Immunopathogenesis of acute central nervous system disease produced by lymphocytic choriomeningitis virus. II. Adoptive immunization of virus carriers

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.

Immunopathogenesis of acute central nervous system disease produced by lymphocytic choriomeningitis virus. I. Cyclophosphamide-mediated induction by the virus-carrier state in adult mice

A single dose of 150 mg/g of cyclophosphamide (CY), given 3 days after intracerebral (i.c.) inoculation of lymphocytic choriomeningitis (LCM) virus, protected over 90% of adult BALB/c mice against acutely fatal choriomeningitis. Surviving mice became persistently infected carriers, with high virus titers in blood and brain. Immunofluorescent examination of the brain showed that in CY-induced carriers infection was initially confined to the choroid plexus, ependyma, and leptomeninges, but over the next 30 days gradually spread to the neural parenchyma, most notably to the molecular layer of the cerebellum. By contrast, LCM virus-carrier mice produced by neonatal virus injection and examined as adults, showed a much less marked infection of choroid plexus and much more widespread infection of parenchyma, with a different distribution among brain nuclei, including heavy infection of the Purkinje cells of the cerebellum.

The replication of the Kilham rat virus (RV) in various host systems: immunofluorescent studies

The replicative cycle of the Kilham rat virus (RV-13) in rat embryo (RE), hamster embryo (HE), and L-929 cell cultures was studied under conditions of high viral input multiplicity. The synthesis of RV antigen in infected cells was followed by the indirect fluorescent antibody (FA) technique and correlated with the appearance of extracellular hemagglutinin. The synthesis of specific antigen in RE and HE cell cultures appeared to follow a similar pattern. Cytoplasmic fluorescence was observed early in the replicative cycle of RV in both host systems. Nuclear fluorescence was detected 6–8 h later after a decline in the number of cells exhibiting cytoplasmic fluorescence. Nuclear fluorescence appeared more extensive and more intense in RE cells. In addition, a significantly higher hemagglutinin titer was obtained from the infection of RE cells. The replicative cycle of RV in L-929 cells appeared aborted. Although the synthesis of RV structural antigen was detected in the cytoplasm of these cells, subsequent nuclear fluorescence was totally absent and extracellular hemagglutinin was not detected.