary viral infection has been debated for many years, in part because of the inconclusive nature of the relevant evidence 1,2 . The ability of children with defective immunoglobulin synthesis to recover uneventfully from certain viral infections 3 , and the recognition of non-immune host defences such as interferon 4 , have suggested that the immune response plays a small part. The recent development of an increasing variety of techniques for the production of immunosuppression permits a re-examination of the question. Using the potent alkylating agent, cyclophosphamide 5,6 , we have found that administration of immunosuppressive doses of the drug converts a silent abortive arbovirus infection of the rodent central nervous system (CNS) into a lethal encephalitis.