Studies on poxvirus infections in irradiated animals

If rabbits were given total body irradiation and infected wih vaccinia virus (strain Elstree) a severe disease developed with a viraemia lasting up to 12 days. The clearance of the virus from the peripheral blood was severely impaired by x-ray doses above 800 R. The attenuated vaccinia virus strain MV did not turn virulent, if it was injected to irradiated rabbits. With caution it can be assumed that live vaccines, containing attenuated viruses, may be given to immunosuppressed persons. Rats are not susceptible to ectromelia-virus (mouse-poxvirus); overt clinical sympatoms, however, with a mortality of 30 per cent developed in irradiated rats. This proofs that specific poxviruses can be transferred to another species. As the experimental conditions are unnatural, this may occur only rarely in immunosuppressed persons. After intracerebral infection of Balb-C-mice with low doses of vaccinia virus two types of infection were seen: 1. a severe cytocidal infection of leptomeninges, chorioid plexus and vessels; 2. a noncytocidal, latent infection of glial cells and neurons. Several animals developed a picture resembling experimental allergic encephalomyelitis. It seems that irradiation altered the antigenic conditions of the cytoplasmic membranes in non-cytocidally infected cells. The model might explain some processes in the pathogenesis of demylinating diseases.