Defective and delayed myxovirus infections

Accidental persistent infection of cell lines by Newcastle disease virus, showing three unusual features--defective neuraminidase, temperature sensitivity and intranuclear inclusions

A persistent, defective infection by an unknown strain of Newcastle disease virus (NDV) appeared accidentally in established lines of pig, ox and sheep kidney cells. Virus particles released from the persistently infected cells were not infectious and were deficient in neuraminidase activity. Synthesis of some of the virus-specified proteins in the persistently infected cells was temperature-sensitive. Co-cultivation of mixed populations of carrier cells and healthy chick embryo cells induced cell fusion with the formation of multinucleate heterokaryons and intra-nuclear inclusions. The development of inclusions in the chicken nuclei was not accompanied by 'rescue' of infectious NDV.

Subacute sclerosing panencephalitis: measles encephalitis of temperate evolution?

Subacute sclerosing panencephalitis is a rare disorder of late childhood and early adolescence Affected patients usually show behavioural and intellectual disturbance and involuntary movements before dying in coma after about 12 months. At some stage most have characteristic electroencephalographic abnormalities. Pathologically, changes in the brain are those of subacute encephalitis with a variable gliosis of the white matter, and sometimes intranuclear inclusion bodies in neurones and glial cells.

Recent studies in many patients have shown high levels of circulating anti-measles antibodies, measles antigen in cells in the brain, and sometimes, myxo-virus filaments in cells there. These findings suggest that SSPE may be a slow measles virus infection of the nervous system. Possible explanations for the slow evolution of the encephalitis include disordered immune mechanisms and intracellular persistence of virus in a defective phase.