Detecting a psoriatic antigen analogous to infectious prion proteins

Until now, psoriatic antigen as a specific antigen derived from some infectious agent potentially related to origin of psoriasis has not been identified, thereby strongly arguing against infectious theory of psoriasis. However, the lack of specific psoriasis-associated antigens may be theoretically accounted for by an idea that psoriatic antigen could be analogous to infectious prion proteins (PrPSc analogue). It might be identical to some epidermal protein in psoriasis-free subjects that might differ antigenically from related normal protein by resistance to digestive enzymes similarly to PrPSc. Since PrPSc cytopathogenic effect is associated with its location within cell structures of affected body tissue, by analogy with PrPSc we aimed at identifying a potential carrier of psoriatic antigen by examining peptic hydrolysates of psoriatic squamous elements. Psoriatic squamous elements and epidermal stratum corneum were collected from heel area of healthy subjects with a metal grater for further examination. Squamous elements were homogenized in isotonic saline followed by centrifugation to separate them from soluble components. Homogenates of squamous elements structures and their homogenate supernatants underwent peptic hydrolysis reaction. Antigens and their identity were analysed by Ouchterlony immunoprecipitation in agar with antiserum obtained after immunizing rabbits with homogenate of the psoriatic squamous element structures, before and after hydrolysis, using peptic hydrolysates of squamous element structures and relevant supernatants. It was found that two antigens were precipitated in peptic hydrolysates of homogenates of psoriatic squamous cell structures, underlying acidin-pepsin resistance of antigen carriers. However, compared to the remainder of antigens precipitated in examined substrates only one out of two antigens might be considered as a psoriatic antigen being some PrPSc analogue that was identical to one of supernatant antigens derived from epidermal stratum corneum homogenates collected from healthy subjects. Similar to PrPSc, it differed from antigenically related normal protein by acidin-pepsin resistance. Albeit confirming available reports revealing no psoriasis-associated pathogen-specific antigens, this, nonetheless, might not be sufficient for rejecting infectious theory of psoriasis, as psoriatic antigen exhibits some properties similar to those of PrPSc.

psoriasis, squamous elements, acidin-pepsin, peptic hydrolysis, psoriatic antigen, infectious prion proteins, PrPSc, PrPSc analogue