A precipitation reaction found in patients with hepatitis C as a marker for the purification of virus-like particles

Even after the molecular cloning of the hepatitis C virus (HCV), an HCV-spe cific precipitation reaction has not yet been identified. We attempted to d evelop a precipitation system exclusively for anti-HCV-positive sera as a f irst step in finding an HCV-specific antigen and HCV-associated particles. In some patients being in a final stage of different liver diseases, we fou nd sera (179/132,761; designated 'a-CK') which specifically precipitated wi th anti-HCV- and HCV-RNA-positive sera (designated 'CK'). When CK-positive sera were searched for in patients with various liver diseases using standa rd a-CK-positive plasma, CK was detected in 420 (57.9%) of 726 anti-HCV-pos itive sera and in none of the 1,630 anti-HCV-negative ones. The nature of C K and a-CK has not been fully clarified yet; CK demonstrated inter-py mobil ity, whereas a-CK showed P-globulin mobility; CK was not detected in cryopr ecipitate, but HCV RNA was present in precipitates of CK-positive plasma in cubated with one that was a-CK positive, Transmission electron microscopy r evealed two size ranges of particles in the precipitate of CK- and a-CK-pos itive plasmas, 23-38 nm and 48-65 nm, We have found a novel precipitation s ystem which is exclusive to anti-HCV-positive sera and which specifically p recipitates an HCV-RNA-containing serum fraction and particles, This system can be useful for the purification and characterization of the circulating particles. Furthermore, it may be a new approach to the nature of HCV-RNA- carrying material.