Replication of TBE and Langat viruses in cells from immune individuals.

The replication of TBE virus and Langat virus in cells of immune and non-immune individuals was compared in phytohemagglutinin (PHA)-stimulated and non-PHA-stimulated cultures and also following infection with low and high infection multiplicity. Following infection of spleen cells from Langat-immune mice with Langat virus having a high infection multiplicity, higher virus replication rates than in non-immune cells were found to be present. Replication of Langat virus was generally superior to that of TBE virus. Virus replication was generally reduced by PHA stimulation of spleen cells. Langat virus did not replicate in human peripheral leukocytes. TBE virus replicated equally well in cells from a patient with TBE history and in cells from a non-immune person.