Lymphocytic choriomeningitis (LCM) virus carriers were established by intracerebral inoculation of adult BALB/c mice followed by a single dose of cyclophosphamide (CY) (150 mg/kg) 3 days after infection, and by intracerebral injection within 24 hr of birth. These carriers were then adoptively immunized with spleen cells or serum from immune or normal BALB/c donors.

Transfer of immune spleen cells into drug-induced carriers consistently resulted in acutely fatal choriomeningitis, histologically strikingly similar to classical LCM. Normal spleen cells or immune serum failed to produce either central nervous system (CNS) pathology or illness with any regularity. In addition, focal necrosis of the cerebellum was seen after adoptive immunization of drug-induced carriers but only when mice received cells at least 3 wk after inoculation, which is probably explained by the gradual spread of infection from membranes to the neural parenchyma during the first month after establishment of the carrier state in adult mice.

Immune spleen cells, when transferred to neonatal carriers, led to a decrease in virus titers in blood and brains and to development of antibody without acute CNS disease.

It appears that the production of fatal choriomeningitis after LCM infection is determined in part by the distribution of viral antigen, and this is markedly different in neonatal and drug-induced carriers at the time of cell transfer. Another factor of potential importance is the much higher level of circulating viral antigen in the plasma of neonatal than in that of drug-induced LCM carriers.

Classical LCM disease can only be transferred by immune lymphoid cells and not by antiserum. Furthermore, little or no complement-fixing (CF) antibody was found in the plasma of mice dying of acute choroiditis. These observations strongly suggest that acute choroiditis is dependent upon the cell-mediated immune response.

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