Purification and partial characterization of a soluble suppressor factor from papillomavirus-infected patients

A molecular form of soluble suppressor factor was identified in serum-free supernatant fluid of cultured peripheral blood mononuclear cells (PBMC) from patients with severe forms of papillomavirus infections (epidermodysplasia verruciformis and large treatment-resistant condyloma acuminatum). The papillomavirus-induced soluble suppressor factor (SSF-H) was highly purified by gel filtration, anion-exchange chromatography, chromatofocusing, hydrophobic chromatography, and nondissociating polyacrylamide gel electrophoresis (PAGE). The factor exhibited an apparent molecular weight of 67 kDa as determined by sodium dodecylsulfate-PAGE. The isoelectric point ranged from 4.8 to 5.2 as judged by chromatofocusing. The biologic activity of the SSF-H during purification and in subsequent characterization was examined by in vitro CTLL bioassay. Purified SSF-H was stable at 56°C for 1 h and in the pH range of 4.0 to 8.0. Complete inactivation was observed at 80°C. Trypsin and proteinase K treatment destroyed the biologic activity associated with purified SSF-H. This factor seems to be different in its molecular weight and other physicochemical properties from the known suppressor factors that affect lymphocyte functions.