Expression and immunological evaluation of the Escherichia coli ‐derived hepatitis C virus envelope E1 protein

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Abstract
Immunological response against envelope protein E1 is very important in natural hepatitis C virus (HCV) infection, although it is insufficient to clear the viraemia. The HCV genomic region encoding the first 149 amino acids of the envelope E1 protein (E1340, amino acids 192–340) was expressed in Escherichia coli (to a level of 30% of the whole cellular proteins) and purified to 85%. We measured the immune response in rabbits and mice as well as the reactivity against 37 human sera raised against the whole recombinant protein and E1‐encoding peptides. From this, 51.1% of human sera were found to react with E1340. High‐level antibodies against E1340 were obtained in rabbits and mice when immunized. These antibodies had a similar peptide‐recognition pattern to that described previously for human sera. The most reactive region was located at the N‐terminus of the E1 protein. Cellular immunity in mice was evaluated by delayed‐type hypersensitivity assay. It revealed the induction of a CD4+ T‐cell‐mediated response by this protein. This E1340 protein and the animal‐derived anti‐E1 sera are immunological tools that could aid in the monitoring and development of anti‐HCV therapies.