On the replication and spread of rabies virus in the human central nervous system

Ultrastructural and immunohistochemical studies on the brains of two autopsy cases of human rabies revealed: By the peroxidase-antiperoxidase method, viral antigens were present in all eosinophilic inclusions detected in formalin fixed paraffin sections. Numerous antigenic masses, which apparently corresponded to the matrices and cylindrical particles in neurites revealed by electron microscopy, were present in the neuropil remote from neuronal perikarya. There were virions in the intercellular spaces and virus-budding from the plasma membrane into the extracellular space in the absence of a matrix, strongly indicating that rabies virus in the human central nervous system could spread through the intercellular spaces and that the replication of the virus was not necessarily accompanied by the formation of inclusion bodies. The synapse was involved in rabies as indicated by virions in the synaptic terminals. The implications of these observations are discussed in conjunction with the results of previous in vitro and animal experiments.