A candidate vaccine based on the hepatitis C E1 protein: tolerability and immunogenicity in healthy volunteers.

The tolerability and immunogenicity of the hepatitis C virus E1 protein as a candidate vaccine was examined in a Phase I, single-arm study. Twenty healthy male volunteers were injected in the deltoid muscle at weeks 0, 3 and 6 with 20 microg recombinant E1 adsorbed on alum. A fourth (booster) dose was administered to 19 subjects at week 26. The candidate therapeutic vaccine was well tolerated. Three vaccine doses induced a clear humoral anti-E1 response that was boosted by a fourth dose. A strong, specific cellular immune response towards E1 was elicited in all vaccine recipients, which included a clear Th1 type response in all but one of the subjects.