Hepatitis C virus and hepatitis B virus bind to heparin: purification of largely IgG-free virions from infected plasma by heparin chromatography

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Abstract
Binding to heparin of hepatitis C virus (HCV) and hepatitis B virus (HBV) from chronic carriers was investigated. Eighty per cent of HCV RNA from an agammaglobulinaemic patient (IgG-free virus) was retained on immobilized heparin and eluted with > or =0.4 M NaCl, in contrast to approximately 20 % from immunocompetent chronic carriers (with < or =8 % IgG-free virus). Increased binding to heparin of the HCV fraction that was not retained by a protein G column suggested that antibodies complexed to the virions partially inhibited the interaction. A higher proportion (15-80 %) of HBV from chronic carriers bound to heparin and eluted with > or =0.4 M NaCl. After washing of the heparin columns with 0.3 M NaCl, <1 % of total plasma proteins co-eluted with HCV or HBV. By this one-step heparin chromatography, without ultracentrifugation, IgG-free HCV and IgG-free HBV were preferentially purified from human plasma by 1000-fold and greater than 500-fold, respectively. Following assessment with an anti-E2 envelope protein antibody, the amount of immunoprecipitated HCV particles after heparin purification was similar to that in the original plasma, suggesting that undamaged virions were purified. This was further supported by heparin-purified HCV binding to lymphocyte cell lines in a dose-dependent manner. Intact HBV particles were detected by electron microscopy. It was concluded that HCV and HBV from chronically infected patients bind to heparin, the closest homologue of liver heparan sulfate, and that heparin chromatography is an efficient and gentle method for purifying these viruses from human plasma. In the absence of cell-culture systems or alternative robust purification methods, heparin chromatography may help greatly in binding and infectivity studies.