Folding and dimerization of Hepatitis C Virus E1 and E2 glycoproteins in stably transfected CHO cells

The recombinant E1E2 heterodimer of the hepatitis C virus is a candidate for a subunit vaccine. Folding analysis of E1 and E2 glycoproteins, stably expressed in CHO cells, showed that E1 folding was faster and more efficient than E2. The oxidized DTT-resistant conformation of E1 was completed within 2 h post-synthesis, while E2 not only required up to 6 h but also generated non-native species. Calnexin was found to assist E1 folding, whereas no chaperone association was found with E2. The assembly of E1 and E2 was assessed by co-immunoprecipitation and sedimentation velocity analysis. We found that the formation of native E1E2 heterodimers paralleled E2 oxidation kinetics, suggesting that E2 completed its folding process after association with E1. Once formed, sedimentation of the native E1E2 heterodimers was consistent with the absence of additional associated factors. Taken together, our data strongly suggest that productive folding of the major HCV spike protein E2 is assisted by E1.