Mumps virus infection of the developing mouse brain--appearance of structural virus proteins demonstrated with monoclonal antibodies.

Newborn mice and hamsters were inoculated intracerebrally with mumps virus strains of high and low neurovirulence, Kilham and RW, respectively and with an egg-adapted patient isolate. The presence of viral antigen in brain tissue was analyzed with the immunofluorescence technique employing monoclonal antibodies against nucleoprotein (NP), polymerase (P), matrix (M), hemagglutinin-neuraminidase (HN) and fusion (F) mumps virus components. As expected, hamsters developed a fatal encephalitis eight to nine days after infection with the Kilham strain and synthesis of all five structural viral antigens was identified. In contrast, mice infected with any of the virus strains did not develop signs of disease, but in brain material collected on days nine and 12 after infection viral antigen was present in many neurons. However, only NP and P antigens were demonstrable and no infectious virus was present. The antibody response in mice developed later than in hamsters. Neurons in the mouse brain may exert a host cell restriction on the virus maturation, and mice offer a suitable host for the establishment of defective, persistent mumps virus infections.