Abstract
Two plaque purified mutants, JHM-1a and JHM-2c of mouse hepatitis virus were examined on neuropathogenicity for mice. After intracerebral inoculation with 104 PFU of JHM-1a virus 30% of weanling ICR mice died within 7 days showing viral growth in the brain equivalent to that of the original JHM, while all JHM-2c infected mice survived with very low-titered virus. At early stage of JHM-1a infection mice showed much less extensive encephalomyelitis than in case of the original JHM although almost the same amount of viral antigen was detectable in neurons and glial cells of animals infected with both viruses. Infected mice showed fusion of oligodendrocytes and neurons without significant inflammatory response. With JHM-2c of lower-neurovirulence viral antigen was seen in glial cells rather than neurons. At 4 weeks postinfection viral antigen was detected within oligodendrocytes and demyelination was produced in mice infected with both mutant viruses.
