Invasion of mouse brain by Mount Elgon bat virus.

Mount Elgon bat virus killed mice up to 13 days of age when given intranasally. Virus reached the brain of these mice via the olfactory nerve route without obvious multiplication in any tissues other than the nasal mucosa of 1- to 6-day-old mice and in the absence of viraemia or circulating virus neutralizing antibody. Large amounts of interferon were, however, synthesized in brain where virus grew to high titres. In mice older than 13 days virus did not multiply in brain but it reached the olfactory bulbs and persisted until virus neutralizing antibody appeared in the nasopharynx. No antibody was detected in blood of the resistant mice, nor was interferon detected in their brains or nasal mucosa. Immunosuppression of the resistant mice with cyclophosphamide resulted in moderate virus growth in mid- and hind-brain accompanied by interferon synthesis and death of the mice. The local immune response prevented invasion of mid- and hind-brain in the resistant mice.