A virus-like particle associated with psoriasis.

Virus-like particles were demonstrated by electron microscopy of specimens from psoriatic plaques. Cell cultures established from plaques released particles, showing the morphological features of a retrovirus, for a prolonged period. The particles had a buoyant density of 1.17 g/cc and contained a surface protein of Mr 70,000 which bound to concanavalin A and therefore probably was of glycoprotein nature. A major internal protein of Mr 30,000 and two minor proteins of Mr 18,000 and 15,000 were detected. The composition of the proteins therefore resembled that of murine C-type retrovirus. Patients with psoriasis release virus-like particles in their urine which have a different morphology to the particles from cell cultures. A similar difference could be observed in particles from cell cultures after treatment with normal urine. Patients with psoriatic arthritis had serum immune complexes. The complexes contained distorted particles which could not be identified as virions on a morphological basis. A radio immunoassay was performed which demonstrated common antigens in the virus-like particles isolated from psoriatic urines, immune complexes and cell cultures.