The hypervariable region (E2HV) of the putative hepatitis C virus (HCV) glycoprotein E2/NS1, between about amino acid 384 to about amino acid 414, is a rapidly evolving region of HCV, and is likely to be under positive immune selection. A newly discovered motif within this hypervariable region is immunogenic and conserved with respect to the character of the amino acids. In many isolates, this motif falls between amino acids 401 to 406 or 407. The discovery of this motif allows for additional materials and methods to treat and diagnose HCV.