Non-productive paramyxovirus infection: Nariva virus infection in hamsters.

The pathogenesis of infection with Nariva virus (NV)--recently classified as a paramyxovirus--was studied in the hamster, an animal closely related to the natural host. Intracranial inoculation of suckling hamsters produces an acute necrotizing encephalitis with large amounts of infectious virus and virus antigen in the brain. In contrast, weanling hamsters have only small amounts of infectious virus and only early in the disease, when they are well; later, when clinically ill, they have a non-productive infection with continuing evidence of viral antigen, but no detectable infectious virus. Weanlings die later than sucklings with less cerebral parenchymal necrosis. The integrity of the immune system affects the expression of NV since brain tissue from anti-lymphocyte serum (ALS) treated infected weanling hamsters have more infectious virus, and for longer periods, than brain tissue from untreated infected weanling hamsters. Changing susceptibility of the host's neural cells may also be involved in determining the course of the illness and expression of the virus since: 1) ALS treatment does not influence the clinical course of the disease or pathology, 2) ALS treated weanlings still have much lower levels of infectious virus than sucklings, 3) infected weanling and suckling hamsters have a similar time course of development of NV neutralizing antibody.