Demonstration of viral antigen and immunoglobulin (IgG and IgM) in brain tissue of pigs experimentally infected with haemagglutinating encephalomyelitis virus.

Haemagglutinating encephalomyelitis virus (HEV) was inoculated either orally or intranasally into ten 3-day-old gnotobiotic piglets. All infected pigs showed inappetence and listlessness, but there were no clinical signs of nervous disorder. Severe encephalomyelitis, characterized by neuronophagia, focal gliosis and perivascular cuffing, was observed in the brain stem and cerebral cortex. Nasally infected pigs, in particular, developed lesions in the area of the stria olfactoria and tractus olfactorius. Coincident with the encephalitic changes, HEV antigen was observed first in the trigeminal ganglion cells and then in degenerating neurones. Immunoglobulin (IgG and IgM)-containing cells were also found in perivascular cuffs and glial foci. They appeared at first on PID 7 and after that increased in number. These findings suggest that these encephalitic lesions are a specific immune response to HEV following its multiplication in the central nervous system.